NIST NCSTAR 1-6A

Federal Building and Fire Safety Investigation of the

World Trade Center Disaster

Passive Fire Protection

Nicholas J. Carino

Monica A. Starnes

John L. Gross

Jiann C. Yang

Scott R. Kukuck

Kuldeep R. Prasad

Richard W. Bukowski

National Institute of Standards and Technology • Technology Administration • U.S. Department of Com.

NIST NCSTAR 1-6A

Federal Building and Fire Safety Investigation of the

World Trade Center Disaster

Passive Fire Protection

Nicholas J. Carino*

Monica A. Starnes**

John L. Gross

Jiann C. Yang

Scott R. Kukuck***

Kuldeep R. Prasad

Richard W. Bukowski

Building and Fire Research Laboratory

National Institute of Standards and Technology

'Retired

"Current affiliation: Johns Hopkins University

Applied Physics Laboratory

Laurel, Maryland

***Current affiliation: U.S. Army Research Laboratory

Aberdeen Proving Grounds, Maryland

September 2005

U.S. Department of Commerce

Carlos M. Gutierrez, Secretary

Technology Administration Michelle O' Neill, Acting Under Secretary for Technology

National Institute of Standards and Technology

William Jeffrey, Director
Disclaimer No. 1

Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the National Institute of Standards and Technology.

Disclaimer No 2 The policy of NIST is to use the International System of Units (metric units) in all publications. In this document,

however, units are presented in metric units or the inch-pound system, whichever is prevalent in the discipline.

Disclaimer No. 3

Pursuant to section 7 of the National Construction Safety Team Act, the NIST Director has determined that certain evidence received by NIST in the course of this Investigation is "voluntarily provided safety-related information" that is "not directly related to the building failure being investigated" and that "disclosure of that information would inhibit the

voluntary provision of that type of information" (15 USC 7306c).

In addition, a substantial portion of the evidence collected by NIST in the course of the Investigation has been

provided to NIST under nondisclosure agreements.

Disclaimer No. 4 NIST takes no position as to whether the design or construction of a WTC building was compliant with any code

since, due to the destruction of the WTC buildings, NIST could not verify the actual (or as-built) construction, the properties and condition of the materials used, or changes to the original construction made over the life of the

buildings. In addition, NIST could not verify the interpretations of codes used by applicable authorities in determining

compliance when implementing building codes. Where an Investigation report states whether a system was

designed or installed as required by a code provision, NIST has documentary or anecdotal evidence indicating

whether the requirement was met, or NIST has independently conducted tests or analyses indicating whether the requirement was met.

Use in Legal Proceedings

No part of any report resulting from a NIST investigation into a structural failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action for damages arising out of any matter mentioned in such report (15 USC 281a; as amended by P.L. 107-231).

National Institute of Standards and Technology National Construction Safety Team Act Report 1-6A

Natl. Inst. Stand. Technol. Natl. Constr. Sfty. Tm. Act Rpt. 1-6A, 326 pages (September 2005)

CODEN: NSPUE2

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 2005

For sale by the Superintendent of Documents, U.S. Government Printing Office

Internet: bookstore.gpo.gov — Phone: (202) 512-1800 — Fax: (202) 512-2250

Mail: Stop SSOP, Washington, DC 20402-0001
Abstract

This report deals with the passive fire protection used in the World Trade Center (WTC) towers. The

main objective is to provide background information that can be used to assess the in-place conditions of

the passive protection before and after aircraft impact. The report includes a review of key building code

provisions related to structural fire protection. It also includes a review of key decisions related to passive

fire protection made during design, construction, and occupancy of the towers. Copies of documents to support key findings are included in an Appendix. A summary is provided of available data on in-place

measurements of the sprayed fire-resistive materials (SFRMs) applied to the floor trusses and to core members. Measurements of thermophysical properties of the passive fire protection materials, including

gypsum panels, are presented. The effects of gaps in thermal insulation and the effects of variability of

insulation thickness are evaluated. The rationale for selecting the effective thickness of thermal insulation

for use in thermal-structural analyses is presented. Measurements of adhesive and cohesive strengths of a selected SFRM are summarized. Simplified models are presented for estimating the acceleration required

to dislodge SFRM from planar surfaces and encased round bars. The report concludes with a summary of

key findings.

Keywords: adhesive strength, building code, cohesive strength, construction classification, density,

equivalent thickness, retrofit, specific heat capacity, sprayed fire-resistive materials (SFRM), thermal

conductivity, thermal insulation, thickness, thickness variability, World Trade Center.

NISTNCSTAR 1-6A, WTC Investigation in
Abstract

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IV NISTNCSTAR 1-6A, WTC Investigation
Table of Contents

Abstract iii

List of Figures ix

List of Tables xiii

List of Acronyms and Abbreviations xv

Metric Conversion Table xvii

Preface xix

Acknowledgments xxix

Executive Summary xxxi

Chapter 1 Introduction 1

1 . 1 Fire-Resistive Materials 1

1 .2 Scope of Report 2

Chapter 2 Building Code Concepts for Structural Fire Resistance 5

2. 1 Origins and Intent of Building Codes 5

2.2 Construction Types 5

2.3 Fire Resistance of Structural Elements 6

Chapter 3 Historical Review Related to Passive Fire Protection of WTC Towers 9

3.1 Agreements Between Port Authority and New York City Department of Buildings and Fire

Department 9

3.2 New York City Building Code Requirements 10

3.2. 1 Occupancy Groups 10

3.2.2 Construction Classification and Fire Rating 1

1

3.3 Classification of WTC Towers 12

3.3.1 Specifications for Passive Fire Protection 12

3.3.2 Response to Local Law 5/1973 13

3.4 Selection of Fire-resistive Materials 14

3.4. 1 Floor Trusses 14

3.4.2 Perimeter Columns 16

3.4.3 Core Columns 18

NIST NCSTAR 1-6A, WTC Investigation v
Table of Contents

3.5 Specified Thickness of Fire-resistive Materials 18

3.5.1 During Construction 18

3.5.2 Report on 1975 Fire 21

3.5.3 In-Place Thickness and Upgrading of SFRM 24

3.5.4 Need for Fire Endurance Tests 26

3.5.5 Calculations of SFRM Thickness for Core Members 26

3.6 Maintenance of SFRM in Elevator Shafts 29

3.6.1 Bond Strength 29

3.6.2 Inspections 30

3.7 General Conditions of SFRM on Floor Trusses 30

Chapter 4

As-Applied Thickness of SFRM 37

4. 1 Truss-Supported Floor System 37

4.2 Analysis of Photographs 40

4.3 Port Authority Data on Upgraded SFRM on Trusses 42

4.4 Column SFRM Thickness 49

Chapter 5 Effect of SFRM Geometry on Thermal Response 51

5.1 Effects of Thickness Variability and Gaps in SFRM 51

5.2 Equivalent Thickness 57

5.3 Recommended Thickness of SFRM for Thermal Analyses 60

Chapter 6 Thermophysical Properties 63

6. 1 ASTM Test Methods for SFRMs 64

6.2 Reported SFRM Properties 65

6.3 Measured Thermophysical Properties of SFRMs 65

6.3.1 Sample Preparation 66

6.3.2 Thermal Conductivity Measurements , 67

6.3.3 Specific Heat Capacity Measurements 69

6.3.4 Density Measurements 72

6.3.5 Concluding Remarks 74

6.4 Thermophysical Properties of Gypsum Panels 75

6.4.1 Samples 75

6.4.2 Thermal Conductivity Measurements 75

vi NISTNCSTAR 1-6A, WTC Investigation
Table of Contents

6.4.3 Specific Heat Capacity Measurements 78

6.4.4 Density Measurements 80

Chapter 7 Adhesive and Cohesive Strength 83

7. 1 Reported In-Place Density and Bond Strength 83

7.2 Specimen Preparation and Test Procedures 87

7.2.1 Preparation of Test Plates 87

7.2.2 Test Methods 87

7.2.3 Preparation of Test Specimens 89

7.3 Test Results 95

7.3.1 Density 95

7.3.2 In-Plane Cohesive Strength 97

7.3.3 Adhesive Strength 98

7.3.4 Cohesive Strength Normal to Surface 104

7.3.5 Adhesive Strength Versus Cohesive Strength Normal to Surface 107

7.4 Simplified Approach to Predict Dislodging of SFRM 108

7.4. 1 Debris Impact Study 1 1

3

Chapter 8 Summary 115

8.1 Findings 115

Chapter 9 References 119

Appendix A

Referenced Documents 123

Appendix B

Thermophysical Properties Test Data 253

Appendix C

Sprayed Fire-Resistive Material 263

NIST NCSTAR 1-6A, WTC Investigation vii
Table of Contents

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Vlll NISTNCSTAR 1-6A, WTC Investigation
List of Figures

Figure P-l. The eight projects in the federal building and fire safety investigation of the WTC

disaster xxi

Figure 1-1. Examples of sprayed fire-resistive materials: (left) material based on gypsum and

vermiculite aggregate; (right) material based on mineral fibers and cementitious

binder 2

Figure 3-1. Mock up of floor truss system 14

Figure 3-2. Schematic of composite floor truss system 15

Figure 3-3. Demonstration of application of Monokote sprayed fire-resistive material to floor

trusses 16

Figure 3—4. Thermal insulation for perimeter columns 17

Figure 3-5. Intersection of main truss and bridging truss showing general good coverage of SFRM

on truss members but thickness varies on web bars 33

Figure 3-6. Intersection of main truss and bridging truss showing thinner SFRM on members of

bridging truss 33

Figure 3-7. Connection of main truss to spandrel beam showing relatively thin SFRM on truss seat and no SFRM on damper 34

Figure 3-8. End of main truss showing low thickness of SFRM on truss members and no SFRM

on damper saddle 34

Figure 3-9. Intersection of main truss and bridging truss showing thin SFRM on the ends of some web bars; SFRM was not applied to the metal decking 35

Figure 3-10. Example of damage to SFRM during installation of utilities 35

Figure 4-1. (a) Dotplot of average thickness from floor trusses for floors 23 and 24, (b) normal

probability plot of all average thickness values, and (c) normal probability plot of

average thickness with four values (six points) excluded 39

Figure 4-2. Example of measurement procedure used to estimate SFRM thickness from

photographs 41

Figure 4-3. (a) Normal probability plot of estimated SFRM thickness based on photographs, and

(b) normal probability plot of natural logarithms of thickness (Data provided by

PANYNJ) 43

Figure 4-4. (a) Dotplot of individual thickness measurements on floor trusses from Port Authority

Construction Audit Reports, (b) histogram of thickness measurements, (c) normal

probability plot of thickness measurements, (d) histogram of natural logarithms of

thickness measurements, and (e) normal probability plot of natural logarithm of

thickness measurements 47

NISTNCSTAR 1-6A, WTC Investigation ix
List of Figures

Figure 4-5. SFRM thickness on floor trusses in upgraded portions of WTC towers: (a) individual

measurements in WTC 1, (b) average thickness in WTC 1, (c) individual

measurements in WTC 2, and (d) average thickness in WTC 2 (data provided by

PANYNJ) 48

Figure 4-6. Thickness of re-applied SFRM in elevator shaft 10/11 of WTC 1 : (a) Individual and

average thickness for core columns, (b) normal probability plot of individual

measurements on columns, (c) individual and average thickness for core beams, and

(d) normal probability plot of individual measurements on beams (data provided by

PANYNJ) 50

Figure 5—1. Model used to study effects of SFRM thickness and variability of thickness on steel temperature: (a) physical model used in analyses (points 1 to 5 are locations where

temperatures are monitored), (b) finite element mesh used to represent physical model,

and (c) finite element model to represent variable thickness of SFRM (purple) (the

elements in red represent material of high thermal conductivity) 52

Figure 5-2. Temperature distribution after 1 h of exposure to gas temperature of 1,100 °C

(1,373 K) 53

Figure 5-3. Variation of steel temperature (at a point 6 in. from end of plate) with time for

different average thicknesses of fire-resistive material (shown as numbers on the

curves): (a) uniform thickness, and (b) variable thickness with standard deviation =

1 in 54

Figure 5-4. Example of "gap" in fire-resistive material on diagonal member of a bridging floor

truss 55

Figure 5-5. Effects of gap in fire-resistive material: (a) model of plate with SFRM having 2 in. uniform thickness and 12 in. gap, (b) isotherms (K) at time = 50 min with 12 in. gap, and (c) isotherms without gap 56

Figure 5-6. Example of plot matrix from sensitivity study of the effects of missing SFRM and

variability of SFRM thickness on steel temperature. Each graph is a temperature

history of the steel at point #2 (see Fig. 5-5 for location) for different thicknesses of

SFRM. 57

Figure 5-7. (a) Randomly generated thickness profiles with average thickness of 0.75 in. and

standard deviation of 0.3 in., (b) cumulative element size, and (c) deformation of 1 in. bar compared with deformation for uniform thickness of thermal insulation 59

Figure 5-8. (a) Randomly generated thickness profiles with average thickness of 2.5 in. and

standard deviation of 0.6 in., (b) normal probability plots of thickness values, and

(c) defonnation of 1 in. bar compared with deformation for uniform thickness of

thermal insulation 61

Figure 6-1 . BLAZE-SHIELD DC/F sample used for thermophysical property measurements 66

Figure 6-2. BLAZE-SHIELD II sample used for thermophysical property measurements 66

Figure 6-3. Monokote MK-5 sample used for thermophysical property measurements 67

Figure 6-4. Thermal conductivities of the three SFRMs as a function of temperature 68

x NISTNCSTAR 1-6A, WTC Investigation
List of Figures

Figure 6-5. Comparison of BLAZE-SHIELD DC/F specific heat capacity measurements from

Harmathy (1983) with present results from Laboratory A 70

Figure 6-6. Comparison of specific heat capacity measurements from Laboratory B with results from Laboratory A 71

Figure 6-7. Comparison of specific heat capacity measurements for BLAZE-SHIELD DC/F from

Laboratory B with the results from Harmathy (1983) 72

Figure 6-8. Bulk densities of the three SFRMs as a function of temperature 74

Figure 6-9. Thermal conductivities of the four gypsum materials as a function of temperature 76

Figure 6-10. Comparison of the thermal conductivity measurements from Laboratory B with the

data from Mehaffey et al. (1994) for 5/8 in. thick gypsum panel A .77

Figure 6-11. Comparison of thermal conductivity measurements from Laboratory B with other

literature values for Vi in. thick gypsum panel and 5/8 in. thick gypsum panel B 78

Figure 6-12. Comparison of specific heat capacities for the four gypsum materials 79

Figure 6-1 3. Bulk densities of the four gypsum materials as a function of temperature 81

Figure 7-1 . Bond strength test using screw cap in accordance with ASTM E 736 84

Figure 7-2. Cohesive failure of SFRM using ASTM E 736 test (dashed circle is approximate

location of cap before being pulled off 84

Figure 7-3. In-place density of BLAZE-SHIELD Type II on floor trusses from Port Authority test reports during the period 1997-1999 86

Figure 7-4. In-place bond strength of BLAZE-SHIELD Type II using ASTM E 736 from Port Authority test reports during the period 1997-1999 86

Figure 7-5. Spraying steel plates with BLAZE-SHIELD DC/F 88

Figure 7-6. Schematic of "pull-off test method used to measure cohesive and adhesive strengths 88

Figure 7-7. Technique used to measure both "adhesive" and "cohesive" strength in the same

specimen 89

Figure 7-8. Method to measure cohesive strength parallel to SFRM surface (in-plane cohesive

strength) 90

Figure 7-9. Cutting the SFRM layer into five strips 90

Figure 7-10. Five specimens obtained from single plate; top three specimens are used for density

and in-plane cohesive strength, bottom specimens are used for adhesion/cohesion

tests 91

Figure 7-11. Aluminum plate being bonded to the top surface of SFRM specimen; the wooden

fixture is used to maintain the correct alignment of the plate 92

Figure 7-1 2. Preparing the SFRM specimen for adhesion/cohesion test 92

Figure 7-1 3. Manual application of tensile load using digital force gauge 93

Figure 7-14. Results of first loading: specimen on left had a cohesive failure in the bulk SFRM,

specimen on right failed near the SFRM/steel interface 93

NISTNCSTAR 1-6A, WTC Investigation xi
List of Figures

Figure 7-15. Results of second tests after repair: specimen on left had adhesive failure and

specimen on right had cohesive failure 94

Figure 7-16. SFRM specimen after measuring in-plane cohesive strength 94

Figure 7-1 7. Density of BLAZE-SHIELD DC/F specimens 96

Figure 7-18. Air-dry density of BLAZE-SHIELD DC/F from NIST/UL floor truss fire endurance

tests (NIST NCSTAR 1-6B) 97

Figure 7-19. In-plane cohesive strength for BLAZE-SHIELD DC/F specimens 98

Figure 7-20. Example of "adhesive" failure of SFRM (original location of test specimens are the

gaps in the two strips); photo on left is magnified view of thin layer of paste and fibers

(the marks around the perimeter is red ink used to locate field of view) 99

Figure 7-21. Example of lack of adhesion in VA in. SFRM on steel plate with primer 100

Figure 7-22. Examples of good adhesion in specimens with unprimed steel plates: (top) 3A in. SFRM specimen before testing; (bottom) 1

XA in. SFRM specimen after completion of

tests 102

Figure 7-23. Adhesive strength of BLAZE-SHIELD DC/F specimens for primed and unprimed

steel plates 103

Figure 7-24. Examples of cohesive failure in VA in. SFRM specimens 104

Figure 7-25. Comparative testing: current method versus ASTM E 736 method: (top) locations of

two screw cap tests; (bottom) after completion of tests 105

Figure 7-26. Cohesive strength normal to surface for BLAZE-SHIELD DC/F specimens for primed

and unprimed steel plates 106

Figure 7-27. Comparison of adhesive strength with cohesive strength normal to surface (P = primed

steel, NP = bare steel) 108

Figure 7-28. Derivation of acceleration to dislodge SFRM from planar substrate 1 10

Figure 7-29. Derivation of acceleration to dislodge SFRM surrounding a round bar Ill

xn NIST NCSTAR 1-6A, WTC Investigation
List of Tables

Table P-l . Federal building and fire safety investigation of the WTC disaster xx

Table P-2. Public meetings and briefings of the WTC Investigation xxiii

Table 3—1. Area and height limitations for unsprinklered buildings for Noncombustible

Construction (Group 1) with a Business occupancy (NYCBC 1968) 12

Table 3-2. Specified fire-resistive materials after April 1970 21

Table 3-3. Information in Sweets Catalogs regarding BLAZE-SHIELD products applied directly

to beams, girders, or spandrels (with protected deck) from 1960 to 1972 23

Table 3—4. Design thickness of thermal insulation for reapplication to accessible columns in elevator shafts 12 and 13 of WTC 1 28

Table 3-5. Design thickness of thermal insulation for reapplication to accessible columns and

beams in elevator shafts 6 and 7 of WTC1 29

Table 4-1 . Average fireproofing thickness from six measurements taken in 1994 on each of

16 random floor trusses on floors 23 and 24 of WTC 1 38

Table 4-2. Summary of Port Authority test reports for upgraded SFRM on floor trusses (30-P) 45

Table 6-1 . Summary of SFRMs used in WTC 63

Table 6-2. Current ASTM test methods for SFRMs 64

Table 6-3. Properties from tests of SFRMs reported by manufacturers 65

Table 6-4. Measured thermal conductivity as a function of temperature 68

Table 6-5. Calculated specific heat capacity of the three SFRMs 69

Table 6-6. Mass loss of SFRMs with increasing temperature 73

Table 6-7. Thermal expansion results of SFRMs 73

Table 6-8. Calculated densities of SFRMs 74

Table 6-9. Thermal conductivities of gypsum materials 76

Table 6-10. Bulk densities of the four gypsum materials 80

Table 7-1 . Density and bond strength of SFRM on floor trusses reported by the Port Authority of

New York and New Jersey (30-P) 85

Table 7-2. Test matrix 95

Table 7-3 . Density of BLAZE-SHIELD DC/F specimens 95

Table In-plane cohesive strength for BLAZE-SHIELD DC/F specimens 98

NIST NCSTAR 1-6A, WTC Investigation xiii
List of Tables

Table 7-5. Adhesive strength of BLAZE-SHIELD DC/F specimens 103

Table 7-6. Summary of adhesive strength results 104

Table 7-7. Cohesive strength normal to surface for BLAZE-SHIELD DC/F specimens 106

Table 7-8. Summary of cohesive strengths normal to surface 107

Table 7-9. Comparison of average adhesive strength and average cohesive strength normal to surface 108

Table 7-10. Acceleration required to dislodge SFRM from planar surface for different values of

density, thickness, and bond strength (adhesive or cohesive) 110

Table 7—11. Acceleration required to dislodge SFRM from encased bar for different values of bar

diameter, SFRM thickness, SFRM in-plane cohesive strength, and strength ratio (alpha) 112

XIV NISTNCSTAR 1-6A, WTC Investigation
List of Acronyms and Abbreviations

Acronyms

ASTM ASTM International (formerly American Society for Testing and Materials)

BFRL Building and Fire Research Laboratory

BOCA Building Officials and Code Administrators

DSC Differential Scanning Calorimetry

DTA Differential Thermal Analysis

ER&S Emory Roth & Sons

FDNY New York City Fire Department

IBC International Building Code

ICBO International Conference of Building Officials

ICC International Code Council

LERA Leslie E. Robertson Associates

NCST National Construction Safety Team

NIST National Institute of Standards and Technology

NYCDOB New York City Department of Buildings

SHCR Skilling, Helle, Christiansen, & Robertson

SFRM sprayed fire-resistive material

STA Simultaneous Thermal Analyzer

TGA Thermal Gravimetric Analysis

UBC Uniform Building Code

UL Underwriters Laboratories, Inc. USM United States Mineral Products Co.

WF wide flange (a type of structural steel shape now usually called a W-shape). ASTM A 6

defines them as "doubly-symmetric, wide-flange shapes with inside flange surfaces that are substantially parallel."

WTC World Trade Center

WTC 1 World Trade Center 1 (North Tower)

WTC 2 World Trade Center 2 (South Tower)

WTC 7 World Trade Center 7

NISTNCSTAR 1-6A, WTC Investigation xv
List of Acronyms and Abbreviations

Abbreviations

a acceleration

Btu British thermal unit

°C degrees Celsius

d; steel bar diameter

do outside diameter of SFRM on round bar

°F degrees Fahrenheit

fb cohesive strength normal to surface or adhesive strength

ft in-plane cohesive strength of SFRM

ft foot

ft

2 square foot

g acceleration of gravity

g gram

h hour

in. inch

J joule

K kelvin (absolute temperature)

kg kilogram

lb pound

m meter

m

2 square meter

m

3 cubic meter

min minute

pcf pounds per cubic foot

psf pounds per square foot

psi pounds per square inch

s second

t thickness of SFRM

W watt a ratio of adhesive strength to in-plane cohesive strength of SFRM

p mass density of SFRM

XVI NISTNCSTAR 1-6A, WTC Investigation
Metric Conversion Table

To convert from

inch (in.)

degree Fahrenheit (°F)

foot (ft)

pcf (pound per cubic foot) (lb/ft"

)

Btun in. (fr h • °F)

psf (pound-force per square foot) (lbf/fr)

psi (pound-force per square inch) (lbf'in

2

)

to

meter (m)

degree Celsius (°C)

meter (m)

kilogram per cubic meter (kg/m3

) W/(m K)

kilopascal (kPa)

kilopascal (kPa)

Multiply by

2.54 E-02

XI °C = (t/ °F-32)/l.

3.048 E-01

1.601 846E+01

1.442 279 E-01

4.788 026 E-02

6.894 757 E+00

NISTNCSTAR 1-6A, WTC Investigation xvn
Metric Conversion Table

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XVlll NISTNCSTAR 1-6A, WTC Investigation
Preface

Genesis of This Investigation

Immediately following the terrorist attack on the World Trade Center (WTC) on September 11, 2001, the

Federal Emergency Management Agency (FEMA) and the American Society of Civil Engineers began

planning a building performance study of the disaster. The week of October 7, as soon as the rescue and

search efforts ceased, the Building Performance Study Team went to the site and began its assessment. This was to be a brief effort, as the study team consisted of experts who largely volunteered their time

away from their other professional commitments. The Building Performance Study Team issued its report in May 2002, fulfilling its goal "to determine probable failure mechanisms and to identify areas of

future investigation that could lead to practical measures for improving the damage resistance of buildings

against such unforeseen events."

On August 21, 2002, with funding from the U.S. Congress through FEMA, the National Institute of

Standards and Technology (NIST) announced its building and fire safety investigation of the WTC

disaster. On October 1, 2002, the National Construction Safety Team Act (Public Law 107-231), was

signed into law. The NIST WTC Investigation was conducted under the authority of the National

Construction Safety Team Act.

The goals of the investigation of the WTC disaster were:

• To investigate the building construction, the materials used, and the technical conditions that contributed to the outcome of the WTC disaster.

• To serve as the basis for: - Improvements in the way buildings are designed, constructed, maintained, and used; - Improved tools and guidance for industry and safety officials; - Recommended revisions to current codes, standards, and practices; and - Improved public safety.

The specific objectives were:

1 . Determine why and how WTC 1 and WTC 2 collapsed following the initial impacts of the

aircraft and why and how WTC 7 collapsed;

2. Determine why the injuries and fatalities were so high or low depending on location,

including all technical aspects of fire protection, occupant behavior, evacuation, and

emergency response;

3. Determine what procedures and practices were used in the design, construction, operation,

and maintenance of WTC 1, 2, and 7; and

4. Identify, as specifically as possible, areas in current building and fire codes, standards, and

practices that warrant revision.

NISTNCSTAR 1-6A, WTC Investigation xix
Preface

NIST is a nonregulatory agency of the U.S. Department of Commerce's Technology Administration. The

purpose of NIST investigations is to improve the safety and structural integrity of buildings in the United

States, and the focus is on fact finding. NIST investigative teams are authorized to assess building

performance and emergency response and evacuation procedures in the wake of any building failure that has resulted in substantial loss of life or that posed significant potential of substantial loss of life. NIST

does not have the statutory authority to make findings of fault nor negligence by individuals or

organizations. Further, no part of any report resulting from a NIST investigation into a building failure or from an investigation under the National Construction Safety Team Act may be used in any suit or action

for damages arising out of any matter mentioned in such report (15 USC 281a, as amended by Public

Law 107-231).

Organization of the Investigation

The National Construction Safety Team for this Investigation, appointed by the then NIST Director, Dr. Arden L. Bement, Jr., was led by Dr. S. Shyam Sunder. Dr. William L. Grosshandler served as Associate Lead Investigator, Mr. Stephen A. Cauffman served as Program Manager for Administration,

and Mr. Harold E. Nelson served on the team as a private sector expert. The Investigation included eight

interdependent projects whose leaders comprised the remainder of the team. A detailed description of

each of these eight projects is available at http://wtc.nist.gov. The purpose of each project is summarized

in Table P-l , and the key interdependencies among the projects are illustrated in Fig. P-l.

Table P-1. Federal building and fire safety investigation of the WTC disaster.

Technical Area and Project Leader Project Purpose

Analysis of Building and Fire Codes and

Practices; Project Leaders: Dr. H. S. Lew

and Mr. Richard W. Bukowski

Document and analyze the code provisions, procedures, and

practices used in the design, construction, operation, and

maintenance of the structural, passive fire protection, and

emergency access and evacuation systems of WTC 1, 2, and 7. Baseline Structural Performance and

Aircraft Impact Damage Analysis; Project

Leader: Dr. Fahim H. Sadek

Analyze the baseline performance of WTC 1 and WTC 2 under

design, service, and abnormal loads, and aircraft impact damage on

the structural, fire protection, and egress systems.

Mechanical and Metallurgical Analysis of

Structural Steel; Project Leader: Dr. Frank

W. Gayle

Determine and analyze the mechanical and metallurgical properties

and quality of steel, weldments, and connections from steel recovered from WTC 1, 2, and 7. Investigation of Active Fire Protection

Systems; Project Leader: Dr. David

D. Evans; Dr. William Grosshandler

Investigate the performance of the active fire protection systems in WTC 1, 2, and 7 and their role in fire control, emergency response, and fate of occupants and responders.

Reconstruction of Thermal and Tenability

Environment; Project Leader: Dr. Richard

G. Gann

Reconstruct the time-evolving temperature, thermal environment,

and smoke movement in WTC 1, 2, and 7 for use in evaluating the

structural performance of the buildings and behavior and fate of

occupants and responders.

Structural Fire Response and Collapse

Analysis; Project Leaders: Dr. John

L. Gross and Dr. Therese P. McAllister

Analyze the response of the WTC towers to fires with and without

aircraft damage, the response of WTC 7 in fires, the performance

of composite steel-trussed floor systems, and determine the most

probable structural collapse sequence for WTC 1, 2, and 7. Occupant Behavior, Egress, and Emergency

Communications; Project Leader: Mr. Jason

D. Averill

Analyze the behavior and fate of occupants and responders, both

those who survived and those who did not, and the performance of

the evacuation system.

Emergency Response Technologies and

Guidelines; Project Leader: Mr. J. Randall

Lawson

Document the activities of the emergency responders from the time

of the terrorist attacks on WTC 1 and WTC 2 until the collapse of

WTC 7, including practices followed and technologies used.

XX NISTNCSTAR 1-6A, WTC Investigation
Preface

IP"

\

NIST WTC Investigation Projects

Building

Performance Study

Recommendations

Government,

Industry,

Professional,

Academic Inp

Figure P-1. The eight projects in the federal building and fire safety

investigation of the WTC disaster.

National Construction Safety Team Advisory Committee

The NIST Director also established an advisory committee as mandated under the National Construction

Safety Team Act. The initial members of the committee were appointed following a public solicitation. These were:

Paul Fitzgerald, Executive Vice President (retired) FM Global, National Construction Safety

Team Advisory Committee Chair

John Barsom, President, Barsom Consulting, Ltd.

John Bryan. Professor Emeritus, University of Maryland

David Collins, President, The Preview Group, Inc.

Glenn Corbett, Professor, John Jay College of Criminal Justice

Philip DiNenno, President, Hughes Associates, Inc.

NIST NCSTAR 1-6A, WTC Investigation xxi
Preface

• Robert Hanson, Professor Emeritus, University of Michigan

• Charles Thornton, Co-Chairman and Managing Principal, The Thornton-Tomasetti Group,

Inc.

• Kathleen Tierney, Director, Natural Hazards Research and Applications Information Center,

University of Colorado at Boulder

• Forman Williams, Director, Center for Energy Research, University of California at San

Diego

This National Construction Safety Team Advisory Committee provided technical advice during the

Investigation and commentary on drafts of the Investigation reports prior to their public release. NIST

has benefited from the work of many people in the preparation of these reports, including the National

Construction Safety Team Advisory Committee. The content of the reports and recommendations,

however, are solely the responsibility of NIST.

Public Outreach

During the course of this Investigation, NIST held public briefings and meetings (listed in Table P—2) to

solicit input from the public, present preliminary findings, and obtain comments on the direction and

progress of the Investigation from the public and the Advisory Committee.

NIST maintained a publicly accessible Web site during this Investigation at http://wtc.nist.gov. The site contained extensive information on the background and progress of the Investigation.

NIST's WTC Public-Private Response Plan

The collapse of the WTC buildings has led to broad reexamination of how tall buildings are designed,

constructed, maintained, and used, especially with regard to major events such as fires, natural disasters,

and terrorist attacks. Reflecting the enhanced interest in effecting necessary change, NIST, with support

from Congress and the Administration, has put in place a program, the goal of which is to develop and

implement the standards, technology, and practices needed for cost-effective improvements to the safety

and security of buildings and building occupants, including evacuation, emergency response procedures,

and threat mitigation.

The strategy to meet this goal is a three-part NIST-led public-private response program that includes:

• A federal building and fire safety investigation to study the most probable factors that contributed to post-aircraft impact collapse of the WTC towers and the 47-story WTC 7

building, and the associated evacuation and emergency response experience.

• A research and development (R&D) program to (a) facilitate the implementation of

recommendations resulting from the WTC Investigation, and (b) provide the technical basis

for cost-effective improvements to national building and fire codes, standards, and practices

that enhance the safety of buildings, their occupants, and emergency responders.

xxii NISTNCSTAR 1-6A, WTC Investigation
Preface

Table P-2. Public meetings and briefings of the WTC Investigation.

Date Location Principal Agenda

June 24. 2002 New York City, NY Public meeting: Public comments on the Draff Plan for the pending WTC Investigation.

August 21. 2002 Gaithersburg, MD Media briefing announcing the formal start of the Investigation.

December 9. 2002 Washington, DC Media briefing on release of the Public Update and N1ST request

for photographs and videos. April 8. 2003 New York City, NY Joint public forum with Columbia University on first-person interviews. April 29-30, 2003 Gaithersburg, MD NCST Advisory Committee meeting on plan for and progress on WTC Investigation with a public comment session. May 7. 2003 New York City. NY Media briefing on release of May 2003 Progress Report.

August 26-27. 2003 Gaithersburg, MD NCST Advisory Committee meeting on status of the WTC

investigation with a public comment session. September 17. 2003 New York City, NY Media and public briefing on initiation of first-person data

collection ^VllvV Hull nroiects L/l \J 1 WI J . December 2-3, 2003 Gaithersburg, MD NCST AHvisorv Committpp mpptint* on status and initial rpmilts

and release of the Public Update with a public comment session. February 12. 2004 New York City, NY Public meeting on progress and preliminary findings with public

comments V- V ' llllllvlllJ on\J 11 issups IOOk-I^iD toI \ ' hp' ' v ponmdprpd 1>K11J1U^1 vU in111 formulating 1 KJ 1 1 1 1 LI HI 1 1 1 1 &L final J. 1 1 1 CI 1 recommendations.

June 18 ""004 New York Citv NY Mpfha /ni lhhp hripflnfT on rplpa^p of Iuyip 7()(}A Pvnovp^K Rpjinvt June 22-23, 2004 Gaithersburg. MD NCST Advisory Committee meeting on the status of and

nrphminarv find in o

- *; from thp W/Tf"1 Invp^tipation with a nnhhr

comment session. i August 24, 2004 Northbrook, 1L Public viewing of standard fire resistance test of WTC floor system at Underwriters Laboratories, Inc. October 19-20, 2004 Gaithersburg, MD NCST Advisory Committee meeting on status and near complete

set of preliminary findings with a public comment session. rNOvemoer zz, ivvh Gaithersburg, MD NCST Advisory Committee discussion on draft annual report to Congress, a public comment session, and a closed session to discuss pre-drafl recommendations for WTC Investigation.

April 5. 2005 New York City, NY Media and public briefing on release of the probable collapse i sentience .iv. 1 111, 1 11 l. for 1 Ul the ' 1 1 V WTC V V A \ towers l\J VV vl O and ttl I\J draft \J1 Ull renorts 1 ^ VJ \J I for 1 \Jl the lllv nroiecls IJ1 \J Ivl/lu onl/ll codes and practices, evacuation, and emergency response. June 23. 2005 New York City, NY Media and public briefing on release of all draft reports for the WTC towers and draft recommendations for public comment.

September 12-13,

2005

Gaithersburg, MD NCST Advisory Committee meeting on disposition of public

comments and update to draft reports for the WTC towers. September 13-15,

2005

Gaithersburg, MD WTC Technical Conference for stakeholders and technical community for dissemination of findings and recommendations

and opportunity for public to make technical comments.

• A dissemination and technical assistance program (DTAP) to (a) engage leaders of the

construction and building community in ensuring timely adoption and widespread use of

proposed changes to practices, standards, and codes resulting from the WTC Investigation

and the R&D program, and (b) provide practical guidance and tools to better prepare facility owners, contractors, architects, engineers, emergency responders, and regulatory authorities

to respond to future disasters. The desired outcomes are to make buildings, occupants, and first responders safer in future disaster events.

NISTNCSTAR 1-6A, WTC Investigation xxin
Preface

National Construction Safety Team Reports on the WTC Investigation

A final report on the collapse of the WTC towers is being issued as NIST NCSTAR 1 . A companion

report on the collapse of WTC 7 is being issued as NIST NCSTAR 1 A. The present report is one of a set that provides more detailed documentation of the Investigation findings and the means by which these

technical results were achieved. As such, it is part of the archival record of this Investigation. The titles of the full set of Investigation publications are:

NIST (National Institute of Standards and Technology). 2005. Federal Bui/ding and Fire Safety

Investigation ofthe World Trade Center Disaster: Final Report on the Collapse ofthe World Trade

Center Towers. NIST NCSTAR 1. Gaithersburg, MD, September.

NIST (National Institute of Standards and Technology). 2006. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Final Report on the Collapse of World Trade Center 7. NIST NCSTAR 1 A. Gaithersburg, MD.

Lew, H. S., R. W. Bukowski, and N. J. Carino. 2005. Federal Building and Fire Safety Investigation of

the World Trade Center Disaster: Design, Construction, and Maintenance ofStructural and Life Safety

Systems. NIST NCSTAR 1-1. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Fanella, D. A., A. T. Derecho, and S. K. Ghosh. 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Design and Construction ofStructural Systems.

NIST NCSTAR 1-1 A. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Ghosh, S. K., and X. Liang. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Comparison ofBuilding Code Structural Requirements. NIST

NCSTAR 1-1B. National Institute of Standards and Technology. Gaithersburg, MD, September.

Fanella, D. A., A. T. Derecho, and S. K. Ghosh. 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Maintenance and Modifications to Structural

Systems. NIST NCSTAR 1-1C. National Institute of Standards and Technology. Gaithersburg,

MD, September.

Grill, R. A., and D. A. Johnson. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Fire Protection and Life Safety Provisions Applied to the Design and

Construction of World Trade Center I, 2, and 7 and Post-Construction Provisions Applied after Occupancy. NIST NCSTAR 1-1D. National Institute of Standards and Technology. Gaithersburg,

MD, September.

Razza, J. C, and R. A. Grill. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Comparison of Codes, Standards, and Practices in Use at the Time ofthe

Design and Construction of World Trade Center I, 2, and 7. NIST NCSTAR 1-1E. National

Institute of Standards and Technology. Gaithersburg, MD, September.

Grill, R. A., D. A. Johnson, and D. A. Fanella. 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Comparison ofthe 1968 and Current (2003) New

xxiv NIST NCSTAR 1-6A, WTC Investigation
Preface

York City Building Code Provisions. NIST NCSTAR 1-1F. National Institute of Standards and

Technology. Gaithersburg, MD, September.

Grill. R. A., and D. A. Johnson. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Amendments to the Fire Protection and Life Safety Provisions ofthe New

York City Building Code by Local Laws Adopted While World Trade Center 1, 2, and 7 Were in Use. NIST NCSTAR 1-1G. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Grill R. A., and D. A. Johnson. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Post-Constmction Modifications to Fire Protection and Life Safety Systems

of World Trade Center 1 and 2. NIST NCSTAR 1-1H. National Institute of Standards and

Technology. Gaithersburg, MD, September.

Grill. R. A., D. A. Johnson, and D. A. Fanella. 2005. Federal Building and Fire Safety Investigation

ofthe World Trade Center Disaster: Post-Construction Modifications to Fire Protection, Life

Safety, and Structural Systems of World Trade Center 7. NIST NCSTAR 1-1 1. National Institute of

Standards and Technology. Gaithersburg. MD, September.

Grill. R. A., and D. A. Johnson. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Design, Installation, and Operation ofFuel System for Emergency Power in World Trade Center 7. NIST NCSTAR 1-1 J. National Institute of Standards and Technology.

Gaithersburg, MD. September.

Sadek. F. 2005. Federal Building and Fire Safety Investigation of the World Trade Center Disaster:

Baseline Structural Performance and Aircraft Impact Damage Analysis ofthe World Trade Center

Towers. NIST NCSTAR 1-2. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Faschan. W. J., and R. B. Garlock. 2005. Federal Building and Fire Safety Investigation ofthe World Trade Center Disaster: Reference Structural Models and Baseline Performance Analysis of

the World Trade Center Towers. NIST NCSTAR 1-2A. National Institute of Standards and

Technology. Gaithersburg, MD, September.

Kirkpatrick. S. W., R. T. Bocchieri, F. Sadek, R. A. MacNeill, S. Holmes, B. D. Peterson,

R. W. Cilke, C. Navarro. 2005. Federal Building and Fire Safety Investigation ofthe World Trade

Center Disaster: Analysis ofAircraft Impacts into the World Trade Center Towers, NIST

NCSTAR 1-2B. National Institute of Standards and Technology. Gaithersburg, MD, September.

Gayle, F. W., R. J. Fields, W. E. Luecke, S. W. Banovic, T. Foecke, C. N. McCowan, T. A. Siewert, and

J. D. McColskey. 2005. Federal Building and Fire Safety Investigation ofthe World Trade Center

Disaster: Mechanical and Metallurgical Analysis ofStmctural Steel. NIST NCSTAR 1-3. National

Institute of Standards and Technology. Gaithersburg, MD, September.

Luecke, W. E., T. A. Siewert, and F. W. Gayle. 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Contemporaneous Structural Steel

Specifications. NIST Special Publication 1-3 A. National Institute of Standards and Technology.

Gaithersburg, MD, September.

NIST NCSTAR 1-6A, WTC Investigation XXV
Preface

Banovic, S. W. 2005. Federal Building and Fire Safety Investigation ofthe World Trade Center

Disaster: Steel Inventory and Identification. NIST NCSTAR 1-3B. National Institute of Standards

and Technology. Gaithersburg, MD, September.

Banovic, S. W., and T. Foecke. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Damage and Failure Modes ofStructural Steel Components. NIST

NCSTAR 1-3C. National Institute of Standards and Technology. Gaithersburg, MD, September.

Luecke, W. E., J. D. McColskey, C. N. McCowan, S. W. Banovic, R. J. Fields, T. Foecke,

T. A. Siewert, and F. W. Gayle. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Mechanical Properties ofStructural Steels. NIST NCSTAR 1-3D.

National Institute of Standards and Technology. Gaithersburg, MD, September.

Banovic, S. W., C. N. McCowan, and W. E. Luecke. 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Physical Properties ofStructural Steels. NIST

NCSTAR 1-3E. National Institute of Standards and Technology. Gaithersburg, MD, September.

Evans, D. D., R. D. Peacock, E. D. Kuligowski, W. S. Dols, and W. L. Grosshandler. 2005. Federal

Building and Fire Safety Investigation ofthe World Trade Center Disaster: Active Fire Protection

Systems. NIST NCSTAR 1-4. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Kuligowski, E. D., D. D. Evans, and R. D. Peacock. 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Post-Construction Fires Prior to September 11,

2001. NIST NCSTAR 1-4A. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Hopkins, M., J. Schoenrock, and E. Budnick. 2005. Federal Building and Fire Safety Investigation

ofthe World Trade Center Disaster: Fire Suppression Systems. NIST NCSTAR 1-4B. National

Institute of Standards and Technology. Gaithersburg, MD, September.

Keough, R. J., and R. A. Grill. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Fire Alarm Systems. NIST NCSTAR 1-4C. National Institute of Standards

and Technology. Gaithersburg, MD, September.

Ferreira, M. J., and S. M. Strege. 2005. Federal Building and Fire Safety Investigation ofthe

World Trade Center Disaster: Smoke Management Systems. NIST NCSTAR 1-4D. National

Institute of Standards and Technology. Gaithersburg, MD, September.

Gann, R. G., A. Hamins, K. B. McGrattan, G. W. Mulholland, H. E. Nelson, T. J. Ohlemiller,

W. M. Pitts, and K. R. Prasad. 2005. Federal Building and Fire Safety Investigation ofthe World Trade

Center Disaster: Reconstruction ofthe Fires in the World Trade Center Towers. NIST NCSTAR 1-5. National Institute of Standards and Technology. Gaithersburg, MD, September.

Pitts, W. M., K. M. Butler, and V. Junker. 2005. Federal Building and Fire Safety Investigation of

the World Trade Center Disaster: Visual Evidence, Damage Estimates, and Timeline Analysis.

NIST NCSTAR 1-5 A. National Institute of Standards and Technology. Gaithersburg, MD,

September.

xxvi NIST NCSTAR 1-6A, WTC Investigation
Preface

Hamins. A., A. Maranghides, K. B. McGrattan, E. Johnsson, T. J. Ohlemiller, M. Donnelly,

J. Yang. G. Mulholland, K. R. Prasad, S. Kukuck, R. Anleitner and T. McAllister. 2005. Federal

Building and Fire Safety Investigation ofthe World Trade Center Disaster: Experiments and

Modeling ofStructural Steel Elements Exposed to Fire. NIST NCSTAR 1-5B. National Institute of

Standards and Technology. Gaithersburg, MD, September.

Ohlemiller. T. J., G. W. Mulholland. A. Maranghides. J. J. Filliben, and R. G. Gann. 2005. Federal

Building and Fire Safety Investigation ofthe World Trade Center Disaster: Fire Tests ofSingle

Office Workstations. NIST NCSTAR 1-5C. National Institute of Standards and Technology.

Gaithersburg, MD. September.

Gann, R. G.. M. A. Riley, J. M. Repp, A. S. Whittaker, A. M. Reinhorn, and P. A. Hough. 2005.

Federal Building and Fire Safety Investigation ofthe World Trade Center Disaster: Reaction of

Ceiling Tile Systems to Shocks. NIST NCSTAR 1-5D. National Institute of Standards and

Technology. Gaithersburg, MD, September.

Hamins. A., A. Maranghides. K. B. McGrattan, T. J. Ohlemiller, and R. Anleitner. 2005. Federal

Building and Fire Safety Investigation ofthe World Trade Center Disaster: Experiments and

Modeling ofMultiple Workstations Burning in a Compartment. NIST NCSTAR 1-5E. National

Institute of Standards and Technology. Gaithersburg, MD, September.

McGrattan. K. B., C. Bouldin, and G. Forney. 2005. Federal Building and Fire Safety

Investigation ofthe World Trade Center Disaster: Computer Simulation of the Fires in the World

Trade Center Towers. NIST NCSTAR 1 -5F. National Institute of Standards and Technology.

Gaithersburg. MD. September.

Prasad. K. R., and H. R. Baum. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Fire Structure Interface and Thermal Response ofthe World Trade Center

Towers. NIST NCSTAR 1-5G. National Institute of Standards and Technology. Gaithersburg,

MD, September.

Gross, J. L., and T. McAllister. 2005. Federal Building and Fire Safety Investigation ofthe World Trade

Center Disaster: Structural Fire Response and Probable Collapse Sequence ofthe World Trade Center

Towers. NIST NCSTAR 1-6. National Institute of Standards and Technology. Gaithersburg, MD,

September.

Carino, N. J., M. A. Starnes. J. L. Gross, J. C. Yang, S. Kukuck, K. R. Prasad, and R. W. Bukowski.

2005. Federal Building and Fire Safety Investigation ofthe World Trade Center Disaster: Passive

Fire Protection. NIST NCSTAR 1-6A. National Institute of Standards and Technology.

Gaithersburg. MD. September.

Gross, J., F. Hervey, M. Izydorek, J. Mammoser, and J. Treadway. 2005. Federal Building and

Fire Safety Investigation ofthe World Trade Center Disaster: Fire Resistance Tests ofFloor Truss

Systems. NIST NCSTAR 1-6B. National Institute of Standards and Technology. Gaithersburg,

MD, September.

Zarghamee, M. S., S. Bolourchi, D. W. Eggers, O. O. Erbay, F. W. Kan, Y. Kitane, A. A. Liepins,

M. Mudlock, W. I. Naguib, R. P. Ojdrovic, A. T. Sarawit, P. R Barrett, J. L. Gross, and

NIST NCSTAR 1-6A. WTC Investigation xxvii
Preface

T. P. McAllister. 2005. Federal Building and Fire Safety' Investigation ofthe World Trade Center

Disaster: Component, Connection, and Subsystem Structural Analysis. NIST NCSTAR 1-6C.

National Institute of Standards and Technology. Gaithersburg, MD, September.

Zarghamee, M. S., Y. Kitane, O. O. Erbay, T. P. McAllister, and J. L. Gross. 2005. Federal

Building and Fire Safety Investigation ofthe World Trade Center Disaster: Global Structural

Analysis ofthe Response ofthe World Trade Center Towers to Impact Damage and Fire. NIST

NCSTAR 1-6D. National Institute of Standards and Technology. Gaithersburg, MD, September.

McAllister, T., R. W. Bukowski, R. G. Gann, J. L. Gross, K. B. McGrattan, H. E. Nelson, L. Phan,

W. M. Pitts, K. R. Prasad, F. Sadek. 2006. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: Structural Fire Response and Probable Collapse Sequence of World Trade

Center 7. (Provisional). NIST NCSTAR 1-6E. National Institute of Standards and Technology.

Gaithersburg, MD.

Gilsanz, R., V. Arbitrio, C. Anders, D. Chlebus, K. Ezzeldin, W. Guo, P. Moloney, A. Montalva,

J. Oh, K. Rubenacker. 2006. Federal Building and Fire Safety Investigation ofthe World Trade

Center Disaster: Structural Analysis ofthe Response of World Trade Center 7 to Debris Damage

and Fire. (Provisional). NIST NCSTAR 1-6F. National Institute of Standards and Technology.

Gaithersburg, MD.

Kim, W. 2006. Federal Building and Fire Safety Investigation ofthe World Trade Center

Disaster: Analysis ofSeptember 11, 2001, Seismogram Data. (Provisional). NIST NCSTAR 1-6G.

National Institute of Standards and Technology. Gaithersburg, MD.

Nelson, K. 2006. Federal Building and Fire Safety Investigation ofthe World Trade Center

Disaster: The Con Ed Substation in World Trade Center 7. (Provisional). NIST NCSTAR 1-6H.

National Institute of Standards and Technology. Gaithersburg, MD.

Averill, J. D., D. S. Mileti, R. D. Peacock, E. D. Kuligowski, N. Groner, G. Proulx, P. A. Reneke, and

H. E. Nelson. 2005. Federal Building and Fire Safety Investigation of the World Trade Center Disaster:

Occupant Behavior, Egress, and Emergency Communication. NIST NCSTAR 1-7. National Institute of

Standards and Technology. Gaithersburg, MD, September.

Fahy, R., and G. Proulx. 2005. Federal Building and Fire Safety Investigation ofthe World Trade

Center Disaster: Analysis ofPublished Accounts ofthe World Trade Center Evacuation. NIST

NCSTAR 1-7A. National Institute of Standards and Technology. Gaithersburg, MD, September.

Zmud, J. 2005. Federal Building and Fire Safety Investigation ofthe World Trade Center

Disaster: Technical Documentation for Survey Administration. NIST NCSTAR 1-7B. National

Institute of Standards and Technology. Gaithersburg, MD, September.

Lawson, J. R., and R. L. Vettori. 2005. Federal Building and Fire Safety Investigation ofthe World

Trade Center Disaster: The Emergency Response Operations. NIST NCSTAR 1-8. National Institute of

Standards and Technology. Gaithersburg, MD, September.

xxvin NIST NCSTAR 1-6A, WTC Investigation
Acknowledgments

Mr. Dale Bentz. Research Chemical Engineer in the Inorganic Materials Group of the Building and Fire

Research Laboratory at NIST, is acknowledged for his contributions in conducting thermophysical

property tests for gypsum materials.

NISTNCSTAR 1-6A, WTC Investigation XXIX
Acknowledgments

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xxx NIST NCSTAR 1-6A, WTC Investigation
Executive Summary

The structural steel in the World Trade Center (WTC) towers was protected against the effects of fire with

sprayed fire-resistive materials (SFRMs) or rigid fire-rated gypsum panels. The majority of the types of

SFRMs used in the WTC towers are packaged as dry ingredients composed of a binder and insulation

materials. At the job site, water is added by a pressurized system as the materials are sprayed onto the

steel. The water mixes with the cementitious materials and provides "stickiness" that allows the SFRM to adhere weakly to the steel. With time, the cementitious materials harden, and excess water evaporates.

When dry, SFRMs provide an insulation barrier to limit excessive temperature rise in the protected steel member during a fire.

The thermal-structural analysis of the WTC towers focused on two objectives: (1) analysis of the

undamaged buildings exposed to conventional building fires, and (2) analysis of the buildings damaged

by the aircraft impact and exposed to the subsequent fires. To reduce the uncertainties in the calculated

thermal histories of various structural elements, the condition of the passive fire protection as it existed on September 11, 2001, was estimated as accurately as possible. In addition, reasonable estimates of the extent of SFRM dislodged by aircraft impact and the resulting debris field had to be made.

To provide context for the information in this report, an overview of concepts used in U.S. building codes

for structural fire resistance is presented first. This is followed with a summary of the construction

history of the sprayed fire-resistive materials in WTC 1 and WTC 2. To gain an understanding of the

effect of SFRM thickness and its variability on the steel temperature during exposure to fire, results are presented of a sensitivity study based on a simple finite-element model. This is followed by a quantitative assessment of in-place thickness and its variability based on available data. The rationale for the thickness of SFRM to be used in the structural fire endurance analyses is presented. The tests conducted to determine the thermal properties of insulation materials similar to those used in the WTC

towers are reviewed. The results of mechanical property tests conducted on laboratory specimens are presented, and a simplified approach for estimating the acceleration required to dislodge thermal

insulation during impact is discussed.

BUILDING CODE CONCEPTS FOR STRUCTURAL FIRE RESISTANCE

Fire-induced collapse of buildings is regulated generally through limits on the height and the area per

floor as a function of the types and degree of fire resistance of materials used in the structural elements.

These material characteristics are categorized as types of construction, and the associated limits are contained in so-called "heights and areas tables," which are a cornerstone of most prescriptive building

codes.

The intent of building height limits is to restrict taller buildings to non-combustible structural members,

and the greatest fire resistance is assigned to members supporting multiple floors. The primary concern

with combustible structural members is that they can become ignited by an exposing fire and can continue

to burn (often in concealed spaces) even after the exposing fire has been extinguished, leading to collapse.

The intent of increased fire resistance for members supporting multiple floors is directly related to the

NISTNCSTAR 1-6A, WTC Investigation XXXI
Executive Summary

higher risk of property loss in the event of failure of multiple floors. Fire resistance requirements,

however, do not take into account the actual number of stories being supported by these elements.

Construction Types

The main categories of constructions defined in model building codes are Type I (fire resistive), Type II (non-combustible), Type III (ordinary), Type IV (heavy timber), and Type V (combustible). Construction

Types I and II include non-combustible exterior and interior bearing walls and columns, where fire resistance ratings are greatest for Type I, and Type II is any (non-combustible) construction not meeting

Type I requirements. Within each construction type are several sub-categories determined by the fire resistance ratings of the columns (vertical structural elements that support gravity loads and resist the

actions of lateral loads), beams (horizontal structural elements that support predominantly gravity loads),

and floor systems. In some model codes these sub-categories are identified by letters following the type

(e.g., IB or 3 A) (IBC 2003) or by a set of three numbers that represent the fire resistance required (in

hours) of exterior bearing walls; columns, beams, girders, trusses, and arches, supporting bearing walls,

columns or loads from more than one floor; and floor construction, respectively (e.g., Type I [3,3,2]).

Fire Resistance of Structural Elements

Building codes require that structural elements be protected to achieve a specified fire resistance rating,

expressed in hours. The fire rating of structural materials and assemblies is generally determined through

testing, and in the United States, such testing is frequently conducted in accordance with ASTM Test Methods E 1 19. The intent is for the building to withstand design loads (including fire) without local

structural collapse until occupants can escape and the fire service can complete search and rescue

operations.

Building codes generally require the highest fire resistance for columns and elements supporting multiple

floors, and somewhat less resistance for columns supporting single floors, for beams, and for floors. The

required fire resistance ratings have been reduced in recent years as fire sprinklers have become universal

in new high-rise buildings and common in most other commercial buildings. In the past, high-rise

buildings generally required a 4 h rating for columns; this was reduced to 3 h in recent model codes, and

can be as low as 2 h in current model codes based on the additional mandatory requirement for sprinklers.

Some model codes allow a reduction in fire-resistance rating for high-rise buildings that have been

retrofitted with sprinklers.

HISTORICAL REVIEW RELATED TO PASSIVE FIRE PROTECTION

Port Authority Relationships with New York City Department of Buildings and Fire

Department

As an interstate agency, The Port Authority of New York and New Jersey (Port Authority or PANYNJ)

was not required to comply with the New York City Building Code or any other building code in the

design and construction of the WTC towers. The Port Authority, however, made explicit statements that

it would comply with the New York City Code. In a letter dated May 15, 1963, the Port Authority

instructed its consulting engineers and architects to comply with the New York City Building Code. In the areas where the Code was not explicit or where technological advances made portions of the Code

xxxn NISTNCSTAR 1-6A, WTC Investigation
Executive Summary

obsolete, it directed that design could be based on acceptable engineering practice. At this time, the 1938

edition of the New York Building Code was in effect and a revised Code was being drafted. In September 29, 1965, the Port Authority instructed its consultants to revise WTC design plans to comply

with the second and third drafts of the Code revision. The revised Building Code became effective in December 1968.

In 1993, the Port Authority' and the New York City Department of Buildings entered into a memorandum

of understanding to establish procedures to be followed by the Port Authority for any building

construction project located in the City's jurisdiction. Among the key points, it was agreed that:

• Each project would be reviewed and examined for compliance with the Code;

• All plans would be prepared, sealed, and reviewed by New York State licensed professional

engineers or architects: and.

• The Port Authority engineer or architect approving the plans would be licensed in the State of

New York and would not have assisted in the preparation of the plans.

A supplement to this memorandum of understanding was executed in June 1995, which permitted tenants

to use New York State licensed architects or engineers, in lieu of a Port Authority review, to certify that construction plans conformed to the Code and that construction was performed in accordance with the

plans. In September 1995. the supplement was modified to permit a single licensed consultant to certify the plans and the construction, except if the alteration would change the occupancy group of the space.

In 1993, the Port Authority signed a memorandum of understanding with The Fire Department of the City

of New York (FDNY). The agreement restated the Port Authority's policy to implement

recommendations after a fire safety inspection of a Port Authority facility by a local fire department. The

agreement included the following points:

• The FDNY shall have the right to conduct fire safety inspections at any Port Authority facility in New York City.

• FDNY will issue to the Port Authority a letterhead report of its fire safety inspections for correction of any deficiencies.

• The Port Authority will continue to assure that new or modified fire safety systems comply with

"local codes and regulations."

In 1995, the memorandum of understanding with FDNY was amended with respect to additions to or modifications of fire safety systems. The Port Authority agreed to notify the Bureau of Fire Protection

prior to installing new systems or modifying existing systems. In addition, plans for these systems were

to be prepared by New York State licensed professional engineers or architects.

New York City Building Code Requirements

Application of the 1968 New York City Building Code provisions affected the assigned building

classification and, thus, the required fire rating of the WTC towers and their structural members. The

NISTNCSTAR 1-6A, WTC Investigation xxxiii
Executive Summary

WTC towers were classified as Occupancy Group E—Business. The 1968 Code identified two

construction groups: Noncombustible Construction (Group 1 ) and Combustible Construction (Group 2). The WTC towers were classified as Construction Group 1 because their walls, exit ways, shafts, structural members, floors, and roofs were constructed of noncombustible materials. At the time of design and

construction, the towers were not sprinklered.

The 1968 New York City Building Code defined five Classes within Construction Group 1. For Business

occupancy, each Class required a fire endurance rating as follows:

Class 1A: 4 hour protected

Class IB: 3 hour protected

Class 1C: 2 hour protected

Class ID: 1 hour protected

Class IE: unprotected

Construction Classes 1A and IB permitted buildings of unlimited height. Thus, the WTC towers could

have been designed to meet either Class 1 A or Class IB requirements.

Classification of WTC Towers

It was the practice at the time, and continues to be the practice, for the architect to establish the building

classification, fire rating of members and systems, and thermal protection requirements. The review of

documents uncovered during the investigation indicated a discrepancy in the classification, and, therefore,

in the fire ratings to be used in the design of the towers. Documents issued in the early stages of the

design appear to indicate that the towers were classified as Class 1 A. With the directive in 1965 to comply with the 1968 New York City Building Code, it appears that the towers were classified ultimately

as Class IB.

According to Section C26-314.1 of the 1968 New York City Building Code, construction

classification IB provided, in part, the following fire protection requirements:

• Columns, girders, trusses, other than roof trusses, and framing supporting more than one floor

shall have 3 hour fire endurance;

• Columns, girders, trusses, other than roof trusses, and framing supporting one floor shall have

2 hour fire endurance

• Floor construction including beams shall have 2 hour fire endurance.

• Enclosure of vertical shafts, exits, passage-ways, and hoistways shall have 2 hour fire endurance;

and

xxxiv NISTNCSTAR 1-6A, WTC Investigation
Executive Summary

• Roof construction including beams, trusses, and framing including arches, domes, shells, cable

supported roofs, and roof decks (for buildings over one story in height) shall have 2 hour fire endurance.

Thus, the columns were required to have a 3 hour fire endurance rating, and the floor system was required

to a have a 2 hour rating when tested in accordance with ASTM E 1 19.

Response to Local Law 5/1973

In 1973, New York City Local Law No. 5 amended the New York City Building Code (effective

January 18, 1973). Local Law No. 5 required, in part, the retrofit of existing unsprinklered office

buildings 100 ft or higher. The New York City Department of Buildings permitted either:

• Subdividing the floor area into compartments of specified square footage by fire separations (1 h

or 2 h fire rated depending on the size of the compartment), or

• Providing sprinkler protection.

A code compliance evaluation conducted in 1997 indicated that that all tenant floors in the two towers

had been retrofitted with sprinklers (sprinklered) with the exception of four floors in WTC 1. In a 1999

update by the Port Authority it was noted that all tenant floors had been sprinklered and work was

underway to complete sprinklenng of the sky lobbies. In 2000, a property condition assessment report

stated that the WTC towers were classified as "Class IB - noncombustible, fire-protected, retrofitted with

sprinklers in accordance with New York City Local Law 5/1973."

Selection of Fire-Resistive Materials

Classification of a building leads to its overall fire endurance rating and ratings of the various structural components. The New York City Building Code, however, does not prescribe how the required fire endurance rating is to be achieved. The Port Authority chose to protect the main structural components

such as columns, spandrel beams, and floor trusses with sprayed fire-resistive material. This thermal

protection technique was an established method for protecting columns, beams, and walls. In the 1960s,

however, composite steel joist-supported floor systems were usually protected using "lath and plaster"

enclosures or fire-rated ceiling tiles.

Since application of sprayed fire-resistive materials to floor trusses was an innovative fire protection

method, the Port Authority arranged for demonstrations to establish its feasibility for the World Trade

Center. The demonstrations were considered to be successful and in November 1968, the Port Authority

awarded the contract for "spray fireproofing" of the interior portions (floor system and core) of the WTC

towers. The fire protection of the exterior columns was included in the contract for the exterior aluminum

cladding.

Several materials were considered for the sprayed thermal insulation. The exterior columns required

insulation not only for fire protection but also to control column temperatures under service conditions.

Alcoa recommended for the exterior columns the use of a sprayed material produced by U.S. Mineral

Products, Co. known as BLAZE-SHIELD Type D. The same material was eventually selected for the

floor trusses and core beams and columns. This product, however, contained asbestos fibers. On April

NISTNCSTAR 1-6A, WTC Investigation XXXV
Executive Summary

13, 1970, New York City issued restrictions on the application of sprayed thermal insulation containing

asbestos. The use of BLAZE-SHIELD Type D was discontinued in 1970 at the 38th floor of WTC 1

The asbestos-containing material was subsequently encapsulated with a sprayed material that provided a hard coating. A green dye was added to the encapsulating material so that the asbestos containing SFRM

could be identified. Thermal protection of the remaining floors of WTC 1 and all of WTC 2 was carried out using BLAZE-SHIELD Type DC/F, a product that contained mineral wool (glassy fibers) in place of

the crystalline asbestos fibers. On the basis of tests, it was reported that the thermal properties of

BLAZE-SHIELD Type DC/F were equal to or "slightly better" than those of BLAZE-SHIELD Type D.

Specified Thickness of Fire-Resistive Material

The thickness of fire-resistive material necessary to achieve the required fire endurance was assessed in 1965, more than three years before the award of the thermal protection contract. At that time, the

Architect of Record recommended 1 in. of thermal protection for the top and bottom chords of the floor

trusses and 2 in. for other members of the trusses. WTC project specifications for sprayed fire protection

do not provide required material thickness or hourly ratings. In October 1969, the manager of project

planning for the WTC provided the following instructions to the contractor applying the sprayed fire protection:

"...Tower 'A

1 columns that are less than 14WF228 will require 2 3/16"

thick of 'Cafco Glaze [sic]-Shield 'Type D" spray-on fireproofing. All

Tower columns equal to or greater than 14WF228 will require 1 3/16" of

fireproofing...

All Tower beams, spandrels and bar joists requiring spray-on

fireproofing are to have a 1/2" covering of 'Cafco.'

The above requirements must be adhered to in order to maintain the

Class 1-A Fire Rating of the New York City Building Code."

NIST's review of available documents has not uncovered the reasons for selecting BLAZE-SHIELD or

the technical basis for specifying lA in. thickness of insulation for the floor trusses. The last sentence in the above excerpt indicates that in October 1969, the towers were considered as Class 1A construction.

In February 1975, a fire occurred in WTC 1, spreading from the 9th to the 19th floor. After the fire, the Port Authority contracted Skilling, Helle, Christiansen, Robertson (SHCR), the Structural Engineer of

Record for the design of the WTC towers, to assess the resulting structural damage and to report, in general, on the fire resistivity of the floor system. In its report dated April 1, 1975, SHCR communicated

to the Port Authority that the fire did not cause structural damage, but it caused buckling of some top

chord members of main trusses, buckling of bridging trusses, and distortion of deck support angles. The

report provided valuable information on the history of the passive fire protection of the towers.

The 1975 post-fire report by SCHR stated further that thermal protection of the top chords of the floor

trusses was not necessary, except for the corners of the buildings where the floor acted as a two-way

system in bending. Additionally, it was stated that protection of the bridging trusses was not required

because the bridging trusses were "not required as a part of the structural system."

xxxvi NIST NCSTAR 1-6A, WTC Investigation
Executive Summary

In February 2003, NIST asked the Port Authority a series of questions related to the sprayed thermal

protection for the floor system. The Port Authority replied in March that the top chords of the main

trusses and the bridging trusses were protected.

Upgrading SFRM on Floor Trusses

In 1995. the Port Authority performed a study to establish requirements for retrofit of sprayed insulation

to the floor trusses during major alterations (new construction) when tenants vacated spaces in the towers. The study estimated the thermal protection requirements based on "the fireproofing requirements" for

Design No. G805 contained in the Fire Resistance Directory published by Underwriters Laboratories.

The study concluded that "a two hour fire rating for the steel floor joist trusses can be achieved by

applying a 1 Vi inch thickness of spray-on mineral fiber fire protection material directly to the steel truss chords and webs." In the years between 1995 and 2001, thermal protection was upgraded in a number of

the floors affected by the fires on September 11, 2001. Specifically, in WTC 1, floors 92 through 100 and

102 were upgraded: and in WTC 2, floors 77, 78, 88, 89, 92, 96, and 97 were upgraded.

In 1999, the Port Authority established "guidelines regarding fireproofing repairs, replacement, and

upgrades" for the towers. The guidelines for in tenant spaces may be summarized as follows:

• For full floors undergoing new construction or renovation, the floor trusses should be protected

with 1 V2 in. of sprayed mineral fiber fire-resistive material. Retrofit of thermal protection

requires removal of existing material and controlled inspection.

• For "tenant spaces less than a full floor undergoing either new construction or renovation," the

floor trusses "need only meet the original construction standard. Fireproofing shall be inspected

and patched as required to the greater of % in. or to match existing" if it has already been

upgraded to 1 Vi in.

In July 2000, an engineering consultant, commissioned by the Port Authority to conduct a fire- engineering assessment of the fire protection of the floor trusses, issued a report on the requirements of

the fire resistance of the floor system of the towers. This report stated that BLAZE-SHIELD DC/F was

used on the majority of the floor trusses. Based on calculations and risk assessment, the consultant

concluded that:

• "The structural design has sufficient inherent fire performance to ensure that the fire condition is never the critical condition with respect to loading allowances.

• A single coat application is possible.

• Significant savings are possible.

• The target reduction of fiber content and increased long term durability can be achieved.

• Alternative materials should be considered."

As quoted, the report states that significant savings were possible by reducing the fiber content and

considering alternative materials. The report suggested that the thickness of the SFRM could be reduced

to V2 in. if the material properties at ambient temperature are applicable at higher temperatures. The

NISTNCSTAR 1-6A, WTC Investigation xxxvn
Executive Summary

report recognized the lack of available temperature-dependent material data for BLAZE-SHIELD Type

DC/F. Thus, considering the uncertainties in the material properties and having the understanding of

material degradation with temperature and time, it was recommended that 1 .3 in. of fire-resistive material

be used for the floor trusses.

Later, in December 2000, the final draft of a report on Property Condition Assessment of World Trade

Center Portfolio stated that, based on existing conditions "The rating of the structural fireproofing in the

Towers and subgrade has been judged to be an adequate 1 hour rating considering the fact that all Tower

floors are now sprinklered." The report also noted the ongoing Port Authority program to upgrade the

fire-resistive material thickness to 1

lA in. in order to achieve a 2 hour fire rating.

Need for Fire Endurance Tests

The fire protection of a truss-supported floor system by directly applying sprayed fire-resistive material to the trusses was innovative and not consistent with prevailing practice at the time the WTC towers were

designed and constructed. While the benefits of conducting fire endurance tests were realized by

individuals involved in the 1967 demonstrations of the application of SFRM, apparently no tests were

conducted on the floor system used in the WTC towers. The Architect of Record and the Structural

Engineer of Record stated that the fire rating of the floor system of the WTC towers could not be

determined without testing. Communication from the Port Authority in 2003 confirms that there is no

record of fire endurance testing of assemblies representing the thermally protected floor system.

Maintenance of SFRM in Elevator Shafts

Throughout the life of the WTC towers, the structural members that required the largest amount of

inspection and maintenance within the core were the exposed columns and beams within the elevator

shafts. These columns and beams were the only accessible fire-protected elements in the buildings.

Adhesion failures were common, likely because of the exposed conditions of the columns and the

inherently low strength of the SFRM.

Inspections of the shafts and accessible columns were reported as early as 1971 . Problems were noted in the form of fallen insulation or with the over-spray material used to provide a harder surface. In 1993, the Port Authority commissioned Leslie E. Robertson Associates to carry out a continuing program to appraise the condition of the accessible columns located in the cores of the towers. The columns were

inspected visually for signs of rusting, cracking, bowing, and loss of thermal insulation. During the first inspection, carried out in 1993, particular shafts were chosen based on the quantity and types of accessible

columns, and the convenience to the Port Authority. Subsequent inspections involved sampling of the

structural components and assemblies, which were more important to the structural integrity of the

towers, and at locations with a relatively higher potential for defects and problems. The inspection report

stated that the accessible columns in selected elevator shafts in WTC 1 and WTC 2 were "generally in good condition, no structural deficiencies such as cracking or bowing were found, the most common

irregularities observed were missing fireproofing and light surface rusting of the exposed steel." Based on

the inspections, LERA recommended "that remedial action to be taken where spray fireproofing is damaged, deteriorated or missing and where there is corrosion of the column base due to water leaks at elevator pits." Earlier in 1992, LERA performed calculations to determine the thickness of replacement

thermal insulation for selected beams and columns within elevator shafts.

XXXVlll NISTNCSTAR 1-6A, WTC Investigation
Executive Summary

AS-APPLIED THICKNESS OF SFRM

1994 Measurements from WTC 1 Floors 23 and 24

In its search of documents, NIST found no information related to measurements of the thickness of

thermal insulation taken during original construction. Reviewed documents, however, indicate that thickness appears to have been checked during construction. Recorded infonnation on the in-place

condition of the sprayed thermal insulation for the floor system first appeared in 1990 in the form of

"Sample Area Data Sheets,'* which provided qualitative comments on the state of the in-place SFRM.

Information regarding quantitative inspection of existing fire-resistive material appeared in documentation from 1994. That year, the Port Authority performed a series of thickness measurements of

the existing SFRM on floors 23 and 24 of WTC 1. Six measurements were taken from "both flanges and

web" of each of 16 randomly chosen trusses on each floor. Measured average thickness varied between

0.52 in. and 1.17 in. For the 32 measurements (16 on each floor), the overall average was 0.74 in., and

the standard deviation of these averages was 0.16 in. Four of the 32 floor trusses had average thicknesses

between 0.52 in. and 0.56 in. These measurements suggest that the minimum average thickness exceeded

lA in. Analysis of the reported mean thicknesses indicated that a lognormal distribution gave a better representation of the distribution rather than did a normal distribution.

Analysis of Photographs

Additional SFRM thickness data were developed by evaluating photographs of floor trusses taken during

inspections. Two groups of photographs were used. The first group included images of floor trusses from WTC 1 (floors 22, 23, and 27). These photographs were taken in the mid-1990s and illustrated conditions before the upgrade carried out by the Port Authority. Thus, SFRM thickness on the

photographed trusses would be expected be at least V2 in. The second group of photographs, taken in 1998, illustrated conditions after the upgrade program that was initiated in 1995. The photographs were

of trusses for floor 3 1 and below in WTC 1 . Selection of the photographs to be used to estimate thickness

of SFRM was based on clarity of SFRM edges and the presence of a feature of known dimensions to provide a reference measurement.

For floors that had not been upgraded, it was observed that the estimated thickness of SFRM on the webs

(inclined bars) of the main trusses tended to be greater than that on either the diagonal stmts or on the

webs of the bridging trusses. Hence, estimates of SFRM thickness for non-upgraded floors were divided

into three groups:

• Webs (inclined bars) of main trusses,

• Webs (inclined bars) of bridging trusses, and

• Diagonal strut at the exterior wall end of the truss.

It was not possible to estimate the thickness of the SFRM on any truss element except the round web bars. Consequently, for the upgraded floors in WTC 1 that were included in the second group of photographs,

only estimates of the thickness on the web bars of the main trusses were made. The average, standard

NISTNCSTAR 1-6A, WTC Investigation XXXIX
Executive Summary

deviation, and coefficient of variation were computed for the total number of measurements in each of

these groups. The results are summarized as follows:

• Main trusses before upgrade (85 measurements): Average thickness 0.6 in., standard deviation = 0.3 in., and coefficient of variation = 0.5.

• Bridging trusses before upgrade (52 measurements): Average thickness 0.4 in., standard deviation = 0.25 in., and coefficient of variation = 0.6.

• Diagonal struts before upgrade (26 measurements): Average thickness 0.4 in., standard deviation

- 0.2 in., and coefficient of variation = 0.5.

• Main trusses after upgrade (52 measurements): Average thickness 1 .7 in., standard deviation = 0.4 in., and coefficient of variation = 0.2.

Port Authority Data on Upgraded SFRM on Trusses

In the 1990s, the thermal protection for some floor trusses was upgraded to a specified thickness of VA in. as tenants vacated their spaces. According to the Port Authority, 18 floors of WTC 1 and 13 floors of

WTC 2 were upgraded. The Port Authority also stated that: "The entire impact zone for Tower 1 (92-99) was upgraded with 1 V" spray-on fireproofing. Only the 78

th floor was upgraded with the 1

lA" spray-on

fireproofing within the impact zone in Tower 2 (78-84)." The Port Authority provided Construction

Audit Reports that included the density, average thickness, and strength characteristics of the upgraded

SFRM (BLAZE-SHIELD II) as of 2000. In 2004, the Port Authority provided NIST reports of the

individual measurements for many of the average thicknesses recorded in the Construction Audit Reports.

These individual measurements permitted analysis of the variation of thickness at a cross section of a

truss member and the variation in average thickness from truss to truss. A total of 1 8 data sets for WTC 1 (including floors 93, 95, 98, 99, and 100) and 14 data sets for WTC 2 (including floors 77, 78, 88, 89, and

92) were analyzed.

Data analysis indicated that the thickness measurements from the two towers represented similar

distributions, and so the data were combined. It was also found that the distribution of thickness values

could be approximated as lognormal distribution.

The overall average thickness determined from the 256 individual measurements was found to be 2.5 in. with a standard deviation of 0.6 in. Thus, the average thickness on the upgraded upper floors appears to be greater than that estimated from photographs taken on upgraded lower floors.

The overall standard deviation of 0.6 in. includes two contributions: (1) the variation of thickness at a cross section (within-truss variability), and (2) the variation of average thickness between trusses (between-truss variability). From analysis of variance, it was found that the within-truss standard

deviation was 0.4 in., and the between-truss standard deviation was also 0.4 in. The within-truss standard

deviation of 0.4 in. is similar to the standard deviation of the estimated individual thicknesses obtained

from analysis of the photographs of upgraded main trusses.

xl NISTNCSTAR 1-6A, WTC Investigation
Executive Summary

Column SFRM Thickness

NIST requested that the Port Authority provide available information on the actual thickness of fire- resistive material on the exterior and interior columns of the WTC towers. The Port Authority replied

that, due to inaccessibility of exterior columns and core columns, there were no records of SFRM

thickness measurements for these elements. The only available measurements were for thickness of

SFRM that was reapplied to accessible beams and columns within elevator shafts.

The most complete data set included measurements on beams and columns taken within shaft 10/11 in WTC 1. These measurements were taken in April 1999 and included measurements from floor 1 to floor 45. The thicknesses were recorded to the nearest 1/8 in., with a few thicknesses recorded to the nearest 1/16 in. The columns included 10 to 18 replicate measurements, and the beams included 1 1 to 16 replicate measurements.

The average thickness for the columns was found to be 0.82 in., with a standard deviation of 0.20,

resulting in a coefficient of variation is 0.24. The average thickness for the beams was 0.97 in., with a standard deviation is 0.21 in., for a coefficient of variation is 0.21. The infonnation from the Port Authority indicated that the minimum required thicknesses for the SFRM (Monokote Type Z-106) that was reapplied to the columns and beams were Vi in. and 3A in., respectively.

The data described above may not have a direct bearing on the outcome of the investigation because they

deal with lower stories. They do, however, provide some useful information on the variability of SFRM

applied to beams and columns. As might be expected, the variation in thickness of SFRM for the beams

and columns is lower than the variation computed for the floor trusses. The flat surfaces of the beams and

columns result in more uniform application of the sprayed fire-resistive material than for the slender truss members.

EFFECT OF SFRM GEOMETRY ON THERMAL RESPONSE

As would be expected, and as confirmed by analyses of available data, the thickness of thermal insulation can have high variability. The effects of thickness variation on thermal response of a member are not

well known. A sensitivity study using the finite element analysis to simulate heat transfer was conducted

to investigate the sensitivity of steel temperature rise to the variability in SFRM thickness.

Effects of Thickness Variability and Gaps in SFRM

A finite element model for thermal analysis was developed for a plate protected on both faces with SFRM

of variable thickness. A random number generator was used to assign a lognormally distributed random

thickness of insulation along the length of the plate, and the plate was subjected to a thermal flux

representative of a 1,100 °C fire. A parametric study was conducted with average thickness of fire- resistive material varying from 0 in. to 2 in. in increments of % in. and a standard deviation varying from

0 to 1 in. Steel temperatures at five locations in the plate were recorded at 30 min, 60 min, 90 min, and

120 min of exposure to the thermal flux.

The simulations showed that when the SFRM thickness is variable, the isotherms in the steel follow the

shape of the SFRM surface contour. Thus, the temperature history at any point in the steel depends on the

NISTNCSTAR 1-6A, WTC Investigation xli
Executive Summary

local thickness of the insulation. If the time to reach a specified high temperature is used as an indicator

of protection efficiency, it was shown that an increase in thickness variability reduced the time to reach

the critical temperature. Conversely, for a given time to reach a critical temperature, the required average

thickness of thermal insulation increased with increasing variability in thickness of SFRM.

In addition to the effect of variation in thickness, the effect of missing SFRM over a portion of a member

was studied. As expected, the bare steel at the missing insulation reached the gas temperature quickly,

but more importantly the "gap" in the insulation led to transmission of heat into the interior steel.

The combined effects of variation in insulation thickness and extent of missing material were examined

by a factorial study with the following factors:

• Average thickness of insulation varying from 0 in. to 2.0 in. in 1/4 in. increments;

• Standard deviation of insulation thickness of 0 in., 0.25 in., 0.5 in., 0.75 in., and 1.0 in.; and

• Length of missing insulation varying from 0 in. to 30 in., in 6 in. increments.

The results were summarized by a series of temperature-time plots representing the response for different

combinations of the three factors. As expected, increasing the variability of insulation thickness or gap

length reduced the time to reach a given critical temperature. Because there was not sufficient

information to determine the frequency of occurrence of these gaps or their typical locations, gaps in insulation were not considered in the thermal modeling.

Thermally Equivalent Thickness of SFRM

The sensitivity study indicated that increased variation in thickness reduced the "effective thickness" of

the SFRM. It would be impractical to attempt to account for the variation in SFRM thickness in the

thermal modeling of the WTC towers by introducing variable thickness insulation material in the finite- element models. As an alternative, a "thermally equivalent uniform thickness" was determined that would result in the same thermo-mechanical response of a member as the variable thickness thermal

protection. In the analyses, an insulated 1 in. diameter by 60 in. long steel bar was subjected to the heat

flux arising from a 1,100 °C fire. The thermal history along the length of the bar was calculated, and that history was used to calculate the length change of the unrestrained bar under a tensile stress of 12,500 psi.

The bar was assumed to be similar to the steel used in the WTC floor trusses, and the temperature

dependence of the coefficient of thermal expansion and the modulus of elasticity were based on NIST

measurements.

The average SFRM thickness and variability in thickness used in the models were based on the

measurements for the web bars of the main trusses with both the original insulation and upgraded

insulation. The following values were investigated:

• Original conditions: Average thickness = 0.75 in., standard deviation = 0.3 in., lognormal

distribution.

• Upgraded conditions: Average thickness = 2.5 in., standard deviation = 0.6 in., lognormal

distribution.

xlii NISTNCSTAR 1-6A, WTC Investigation
Executive Summary

The variation of thermal insulation thickness along the length of the bar was established by using a pseudo random number generator to select values from a lognormal distribution with central value and

dispersion consistent with the above average values and standard deviation. Three sets of random data were generated for each condition.

When the randomly selected thicknesses of each element were applied to the bar, it resulted in abrupt

changes in insulation thickness along the length of the bar. This resulted in a "rough" surface texture that was not representative of actual conditions. As an alternative, five-point averaging was used to reduce the

roughness of the insulation profile and produce a profile that was consistent with photographic evidence.

Care was taken to ensure the "smoothed" profiles maintained the required dispersion.

The calculated thermal histories of the bar elements were used to calculate the unrestrained length

changes of the bar due to thermal expansion and the applied stress. For comparison, elongations of the

bar with different uniform thicknesses of thermal insulation were calculated. The "thermally equivalent

thickness" was taken as the uniform thickness that resulted in approximately the same elongation of the

bar as produced with the variable thickness insulation.

On the basis of these analyses, it was concluded that SFRM with an average thickness of 0.75 in. and a standard deviation of 0.3 in. provides protection equivalent to 0.6 in. of uniform thickness. Similarly, an

average SFRM thickness of 2.5 in. with a standard deviation of 0.6 in. is equivalent to 2.2 in. of uniform

thickness.

Recommended Thickness of SFRM for Thermal Analyses

Analyses of available data on SFRM thickness in the WTC towers and thermal modeling revealed the

following:

• From measurements of SFRM thickness, the average values exceeded the specified thickness.

• SFRM thickness was variable, and the distribution of thickness in the floor trusses appeared to be

described best by a lognormal distribution.

• The standard deviation of SFRM thickness on the trusses varied between about 0.3 in. and 0.6 in.

• The standard deviation of SFRM on columns and beams from the core tended to be lower, with a value of 0.2 in. for the available data.

• No information was available on the SFRM thickness on the exterior columns and spandrel

beams.

• Variation in thickness reduces the effectiveness of SFRM, and the equivalent uniform thickness was less than the average thickness.

Based on findings stated above, the following uniform thicknesses for the undamaged SFRM were

determined for use in calculating thermal response of the WTC towers under various fire scenarios:

• Original SFRM thickness on floor trusses: 0.6 in.

NISTNCSTAR 1-6A, WTC Investigation xliii
Executive Summary

• Upgraded SFRM thickness on floor trusses: 2.2 in.

• Thermal protection on other elements: the specified thickness.

The choice of specified thickness for those members lacking data is justified by the following offsetting

factors: (1) measured average thicknesses exceed specified values, and (2) variation in thickness reduces

the effectiveness of the SFRM.

THERMOPHYSICAL PROPERTIES

To provide thennophysical property data for modeling the fire-structure interaction of the towers, the

thermal conductivity, specific heat capacity, and density of the SFRMs used in the WTC towers were

determined as a function of temperature up to 1,200 °C (2,190 °F). Since there are no ASTM test methods for characterizing the thermophysical properties of SFRMs as a function of temperature, ASTM

test methods developed for other materials were used. Samples were prepared by the manufacturers of

the fire-resistive materials, which included BLAZE-SHIELD DC/F, BLAZE-SHIELD II, and Monokote

MK-5. Since Monokote MK-5 is no longer on the market, the samples were manufactured specially for

this study according to the original MK-5 formulation. Testing services were provided under contract by a commercial testing agency.

Thermal Conductivity

The thermal conductivity measurements were performed according to ASTM C 1113, Standard Test Method for Thermal Conductivity of Refractories by Hot Wire (Platinum Resistance Thermometer

Technique). The room temperature values were in general agreement with the manufacturer's published

values for BLAZE-SHIELD DC/F and BLAZE-SHIELD II. No published values were available for

Monokote MK-5. The thermal conductivities increased with temperature.

Specific Heat Capacity

Specific heat capacity determinations were made with the same instrument as for thermal conductivity

with a slight modification. A thermocouple was added to the system, which permitted determination of

the thermal diffusivity of the material. Knowing the thermal conductivity, the thermal diffusivity, and the

density obtained from other tests, the specific heat capacity was calculated. The inherently indirect nature of the technique used precluded the direct measurements of specific heat capacity peaks associated with

chemical reactions.

To examine the chemical reactions associated with heating of SFRMs, samples were sent to another

laboratory under contract to perform differential scanning calorimetry (DSC) measurements in accordance with ASTM E 1269, Standard Test Method for Determining Specific Heat Capacity by

Differential Scanning Calorimetry. Differential thermal analysis (DTA) is a "fingerprinting" technique

that provides information on the chemical reactions, phase transformations, and structural changes that occur in a specimen during a heating or a cooling cycle. These tests revealed large peaks in the specific

heat capacities in the range of 125 °C to 140 °C.

xliv NIST NCSTAR 1-6A, WTC Investigation
Executive Summary

Density

Bulk densities of the SFRMs were not measured directly (except at room temperature) but were

calculated from thermal gravimetric analysis (TGA) and thermal expansion measurements. The TGA

tests to measure mass loss were performed according to ASTM E 1131, Standard Test Method for Compositional Analysis by Thermogravimetry. Thermal expansion measurements were performed

according to ASTM E 228, Standard Test Method for Linear Thermal Expansion of Solid Materials.

Since the materials were not isotropic, separate measurements were performed in the plane of the SFRM

sample and perpendicular to the free surface of the sample. From the thermal expansion measurements,

the change in volume for each material was calculated at each temperature. The density values were

calculated from the results of the TGA and thermal expansion. The room temperature densities were

15.7 pcf for BLAZE-SHIELD DC/E, 20.8 pcf for BLAZE-SHIELD II, and 19.4 pcf for Monokote MK-5.

Thermophysical Properties of Gypsum Panels

Thermophysical properties of four representative types of commercially available gypsum panels were

examined. The materials were:

1 . 5/8 in. thick gypsum panel A,

2. Vi in. thick gypsum panel,

3. 5/8 in. thick gypsum panel B, and

4. 1 in. thick gypsum liner panel.

Thermal conductivity was measured using the heated probe technique described in ASTM D 5334,

Standard Test Method for Determination of Thermal Conductivity of Soil and Soft Rock by Thermal

Needle Probe Procedure. In general, the thermal conductivity initially decreased as the temperature

increased to 200 °C and then increased with increasing temperature above 300 °C.

Specific heat capacities of the cores of the four gypsum panel samples were measured using a differential scanning calorimeter according to ASTM E 1269, Standard Test Method for Determining Specific Heat

Capacity by Differential Scanning Calorimetry. The four panels had similar specific heat capacities as a function of temperature, with a high peak at about 150 °C and a smaller peak at about 250 °C.

Densities were calculated from the thermogravimetric analysis (TGA) and linear thermal expansion

measurements. All four materials show the same trend as a function of temperature. The variation of

density with temperature is associated with the mass loss and the change in volume of the gypsum

material.

ADHESIVE AND COHESIVE STRENGTH

To analyze the thermo- structural response of the WTC towers during the fires after the aircraft impacts, it was necessary to estimate the extent of dislodged thermal insulation on structural members.

NISTNCSTAR 1-6A, WTC Investigation xlv
Executive Summary

Dislodgement could occur as a result of direct impact by debris or due to inertial forces as a result of the

aircraft impact. Photographic evidence suggested that thermal insulation was dislodged from portions of

exterior columns of the towers that were likely not subjected to direct impact by debris. This study

focused on dislodgement due to inertial forces.

The magnitude of the inertial forces depends on the density and thickness of the thermal insulation. The

insulation would dislodge if the stresses resulting from inertial forces exceed the strength of the

insulation. Therefore, the focus of the NIST study was to determine tensile strength characteristics of the

thermal insulation. In addition, a simplified approach was developed for estimating the magnitude of

accelerations required to dislodge thermal insulation.

In-place Density and Bond Strength

The Port Authority provided data on in-place density and bond strength characteristics of the thermal

insulation (BLAZE-SHIELD II) applied to the floor trusses during tenant alterations. According to the

manufacturer, BLAZE-SHIELD II is about 20 percent denser and has about 20 percent greater

adhesive/cohesive strength than BLAZE-SHIELD DC/F. The Port Authority test reports indicate that bond strength was determined in accordance with ASTM E 736, Standard Test Method for Cohesion/Adhesion of Sprayed Fire Resistance Materials Applied to Structural Members. The method

involves gluing ajar screw cap to the surface of the thermal insulation, and after the glue has cured, the

cap is pulled. The force required to pull off the cap is divided by the area of the cap and reported as the "cohesive/adhesive strength." Failure is described as "cohesive" if it occurs within the insulation and is defined as ""adhesive" if it occurs at the interface with the substrate.

Analysis of the reported density values indicated no statistically significant differences between the

average SFRM densities in the two towers. The overall average density was 18.9 pcf with a standard

deviation of 3.2 pcf, giving a coefficient of variation of 16 percent.

Analysis of the bond strength values indicated that there were statistically significant differences between

the average bond strengths for the different floors, but there was no statistically significant difference

between the average bond strengths for the two towers. The overall average bond strength was 302 psf,

with a standard deviation of 91 psf, giving a coefficient of variation of 30 percent. This average value is less than the "tested performance" value of 360 psf indicated in the manufacturer's catalogs, but this published value is for tests under controlled conditions and may not be representative of field strengths.

The manufacturer's product literature dated February 2002 refers to average bond strength of 150 psf as "standard performance," and the same value is used in its guide specification for BLAZE-SHEILD II.

Specimen Preparation and Test Procedures

While the in-place bond strength data for BLAZE-SHIELD II reported by the Port Authority appear to indicate acceptable performance, ASTM E 736 tests do not provide sufficient information for predicting

whether insulation would be dislodged from structural members under various impact conditions. The

standard test does not provide unambiguous values of cohesive and adhesive strengths and it does not provide tensile strength in a direction parallel to the surface, that is, the in-plane cohesive strength. Thus,

tests were conducted by NIST to determine different tensile strength properties of sprayed thermal

xlvi NISTNCSTAR 1-6A, WTC Investigation
Executive Summary

insulation. BLAZE-SHIELD DC/F was used because the Port Authority data did not include tests of this material.

Test specimens were made by applying the SFRM to % in. steel plates measuring 8 in. by 16 in. One half

of the plates were coated with primer paint. Nominal SFRM thicknesses of 3A in. and IV2 in. were

applied. Thickness was built up in several passes of the spray nozzle. Gentle hand rubbing was used to remove local high spots and produce reasonably uniform thicknesses. The plate specimens were allowed

to dry for over five months in the laboratory before testing. Companion specimens were weighed

periodically for loss of water and it was found that the 1 V2 in. thick specimen reached equilibrium in about one month.

Tests were devised to determine adhesive strength, cohesive strength normal to the surface, and cohesive

strength parallel to the surface of the SFRM. The first two properties were determined by adapting the pull-off test method described in ASTM C 1583, Standard Test Method for Tensile Strength of Concrete

Surfaces and the Bond Strength or Tensile Strength of Concrete Repair and Overlay Materials by Direct

Tension (Pull-off Method). The SFRM layer was cut carefully in two orthogonal directions to create a prismatic test specimen, and a 3/8 in. by 2.7 in. by 2.7 in. aluminum plate was glued to the surface. The

advantages of this approach over the ASTM 736 technique are that the resisting area is easily determined

and it offers the ability to measure both adhesive and cohesive strengths.

From each plate, three specimens were prepared for measuring both density and in-plane cohesive

strength, and two specimens were prepared for measuring adhesive strength and cohesive strength normal

to the surface. Prismatic specimens were prepared by carefully removing strips of SFRM from the steel plates and sanding them to obtain uniform thickness. These specimens were weighed to determine their densities. Then the specimens were glued to a steel plate and a small plate was glued to the other end for application of a tensile load.

The adhesive strength and cohesive strength normal to the surface were obtained using the modified pulloff procedure. An aluminum plate was bonded to the top surface of the SFRM using a fast curing, twocomponent urethane foam adhesive. After the adhesive had cured, the SFRM layer was cut to produce a prismatic test specimen. A hook was screwed into the aluminum plate, and a load was applied by hand

using a 50-lb digital force gauge. The average length and width of the failure area was measured and

used to compute the adhesive or cohesive strength. After the first test, the specimen was repaired with the same polyurethane adhesive and the test was repeated. If the first test was an adhesive failure, the second

test of the repaired specimen measured cohesive strength of the bulk SFRM. If the first test resulted in cohesive failure, the specimens were repaired and retested until an adhesive failure was obtained.

Test Results

Table E-l summarizes the results of the test described in the previous section.

Table E-1. Summary of physical characteristics of BLAZE-SHIELD DC/F specimens

tested at NIST.

Property

Bare Steel Primed Steel

Va in. V/i in % in. l'/zin.

Density (pcf) 27.2 (0.8y 29.7(1.3)

NISTNCSTAR 1-6A, WTC Investigation xlvii
Executive Summary

ln-plane cohesive strength (psf) 1120(390) 1740(540)

Adhesive strength (psf) 450(63) 666 (151) 185 (96) 171

b

( 196)

Cohesive strength normal to surface (psf) 433 (99) 610 (142) 367 (79) 595 (163)

a. First number is the average and the number in parentheses is the standard deviation.

b. Based on testing selected samples.

The densities of the BLAZE-SHIELD DC/F measured in this study were higher than published in the

manufacturer's catalogs and higher than the in-place average density of 18.9 pcf reported in Port Authority test reports for BLAZE-SHIELD II. The difference in average densities of the two thicknesses was statistically significant. The higher values in this study are attributed to the details of the specimen

preparation procedures, which tended to result in denser test specimens than would be representative of

field application.

The difference in average adhesive strength for the two SFRM thicknesses is statistically significant. The

relative strengths are consistent with the difference in density for the two thicknesses.

The presence of primer reduced the adhesive strength, especially for the VA in. thick specimens. Twothirds of the thicker SFRM plates had no adhesion to the coated steel plates.

Analysis of the cohesive strength normal to the surface indicated that there was no statistically significant

effect due to the presence or absence of primer. This is logical, because the condition of the steel surface

is not expected to influence the properties of the bulk SFRM. There was a statistically significant

difference in the average strengths for the two thicknesses, with the VA in. SFRM having higher strength.

For comparison with the measured cohesive strength normal to the surface, two tests were done in

accordance with ASTM E 736. The results of the two tests were in agreement with those obtained by the

pull-off technique. This suggests that the ASTM E 736 procedure probably provides a measure of

cohesive strength.

A comparison was made of the adhesive strength and cohesive strength normal to the surface for the

plates made with bare steel. A formal analysis of variance indicated that there is an 8 percent probability

that the difference could be the result of randomness. Generally, if this probability is greater than

5 percent, it can be concluded that the difference is not statistically significant. Thus, for the case of good

adhesion, the test results do not contradict the assumption that the adhesive strength and cohesive strength

normal to the surface are equal. If this assumption is accepted, the average of the adhesive and cohesive

strengths is 409 psf for the 3/4 in. SFRM, and the average is 622 psf for the 1

lA in. SFRM. These values

are considerably greater than the manufacturer's published strength of 295 psf obtained using the ASTM

E 736 method under laboratory conditions.

Simplified Approach to Predict Dislodging of SFRM

When a member is subjected to an impact, it will undergo various modes of vibration. These vibrations

result in local cyclic accelerations that are transferred to the SFRM by forces at the interface between the

steel and the SFRM. The forces are proportional to the mass of the SFRM, and if they exceed the

adhesive or cohesive strength of the SFRM, the SFRM will separate from the member. Two limiting cases are considered:

xlviii NISTNCSTAR 1-6A, WTC Investigation
Executive Summary

• Case 1 is a planar element with SFRM applied to one face of the element. This would be

representative of SFRM applied to large webs and flanges of beams and columns. In this case, adhesive strength or cohesive strength normal to the surface would be the controlling SFRM

properties.

• Case 2 is a slender bar encased with SFRM. This would be representative of SFRM applied to elements of the floor trusses. In this case, in-plane tensile strength and bond strength are the

controlling SFRM properties.

To arrive at the ranges of accelerations that could be expected to dislodge SFRM from a planar surface,

the following plausible ranges of values were assumed:

• SFRM thickness: 0.75 in and 2.5 in.;

• SFRM density: 15 pcf and 25 pcf 1

;

• SFRM bond strength: 1 00 psf and 500 psf

For the combination of low thickness, low density, and high bond strength, the required acceleration is about 530 g, where g is the gravitational acceleration. For the other extreme combination of high

thickness, high density, and low strength, the required acceleration is about 20 g. For values

representative of the upgraded thermal insulation on the floor trusses, an acceleration of about 80 g would

be required to dislodge a 2.5 in. thick layer of well-bonded SFRM from a planar surface.

To arrive at the ranges of accelerations that could be expected to dislodge SFRM from a round bar, the

following ranges of values were assumed:

• Bar diameter: 0.9 in. and 1.2 in;

• SFRM thickness: 0.75 in. and 2.5 in.;

• Density: 15 pcf and 25 pcf;

• In-plane cohesive strength: 500 pcf and 2,000 psf; and

• Ratio of bond strength to in-plane cohesive strength: 0 and 0.3.

The smallest required acceleration is about 40 g, which corresponds to a large bar having a thick layer of

the higher density SFRM with low strength. At the other extreme, the required acceleration is about

730 g. For a 1 .2 in. diameter bar with 2.5 in. thickness of SFRM and density of 19 pcf, which are representative of the conditions of the upgraded insulation on the floor trusses, the acceleration required

to dislodge the SFRM would vary from 55 g to 230 g, depending on the strength characteristics within the

assumed ranges given above.

These simplified models are intended to provide insight into the important variables that affect the

magnitude of the disturbance (that is, acceleration) required to dislodge SFRM from different kinds of

These numbers need to be converted to units of mass by dividing by the gravitational acceleration.

NISTNCSTAR 1-6A, WTC Investigation xlix
Executive Summary

structural members. These models do not consider the fact that the applied acceleration in an actual

structure subjected to impact would vary with time. Also these models apply to members not directly

impacted by debris.

NISTNCSTAR 1-6A, WTC Investigation
Chapter 1 Introduction

When steel is heated it loses strength and stiffness. This characteristic allows steel to be formed into

different shapes with relatively little effort. When steel is used in a structure, however, measures have to be taken to protect the steel from premature temperature rise in case of fire. The objective is for the

structure to remain stable for the time needed to permit evacuation of occupants and for fire service

personnel to complete search and rescue operations. This report deals with the passive fire protection

materials used in the WTC towers.

1 .1 FIRE-RESISTIVE MATERIALS

The investigation revealed that structural steel in the World Trade Center (WTC) towers was protected

against the effects of fire with sprayed fire-resistive materials (SFRMs)2 or rigid fire-rated gypsum panels.

There are many types of SFRMs, but they can be characterized in terms of how they protect the steel and

their density (Gewain et al. 2003). One class of SFRMs protects the steel by providing a material with a low thermal conductivity, such as mineral fibers. The fibers and binder are packaged as dry ingredients,

and water is added by a pressurized system as the materials are sprayed onto the steel. The water mixes

with the binder materials and provides "stickiness" that allows the SFRM to adhere weakly to the steel. With time, the binder hardens, and excess water evaporates. When dry, these SFRMs provide a low

thermal conductivity barrier to reduce the rate of temperature rise during a fire.

The other class of SFRMs can be termed as "energy absorbing" (Gewain et al. 2003). This means that they incorporate cementitious materials that have chemically bound water (water of crystallization).

When the material is heated, energy is absorbed in transforming the chemically bound water to free water,

and this hinders the temperature rise of the coated steel. Examples of cementitious materials that have

been used successfully include gypsum and magnesium oxychloride (Gewain et al. 2003). These types of

SFRMs may also include very low-density aggregate particles, such as vermiculite or perlite, to reduce

density and thermal conductivity. Cementitious SFRMs are typically mixed with water to produce a cohesive and pumpable mixture that is sprayed onto the steel.

Figure 1-1 is a photograph of two types of SFRMs. The material on the left is a gypsum based

cementitious SFRM containing vermiculite aggregate, and the material on the right is a fibrous SFRM.

Note that the cementitious SFRM specimen in the photograph was prepared by casting in a mold, not by

spraying onto a surface. Thus, the surface texture is not representative of what would be obtained in the

field.

Sprayed fire-resistive materials are also characterized by their density. Low-density materials have

densities in the range of 15 lbs/ft

3 to 20 lbs/ft3

; medium density materials are generally in the range of

20 lbs/ft

3 to 40 lbs/ft

3

. The density of the SFRM is closely related to its cohesive strength and its

2 These sprayed fire-resistive materials are commonly referred to as "fireproofing." This term is, however, not used in the

technical literature. In this report "SFRM" and "thermal insulation" are used to refer to the passive fire protection materials.

NISTNCSTAR 1-6A, WTC Investigation l
Chapter 1

durability. Low-density SFRMs can be removed readily with hand tools and are not suitable for applications where the surface is exposed to weather or abrasion in service (Gewain et al. 2003).

Figure 1-1. Examples of sprayed fire-resistive materials: (left) material based on gypsum

and vermiculite aggregate; (right) material based on mineral fibers and cementitious

binder.

Analysis of the effects of the fires on the structural capacity of the damaged WTC towers as a function of

time requires knowledge about the condition of fire-resistive materials on the various structural components, namely, the exterior columns, the spandrel beams, the floor trusses, and the core columns.

Because of the method of application, sprayed fire-resistive material will have variable thickness,

especially when applied to long, thin elements such as the diagonals and chords of the floor trusses. In

addition, some insulation was dislodged during the impact, either from direct impact by debris or from

vibrations of the members. The thermal properties of the insulation also need to be known as a function

of temperature.

The thermal-structural analysis of the WTC towers focused on two objectives: (1) analysis of the

undamaged buildings exposed to conventional building fires, and (2) analysis of the buildings damaged

by the aircraft impact exposed to the subsequent fires. To reduce the uncertainties in the calculated

thermal histories of various structural elements, the thermophysical properties and condition of the

passive fire protection as it existed on September 11, 2001, had to be estimated as accurately as possible.

In addition, reasonable estimates of the extent of SFRM dislodged by the aircraft impact and the resulting

debris field had to be made.

To provide context for the information in this report, an overview of concepts used in U.S. building codes

for structural fire resistance is presented first. This is followed with a summary of the construction

history of the sprayed fire-resistive material in WTC 1 and WTC 2. To gain an understanding of the

effect of SFRM thickness and its variability on the steel temperature during exposure to fire, results are presented of a sensitivity study based on a simple finite-element model. This is followed by a quantitative assessment of in-place thickness and its variability based on available data. The rationale for

Source: NIST.

1.2 SCOPE OF REPORT

2 NIST NCSTAR 1-6A, WTC Investigation
Introduction

the thickness of SFRM to be used in the structural fire endurance analyses is presented. The tests conducted to determine the thermal properties of insulation materials similar to those used in the WTC

towers are reviewed. The results of mechanical property tests conducted on laboratory specimens are presented, and a simplified approach for estimating the acceleration required to dislodge thermal

insulation during impact is discussed.

NISTNCSTAR 1-6A, WTC Investigation 3
Chapter 1

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4 NISTNCSTAR 1-6A, WTC Investigation
Chapter 2

Building Code Concepts for Structural Fire Resistance

2.1 ORIGINS AND INTENT OF BUILDING CODES

Fire-induced collapse of buildings is regulated generally through limits on the height and the area per

floor as a function of the types and degree of fire resistance of materials used in the structural elements.

These material characteristics are categorized as types of construction, and the associated limits are contained in so-called "heights and areas tables," which are a cornerstone of most prescriptive building

codes.

As discussed in NIST NCSTAR 1-1, the origins of building codes in the United States can be traced to insurance regulations developed in the late 19th century to limit property losses in fires (Bukowski 1997).

Thus, the intent of building height limits is to restrict taller buildings to non-combustible structural members, and the greatest fire resistance is assigned to members supporting multiple floors. The primary

concern with combustible structural members is that they can become ignited by an exposing fire and can

continue to burn (often in concealed spaces) even after the exposing fire has been extinguished, leading to collapse. The intent of increased fire resistance for members supporting multiple floors is directly related

to the higher risk of property loss in the event of failure of multiple floors. Fire resistance requirements,

however, do not take into account the actual number of stories being supported by these elements. Thus,

the same ratings are required irrespective of whether columns support 10 stories or 100 stories.

The other important height factor is the definition of a high-rise building. This is based generally on the

height above which fire department ladders will not reach, requiring that fires be fought from inside,

which is significantly less effective (and more dangerous for the firefighters). In an exterior attack, hose

streams can be brought to bear from several sides, and so-called master streams can apply large volumes

of water. An interior attack is limited to hand-held hoses supplied from standpipes and working from

interior stairways. Traditionally, high-rise buildings have been defined as those that exceed 75 ft (or six

stories above grade) in height, but some newer model codes increase this height to 100 ft as modern fire department ladders are taller.

The intent of floor area limits is less obvious, but is generally attributed to limiting property risk and to limiting the size (area involved on any floor) of the fire to that which can be dealt with by the fire department, with the number of people and equipment typical of an initial response.

Construction types (or groups) are defined in the model building codes and in NFPA 220 (NFPA 220,

1999) and, while there are some variations in categories, they are reasonably consistent. The main

This reference is to one of the companion documents from this Investigation. A list of these documents appears in the Preface

2.2 construction types

to this report.

NIST NCSTAR 1-6A, WTC Investigation 5
Chapter 2

categories are Type I (fire resistive), Type II (non-combustible), Type III (ordinary), Type IV (heavy

timber) and Type V (combustible).

Types I and II are constructed with non-combustible exterior and interior bearing walls and columns,

where fire resistance ratings are greatest for Type I, and Type II is any (non-combustible) construction not meeting Type I requirements. Type III is where exterior bearing walls are non-combustible, and interior bearing walls and some columns may employ approved combustible materials. Type IV is known as heavy timber, which utilizes large, solid cross section wooden members such as in post-and-beam

construction. Type V is traditional wood frame construction. Common non-combustible structural elements employ steel or reinforced concrete. Combustible structural elements are usually solid wood,

engineered wood, and laminates.

Combustibility of the materials in the structural element is determined in accordance with ASTM E 136

(ASTM 2004a) in which the material is placed in a furnace at 750 °C (1,380 °F). Some minor surface

burning (e.g., from paint or coatings) is allowed in the first 30 seconds, but there cannot be any significant

energy released as determined by more than 30 °C (54 °F) increase in the furnace temperature, and the

sample cannot lose more than half its initial mass. Materials that pass are designated non-combustible,

and the rest are combustible. In 1973, an in-between category of "limited combustible" was added to ASTM E 136 to regulate some structural materials.

Within each construction type are several sub-categories determined by the fire resistance ratings of the

columns (vertical structural elements that support predominantly gravity loads and the actions of lateral loads), beams (horizontal structural elements that support predominantly live loads), and floor supports.

In some model codes these sub-categories are identified by letters following the type (e.g., IB or IIIA)

(IBC 2003) or by a set of three numbers that represent the fire resistance required (in hours) of the

exterior bearing walls; columns, beams, girders, trusses and arches supporting bearing walls, columns, or loads from more than one floor; and floor construction, respectively (e.g., Type I [3, 3, 2]) (NFPA 5000,

2003). The Annex of NFPA 220 (2006 Edition) includes a table that cross-references different

construction types in various model codes.

2.3 FIRE RESISTANCE OF STRUCTURAL ELEMENTS

Building codes require that structural elements be protected to achieve a specified fire resistance rating,

expressed in hours (Buchanan 2001; Bukowski 2003). The fire resistance rating of structural materials

and assemblies is generally determined through testing, and in the United States, such testing is frequently

conducted in accordance with ASTM Test Method E 1 19 (refer to NIST NCSTAR 1-6B4 for a discussion

of this procedure). The objective of requiring minimum fire ratings is for the building to support design

loads (including fire) without local structural collapse until occupants can escape and the fire service can complete search and rescue operations. Further, in high-rise buildings, local collapse is to be prevented

while the fire service undertakes suppression operations.

With regard to total collapse, the intent of the code is for this not to occur for any design condition

(including design fires), but it is recognized that collapse might occur in an extreme event

4 This reference is to one of the companion documents from this Investigation. A list of these comments appears in the Preface

to this report.

6 NIST NCSTAR 1-6A, WTC Investigation
Building Code Concepts for Structural Fire Resistance

(Buchanan 2001: Bukowski 2003). For an extreme event, collapse should not occur until the building has

been evacuated of both occupants and firefighters.

Building codes generally require the highest fire resistance for columns and elements supporting multiple

floors, and somewhat less resistance is required for columns supporting single floors, for beams, and for

floors. For example, NFPA 5000, Building Construction and Safety Code (NFPA 5000, 2003), requires

exterior bearing walls or columns supporting one or more floors to have the same fire resistance rating,

but for interior bearing walls or columns the fire resistance rating is one hour less if only a single floor is supported. Historically, similar requirements were found in other model codes such as the Building

Officials and Code Administrators (BOCA) Basic Building Code and the Southern Building Code

Congress International (SBCCI) Standard Building Code, which have been replaced by the International

Code Council's International Building Code (Bukowski 1997).

The required fire resistance ratings have been reduced in recent years as fire sprinklers have become

universal in high-rise buildings and common in most other commercial buildings (Messersmith 2002).

Where high-rise buildings generally required a 4 h rating for columns, this has been reduced to 3 h in recent codes, and can be as low as 2 h in current model codes based on the additional mandatory

requirement for sprinklers. This reduction in fire rating requirements for structural components in sprinklered buildings is usually referred to as sprinkler "trade-offs" (Buchanan 2001; Messersmith 2002).

NISTNCSTAR 1-6A, WTC Investigation 1
Chapter 2

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8 NISTNCSTAR 1-6A, WTC Investigation
Chapter 3

Historical Review Related to Passive Fire Protection of

WTC Towers

3.1 AGREEMENTS BETWEEN PORT AUTHORITY AND NEW YORK CITY

DEPARTMENT OF BUILDINGS AND FIRE DEPARTMENT

The World Trade Center (WTC) towers were built by the Port of New York Authority, which in 1972

became known as the Port Authority of New York and New Jersey and is hereinafter referred to as the Port Authority. As an interstate agency created under a clause of the U.S. Constitution permitting

compacts between states, the Port Authority is not bound by any local authority having jurisdiction, in

this case the New York City (City) Department of Buildings. Thus, the Port Authority was not required

to comply with the New York City Building Code or any other building code; however, the Port Authority made explicit statements that it would comply with the Code.

In a letter dated May 15, 1963 (see Appendix A Fig. A-l), the Port Authority instructed its consulting

engineers and architects to comply with the New York City Building Code. In the areas where the Code

was not explicit or where technological advances made portions of the Code obsolete, it directed that design may be based on acceptable engineering practice. At that time, the 1938 edition of the New York

Building Code was in effect, and a revised code was being drafted. On September 29, 1965, in a letter from Malcolm P. Levy to Minoru Yamasaki, the Port Authority instructed the designers of the WTC

towers to revise the design plans to comply with the second and third drafts of the Code revision (see

Appendix A Fig. A-2). The revised Building Code became effective in December 1968.

In 1993, the Port Authority and the New York City Department of Buildings entered into a Memorandum

of Understanding (see Appendix A Fig. A-3) establishing procedures to be followed by the Port Authority

for any building construction project undertaken by the Port Authority or any of its tenants at buildings

owned or operated by the Port Authority and located in the City's jurisdiction. While the long-standing

policy of the Port Authority was that its buildings meet or exceed the New York City Building Code

(Code) requirements, the 1993 agreement restated the commitment. Among other key points, it was

agreed that:

• Each project would be reviewed and examined for compliance with the Code;

• All plans would be prepared, sealed, and reviewed by New York State licensed professional

engineers or architects; and,

• The Port Authority engineer or architect approving the plans would be licensed in the State of

New York and would not have assisted in the preparation of the plans.

A supplement to this memorandum of understanding was executed in June 1995, which permitted tenants

to use New York State licensed architects or engineers, in lieu of a Port Authority review, to certify that construction plans conformed to the Code and that construction was performed in accordance with the

plans (see Appendix A Fig. A-4). In September 1995, the supplement was modified to permit a single

NISTNCSTAR 1-6A, WTC Investigation 9
Chapter 3

licensed consultant to certify the plans and the construction, except if the alteration would change the

occupancy group of the space.

"In order to maintain and enhance the safety" of its facilities, the Port Authority "adopted a policy

providing for the implementation of fire safety recommendations made by local government fire departments after a fire safety inspection of a Port Authority facility" as stated in the introduction of a Memorandum of Understanding between The Fire Department of the City of New York (FDNY) and the Port Authority of New York and New Jersey executed on December 30, 1993 (see Appendix A Fig. A-5).

The purpose of the agreement was to restate the Port Authority's commitment to the policy, and the

agreement included the following statements:

• "FDNY, acting through its Bureau of Fire Prevention ("BFP"), shall have the right to conduct fire safety inspections at any Port Authority facility located in the City of New York..."

• "BFP will issue a letterhead report of its fire safety findings and recommendations for corrective

action with respect to any deficiencies forming a part of such findings addressed to the Port Authority's General Manager of Risk Management operations. .."

• ". . .The Port Authority policy is and will continue to be to assure that such new or modified fire safety systems are in compliance with local codes and regulations..."

In 1995, the Memorandum of Understanding between FDNY and the Port Authority was amended with

respect to additions to or modifications of fire safety systems. The Port Authority was required to notify

the Bureau of Fire Protection prior to installing new systems or modifying existing systems. In addition,

plans for these systems were to be prepared by New York State licensed professional engineers or

architects (see Appendix A Fig. A-5).

3.2 NEW YORK CITY BUILDING CODE REQUIREMENTS

3.2.1 Occupancy Groups

Application of the New York City Building Code provisions affected, among other things, the assigned

building classification and, thus, the required fire rating of the WTC towers and their structural members.

It should be recalled that the Code was under revision during the design of the WTC towers.

Sub-article 301.0 of the 1968 New York City Building Code established occupancy classifications based on the use of a building and spaces. It divided occupancy into nine groups, A through I, as follows:

• A—High Hazard;

• B—Storage;

• C—Mercantile;

• D—Industrial;

• E—Business;

10 NISTNCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

• F—Assembly;

• G—Educational;

• H—Institutional; and,

• I—Residential.

As office buildings, the WTC towers were classified as Occupancy Group E. This classification was

confirmed in a letter dated May 14, 1969 from Malcolm P. Levy of the World Trade Department to Milton Gerstman of Tishman Realty & Construction Company, Inc. (see Appendix A Fig. A-6).

3.2.2 Construction Classification and Fire Rating

Additionally, there were other factors that determined the "classification" of a building and, consequently,

its required fire rating: combustible versus noncombustible construction, sprinklered versus unsprinklered

spaces, and building height and floor area limitations. Sub-articles 314.0 and 315.0 of the 1968 Code

identified two construction groups: Noncombustible Construction (Group 1) and Combustible

Construction (Group 2). The WTC towers were classified as Construction Group 1 because their walls,

exit ways, shafts, structural members, floors, and roofs were constructed of noncombustible materials.

The investigation revealed that at the time of design and construction, the towers were not sprinklered.

The 1968 New York City Building Code defined five Classes within Construction Group 1. For Business

occupancy, each Class required a fire endurance rating as follows (NYCBC 1968):

• Construction Group 1A: 4 hour protected

• Construction Group IB: 3 hour protected

• Construction Group 1C: 2 hour protected

• Construction Group ID: 1 hour protected

• Construction Group IE: unprotected

As mentioned in Section 2.3, fire endurance is a rating, given in hours, established in accordance with the ASTM E 1 19. Fire endurance is also referred to as fire rating or fire index.

To provide perspective, the 1961-1962 revision to the 1938 New York City Building Code required that the 1 1 0 story towers be classified as "Class 1 - Fireproof Structures," which includes office buildings

(NYCBC 1961-1962). This meant that the columns were required to have 4 hour fire endurance while the

floor system was required to have 3 hour fire endurance.

In Sub-articles 405.0 and 406.0 of the 1968 New York City Building Code, area and height limitations for unsprinklered buildings of Construction Group 1 with a Business Occupancy were as presented in Table 3-1 (NYCBC 1968). The WTC towers, WTC 1 and WTC 2, had roof heights of 1,368 ft and

1 ,362 ft, respectively, and each tower had a floor area of approximately 43,100 ft

2

. As Table 3-1

indicates, the WTC towers could have been classified as either Class 1 A or Class IB.

NISTNCSTAR 1-6A, WTC Investigation l l
Chapter 3

Table 3-1. Area and height limitations for unsprinklered buildings for Noncombustible

Class 1A Class IB Class 1C Class ID Class IE

Area No Limit No Limit No Limit 17,500 ft

2 10,500 ft

2

Height No Limit No Limit 85 ft 75 ft 40 ft

3.3 CLASSIFICATION OF WTC TOWERS

It was the practice at the time, and continues to be the practice, for the architect to establish the building

classification, fire rating of members and systems, and thermal protection requirements. On the subject of

fire rating in accordance with the New York City Building Code revision effective December 6, 1968, a Port Authority memorandum dated January 15, 1987, from Lester S. Feld to Robert J. Linn states that Emery Roth & Sons (ER&S), the Architect of Record for the towers, had classified the WTC towers as Class IB since there was "no economic advantage in using Class 1 A Construction" (see Appendix A

Fig. A-7).

According to the 1968 New York City Building Code, construction classification IB provided, in part, the

following fire protection requirements:

• Enclosure of vertical shafts, exits, passage-ways, and hoistways shall have a 2 hour fire endurance;

• Columns, girders, trusses, other than roof trusses, and framing supporting one floor shall have a 2 hour fire endurance;

• Columns, girders, trusses, other than roof trusses, and framing supporting more than one floor

shall have a 3 hour fire endurance; and

• Floor construction including beams shall have a 2 hour fire endurance.

• Roof construction including beams, trusses, and framing including arches, domes, shells, cable

supported roofs, and roof decks (for buildings over one story in height) shall have a 2 hour fire endurance.

Generally, fire ratings would appear on the application submitted for approval to the New York City

Department of Buildings. In the case of the towers, however, no plans or forms were filed because the Port Authority was not subject to the New York City Building Code (see Appendix A Fig. A-7).

3.3.1 Specifications for Passive Fire Protection

In the case of the WTC towers, there appears to have been a problem related to the sprayed fire-resistive material specifications. A letter dated February 11, 1969, from Douglas Fernandez of Emery Roth &

Sons to Joseph A. Schwartzman of the Port Authority indicates that in early 1 969 the Port Authority had

rewritten the SFRM specifications (see Appendix A Fig. A-8). In the process of rewriting, the following

key paragraph specifying the fire rating requirements for the structural members was apparently omitted:

12 NISTNCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

"Finished thicknesses of applied material over the various component

steel parts requiring fireproofing shall be great enough to qualify the

fireproofed parts for a three (3) hour rating (support beams, steel deck

work) and a four (4) hour rating for all pick-up girders, if any, and

columns."

ER&S continued:

"We cannot be expected to accept responsibility for specifications which

have been revised in such a manner; that which we originally stated clearly and simply, has become a meaningless document."

3.3.2 Response to Local Law 5/1973

In 1973, New York City Local Law No. 5 amended the New York City Building Code (effective

January 18, 1973). Local Law No. 5/1973 required, in part, the retrofit of existing unsprinklered office

buildings 100 ft or higher and having heating, ventilating, and air conditioning (HVAC) systems that serv e more than the floor on which the equipment is located. To conform to Local Law 5/1973, the New

York City Department of Buildings permitted either (NYCLL5/73 1973):

• Subdividing the floor area into compartments of specified square footage by fire separations ( 1 h

or 2 h fire rated depending on the size of the compartment), or

• Providing sprinkler protection.

Owners of unsprinklered buildings were required to comply according to the following timetable from the

effective date of the law (NYCLL5/73 1973):

• At least 1/3 of the non-complying floor area shall be completed in 5 years;

• At least 2/3 of the non complying floor area shall be completed in 10 years; and,

• The entire building shall be completed in 15 years. A code compliance evaluation conducted in 1997 indicated that that all tenant floors in the two towers

had been retrofitted with sprinklers (sprinklered) with the exception of four floors in WTC 1. In a 1999

update by the Port Authority it was noted that all tenant floors had been sprinklered and work was

underway to complete sprinklering of the sky lobbies (see Appendix A Fig. A-9).

The 1999 revision of the New York City Building Code placed a 75 ft height limitation on unsprinklered

buildings of Construction Groups 1 A, IB. 1C, and ID. Sprinklered buildings, however, had no height

limitations for Construction Group 1A, IB, and 1C. Thus, the retrofitted WTC towers could have been

reclassified as Class 1C (2 hour protected) (NYCBC 2001 ). As Class 1C, the columns and floor systems

would have required 2 h and 1

XA h fire ratings, respectively.

In preparation for leasing the WTC buildings to Silverstein Properties in 2000, the Port Authority

commissioned a property condition assessment. The report titled "Property Condition Assessment of

World Trade Center Portfolio," which was prepared for the Port Authority by Merritt & Harris, Inc. states

NISTNCSTAR 1-6A, WTC Investigation 13
Chapter 3

that the WTC towers were classified as "Class IB - noncombustible, fire-protected, retrofitted with

sprinklers in accordance with New York City Local Law 5/1973" (see Appendix A Fig. A- 10).

3.4 SELECTION OF FIRE-RESISTIVE MATERIALS

3.4.1 Floor Trusses

Classification of a building leads to its overall fire endurance rating and ratings of the various structural components. The New York City Building Code, however, does not prescribe how the required fire endurance rating is to be achieved. Rather, the means for providing passive fire protection is established

by the Architect of Record and depends, in part, on the structural materials used in the construction.

In the case of the WTC towers, the primary structural material was steel. Steel, in general, requires

passive fire protection to achieve code-prescribed fire ratings. The Port Authority chose to protect the

main structural components such as columns, spandrel beams, and floor trusses with sprayed fire-resistive material. This thermal protection technique was an established method for protecting columns, beams,

and walls. In the 1960s, however, composite steel truss-supported floor systems were usually protected

using "lath and plaster" enclosures or fire-rated ceiling tiles.

Based on copies of construction drawings provided to NIST, it was established that the floor system used

in the towers consisted of open-web floor trusses acting as a composite system with a 4 in. thick

reinforced lightweight concrete slab over metal decking. The main composite trusses, which were used in pairs, were spaced 6 ft 8 in. on center and had a nominal clear span of either 60 ft or 35 ft. The steel floor trusses were fabricated with double-angles for the top and bottom chords and round bars for the webs.

Additionally, the floor system included bridging trusses (perpendicular to main trusses) spaced 13 ft 4 in. on center. Figure 3-1 shows a mock-up of the floor truss system that was manufactured for the WTC

towers by Laclede Steel Co. Figure 3-2 shows the basic configuration of the composite floor truss system.

Source: Photograph from about 1967 from Laclede Steel Co.

Figure 3-1 . Mock up of floor truss system.

14 NISTNCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

Concrete Metal Deck

\ /

Main Truss

Figure 3-2. Schematic of composite floor truss system.

A review of the process involved in the selection of the thermal protection for the floor trusses is provided

in a 1975 report by Skilling, Helle, Christiansen, Robertson (see Appendix A Fig. A-l 1). According to the report, the use of "demountable ceilings" was considered as a possible method by the Port Authority

and its consultants as early as 1963, but other "efficient and economical" protection methods were sought.

By late 1965. the use of sprayed fire-resistive material applied directly to the floor trusses "appears to have been selected."

Since application of sprayed fire-resistive materials to slender steel members, as in the floor trusses, was

an innovative fire protection method and not consistent with prevailing practice, the Port Authority

arranged for demonstrations to establish its feasibility for the World Trade Center. These demonstrations were mentioned in intra-office correspondence by Laclede Steel Co. (see Appendix A Fig. A- 12). The

demonstrations also aimed to provide information on the amount of material loss that could be expected

when spraying the floor truss elements. In August of 1967, application of Zonolite's Monokote was

demonstrated to the Port Authority's engineers (Fig. 3-3) at the Madison, IL plant of Laclede Steel Co.

After observing the demonstrations, Laclede Steel stated:

"With the successful application of spray-on insulation an entire new

scheme of fire safe building construction is possible for steel joists in that the fire protection of the joists would permit the installation of low cost acoustical ceilings with access to utility lines that have not be[en]

possible in the two hour rated buildings before."

and

"In any event, the fireproofing of joists seems to be a problem now

solved, and in the World Trade Center as well as in other steel joist

structures, we may be sure that an economical fireproofing can be

effected in the field without the expense of heavy ceiling construction."

NISTNCSTAR 1-6A, WTC Investigation 15
Chapter 3

Source: Provided by Laclede Steel Co.

Figure 3-3. Demonstration of application of Monokote sprayed fire-resistive material to

floor trusses.

A similar demonstration of a sprayed thermal insulation from U.S. Mineral Products Co. was conducted

in September 1967 (see Appendix A Fig. A- 13). In other construction documents and correspondence

reviewed by NIST, this material produced by U.S. Mineral Products Co. was identified typically as CAFCO D or CAFCO Type D.

5

In November 1968, the Port Authority authorized award of Contract WTC-1 13.00 on Spray Fireproofing

to Mario & Di Bono Plastering Co., Inc. (see Appendix A Fig. A- 14). The company was the

subcontractor to Alcoa for application of sprayed thermal insulation to the exterior columns, and the Port Authority reasoned that "contract administration problems would be minimized and coordination between

fireproofing work on the interior structural steel and the exterior columns would be facilitated if a single contractor were to perform such work" (see Appendix A Fig. A- 15).

3.4.2 Perimeter Columns

By May 1966, several thermal insulation materials were being considered for the perimeter columns (see

Appendix A Fig. A- 16). This insulation was needed not only for fire protection but also to control steel temperatures under service conditions (see next paragraph). The materials under consideration were

Spraycraft (sprayed asbestos fiber), Monokote6 (sprayed cementitious vermiculite), U.S. Gypsum Fire

Code (laminated gypsum board), Vonco (sprayed magnesium oxychloride material), and BLAZE5 CAFCO is the acronym for Columbia Acoustics and Fireproofing Co., a subsidiary of U.S. Mineral Products Co. In other NIST NCSTAR reports and elsewhere in this report, the same material may be referred to as BLAZE-SHIELD D (or BLAZESHIELD Type D).

6 The document shown in Fig. A- 16, refers to this material as "Monocoat."

16 NIST NCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

SHIELD Type D. The thermal insulation for the inside face of the columns was assumed to be 1 3/8 in. gypsum plaster, having a conductivity of 1.56 Btu-in/hr-ft

2 - 0F. An overall transmission coefficient of

0.396 Btu/hrft~-°F between the room and column was also assumed for calculation purposes (see

Appendix A Fig. A- 17).

In December 1966. Aluminum Company of America (Alcoa) presented its proposal for participation in the wall construction of the World Trade Center towers. The proposal stated (see Appendix A Fig. A- 18):

"The "'insulation materials applied to the structural steel components of

the wall (columns and spandrels) must serve to control column

temperature to a minimum of 50° with 70° inside and 0° outside, provide

fireproofing to meet a four hour test on a heavy column, and minimize

heat loss and gain to satisfy HVAC requirements.

Alcoa proposed the application of BLAZE-SHIELD (of a type described in UL report R3749-10) to three

sides of exterior columns. The fire-resistive material would be thick enough to provide 4 h fire rating.

Specifically, Alcoa proposed fire-resistive material thicknesses of 1 7/16 in. for exterior columns and lA

in. for spandrels (see Appendix A Fig. A- 18).

For the inside face of the columns. Alcoa proposed to apply a high "k" value (thermal conductivity)

material. This application would provide thermal protection while permitting heat migration from the room air to the column steel under service conditions. Figure 3-4 illustrates the thermal protection design

for the perimeter columns.

1-6"

Panel

Typical Column

Aluminum Cover Figure 3-4. Thermal insulation for perimeter columns.

NISTNCSTAR 1-6A, WTC Investigation 17
Chapter 3

On August 3-4, 1967, an inspection of the quality of fire-resistive material application on an exterior

column and spandrel was carried out on a mock-up developed at the Alcoa-Cupples plant in St. Louis,

MO. Representatives of Mario & Di Bono Plastering Co., Inc, United States Mineral Products Co., and

the Port Authority were present during the inspection. Columns and spandrels were sprayed using

BLAZE-SHIELD Type D. In an internal Port Authority memorandum dated August 8, 1967, it was noted

that the application of thermal insulation "was done in a workmanship like manner... with ease and very

little spillage" (see Appendix A Fig. A- 19).

3.4.3 Core Columns

Copies of architectural drawings provided to NIST indicated that the core columns were protected with

fire-rated gypsum wallboard, sprayed fire-resistive material, or a combination of these. Core columns

located in rentable and public spaces, in closets, and mechanical shafts were enclosed typically with two

layers of Vi in. gypsum wallboard and were inaccessible for inspection. The extent of gypsum enclosure

around a core column varied depending on the location of the column within the core (see NIST

NCSTAR 1-6). In all cases, however, sprayed fire-resistive material was applied on those faces that were

not in direct contact with the gypsum enclosure. Again, the selected sprayed fire-resistive material was BLAZE-SHIELD Type D.

Columns located at the elevator shafts were the only columns in the core that were not enclosed and thus were accessible for routine inspections. The columns located at the elevator shafts were protected

originally with BLAZE-SHIELD Type D., but other materials were used when dislodged thermal

insulation was reapplied (see Chapter 4).

3.5 SPECIFIED THICKNESS OF FIRE-RESISTIVE MATERIALS

3.5.1 During Construction

The thickness of fire-resistive material necessary to achieve the required fire endurance was being

assessed in 1965, more than three years before the award of the thermal protection contract. Correspondence from Julian Roth (ER&S) to Malcolm P. Levy (Port Authority) stated that "the one-inch

thick material meets the 3 hour requirements of both the new code and Underwriters. (See Appendix A

Fig. A-20). Follow-on correspondence from Julian Roth to Malcolm Levy stated the following (see

Appendix A Fig. A-21):

"Although the one-inch spray-on fireproofing meets the 3 hour requirements of both the

proposed Building Code and Underwriters, advance information from manufacturers

indicates that if the truss were required to be fire-tested, then two inches of material

would be required for the light angle members. We are therefore revising our working

drawings to indicate a one inch thickness of spray-on fireproofing around the top and

bottom chords of the trusses, and two-inch thickness for all other members of the

trusses."

Neither of these communications identified the manufacturer or type of fire-resistive material.

L8 NIST NCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

WTC project specifications for spray-applied fire-resistive material do not provide required material

thickness or hourly ratings. Correspondence in September 1969 from Mario & Di Bono Plastering Co. to Tishman Realty & Construction Co. indicated the following thicknesses (see Appendix A Fig. A-22):

"1. Beams throughout buildings -

XA inch.

2. Columns 1 3/16 inches.

3. Elevator columns - 1 inch total including overspray.

4. Bar joist - 1 inch overall thickness.

5. All beams in MER rooms and utility rooms will be Vi inch thickness

with overspray. No tamping or shaping of Cafco type D."

A letter dated October 30, 1969, from Robert J. Linn (manager, Project Planning, WTC) to Mario & Di

Bono Plastering Co. stated, in part (see Appendix A Fig. A-23):

"...Tower 'A' columns that are less than 14WF228 will require 2 3/16"

thick of 'Cafco Glaze-Shield 'Type D" spray-on fireproofing. All

Tower columns equal to or greater than 14WF228 will require 1 3/16" of

fireproofing. .

All Tower beams, spandrels and bar joists requiring spray-on

fireproofing are to have a 1/2" covering of 'Cafco.

7

The above requirements must be adhered to in order to maintain the

Class 1-A Fire Rating of the New York City Building Code."

NIST's review of available documents has not uncovered the reasons for selecting BLAZE-SHIELD

Type D or the technical basis for specifying Vz in. thickness of insulation for the floor trusses. Note that

this letter indicates that in October 1969 it appeared that the towers were considered as Class 1A

construction.

Technical literature from U. S. Mineral Products Co. (USM) dated 1966-1967, included a table indicating

that Vz in. of BLAZE-SHIELD Type D would provide a 4 hour rating for beams, girders and spandrels,

citing authority of UL tests performed according to ASTM E 1 19 (see Appendix A Fig. A-24). The

1966-1967 USM product literature does not address bar joists with thermal insulation sprayed directly on

the truss members. Instead, the fire protection for joists was shown as an enclosure of thermal insulation.

By way of comparison, the product catalog recommended 2-3/16 in. of BLAZE-SHIELD Type D for light

columns (columns lighter than W14x228) to achieve the same 4 hour rating.

The October 30, 1969 letter from Linn to Di Bono did not make explicit reference to the required

thickness of thermal insulation for core box columns or exterior built-up columns. Alcoa was the supplier

of the aluminum cladding on the exterior columns (Contract WTC 400.00). As indicated in Fig. A- 18 of

Appendix A, Alcoa's contract included providing thermal insulation for the exterior columns and

spandrels. The following "Note 1 1" was included among the "General Notes" of the Alcoa drawings for exterior cladding (See Appendix A Fig. A-25):

1 1 . Exterior column and spandrel fireproofing-Cafco Blaze Shield

Type D Fireproofing. Interior column and spandrel fireproofingVermiculite plaster aggregate fireproofing with finished plaster coat on exposed areas of columns. (3 hr on spandrels, 4 hr on cols)

NISTNCSTAR 1-6A, WTC Investigation 19
Chapter 3

Fireproofing Thickness

Rating Cafco Vermiculite Aggregate

4 hr (heavy column) 1 3/16'

n 7/8

3 hr (spandrels) 1/2' 1/2'

ii

Note the 4 h and 3 h ratings within the parentheses are consistent with Class 1 A construction.

In a letter dated July 25, 1966, from Emery Roth and Sons to the Port of New York Authority, it is stated "Since the deck is non-structural it will not be fire proofed" (see Appendix A Fig. A-26). As discussed in Section 3.7, photographs taken after construction show that in some areas the underside of the metal deck was not protected, while in other areas fire-resistive material appears to be present but of undetermined

thickness and possibly resulting from over spray. Photographs also show that the dampers and damper

saddles were not protected. Additionally, it is unclear whether the bridging trusses were required to be

protected in all areas.

On April 13, 1970, New York City issued restrictions on the application of sprayed thermal insulation

containing asbestos. Since asbestos fiber was a key component of BLAZE-SHIELD Type D, the use of

this material was discontinued in 1970 at the 38th floor of WTC 1 (see Appendix A Fig. A-27). The

asbestos-containing material was "subsequently encapsulated with a spray-on hardening materiar and left in place. Thermal protection of the remaining floors of WTC 1 and all of WTC 2 was carried out using

BLAZE-SHIELD Type DC/F, a product that contained mineral wool (glassy fibers) in place of the

crystalline asbestos fibers. In May 1970, the construction manager for the World Trace Center wrote a memorandum that summarized considerations in changing from Type D to Type DC/F (see Appendix A

Fig. A-28). Correspondence dated April 24, 1970 from Underwriters Laboratories, Inc. to the Port Authority) stated that the thermal properties of BLAZE-SHIELD Type DC/F were equal to or "slightly

better" than those of BLAZE-SHIELD Type D (see Appendix A Fig. A-29). There is no record that the

required thickness of the fire-resistive material was reconsidered following the change to Type DC/F.

Table 3-2 summarizes information on the fire-resistive materials for the WTC towers after April 1970

based on the reviewed construction documents and correspondence. The "Implied Class" refers to the

construction classification implied by the hourly ratings or classification mentioned in correspondence

and construction documents.

20 NISTNCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

Table 3-2. Specified fire-resistive materials after April 1970.

Structural

Component

Members Material Thickness

(in.)

Implied

Class

Rating

(h)

Floor trusses All BLAZE-SHIELD DC/F >/2 1A 3

Interior columns

< 14WF228 BLAZE-SHIELD DC/F 2 3/16 1A 4 > 14WF228 BLAZE-SHIELD DC/F 1 3/16 1A 4

Box

columns

BLAZE-SHIELD DC/F NAa 1A

4

Interior beams All BLAZE-SHIELD DC/F y2 1A 3

Exterior

columns

"Heavy"

Exterior

faces

BLAZE-SHIELD DC/F

1 3/16

1A

4

"Heavy"

Interior face

Vermiculite aggregate 7/8 1A 4

Spandrel

beams

Exterior

face BLAZE-SHIELD DC/F lA 1A 3

Interior face Vermiculite aggregate 54 1A 3

a. NA, not available.

3.5.2 Report on 1975 Fire

In February 1975, a fire took place in WTC 1, spreading from the 9th to the 19th floor (Powers 1975)

7

. Most of the damage occurred on the 1 1th floor where the fire affected 9,000 ft

2

. After the fire, the Port Authority contracted Skilling, Helle, Christiansen, Robertson (SHCR) to assess the resulting structural damage and to report, in general, on the fire resistance of the floor system. In its report dated April 1

,

1975, SHCR communicated to the Port Authority that the fire did not cause structural damage, but it caused buckling of some top chord members of main trusses, buckling of bridging trusses, and distortion

deck support angles (see Appendix A Fig. A-30). The SHCR transmittal letter for the report stated that it was "intended to provide background ... as to the development of the fire-resistive standards for World

Trade Center and looks also at the adequacy of existing systems."

In the transmittal letter, SHCR also indicated that it held itself "as a reporter of facts - as presented in communications gleaned from the files of Port Authority," the architects, and its own files, and that it did

"not purport to have any special expertise not commonly held by other structural engineers."

Furthermore, the letter stated that "The only way to assure the existence of the fire safety of floor systems

is to be found through the participation of a fire safety engineer and/or fire testing."

The SHCR report suggested that the required thickness of BLAZE-SHIELD for the various structural members could have been determined from catalog information (1966-1967 BLAZE-SHIELD product

literature, U.S. Mineral Products Co. [USM]). As mentioned previously, USM's catalog from 1967

indicated that the product had been tested by Underwriters Laboratories, and that for beams, girders, and

spandrels, a thickness of lA in. of BLAZE-SHIELD Type D provided a 4 h rating. As mentioned, the

catalog did not provide any information on thermal protection applied directly to members of bar joists.

7 See also NIST NCSTAR MA.

NISTNCSTAR 1-6A, WTC Investigation 21
Chapter 3

Table 3-3 summarizes the "fire retardant ratings" obtained from Sweets Catalogs

8 from about 1960 to 1972 for USM's BLAZE-SHIELD products applied directly to beams, girders, and spandrels. The

information is based primarily on ASTM E 1 19 fire endurance tests. The table also presents the thermal

conductivity, k, for some of the fire-resistive material (the higher the value of k, the lower the thermal

insulation). Two items are particularly noteworthy. First, the thickness requirement was nearly halved

for BLAZE-SHIELD Type D from 1965 to 1966 based on two different test results. Second, the 1966-

1967 fire rating, based on two different test results, using lA in. of the Standard product (with better insulation properties) is one-half of that with lA in. of the BLAZE-SHIELD Type D product.

The 1975 post-fire report by SCHR stated further that thermal protection of the top chord of the floor

trusses was not necessary, except for the corner 60 ft x 35 ft quadrants of the buildings, where the floor

acted as a two-way system in bending. In the one-way portion of the floor, "the concrete slab becomes

the dominant element of the top chord." Thus, if the shear knuckle remains intact, "the structural integrity

of the top chord is not required." Additionally, for resistance to wind load "the structural steel top chord

provides only a small increment in the diaphragm strength," so the insulation may be omitted, (see

Appendix A Fig. A-30). The report also stated that fire protection of the bridging trusses was not required

because they were used "for reduction in floor 'tremor' and to reduce the effects of differential deflections

associated with gravity loads." Bridging trusses were "not required as a part of the structural system"

and, therefore, insulation could be omitted from them.

The report also addressed the performance of the floor system in the 1975 fire, stating,

"The fire of February, while reported in the press to have been very hot, did not damage a

single primary, fireproofed element. Some top chord members (not needed for structural

integrity), some bridging members (used to reduce floor tremor and the like), and some

deck support angles (used only as construction devices) were buckled in the fire - all were unfireproofed steel."

In February 2003, NIST asked the Port Authority a series of questions related to the sprayed thermal

protection for the floor system. The Port Authority replied in March, and indicated that the top chords of

the main trusses and the bridging trusses were protected (see Appendix A Fig. A-31).

* McGraw Hill Construction, http://sweets.construction.com

22 NISTNCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

Table 3-3. Information in Sweets Catalogs regarding BLAZE-SHIELD products applied

directly to beams, girders, or spandrels (with protected deck) from 1960 to1972.

Year Product

Reported Thermal

Conductivity, k

(Btuin/(hft2 °F))t§

Hour

Rating

(h)

SFRM

Thickness

(in.)

Authority

UL Design No.

1960 BLAZE-SHIELD 0.26

4 2 1/8 ULtest R3749-3

3 1 7/16 UL test CR193-2

2 1 1/8 ULtest CR193-3

1 3 4 Extr.BMS-92J

1965

BLAZE-SHIELD 0.27

4 1 ULI*#R3749-8

3 7/8 ULI# R3789-2

2 1/2 ULI# R3749-6

BLAZE-SHIELD

TypeD

None 4 7/8 ULI# R3749-11

1966

BLAZE-SHIELD

Type D

None 4 1/2 UL1# R3749-13

1966-

1967

BLAZE-SHIELD

Standard

0.27

3 7/8 ULI# R3789-2

2 1/2 UL1# R3749-6

BLAZE-SHIELD

Type D

0.34 4 1/2 ULI# R3749-13

1968

BLAZE-SHIELD

Standard

0.27 2 1/2 ULI# R3749-6

BLAZE-SHIELD

Type D

0.34 4 9/16 UL1# R3749-20

4 1/2 ULI# R3749-13

BLAZE-SHIELD

Type D

4 9/16 98-3 HR

1970 None 4 1 2 86-3 HR

2 1/2 54-2 HR

BLAZE-SHIELD

Type DC/F

4 1/2 86-3 HR

1971 0.29 4 9/16 98-3 HR

2 5/16 310-2 HR

BLAZE-SHIELD

Type DC/F

4 1/2 86-3 HR

1972 0.29 4 9/16 98-3 HR

2 5/16 310-2 HR

T U.S. Mineral Products Co. catalogs incorrectly report units of thermal conductivity as Btu/in/hr/fr/°F.

§ Thermal conductivities are reported only at ambient temperature.

t Reported to be extrapolations based on formulae contained in National Bureau of Standards Report, Fire Resistance Classifications ofBuilding Constructions, Building Materials Structures Report, BMS-92, Washington, DC 1942. Underwriters Laboratory Inc.

NISTNCSTAR 1-6A, WTC Investigation 23
Chapter 3

3.5.3 In-Place Thickness and Upgrading of SFRM

No information has been found related to the results of measurements during construction of the thickness

of thermal insulation, although thickness appears to have been checked during construction (see

Appendix A Fig. A-32). Recorded information on the in-place condition of the sprayed thermal

insulation for the floor system first appears in Sample Area Data Sheets from 1990 (see Appendix A

Fig. A-33). The data sheets commented on the state of the in-place SFRM. As an example, the data sheet

for floor 29 of WTC 1 states the following for the South West quadrant of the floor:

"Fluffy spray-on fireproofing coating the support beams, joists, and deck above the

ceiling. The thickness of the material on the beams and joists was consistently about

1/2". Regarding the deck it ranged from very sparse [sic] in areas to 1/4" in other areas. The areas we sampled were coated with a light green encapsulant."

Similar statements were recorded for the remaining quadrants of the floor. These inspections were related to litigation related to asbestos and focused on the lower floors of WTC 1, where

BLAZE-SHIELD Type D had been applied.

In 1995, the Port Authority performed a study to establish requirements for retrofit of sprayed insulation

to the floor trusses during major alterations (new construction) when tenants vacated spaces in the towers

(see Appendix A Fig. A-34). The study estimated the thermal protection requirements for the floor trusses of the towers based on "the fireproofing requirements" for Design No. G805 contained in the Fire

Resistance Directory (UL 2002) published by Underwriters Laboratories (see Appendix A Fig. A-35).

The study concluded that "a two hour fire rating for the steel floor joist trusses can be achieved by

applying a 1

lA inch thickness of spray-on mineral fiber fire protection material directly to the steel truss chords and webs." In the years between 1995 and 2001, thermal protection was upgraded in a number of

the floors affected by the fires on September 1 1, 2001 . Chapter 4 discusses data made available by the Port Authority on the thickness of the upgraded SFRM.

In 1999, the Port Authority established "guidelines regarding fireproofing repairs, replacement, and

upgrades" for the towers (see Appendix A Fig. A-36). The guidelines for tenant spaces may be

summarized as follows:

• For full floors undergoing new construction or renovation, the floor trusses should be protected

with 1 Vi in. of sprayed mineral fiber fire-resistive material. Retrofit of thermal protection

requires removal of existing material and controlled inspection.

• For "tenant spaces that are less than a full floor, undergoing either new construction or renovation," the floor trusses "need only meet the original construction standard. Fireproofing

shall be inspected and patched as required to the greater of V" or to match existing" if it has

already been upgraded to 1 Vi in.

While the primary material used to provide thermal protection to the floor system was BLAZE-SHIELD

DC/F, small areas with damaged SFRM were patched using the Monokote fire-resistive material instead

of BLAZE-SHIELD. For patching, Monokote was trowelled on rather than sprayed. In February 2000, a consultant to the Port Authority reported that, in the majority of the cases, the existing fire-resistive material required so much patching that it was more effective to replace it (see Appendix A Fig. A-37).

24 NISTNCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

The same report stated that proper application of 114 in. of BLAZE-SHIELD took between 2 and 3 passes. When fewer passes were used, the material usually failed the adhesion tests conducted after application.

The Port Authority provided examples of specifications used in alterations that required reapplication of

thermal insulation. Figure A-38 in Appendix A is an excerpt from the specifications related to 1998

upgrades to public corridors and bathrooms on the 15

th

, 18

th

, and 22nd floors of WTC 2. In this case the

specified fire resistive material was Monokote 6. Figure A-39 is an excerpt from the specifications for a tenant alteration in 2001 on the 48th floor of WTC 2. It is seen that the 2001 specifications are not as detailed as the 1998 specifications with respect to application of fire resistive material.

Buro Happold, an engineering consultant, was commissioned by the Port Authority to "conduct a fire- engineering assessment of the fire-proofing requirements of the open-web, steel joists that support the

floors in the tenant areas of Towers 1 and 2 of the World Trade Center." The final report issued in July

2000, focused on the requirements of the fire resistance of the floor system of the towers. This report

stated that BLAZE-SHIELD DC F was used on the majority of the floor trusses. Based on calculations

and risk assessment, the consultant concluded that (see Appendix A Fig. A-40).

• "The structural design has sufficient inherent fire performance to ensure that the fire condition is never the critical condition with respect to loading allowances.

• A single coat application is possible.

• Significant savings are possible.

• The target reduction of fiber content and increased long term durability can be achieved.

• Alternative materials should be considered."

As quoted, the report states that significant savings could be possible by reducing the fiber content and

considering alternative materials. The report suggested that the thickness of the SFRM could be reduced

to Vi in. if the material properties at ambient temperature are valid at higher temperatures (see

Appendix A Fig. A-40). The report recognized the lack of available temperature-dependent material data

for BLAZE-SHIELD Type DC/F. Thus, considering the uncertainties in the material properties and

having the understanding of material degradation with temperature and time, Buro Happold

recommended a thickness of 1.3 in. of fire-resistive material for the floor trusses.

Later, in December 2000, the final draft of the Property Condition Assessment of World Trade Center

Portfolio, prepared by Merritt & Harris, Inc., was presented to the Port Authority. The report stated that,

based on existing conditions (see Appendix A Fig. A-41): "The rating of the structural fireproofing in the

Towers and subgrade has been judged to be an adequate 1 hour rating considering the fact that all Tower

floors are now sprinklered." The report also noted the ongoing program, established by the Port Authority, to upgrade the fire-resistive material thickness to 1

lA in. in order to achieve a 2 hour fire rating.

NISTNCSTAR 1-6A, WTC Investigation 25
Chapter 3

3.5.4 Need for Fire Endurance Tests

Section C26-501.1 of the 1968 New York City Building Code had the following requirement with respect

to testing to establish fire resistance ratings:

'Tests—Sample of all materials or assemblies of materials required by

this code to have a fire-resistance rating, or flame spread rating, or required to be noncombustible, fire-retardant treated, or slow burning

shall be tested under the applicable test procedures specified

herein... The fire resistance rating of materials and assemblies listed in reference standard RS 5-1 may be use to determine conformance with

the fire resistance requirements of this code..."

The fire protection of a truss-supported floor system by directly applying sprayed fire-resistive material to the trusses was innovative and not consistent with prevailing practice at the time the WTC towers were

designed and constructed. While the benefits of conducting a full-scale fire endurance test were realized

by individuals involved in the 1967 demonstrations of the application of SFRM (see Appendix A

Fig. A-42), apparently no tests were conducted on the specific floor system used in the WTC towers. Emery Roths & sons (ER&S), the Architect of Record, and SHCR, the Structural Engineer of Record,

both stated that the fire rating of the floor system of the WTC towers could not be determined without

testing (see Appendix A Figs. A-26 and A-43). Communication from the Port Authority in 2003 (see

Appendix A Fig. A-31) confirms that there is no record of fire endurance testing of assemblies

representing the thermally protected floor system.

In the 1975 post-fire report, the Structural Engineer of Record noted that a floor truss system similar to

that used in the WTC had been tested in 1970 10 by Underwriters Laboratories (see Appendix A Fig. A44). This test was unrelated to the WTC project, but the test assembly included trusses from Laclede

Steel Co., a normal density concrete floor slab on steel decking, and sprayed thermal insulation. The

thermal insulation was Mono-Kote, a gypsum-based product containing vermiculite aggregate. The

thermal insulation was 1

lA in. thick on the web bars and V2 in. on the sheet metal deck. The test assembly

attained a 3 h rating. In the same 1975 post-fire report, the Structural Engineer of Record noted that Mono-Kote had about twice the thermal conductivity of BLAZE-SHIELD. Based on "many simplifying

assumptions" and approximate calculations, it was estimated that Vi in. of BLAZE-SHIELD applied to

1 in. diameter web bars and chord angles thicker than 3/16 in. would provide a 3 h fire rating (see

Appendix A Fig. A-46). He emphasized "however, that theoretical extrapolations of fire endurance tests must the viewed with caution." He stated further in another section of the 1975 report that: "Without

benefit of a full-scale fire test we cannot establish a rating for the floor assembly."

3.5.5 Calculations of SFRM Thickness for Core Members

In the 1990s, the Port Authority commissioned Leslie E. Robertson Associates (LERA) to perform a

series of structural integrity inspections on the WTC towers (see Section 3.6 and NIST NCSTAR 1-1C).

One of the tasks was to determine the thickness of fire-resistive material required to re-coat accessible

q Reference Standard 5-1 lists the applicable fire protection standards and includes ASTM Test Method E 1 19.

10 The 1975 report refers to the testing date as June 26, 1 969. The actual testing date was February 27, 1970. The former date was that of a drawing that was used in designing the fire endurance test. See Appendix A Fig. A-45 for clarification.

26 NIST NCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

beams and columns that had missing thermal insulation within the elevator shafts. Calculations presented

in a 1992 report illustrate the accepted procedure used to determine the required thickness based on the

size of the members and designs that had been tested and were listed in the Fire Resistance Directory

published by Underwriters Laboratory, Northbrook, Illinois. Extracts from the 1992 report are shown in Appendix A Fig. A-47 to illustrate the procedure. The underlying principle is that the SFRM thickness

used in the UL fire resistance tests can be modified to provide the same fire resistance rating for similar

shaped members, but with different dimensions. These calculations involve a cross-sectional property

known as W/D, where Wis the weight of the structural member per foot and D is the perimeter of the

member through which heat is transferred to the steel. A higher value of W/D means that the member has

a higher ratio of volume to fire exposed surface area and would require less thickness of thermal

insulation to have the same fire rating as a member with a lower W/D value. The UL Fire Resistance

Directory, for example, provides equations for computing the required thickness of SFRM for beams and

columns that are similar to those in the UL designs, but with different W/D values.

The 1992 LERA calculations were for the accessible columns in elevator shafts 12 and 13 in WTC 1. Thicknesses were determined for four types of fire-resistive materials: Monokote Type Z-106,

CAFCO 560. ALBI Duraspray, and ALBI Duraspray 30. These materials are denser and more durable

than the SFRM used to protect the floor trusses, and were intended to provide for better performance

within the elevator shafts. Table 3-4 lists the calculated thickness of Monokote Z-106 to achieve a 3 h fire rating for the accessible columns in shafts 12 and 13. As noted in Appendix A Fig. A-47, the UL

directory provided a thickness conversion equation only for columns protected with Monokote Type

Z-106. For the other fire-resistive materials, the required thickness was the same as in the UL listed designs, even if the W/D values of the WTC columns were different. The following were the required

thicknesses on the columns for the other SFRMs:

• CAFCO 560: thickness = 2 1 1/16 in.

• ALBI Duraspray and Duraspray 30: thickness = 1 1 1/16 in.

Another example of re-application of SFRM to core members is a 1994 document on "Refireproofing

Elevator Shafts 6 & 7 1 WTC" produced for the Port Authority by LERA. The document reported the

required thickness of Monokote Z-106 for columns 903 and 904 and for beams A and B in shafts 6 and 7 of Tower 1 (see Appendix A Fig. A-48). Table 3-5 summarizes the thermal insulation thickness

requirements for those members. Only floors from the second basement to floor 33 were scheduled for reapplication of thermal insulation.

NISTNCSTAR 1-6A, WTC Investigation 27
Chapter 3

Table 3-4. Design thickness of thermal insulation for reapplication to accessible

columns in elevator s hafts 12 and 13ofWTC 1.

Floor

Monokote Type Z- 106

UL-Design

Calculated

Thickness

Column 601

69-79 15/16 in. 15/16 in. 63-68 15/16 in. 13/16 in. 48-62 15/16 in. 11/16 in. 43^7 15/16 in. 9/16 in. 41.42 15/16 in. 7/16 in. 33^0 15/16 in. 9/16 in. 18-32 15/16 in. 7/16 in. 7-17 3/8 in. 3/8 in.

Elevation 274 - 6 3/8 in. 3/8 in. Column 602

69-79 15/16 in. 7/8 in. 54-68 15/16 in. 5/8 in. 43-53 15/16 in. 9/16 in. 41.42 3/8 in. 3/8 in. 36-40 15/16 in. 9/16 in. 18-35 15/16 in. 7/16 in. 7-17 3/8 in. 3/8 in.

Elevation 274 - 6 3/8 in. 3/8 in. Columns 501 and 502

Elevation 310 3/8 in. 3/8 in. Source: 1992 LERA calculations (240-LERA)."

1 ' This refers to the ID number in the NIST document database.

2S NISTNCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

Table 3-5. Design thickness of thermal insulation for reapplication to accessible

columns and beams in elevator shafts 6 and 7 of WTC1.

Floor Column 903 Column 904 Beam A Beam B

B2 3/8 in. 7/16 in. Note 1 15/16 in. Bl 3/8 in. 7/16 in. 1/2 in. Note 1

Elevation 294 3/8 in. 7/16 in. 7/16 in. 15/16 in.

1 3/8 in. 7/16 in. 7/16 in. 1 1/16 in.

Intermediate 3/8 in. 7/16 in. 1/2 in. Note 1

2 3/8 in. 7/16 in. 1/2 in. 1 in. 3-7 3/8 in. 7 16 in. 1/2 in. 1 3/16 in. 8-18 3/8 in. 1/2 in. 1/2 in. 1 3/16 in. 19-33 3/8 in. 5/8 in. 1/2 in. 1 3/16 in. Key: Note l=Beams are concrete encased. Source: 1994 LERA calculations (659-P).

3.6 MAINTENANCE OF SFRM IN ELEVATOR SHAFTS

Based on inspection reports reviewed by the investigation team, the structural members that required the

largest amount of inspection and maintenance within the core were the exposed columns and beams

within the elevator shafts (see also NIST NCSTAR 1-1 C). These columns and beams were the only

accessible fire-protected elements in the buildings. Adhesion failures were common, likely because of the

exposed conditions of the columns (see Appendix A Fig. A-49) and the inherently low strength of the

SFRM.

3.6.1 Bond Strength

Internal memoranda from U.S. Mineral Products Co., dating from 1960 to 1969, warned of the poor

adherence or bond performance of BLAZE-SHIELD, and specifically BLAZE-SHIELD Type D. As

communicated in an intra-office memorandum dated July 29, 1960, vibration tests performed in 1960

apparently indicated poor bond characteristics of CAFCCO BLAZE-SHIELD as manufactured in the

plant compared with laboratory mixtures (see Appendix A Fig. A-50).

In March 1968, the Port Authority investigated the adherence of BLAZE-SHIELD Type D under field conditions. Based on letters from both U.S. Mineral Products Co. and Mario & Di Bono Plastering Co.

relative to an "on-the-job" application of BLAZE-SHIELD in January 1968 to evaluate the ability of the

material to adhere to the steel and to itself, the Port Authority stated in March 1968 that "this material can

be applied successfully to the exterior steel under adverse weather conditions" (see Appendix A

Fig. A-5 1 ). The Port Authority transmitted this information to the New York City Department of

Buildings in January 1970 along with a U.S. Mineral Products Co. report on the material and application

techniques and a product catalog (see Appendix A Fig. A-52).

Adhesion problems with BLAZE-SHIELD Type D, however, were reported in December 1969 during

construction of the World Trade Center. U.S. Mineral Products Co. intra-office correspondence on December 11, 1969 stated that "Of the 20 tons [800 bags] of material sprayed to the 10

th floor exterior

NIST NCSTAR 1-6A, WTC Investigation 2')
Chapter 3

columns on this project, approximately 600-700 bags of the material washed off as clean as a whistle

from the exterior columns on this job" (see Appendix A Fig. A-53).

3.6.2 Inspections

Personnel of the World Trade Center Department inspected sprayed thermal insulation during

construction. After one of these inspections in 1971, the inspector wrote "it was noted that the Cafco

fireproofing treated with Mark II overspray had not cured or hardened according to specifications" due to the extremely cold temperature conditions existing during construction (see Appendix A Fig. A-54). The

inspector recommended that shafts 39, 40, and 41 of WTC 1 be re-sprayed with Mark II sealer. Additional WTC office correspondence dated September 24, 1973 mentioned that the sprayed thermal

insulation had come loose and fallen from perimeter box beams in elevator shafts 10 and 1 1 of WTC 2

(see Appendix A Fig. A-55).

In 1993, the Port Authority commissioned Leslie E. Robertson Associates to carry out a continuing

program to appraise the condition of the accessible columns in the World Trade Center complex. These

inspection programs are described in greater detail in NIST NCSTAR 1-1C. Accessible columns were

those columns that were not enclosed in any kind of architectural finish and could be inspected visually.

All accessible columns were located in the core of the towers. The columns were inspected visually for

signs of rusting, cracking, bowing, and loss of thermal insulation. During the first inspection, carried out

in 1993, particular shafts were chosen based on the quantity and types of accessible columns, and

convenience to the Port Authority. The findings were summarized in LERA's Structural Integrity

Inspection Report for Accessible Columns at 1,2, 4, and 5 WTC dated 29 January 1993 (see Appendix A

Fig. A-56).

Subsequent inspections involved sampling of the structural components and assemblies, which were more

important to the structural integrity of the towers, and at locations with a relatively higher potential for

defects and problems. As indicated in the Structural Integrity Inspection Report dated 14 April 1995, a

statistical sampling approach was used since concurrent visual inspection of all the accessible columns was "not a practical goal" (see Appendix A Fig. A-57). The report stated that the accessible columns in

selected elevator shafts in WTC 1 and 2 were "generally in good condition, no structural deficiencies such

as cracking or bowing were found, the most common irregularities observed were missing fireproofing

and light surface rusting of the exposed steel." Based on the inspections, LERA recommended "that

remedial action to be taken where spray fireproofing is damaged, deteriorated or missing and where there

is corrosion of the column base due to water leaks at elevator pits." LERA also recommended painting

steel with a zinc-rich paint on areas affected by water leaks prior to re-fireproofing. Refer to NIST

NCSTAR 1-1C for a comprehensive discussion of the structural integrity inspection reports.

3.7 GENERAL CONDITIONS OF SFRM ON FLOOR TRUSSES

In accordance with the descriptions of the structural systems described in NIST NCSTAR 1-2A, it was

estimated that each floor that was supported by trusses contained about 4,350 lineal ft of main trusses. Since main trusses are composed of two trusses side-by-side (see Fig. 3-2), there were over 8,700 ft of

main trusses per floor. In addition, each floor contained about 2,000 lineal ft of bridging trusses. Thus,

each floor contained over 10,500 lineal feet (or about two miles) of floor trusses. The actual length of

members that had to be protected with SFRM was, however, at least twice this length, because each truss

30 NIST NCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

cross section included two chord members and a web bar. In order to understand whether the condition of

the thermal insulation played a dominant role in the outcomes on September 11, it was desirable to have

information on the general conditions of the SFRM. Since the total collapses of the buildings dislodged

the SFRM, it was necessary to rely on available photographic evidence.

Two series of photographs provided some insight on the prevailing conditions of the SFRM on the floor

system. One of these was a series of photographs was taken in the mid-1990s by Morse Zehtner

Associates and included images from floors 12, 22, 23, and 27 of WTC 1 and floor 26 of WTC 2. These

photographs showed the following conditions of the thermal protection applied to the truss-supported

floors:

• Some floor trusses had good coverage with SFRM, but the average thickness was not uniform

along the lengths of web bars (see Fig. 3-5).

• Bridging trusses did not appear to have as much SFRM applied (see Fig. 3-6). As mentioned in Section 3.5.2, the Engineer of Record stated that bridging trusses did not require thermal

protection.

• The SFRM applied to the truss seats at the spandrel beams appeared to be thin (see Fig. 3-7).

• In some cases, the ends of main trusses near the spandrel beams appeared to have thinner SFRM,

and the saddles and dampers were not protected (see Fig. 3-7 and Fig. 3-8).

• The SFRM thickness on web bars appeared low in the vicinity of where they connected to the

chords (see Fig. 3-5 and Fig. 3-9).

• The metal decking did not appear to have been protected, which is consistent with the

requirements stated by the Architect of Record (see Section 3.5.1).

• Some damage to SRM was caused when utilities (HVAC, electrical, network cabling, and so

forth) were installed within the ceiling space occupied by the floor trusses (see Fig. 3-10).

A second series of photographs showed the conditions on the 85

th floor of WTC 2 prior to removal (by

water blast) of SFRM by the tenant, who was conducting a major alteration of the space including an upgrade to the thermal insulation in accordance with the guidelines discussed in Section 3.5.3. Photographs 12 and video were taken on March 8, March 20, April 13, and July 17, 2001. The

photographs include close-up views of different features of the thermal insulation applied to the floor trusses and overall views of large sections of the floor truss system, before and after removal of the

SFRM. Based on these photographs, the following observations were made:

• There were no examples of total absence of SFRM on trusses that had not been cleaned by water

blasting.

12 Photographs and videotapes were provided by the former tenant, Harris Beach LLP. They were taken for the tenant by a hired photographer (Forensic Photography International). NIST was not able to locate the photographer to obtain permission to reproduce the photographs in this report. The photographs, however, are available for viewing at NIST and have been

assigned ID number 223-1.

NISTNCSTAR 1-6A, WTC Investigation 31
Chapter 3

• Areas where SFRM had been dislodged had been repaired using a trowel-applied material. Some

of the repairs on lower chords were incomplete, but it is not known whether these repairs had

failed or if the repair material had purposely not been applied to some portions of the chords.

• There were many instances where SFRM had obviously been dislodged in the process of

installing utilities. In some cases hardware was attached directly to the lower chords and SFRM

was dislodged. These damaged areas should have been repaired when the various trades had

completed their work.

• The overall views of the trusses showed that regions of missing insulation where minor in extent when compared with the total area of applied SFRM.

In comparing the overall condition of the SFRM as indicated by these two series of photographs, the

following differences were noted:

• The photographs taken in the 1990s of the lower floors appeared to show more instances of thinly

applied SFRM than the photographs of the 85

th floor taken in 2001.

• The photographs taken in the 1990s appeared to show less damage as a result of installation of

utilities and other services within the space occupied by the trusses.

32 NISTNCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

Figure 3-5. Intersection of main truss and bridging truss showing general good

coverage of SFRM on truss members but thickness varies on web bars.

Figure 3-6. Intersection of main truss and bridging truss showing thinner SFRM on

members of bridging truss.

NISTNCSTAR 1-6A, WTC Investigation 33
Chapter 3

Reproduces! with permission of U.S. Mineral Products 1 Issoiatek International and Morse Zehtner Associates

Figure 3-7. Connection of main truss to spandrel beam showing relatively thin SFRM on

truss seat and no SFRM on damper.

I with permission of U.S. Mineral Products- Co. dfea

tnso-latek International and Morse Zehtner Associates

Figure 3-8. End of main truss showing low thickness of SFRM on truss members and no

SFRM on damper saddle.

34 NISTNCSTAR 1-6A, WTC Investigation
Historical Review Related to Passive Fire Protection

Figure 3-9. Intersection of main truss and bridging truss showing thin SFRM on the

ends of some web bars; SFRM was not applied to the metal decking.

Figure 3-10. Example of damage to SFRM during installation of utilities.

NISTNCSTAR 1-6A, WTC Investigation 35
Chapter 3

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36 NISTNCSTAR 1-6A, WTC Investigation
Chapter 4

As-Applied Thickness of SFRM

Because both towers collapsed totally on September 11, 2001, and most of the sprayed fire-resistive material (SFRM) was either dislodged or abraded (or scraped) off in the collapse, no examples remain of

the "as installed" condition of the SFRM. To make an estimate of the as-applied thickness and variability

in thickness, several sources of information were used, including measurements taken by the Port

Authority, condition surv eys and anecdotal information, and photographs and video clips showing the

condition of the fire-resistive material in selected areas. Each of the structural components or systems is considered here separately.

4.1 TRUSS-SUPPORTED FLOOR SYSTEM

As mentioned in Section 3.5.3, qualitative information on the in-place condition of the SFRM for the

floor system first appeared in Sample Area Data Sheets from 1990. Information regarding quantitative

inspection of existing fire-resistive material appears in documentation from 1994. That year, the Port

Authority' performed a series of thickness measurements of the existing SFRM on floors 23 and 24 of

WTC 1 (see Appendix A Fig. A-58). Six measurements were taken from "both flanges and web" of each

of 16 randomly chosen trusses on each floor at those locations where the SFRM was not damaged or

absent. The averages of six measurements per joist that were recorded on the two floors are presented in Table 4-1. Measured average thickness varied between 0.52 in. and 1.17 in. For the 32 measurements

( 16 on each floor), the overall average was 0.74 in. Four of the 32 floor trusses had average thicknesses

between 0.52 in. and 0.56 in. These measurements suggest that the minimum average thickness exceeded

1/2 in.

As shown in Fig. A-58 in Appendix A, it was stated that, on floor 23,

"... truss members located adjacent to the outside walls (within 3 ft) are devoid of fireproofing material. Visual inspection on floor 24 was not

possible, as this area still has a lowered ceiling in place."

The data in Table 4-1 can be examined further to understand the variability of the SFRM thickness in the

non-upgraded locations. Figure 4-1 (a) shows the average thicknesses measured on the floor trusses of

floors 23 and 24. The values appear to be similar for the two locations in terms of overall average

thicknesses and the variation in average thickness. A formal analysis of variance indeed indicated no

statistically significant differences between the overall mean thicknesses for the two floors. Thus, the two

groups of data can be combined into one group.

Figure 4-1 (b) is a normal probability plot of the average thicknesses shown in Table 4-1. If the data were

from the same distribution they would fall approximately on a straight line in the normal probability plot.

This is expected from the central limit theorem, which states that the sampling distribution of the average

of TV samples from a distribution with mean u and variance a" approaches a normal distribution with mean u and variance a

2/N as N increases (Miller and Freund 1965). It is seen that four points deviate

from an approximately linear relationship. It is, therefore, reasonable to conclude that those points do not

NIST NCSTAR 1-6A, WTC Investigation 37
Chapter 4

belong to the same distribution. These four values are identified with an asterisk in Table 4-1

Figure 4- 1(c) is a normal probability plot with the four values (actually six points) excluded. It is seen

that the remaining points fall close to a straight line. The intercept (0.74 in) and slope (0.12 in.) of the

straight line are the mean and standard deviation of the distribution, respectively. Since each of the

averages in Table 4-1 is obtained from six individual measurements, an estimate of the standard deviation

of the individual measurements of SFRM thickness is 0. 12V6 ~ 0.3 in.

Table 4-1. Average fireproofing thickness from six measurements taken in 1994 on each

of 16 random floor trusses on floors 23 and 24 of WTC 1.

Fireproofing Thickness (in.)

Floor 23 Floor 24

0.60 0.76

0.53* 0.60

0.70 0.90

0.76 0.72

0.88 0.64

0.89 o.so

0.83 0.68

1.17* 0.65

0.88 0.67

0.71 0.77

0.82 0.96 0.52* 0.66

0.69 0.65 0.52* 1.11*

0.64 0.95 0.52* 0.56 *Not considered in estimating thickness variability. Source: Data provided by Port Authority of New York and New Jersey.

38 NIST NCSTAR 1-6A, WTC Investigation
As-Applied Thickness of SFRM

1.2

1

0.8

0.6

0.4

0.2 —

0-

<> t

-

>

»

•

•

i•

•

1

i

f

i i i i , 22 23 24

Floor

25

1.2-

1.1

W 0.9- w

CD I

0.8-

0.7-

0.6-

0.5-

(b)

.01 .1 1 5 10 2030 50 7080 90 95 99 99.9 99.99 Percent

y = 0.737 + 0.1 18 norm(x); R= 0.98378

.01 .1 1 5 10 2030 50 7080 90 95 99 99.9 99.99 Percent

Figure 4-1. (a) Dotplot of average thickness from floor trusses for floors 23 and 24,

(b) normal probability plot of all average thickness values, and (c) normal probability plot

of average thickness with four values (six points) excluded.

NISTNCSTAR 1-6A, WTC Investigation 39
Chapter 4

4.2 ANALYSIS OF PHOTOGRAPHS

Additional data regarding the thickness of SFRM was gathered by evaluating photographic evidence.

Although photographic evidence of the state of the SFRM was limited, two groups of photographs were

located and used for estimating SFRM thickness.

The first group of photographs was provided to NIST by Morse Zehnter Associates and includes images

of floor trusses from WTC 1 (floors 12, 22, 23, and 27) and WTC 2 (floor 26). From this group, only

photographs from floors 22, 23, and 27 of WTC 1 were analyzed. Photographs provided by Morse

Zehnter Associates were taken in the mid-1990s and illustrate the fire-resistive material conditions prior

to the upgrade carried out by the Port Authority. Thus, SFRM thickness on the photographed trusses would be expected to be at least lA in. as specified by the Port Authority on October 1969.

The second group of photographs, taken in 1998, was provided by Gilsanz Murray Steficek (consulting

engineers). This group illustrates the state of fire-resistive material after the upgrade program that was

initiated in 1995. The photographs were of trusses for floor 31 and below in WTC 1.

Selection of which photographed trusses were used to estimate thickness of SFRM was based on clarity

of SFRM edges and whether a feature of known dimensions was present to provide a reference

measurement. Thus, only photographs where reference measurements could be performed were used.

The general approach to the analysis involved the estimation of distances based on the computed

reference length per pixel. The procedure is summarized as follows:

• A feature of known dimension (based on construction drawings) that could be used as reference was located in the photograph. For example, the dimension of the bare vertical leg of a damper

saddle was a dimension that could be obtained from shop drawings.

• In the photograph, the length of the reference dimension was measured in pixels.

• The scaling factor of length per pixel was computed by dividing the known dimension in inches

by the number of pixels. For example, if the vertical leg of the damper saddle was measured as 48.2 pixels in the photograph, and it is known that the actual size of the leg was 3.13 in., the

scaling factor would be 3.13 in./48.2 pixels = 0.065 in. /pixel.

• Only truss webs or struts (diagonal bar at end of truss) located near and in the same plane as the

reference object were selected for analysis. This selection was made to minimize error due to perspective.

• It was assumed that the fire-resistive material on web bars was applied evenly around the

perimeter of the bar. Based on this assumption, a 'Virtuar centerline along the length of the bar was drawn in the photograph.

• Lines were drawn perpendicular to the "virtuar centerline. The number of pixels along the lines from the "virtuar' centerline to the edge of the SFRM was determined from the cursor positions

indicated by the software. Measurements were made at regularly spaced intervals to avoid bias. Figure 4-2 is an example of a series of measurements made on a strut.

40 NISTNCSTAR 1-6A, WTC Investigation
As-Applied Thickness of SFRM

• Each measurement in pixels was multiplied by the scaling factor (in./pixel) to estimate the bar

radius plus SFRM thickness. This provides two measurements at each cross section.

• The radius of the bar was subtracted to provide the estimate of the SFRM thickness.

Figure 4-2. Example of measurement procedure used to estimate SFRM thickness from

photographs.

For floors that had not been upgraded, it was observed that the estimated thickness of SFRM on the webs

of the main trusses tended to be greater than that on either the diagonal struts or on the webs of the

bridging trusses. Hence, estimates of SFRM thickness for non-upgraded floors were divided into three

groups:

• Webs of main trusses,

• Webs of bridging trusses, and

• Diagonal strut at the exterior wall end of the truss.

It was not possible to estimate the thickness of the SFRM on any truss element except the round web bars. Consequently, for the upgraded floors in WTC 1 that were included in the second group of photographs,

only estimates of the thickness on the web bars of the main trusses were made. Figure 4-3 (a) shows

normal probability plots of the SFRM thickness estimated from the photographs. It is seen that the points

for the "upgraded" main trusses follow a generally linear trend, which indicates that the estimated

thicknesses for the upgraded main trusses are approximately normally distributed. The estimated

thicknesses from the non-upgraded floors, however, do not follow linear trends on the normal probability

plot. Figure 4-3 (b) shows normal probability plots of the natural logarithms of the thicknesses. The

transformed values for the non-upgraded thermal protection now follow generally linear trends, which

NISTNCSTAR 1-6A, WTC Investigation 41
Chapter 4

means that a lognormal distribution is more appropriate for the non-upgraded floors. Thus, there is evidence that the original SFRM thickness on the floor trusses follows a log normal distribution.

The reason for a lognormal distribution for SFRM thickness on the non-upgraded floor trusses can be

explained as follows. It is expected that the thickness of SFRM will be variable due to the difficulty in

spraying the material on the relatively thin members. If the overall thickness is low and the variability is high, a normal distribution would require a fraction of the surfaces to have negative values of SFRM

thickness, which is not possible. If the thickness distribution is lognormal, the thickness cannot be zero, and there is a low likelihood of having thickness close to zero. Thus, from a physical point of view, a lognormal distribution of SFRM thickness is more logical than a normal distribution. If the underlying

distribution of SFRM thickness is lognormal, the average thickness overestimates the thickness expected

to be exceeded with 50 percent probability, and the median is the appropriate statistic for the

50-percentile value (Melchers 1999).

The average, standard deviation, and coefficient of variation were computed for the total number of

measurements in each of these groups. The results are summarized as follows:

• Main trusses before upgrade (85 measurements): Average thickness 0.6 in., standard deviation = 0.3 in., and coefficient of variation = 0.5; median = 0.55 in.

• Bridging trusses before upgrade (52 measurements): Average thickness 0.4 in., standard deviation = 0.25 in., and coefficient of variation = 0.6; median = 0.36 in.

• Diagonal struts before upgrade (26 measurements): Average thickness 0.4 in., standard deviation = 0.2 in., and coefficient of variation = 0.5; median = 0.38 in.

• Main trusses after upgrade (52 measurements): Average thickness 1.7 in., standard deviation = 0.4 in., and coefficient of variation = 0.2; median = 1 .80 in.

4.3 PORT AUTHORITY DATA ON UPGRADED SFRM ON TRUSSES

In the 1990s, the floor trusses of several floors were upgraded to a specified thickness of VA in. of fire- resistive material as tenants vacated their space. According to correspondence in 2002 (see Appendix A

Fig. A-59), the Port Authority indicated that 18 floors of WTC 1 and 13 floors of WTC 2 had been

upgraded. The Port Authority also stated that: "The entire impact zone for Tower 1 (92-99) was upgraded

with 1

lA" spray-on fireproofing. Only the 78

th floor was upgraded with the VA" spray-on fireproofing

within the impact zone in Tower 2 (78-84)." The Port Authority provided information from Construction

Audit Reports regarding the characteristics of SFRM that was upgraded as of 2000 in the aircraft impacted regions of the WTC towers. The provided test reports state that the material used for the

upgrade was BLAZE-SHIELD II (see Appendix A Fig. A-60 for an example of such a report).

42 NISTNCSTAR 1-6A, WTC Investigation
As-Applied Thickness of SFRM

2.5

CO

CO

CDc

1.5

.2 1 -

0.5

')

i i i r i i i i i—i—i

1 1

.01 .1 1 5 10 2030 50 70 80 90 95 99 99.9 99.99 Percent

to

CO

CDc

o

"I—i—

.01 .1 1 5 10 20 30 50 70 80 90 95 Percent99 99.9 99.99

Figure 4-3. (a) Normal probability plot of estimated SFRM thickness based on

photographs, and (b) normal probability plot of natural logarithms of thickness (Data

provided by PANYNJ).

Port Authority test reports state that tests of upgraded SFRM were performed in accordance with

ASTM E 605 for thickness and density (ASTM 1993) and in accordance with ASTM E 736 for adhesive/cohesive strength (ASTM 1992). Section 8.1.1 of ASTM E 605-93 requires that thickness

measurements be taken at "One bay per floor or one bay for each 10,000 ft

2

, whichever provides the

greater number of tests." In addition, the test method states that: "Thickness determinations for the

following structural elements shall be conducted in each randomly selected bay: one selected area of

metal deck, concrete slab, or wall section; one column; and one beam (joist or truss)." For each

NISTNCSTAR 1-6A, WTC Investigation 43
Chapter 4

preselected joist (or truss), Section 8.1.5.2 of the test method requires that one 12 in. length be laid out and seven thickness measurements be taken at each end of the 12 in. length. Thus, two sets of thickness

readings are expected for each truss if ASTM E 605-93 were followed. Figure 4 of ASTM E 605-93

shows that there should be seven measurements at each cross section, which are to be distributed as follows: two at the top chord, two at the web, and three at the bottom chord.

Table 4-2 shows the test data provided by the Port Authority for the impact-affected floors.

13 Shown are the average thickness, bond strength, and density for each test area on a given floor. The specified

minimum requirements are 1

lA in. for thickness, 150 psf for bond strength, and 15 lb/ft

3 for density.

Correspondence from the Port Authority in March 2004, clarified that the words "bottom truss" in the test reports referred to the location of the bond test and where the sample was removed for density

measurement (see Appendix A, Fig. A-61 ). Note that some of the average thicknesses shown in Table 4-2 equal or exceed 3.5 in. No photos were available of upgraded floors to show the appearance of

a truss with such high average thickness of SFRJVI. There is no record in the test reports of whether the

top chord and bridging trusses were protected in the upgraded floors.

In 2004, the Port Authority provided NIST reports of the individual measurements for many of the

average thicknesses shown in Table 4-2. 14 With the individual measurements, it was possible to investigate the variation of thickness at a cross section of a truss member and the variation in average

thickness from truss to truss. To permit such analyses, only those data having the same number of

individual measurements at each cross section were used. This resulted in 18 data sets for WTC 1 (including floors 93, 95, 98, 99, and 100) and 14 data sets for WTC 2 (including floors 77, 78, 88, 89, and

92).

13 Transmittal of construction audit material testing reports by Saroj Bhol (PANYNJ), January 21, 2003 (30-P).

14 Electronic file of individual thickness values transmitted by Frank Lombardi (PANYNJ) to NIST on April 7, 2004 (682-P).

44 NISTNCSTAR 1-6A, WTC Investigation
As-Applied Thickness of SFRM

Table 4-2. Summary of Port Authority test reports for upgraded SFRM on

floor trusses (30-P).

WTC

Tower

Floor

Number Specific Location /Tenant

Date of

Report

Average SFRM

thio 1111V. IVknpss 11 1 JO (in \ 1 1 11 • 1

Adhesion/

fnhpsinn (lh/ft2\

Density

79 Mnltinlp tpnant floor 1 1 /74/00 7 4 333 11 6u.u6

\.!iiltinlp tpnant floor

81 Multiple tenant floor 10 24 96 2.7 270 19.0

1 81 Multiple tenant floor

"7 / 1 f IC\C\ 7/16/99 2.3, 2.4, 3.0 352, 463, 315 17.4, 17.6, 17.4

1

<

O I 83 Suite 8jj1 12/15/99 259 16.0 85 Multiple tenant floor 12/24/97 3.5, 2.9, 2.9 162, 180, 288 28.7, 23.7, 18.6

' 85 Multiple tenant floor 6/12/99 2.9 278 15.8

1 85

Multiple tenant floor Suite 8563

O / 1

/" lf\C\ 8/ 16/99 2.8 259 16.4

1 86 Julien Studley Inc. (7000 ft2

)

1 92 Full floor 4/2/97 3.0,2.8,2.8 360, 324. 360 20.3, 15.4, 18.0

1 93 Full floor 8/28/98

1.8, 2.0, 1.8, 2.2,

1.8, 1.9.2.9

117 (153)

+

, 207,

216, 234, 162,

1IOU, 80 716 — 1

'

14.2, 16.6, 16.1,

18.4, 15.1. 17.4, z

7 1 ~K 1 . J 04 fuh Full floor iiuui 1i z/7/77/06 z 1 / y\j H.4 J,^ J.O, ^8 4'-T.J^ 486 HOU, JUH, S04 ZOO 788 7 17 70 S 70 1 OSs J FFull Ull floor 11UU1 8/74/Q8 Of *-T7 70 7 7 7 4 7< 7, Z.Z, Z.^, J.J Z770/ U, JUU, 306 108~0 IO.U, 18 0 ZU.l, 701 704 lu.H

FFull LI X 1 floor 11UU1 1 0/77/Q8 J3 .U, 0 J3 .Z,7 J^7.z 486 tOU, zoo, 788 j.~h 374 70zu.j,S 10i".o,8 10ly.y0 Q7 FFull LiJU floor 11UUI 1i \ji 0/77/08 zz/ yo Z.U, 7 6 Z.Z, 7 7 Z.Z 7 7 JUU, ^60 HUO, 468 468 *tUO 76zu.j,S .i-U.u, 70 0 *-j.y ^^0

Q8 run Full floor i iuui 111If/Il/'/O 0/08 Z.7, 7 0 Z.O, 7 8 Z.J 7 S 407 HVJ / , JJ1, 3S1 JIO SI 8 Jl.J, 313 161U.O,8 101 7.U6 OQyy fFull un floor i iuui 1 1 /70/Q8 Z.O, 7 8 z.z, 7 7 z.z 7 7 704 ZUH, ZZZ, 777 iU4 704 18lo.O,8 161U.U,6 18lo.i4

1 Of) FUll Full floor 11UU1 111/1 /70/08 zw/ yo Z.O, 7 8 J .Z,7 J^4.H Z778/ O, Z778/ O, JJJ 333 16iu.4,4 171 / .J,3 ly.y 10 0

1 07 FUll Full floor 11UU1 qnc/gq 7/ zo/ yy J3 .Z,7 J3 .Z,7 7Z. 11

...... JJJ, JJJ, JlJ 11VJ.J, 6 S 161 U.7,0 ISO 1 J.7

2 77/ / F 1 1 1 1 flnnr F Ull 11UUI 6/0/08 Z.7 7/ 7 1 7 6 , Z.l, z.u ^S1 J J 1 , 108 170, Z!7 707/

1 Q 4 1 Q 4 17 7

2 78 run Full floor nuor 4/VQ8 Lrl J/70 Z.J, 7 S z.o 7 8 788 ZOO, Z770/ VJ 17 0 1 R 1 1 / . w, 10.1

Z7 8S FUll Full FFloor IUUI

2 88OO FUll Full floor 1 IUUI 7/S/00 / / j/ 1 0 7 4 7 1 1 .7, z.^, z. 1 167 1U/, JJJ, 333 157 1 J / 18, 16, 15

2 FUll 1 IUUI Z.O, 7 8 Z./, 7 7 J^0.U J^701 JJJ, *L770i\J 77Z. . 4 11 J.O, S 8 115J.J3

2 92 Full floor 2/26/98 2.8, 3.0, 2.7 342, 360, 297 19.7, 21.1, 19.7

2 96 Full floor

2 97 Full floor

2 98 9

2 99 Half floor 7/28/97 2.1, 3.0 315,252 19.5, 22.7

2 99 Half floor 4/3/98 1.8, 1.7 306, 270 21.9, 19.5

Repeated test

NISTNCSTAR 1-6A, WTC Investigation 45
Chapter 4

An analysis of the individual measurements was carried out to determine the underlying distribution for the measured thicknesses. Figure 4-4(a) is a dotplot of the individual measurements in WTC 1

( 144 measurements) and in WTC 2(112 measurements). It is observed that the central values and ranges

are similar for the two towers, and the two groups of measurements were combined into one group.

Figure 4-4 (b) is the histogram of the individual measurements, and Fig. 4-4 (c) is the corresponding

normal probability plot. A straight line fit to the normal probability plot shows a tendency of the points to deviate from the line. Figure 4-4 (d) is a histogram of the natural logarithms of the individual thickness

values, and Fig. 4-4 (e) is the corresponding lognormal probability plot. A comparison of the probability

plots shows that natural logarithms fall closer to a straight line. Thus, it appears that the thickness of the

upgraded SFRM on the floor trusses is described by a lognormal distribution. This contradicts the

observation based on analysis of photographs from lower floors discussed in the previous section. The

overall average thickness of the 256 individual measurements is 2.5 in. with a standard deviation of

0.6 in. The median was also 2.5 in. Thus, the average thickness on the upgraded upper floors appears to be greater than that estimated from photographs taken on upgraded lower floors.

As shown in Fig. 4-4, there were a number of points representing individual thicknesses of 3 Vi in. or

greater. As mentioned, there are no corroborating data, such as photographs, of such reported high

thicknesses. The probability distributions in Fig. 4-4 show, however, that the high thicknesses were

consistent with the remainder of the distributions. In any case, statistics were recomputed after removing

thicknesses of 3 14 in. and greater (this amounted to 20 out 256 points). The resulting average thickness was reduced to 2.4 in., and the standard deviation was reduced to 0.5 in. The median remained

unchanged. Thus, it was concluded that the high reported thicknesses would not have a dramatic effect on the overall statistics of the SFRM thickness in the upgraded floors.

The overall standard deviation of 0.6 in. includes two contributions: (1) the variation of thickness at the cross section (within-truss variability), and (2) the variation of average thickness between trusses (between-truss variability). Figure 4-5 shows these two components of the thickness variability for the

two towers. Figures 4-5 (a) and (c) show the within-truss variability, and Figs. 4-5 (b) and (d) show the

variation of average thickness of each truss. From analysis of variance, it was found that the within-truss

standard deviation is 0.4 in., and the between-truss standard deviation is also 0.4 in. The within-truss

standard deviation of 0.4 in. is similar to the standard deviation of the estimated individual thicknesses

obtained from analysis of the photographs of upgraded main trusses.

46 NISTNCSTAR 1-6A, WTC Investigation
As-Applied Thickness of SFRM

w

CDc

o

4-

3.5

3-

2.5

2

1.5

1

! 0)

: —

:

#

• •

: •!

i

•

*

•

•

t

• — • *

••

•

---- « —

1

• •

•

•

- -••

----?---

Tower

y = 2.5449 + 0.57398norm(x) R= 0.98583

0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 3.6 4 4.4 4.8 5.2 Thickness, in.

01 .1 5 10 2030 50 7080 9095 99 99.909.99 Percent

0.90833 + 0.2266norm(x) R= 0.99261

i—i—i—i i i i r

5 10 2030 50 7080 9095 99 99.999.99 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Percent Ln (Thickness)

Figure 4-4. (a) Dotplot of individual thickness measurements on floor trusses from Port

Authority Construction Audit Reports, (b) histogram of thickness measurements,

(c) normal probability plot of thickness measurements, (d) histogram of natural

logarithms of thickness measurements, and (e) normal probability plot of natural

logarithm of thickness measurements.

NIST NCSTAR 1-6A, WTC Investigation 47
Chapter 4

id

in0

cO 2 —

: (a)

! WTC 1

; +

+ --+-r~

+ +

--+

-H- 1

+ |

t # #

-.].. \

: * + t

92 94 96 98 Floor

100 102

w

w0

C

3.5-

3

25

2

1.5 0

CD0

: (b) • : • \A/TP 1 • to*

• j

: # •

ft | «

i i i

i ' ' 'i

' ' '

i

' '

' 92 94 96 98 Floor

100 102

if) in0

co

4-

1 -

WTC2^

+

: +

+ +

-- +-• + +

++

1

H

H n i!

-H+

h—H +

1111

75 80 85 Floor

90 95

in

in0

co

0

D)

CD

i_0

><

3.5

2.5

0.5-

WTC 2

•

• :

•t t

•

•

•

•

i i i i 75 80 85 Floor

90 95

Figure 4-5. SFRM thickness on floor trusses in upgraded portions of WTC towers: (a)

individual measurements in WTC 1, (b) average thickness in WTC 1, (c) individual

measurements in WTC 2, and (d) average thickness in WTC 2

(data provided by PANYNJ).

4X NISTNCSTAR 1-6A, WTC Investigation
As-Applied Thickness of SFRM

4.4 COLUMN SFRM THICKNESS

NIST requested that the Port Authority provide available information on the thickness of fire-resistive material for the exterior and interior columns of the WTC towers (see Appendix A Fig. A-62).

Specifically, the request included the following:

• The fire-resistive material used and the thickness on the various plates comprising the exterior

columns and spandrels.

• The fire-resistive material used and the thickness on core columns.

• Confirmation that the wide flange column sections were protected with BLAZE-SHIELD

Type DC/F with specified thickness of 2 3/16 in. for sections smaller than 14WF228 and

1 3/16 in. for 14WF228 and larger.

• Information on in-place SFRM thickness.

The Port Authority replied that, due to inaccessibility of exterior columns and core columns, there were no recent records of SFRM thickness for these elements (see Appendix A Fig. A-62). The only available

measurements of SFRM thickness were for beams and columns accessible within elevator shafts. These

measurements were, however, for re-applied thermal insulation.

The most complete data set included measurements on beams and columns taken within shaft 10/11 in WTC 1 . These measurements were taken in April 1999 and included measurements from floor 1 to floor 45. The thicknesses were recorded to the nearest 1/8 in., with a few thicknesses recorded to the nearest 1/16 in. The columns included 10 to 18 replicate measurements, and the beams included 11 to 16

replicate measurements.

Figure 4-6 (a) shows the individual and average SFRM thickness on the core columns. Analysis of

variance indicated no statistically significant differences among the average values, and all data were

pooled together. The average thickness for the columns is 0.82 in., the standard deviation is 0.20, and the

coefficient of variation is 0.24. The information from the Port Authority indicated that the "minimum

thickness required'" for the columns was Vi in. As noted in Appendix A Fig. A-62, the required thickness was based on calculations performed by LERA for re-applied thermal insulation (Monokote Type Z-106),

similar to what was discussed in Section 3.5.5. Figure 4-6 (b) is the normal probability plot of the

individual thickness measurements. Because most of the thicknesses were reported to the nearest 1/8 in., the points are staggered in steps instead of uniformly distributed. The plot, however, shows that the

points follow a linear trend, and it appears that the thickness of the reapplied SFRM on the core columns

could be described by a normal distribution. Figures 4-6 (c) and (d) show the corresponding plots for the

thickness of SFRM reapplied to beams surrounding shaft 10/1 1 of WTC 1. The average thickness is 0.97 in., the standard deviation is 0.21 in. and the coefficient of variation is 0.21. The information from

the Port Authority indicated that the "minimum thickness required" for the thermal insulation reapplied to the beams was 3/4 in.

The data described above may not have a direct bearing on the outcome of the investigation because they

deal with lower stories. They do, however, provide some useful information on the variability of SFRM

applied to beams and columns. The variation in SFRM thickness for the beams and columns shown in

NISTNCSTAR 1-6A, WTC Investigation 49
Chapter 4

Fig. 4-6 is lower than the variation observed in the floor trusses. This is not unexpected because the

planar surfaces of the beams and columns result in more uniform application of the sprayed fire-resistive material than for the slender truss members. This results in reduced differences in the average thickness

of SFRM on different members and less variability within a member.

1.6

1.4

1.2

C/5 1 n w

1 - u

CDc

u 0.8

0.6

0.4

0.2

y = 0.82308 + 0.1 8921 norm(x) R= 0.96692

~~i I I

i—r~r

(b)

J I i i L_l I i_i I i L

.01 .1 1 5 10 2030 50 7080 90 95 99 99.9 99.99 Percent

1.5-

</) 03C

O

1 -

0.5

(c) Beams individual Average

10

I I 20 30 Floor

40 50

in

tocO

1.8-

1.6-

1.4

1.2

1

-

0.8H

0.6

0.4

0.2

y = 0.96562 + 0.1999norm(x) R= 0.97146

; (d)

•

•

*

.01 .1 1 5 10 2030 50 7080 90 95 99 99.9 99.99 Percent

Figure 4-6. Thickness of re-applied SFRM in elevator shaft 10/11 of WTC 1: (a) Individual

and average thickness for core columns, (b) normal probability plot of individual

measurements on columns, (c) individual and average thickness for core beams, and

(d) normal probability plot of individual measurements on beams (data provided by

PANYNJ).

50 NISTNCSTAR 1-6A, WTC Investigation
Chapter 5

Effect of SFRM Geometry on Thermal Response

The thickness of sprayed fire-resistive material (SFRM) has a great effect on the thermal response of the

structural protected elements for a given fire condition. The effect of the variation of thickness along the

length of a member is, however, not well known. A sensitivity study using finite element modeling of

heat transfer was conducted to investigate the sensitivity of steel temperature to the variability in SFRM

thickness.

5.1 EFFECTS OF THICKNESS VARIABILITY AND GAPS IN SFRM

The simplified model that was used is shown in Fig. 5-1. A 1 in. thick, 60 in. long steel plate (cyan color) was coated with fire-resistive material (purple color) and subjected to the uniform radiative flux arising

from a 1,100 °C fire. As shown in Fig. 5-1 (b), the fire-resistive material is modeled with a layer of finite elements (0.125 in. thick and 0.6 in. long) having the thermal properties of fire-resistive material (purple).

A parametric study was conducted with average thickness of fire-resistive material varying from 0 in. to 2 in. in increments of 1/4 in. The effect of variability in thickness was modeled by imposing a normal

probability distribution on the SFRM thickness along the length of the steel plate. The assumed standard

deviation varied from 0 in. (uniform thickness) to 1 in. A pseudo-random number generator was

employed to determine the thickness at each cross section based on the assumed average thickness and

standard deviation. The layer representing SFRM was taken to be twice the average thickness, and the

thickness of SFRM at any cross section was modeled by assigning a low heat capacity and a high thermal

conductivity to those elements that do not provide thermal protection. Figure 5-1 (c) shows an example

of variable thickness SFRM; in this case, the average thickness is 1 in. and the standard deviation is 3/8 in.

When the model in Fig. 5-1 is exposed to the thermal flux representing a 1,100 °C fire, the surface of the

insulation heats up quickly to the gas temperature (1,100 + 273 = 1,373 K). Numerical simulation was

performed over a 2 h period, and the steel temperature at five locations was recorded at 30 min, 60 min,

90 min, and 120 min of exposure. The temperature recording locations are 6 in. from each end and at 12 in. intervals, which are shown as numbers 1 to 5 in Fig. 5-1 (a). The initial temperature of the model is 300 K.

Figure 5-2 shows temperature contours (in K) through the fire-resistive material and steel at 60 min after

initial exposure for the model shown in Fig. 5-1 (a). The surface temperature of the fire-resistive material

is close to the gas temperature of 1,373 K, while the steel temperature is 31 1 K. If the SFRM were of

uniform thickness, the isotherms would be a series of lines parallel to the plate. It is seen that, when the

thickness is variable, the isotherms follow the shape of the SFRM surface contour. Thus, the temperature

history at any point in the steel depends on the local thickness of the fire-resistive material.

Figure 5-3 shows the steel temperature at the far sensor #1 (6 in. from the end) as a function of time for various insulation thicknesses ranging from 0 in. to 2 in. (the thickness is indicated by the numbers on the

curves). For the case in Fig. 5-3 (a), the fire-resistive material is of uniform thickness, and for the cases in

NISTNCSTAR 1-6A, WTC Investigation 51
Chapter 5

Fig. 5-3 (b), the thickness varies with a standard deviation of 1 in. The time to reach a temperature of

600 °C is used as a measure of relative performance. It is seen that the presence of high variability in thickness has a detrimental effect on the protection provided by the fire-resistive material. For example,

for a uniform thickness of 0.5 in., it takes about 60 min for the steel at point #1 to reach 600 °C, but when

the standard deviation of the thickness is 1 in., the average thickness has to be 1.75 for the same level of

thermal protection.

(a)

1 in. thick steel Thermal insulation^

! \ • I • •

2 in.

2 in.

0.166 in..

0.125 in.

0.6 in

Figure 5-1. Model used to study effects of SFRM thickness and variability of thickness

on steel temperature: (a) physical model used in analyses (points 1 to 5 are locations

where temperatures are monitored), (b) finite element mesh used to represent physical

model, and (c) finite element model to represent variable thickness of SFRM (purple) (the

elements in red represent material of high thermal conductivity).

52 NISTNCSTAR 1-6A, WTC Investigation
Effect of SFRM Geometry on Thermal Response

Figure 5-2. Temperature distribution after 1 h of exposure to gas temperature of

1,100 °C (1,373 K).

NISTNCSTAR 1-6A, WTC Investigation 53
Chapter 5

Sensor Location: Far Left (inch 6 of 60) Case 1: Non-Stochastic & No Gap

1200

1000

tt boo

600

400 —

200

o —

Time (Minutes)

Sensor Location: Far Left (inch 6 of 60) Case 2: Stochastic (SD = 1 in.) & No Gap

1200

1000

200

60 90

Time (Minutes;

Figure 5-3. Variation of steel temperature (at a point 6 in. from end of plate) with time for

different average thicknesses of fire-resistive material (shown as numbers on the

curves): (a) uniform thickness, and (b) variable thickness with standard deviation = 1 in.

54 NISTNCSTAR 1-6A, WTC Investigation
Effect of SFRM Geometry on Thermal Response

In addition to the effect of variation in thickness, it is important to understand the effect of missing SFRM

over a portion of a member. As an example, Fig. 5-4 shows missing SFRM from a diagonal of a bridging

truss of the WTC towers floor system. Note that this photograph is from a lower story and may not be

representative of conditions in the upper stories, especially following the upgrade of thermal insulation.

Figure 5-5 (a) shows an example of a numerical model with missing fire-resistive material. In this case, there is 12 in. of missing SFRM on the steel plate, which is otherwise protected by 2 in. of uniform

thickness fire-resistive material. Figure 5-5 (b) shows the temperature contours (isotherms) at time equal

to 50 min. For comparison, Fig. 5-5 (c) shows isotherms at the same time in a plate with no gap in the

fire-resistive material. As expected, the bare steel at the missing fire-resistive material is at the gas

temperature, but more importantly the "gap" in SFRM leads to a "leakage" of heat into the interior steel.

Figure 5-4. Example of "gap" in fire-resistive material on diagonal member of a bridging

floor truss.

The combined effects of variation in thickness of the fire-resistive material and length of missing material were examined by a factorial study with the following factors:

• Average thickness of fire-resistive material varying from 0 in. to 2.0 in. in 1/4 in. increments;

• Standard deviation of fire-resistive material thickness of 0 in., 0.25 in., 0.5 in., 0.75 in. and

1 .0 in.; and

• Length of missing fire-resistive material varying from 0 in. to 30 in., in 6 in. increments.

NISTNCSTAR 1-6A, WTC Investigation 55
Chapter 5

Insulation

2"

300 700 1100 1400

500 900 1300

Figure 5-5. Effects of gap in fire-resistive material: (a) model of plate with SFRM having

2 in. uniform thickness and 12 in. gap, (b) isotherms (K) at time = 50 min with 12 in. gap,

and (c) isotherms without gap.

The results of the sensitivity study can be summarized in a series of plot matrices, which show the time

histories of the steel temperature for different combinations of gap length and variability in SFRM

thickness. For example, Fig. 5-6 shows the plot matrix for the temperature history at point #2(18 in. from the end of the plate). Each plot contains a series of curves representing different average thicknesses

of fire-resistive material, as in Fig. 5-3. Each column of plots represents a constant value of thickness

variability (standard deviation), and each row represents a constant gap length. The plot in the upper left comer represents the case of uniform thickness of SFRM and no gap, which is the same plot as in Fig. 5-3(a). (Note that for the case of uniform thickness and no gap, the steel temperature at any point in

a cross section is the same along the length of the plate, as shown in Fig. 5-5(c).) For gaps of 24 in. and

30 in., the temperature at point #2 rises rapidly because there is no SFRM on the plate at that location.

This explains the shapes of the curves in the two lower rows. In going from left to right in one of the top

four rows it is seen that as variability of thickness increases, the time histories shift upward, thereby

reducing the time to reach 600°C. This is the same observation as shown in Fig. 5-3. Moving from the

top to the bottom in any column shows the effects of increasing gap length. The effect of gap length

depends, of course, on where the steel temperature is measured. At a point within the portion of steel that

is bare, the temperature rises quickly. At points within the steel that are surrounded with fire-resistive material, the gap provides a path for heat flow, as shown in Fig. 5-5 (b). As a result, points in the steel within the vicinity of the missing SFRM will experience higher temperatures, as indicated by the rising

56 NISTNCSTAR 1-6A, WTC Investigation
Effect of SFRM Geometry on Thermal Response

trend of the curv es in going downward from the top of a column in Fig. 5-6. The National Institute of

Standards and Technology (NIST) does not have sufficient information to determine the frequency of

occurrence of these gaps or their typical locations within the fire-affected floors. Therefore, gaps in insulation were not considered in the thermal modeling.

Standard Deviation (Thickness) (in.) 0 0.25 0.5 0.75 1

0 30 GO 90 120 0 30 60 90 120 0 30 GO 90 120 0 30 60 90 120 0 30 60 30 120 Time (Minutes)

Figure 5-6. Example of plot matrix from sensitivity study of the effects of missing SFRM

and variability of SFRM thickness on steel temperature. Each graph is a temperature

history of the steel at point #2 (see Fig. 5-5 for location) for different thicknesses of

SFRM.

5.2 EQUIVALENT THICKNESS

The sensitivity study summarized in Section 5.1 indicated that variation in the thickness of SFRM

reduced the "effective thickness" of the material. It would be impractical to attempt to account for the

variation in SFRM thickness in the thermal modeling by introducing variable thickness insulation

material in the finite-element models. As an alternative, it was decided to attempt to determine the

"equivalent uniform thickness" of fire-resistive material that would result in the same thermo-mechanical

response of a member as variable thickness thermal protection. An approach similar to the methodology

described in Section 5.1 was used to model a 1 in. diameter by 60 in. long bar with thermal insulation and

subjected to the heat flux arising from a 1,100 °C fire. The bar was subdivided into 0.6 in. long elements,

NISTNCSTAR 1-6A, WTC Investigation 57
Chapter 5

so that there were 100 elements along the length of the bar. The thermal history of the bar was calculated,

and that history was used to calculate the length change of the unrestrained bar under a tensile stress of

12,500 psi. The bar was assumed to be similar to the steel used in the floor trusses, and the temperature

dependence of the coefficient of thermal expansion and the modulus of elasticity were based on NIST

measurements.

The thermal insulation thickness in the models was based on the measurements summarized in Chapter 4

for the web bars of main trusses in the original condition and after the upgrade. Specifically, the

following target values were investigated:

• Original: average thickness = 0.75 in., standard deviation = 0.3 in., lognormal distribution.

• Upgrade: average thickness = 2.5 in., standard deviation = 0.6 in., lognormal distribution.

The variation of thermal insulation thickness along the length of the bar was established by using a pseudo random number generator to select values from a lognormal distribution with central value and

dispersion consistent with the above average values and standard deviation. Three sets of random data were generated for each condition.

When the randomly selected thicknesses of each element were applied to the bar, it resulted in sudden

changes in insulation thickness along the length of the bar. This resulted in a "rough" surface texture as shown by the dotted thickness profile in Fig. 5-7 (a). It was felt that this rough texture (see also

Fig. 5-1 (c) might not be representative of actual conditions, so an alternative approach was to use

five-point averaging to reduce the roughness of the insulation profile. The solid line in Fig. 5-7 (a) shows

such a "smooth" profile. The two profiles in Fig. 5-7 (a) have approximately the same average value and

standard deviation and have similar cumulative distribution of thermal protection thickness as shown in Fig. 5-7 (b).

As stated, the calculated thermal histories of the bar elements were used to calculate the unrestrained

length change of the bar due to thermal expansion and an applied stress of 12,500 psi. For comparison,

the deformation of the bar with different but uniform thickness of thermal insulation was calculated. The

"equivalent thickness" was taken as the uniform thickness that resulted in similar deformation as under

the variable thickness conditions. Figure 5-7 (c) shows the results of these calculations for the original

SFRM thickness. The three continuous curves are the deformation-time relationships for uniform

thickness of 0.4 in., 0.5 in., and 0.6 in. The solid symbols represent the results for three cases with

"rough" texture, and the open symbols are for the "smooth" texture. The following values summarize the

six variable thickness profiles:

• Rough 1 : average = 0.79 in., standard deviation = 0.29 in.

• Rough 2: average = 0.77 in., standard deviation = 0.27 in.

• Rough 3: average = 0.79 in., standard deviation = 0.31 in.

58 NISTNCSTAR 1-6A, WTC Investigation
Effect of SFRM Geometry on Thermal Response

Rough Texture Smooth Texture

10

1.60

1.40

1.20 d

co 1 .00

CO

<D IE 0.80 o

'jz H 0.60

0.40

0.20

(b) mk

Rough Texture Smooth Texture

L

20 30 40

Bar Position, in. 50 60

20 40 60 80 100

Cumulative Number of Elements

0.80 -

120

» 0.60 - c

g

CDE

CD Q

0.40 -

0.20 -

0.00

Rough 1 Rough 2 Rough 3 Smooth 1 Smooth 2 Smooth 3

0.4" Uniform FP

0.5" Uniform FP

0.6" Uniform FP

10 15

Time (min)

30

Figure 5-7. (a) Randomly generated thickness profiles with average thickness of 0.75 in. and standard deviation of 0.3 in., (b) cumulative element size, and (c) deformation of 1 in. bar compared with deformation for uniform thickness of thermal insulation.

NISTNCSTAR 1-6A, WTC Investigation 59
Chapter 5

• Smooth 1 : average = 0.79 in., standard deviation = 0.28 in.

• Smooth 2: average = 0.78 in., standard deviation = 0.31 in.

• Smooth 3: average = 0.78 in., standard deviation = 0.32 in.

Figure 5-7 (c) shows that the "rough" texture reduces the effectiveness of the insulation by a small

amount compared with the "smooth" texture. As noted above, it is believed that the "smooth" texture is more representative of the actual conditions. On the basis of these analyses, it is concluded that SFRM

with an average thickness of 0.75 in. and a standard deviation of 0.3 in. provides protection equivalent to 0.6 in. of uniform thickness.

The results for the upgraded thermal protection are shown in Fig. 5-8. Only the "smooth" texture was

used, and the values for the three cases are as follows:

• Case 1: average = 2.50 in., standard deviation = 0.71 in.

• Case 2: average = 2.43 in., standard deviation = 0.51 in.

• Case 3: average = 2.55 in., standard deviation = 0.63 in.

Figure 5-8 (a) shows the three profiles, and Fig. 5-8 (b) shows the normal probability plots of thickness

values. Because the three randomly generated profiles do not have the same averages and dispersions, the

responses show more scatter than in Fig. 5-7 (c). On the basis of these analyses, it is concluded that an

average SFRM thickness of 2.5 in. with a standard deviation of 0.6 in. is equivalent to 2.2 in. of uniform

thickness.

5.3 RECOMMENDED THICKNESS OF SFRM FOR THERMAL ANALYSES

Analyses of available data on SFRM thickness in the WTC towers and thermal modeling revealed the

following:

• From measurements of SFRM thickness, the average values exceeded the specified thickness.

• SFRM thickness was variable, and the distribution of thickness in the floor trusses appears to be

described best by a lognormal distribution.

• The standard deviation of SFRM thickness on the trusses varied between about 0.3 in. and 0.6 in.

• The standard deviation of SFRM on columns and beams from the core tended to be lower, with a value of 0.2 in. for the available data.

• No information is available on the SFRM thickness on the exterior columns and spandrel beams.

• Variation in thickness reduces the effectiveness of SFRM, and the equivalent uniform thickness is less than the average thickness.

60 NISTNCSTAR 1-6A, WTC Investigation
Effect of SFRM Geometry on Thermal Response

10 20 30 40 Bar Position, in.

50 60

5

4.5

4

d. — 3.5

inin

(Dc

oZ 25

\ (b)

2

1.5

1

3- -

-

• Case 1 Case 2

A Case 3

1.00

.01 .1

~i—i

r~\—l—r~i—I—i 1 r~

5 10 2030 50 7080 90 95 99 99 999.99 Percent

100 Time, min

Figure 5-8. (a) Randomly generated thickness profiles with average thickness of 2.5 in. and standard deviation of 0.6 in., (b) normal probability plots of thickness values, and

(c) deformation of 1 in. bar compared with deformation for uniform thickness

of thermal insulation.

Based on the findings stated above, the following uniform thicknesses for the undamaged SFRM were

determined for use in calculating thermal response of the WTC towers under various fire scenarios:

• Original SFRM thickness on floor trusses: 0.6 in.

• Upgraded SFRM thickness on floor trusses: 2.2 in.

• Thermal protection on other elements: the specified thickness.

The choice of specified thickness for those members lacking data is justified by offsetting factors as follows: (

l ) measured average thicknesses exceed specified values, and (2) variation in thickness reduces

the effectiveness of the SFRM.

NISTNCSTAR 1-6A, WTC Investigation 61
Chapter 5

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62 NISTNCSTAR 1-6A, WTC Investigation
Chapter 6

Thermophysical Properties

Based on information reviewed in this investigation, five sprayed fire-resistive materials (SFRMs) have

been identified in WTC 1, 2, and 7: (1) BLAZE-SHIELD Type D, (2) BLAZE-SHIELD Type DC/F,

(3) BLAZE-SHIELD Type II, (4) Monokote MK-5, and (5) vermiculite aggregate plaster. As mentioned

in Section 3.5.1, the use BLAZE-SHIELD Type D was discontinued in 1978, and it had been used only in the lower stories of WTC 1. Of the four SFRMs, only BLAZE-SHIELD Type II is sold currently in the

U.S., and BLAZE-SHIELD Type DC/F is sold in Canada. Table 6-1 summarizes where these materials were used.

Table 6-1. Summary of SFRMs used in WTC.

Fire-Resistive Material

Locations

Interior Columns Floor Systems Exterior Columns

WTC 1 BLAZE-SHIELD DC/F Yes Yes Outside

BLAZE-SHIELD 11 Yes (Upgrade)

Vermiculite plaster Inside WTC 2 BLAZE-SHIELD DC/F Yes Yes Outside

BLAZE-SHIELD II Yes (Upgrade)

Vermiculite plaster Inside WTC 7 Monokote MK-5 Yes Yes Yes Yes

BLAZE-SHIELD Type DC/F is manufactured by Isolatek International (formerly U.S. Mineral Products

Co., Stanhope, New Jersey) and was used in the interior columns, floor systems, and the exterior faces of

the exterior columns of WTC 1 and WTC 2. BLAZE-SHIELD Type II, also from Isolatek, was used in subsequent upgrades of the passive fire protection to WTC 1 and WTC 2 floor systems. BLAZESHIELD Type DC/F" and Type II are portland cement based products in which mineral fibers are the

primary insulation materials. Monokote MK-5, a gypsum-based SFRM containing vermiculite aggregate, was manufactured by W.R. Grace and Co. (Cambridge, Massachusetts) and used in WTC 7. W.R. Grace

stopped the production of Monokote MK-5 in the 1980s. Vermiculite aggregate plaster, manufactured by

W.R. Grace until the 1970s, was used on the interior faces of the exterior columns of WTC 1 and WTC 2

(see Fig. 3-4).

No information on the thermophysical properties of vermiculite plaster has been located in the open

literature. During the construction of the WTC, the Monokote product was sometimes referred to as sprayed vermiculite. See, for example, Appendix A Fig. A- 17, where the description "Sprayed

(Cementitious) Vermiculite (Monokote)" is used. Discussions with a former researcher at W. R. Grace

and Co. indicated that vermiculite plasters were used before the development of the Monokote product

line, and these plasters had densities of 20 pcf to 25 pcf; any Monokote product used during construction

of the WTC towers would probably have had similar density.

1 Based on this information, the

15 Personal communication from Amie Rosenberg, August 30, 2005 (242-1).

NIST NCSTAR 1-6A, WTC Investigation 63
Chapter 6

thermophysical properties of Monokote MK-5 will be taken to be representative of the vermiculite plaster

specified for the interior face of the exterior columns.

In addition to the SFRMs, the thermophysical properties of four representative types of gypsum boards were examined to provide technical support to other aspects of the WTC investigation.

6.1 ASTM TEST METHODS FOR SFRMS

Since 1977, a number of ASTM test methods have been developed specifically for testing different

characteristics of SFRMs. These methods were developed mainly for characterizing mechanical and

physical properties. For completeness, these test methods are summarized in Table 6-2.

Table 6-2. Current ASTM test methods for SFRMs.

ASTM Designation Summary of Test Method

ASTM E 605 - 93 (Reapproved 2000)

Test Method for Thickness and Density of Sprayed

Fire-Resistive Material (SFRM) Applied to Structural Members

Density and thickness are determined using a thickness gauge, scales, steel rules, and templates

ASTM E 736 - 00

Test Method for Cohesion/Adhesion of Sprayed Fire- Resistive Materials Applied to Structural Members

The cohesion/adhesion of SFRM to structural members

islO determined UVlVl llllllvU usinp 1 1 . ' 1 1 I EL aCI 111V metaltUl or\J 1 nlaslic [ ' 1 i ( . ' \ 1 V can 'l U ' with VV 1111 ait hook a 1 \ ' *_/ IV attached. The cap is attached to the SFRM with a

suitable adhesive. An increasing load, measured by a

scale, is applied manually until failure occurs. ASTM E 759 - 92 (Reapproved 2000)

Test Method for Effect of Deflection on Sprayed Fire- Resistive Material Applied to Structural Members

A cellular steel deck panel sprayed with SFRM is subjected to bending by a vertical center load while

supported horizontally at its ends. ASTM E 760 - 92 (Reapproved 2000)

Test Method for Effect of Impact on Bonding of

Sprayed Fire-Resistive Material Applied to Structural Members

A cellular steel deck with a concrete topping sprayed

with SFRM is subjected to a leather bag drop impact

while supported horizontally at its ends.

ASTM E 761 - 92 (Reapproved 2000)

Test Method for Compressive Strength of Sprayed

Fire-Resistive Material Applied to Structural Members

The compressive strength of SFRM applied to a steel sheet is determined by a compressive load normal to the surface of the specimen.

ASTM E 859 - 93 (Reapproved 2000)

Test Method for Air Erosion of Sprayed Fire-Resistive Materials (SFRMs) Applied to Structural Members

The SFRM is subjected to a tangential air stream for a minimum of 24 h. Collection filters downstream from

the specimen are weighed at frequent intervals to determine the amount of material removed from the specimen.

ASTM E 937 - 93 (Reapproved 2000)

Test Method for Corrosion of Steel by Sprayed Fire- Resistive Material (SFRM) Applied to Structural Members

Replicate panels of bare, shop-coated, and galvanized

steel are sprayed with SFRM and subjected to room

temperature and humidity conditions and to 240 h of

conditioning in a chamber with temperature and

humidity control. Corrosion induced under these conditions is determined by mass loss of the sheets as

related to sheets not so conditioned.

64 NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Properties

6.2 REPORTED SFRM PROPERTIES

For comparison with measurements to be reported in this Chapter, the nominal physical and mechanical

characteristics taken from product literature (see Appendix A Fig. A-63) 16 of the manufacturers of the

SFRMs are listed in Table 6-3.

Table 6-2». Properties from tests of SFRMs reported by manufacturers.

Characteristic ASTM Method SFRM

BLAZE-SHIELD

DC/F

BLAZE-SHIELD

11 Monokote MK 5

Cohesion adhesion E 736 300 psf 360 psf 320 psf

Deflection E 759 No cracks or delaminations

No cracks or delaminationsNo cracks or delaminations

Bond impact E 760 No cracks or delaminations

No cracks or delaminationsNo cracks or delaminations

Compressive

strength

E 761 830 psf 2380 psf 31 10 psf

Air erosion

resistance E 859 0.000 g/m2 0.000 g/m2 0.022 g/m2

Density E 605 13 pcf 16 pcf 20 to 25 pcf

Corrosion resistance E 937 Does not promote

corrosion of steel Does not promotecorrosion of steel Not available

Thermal

conductivity

C 518 0.042 W/(m • K)

@24 °C

0.043 W/(m • K)

@24 °C

Not available

a. Based on laboratory tests under controlled conditions.

b. Based on information from former employee of W.R. Grace, see previous footnote.

6.3 MEASURED THERMOPHYSICAL PROPERTIES OF SFRMS

To provide thermophysical property data for modeling the fire-structure interaction of the towers, the

thermal conductivity, specific heat capacity, and density of each SFRM were determined as a function of

temperature up to 1.200 °C (2,190 °F). Since there are no ASTM test methods for characterizing the

thermophysical properties of SFRMs as a function of temperature, ASTM test methods developed for other materials were used. Testing services were provided by a commercial testing laboratory, through a competitive open procurement. The laboratory (referred to as Laboratory A in this report) is an ISO 9002

certified company. Test results were presented to NIST in the form of a letter report with data and plots

as attachments.

16 In Fig. A-63, thermal conductivity is reported as an R-value per in. thickness. The inverse of this value is the thermal

conductivity. Thus, a reported R value of 3.45 indicates a thermal conductivity of 0.29 Btu-in./(ft2 • °F h) or 0.042 W/(m K).

NISTNCSTAR 1-6A, WTC Investigation 65
Chapter 6

6.3.1 Sample Preparation

Samples of BLAZE-SHIELD DC/F and II were purchased from Isolatek, Inc. in Stanhope, New Jersey,

and samples of Monokote MK-5 were purchased from W.R. Grace and Co. in Cambridge, Massachusetts,

according to their respective application manuals. Since Monokote MK-5 is no longer on the market, it was manufactured specially by W.R. Grace according to the original MK-5 formulation. The samples were made from the same batch of raw materials, shipped to NIST for examination and documentation,

and sent to Laboratory A for testing. The samples were 9 in. long, 4.5 in. wide, and 3 in. thick. These

dimensions were dictated by the test methods used. Three samples of each material were sent for testing.

Two of them were used for the thermal conductivity measurements, and the third was used to prepare

specimens for the other measurements involved. Figures 6-1, 6-2, and 6-3 show photographs of samples

of BLAZE-SHIELD DC/F, BLAZE-SHIELD II, and Monokote MK-5, respectively.

Source: NIST. Figure 6-1. BLAZE-SHIELD DC/F sample used

for thermophysical property measurements.

Source: NIST. Figure 6-2. BLAZE-SHIELD II sample used

for thermophysical property measurements.

66 NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Properties

\

M K S

Source: NIST. Figure 6-3. Monokote MK-5 sample used

for thermophysical property measurements.

6.3.2 Thermal Conductivity Measurements

The thermal conductivity measurements were performed according to ASTM C 1 1 13 (ASTM 1999).

This test method is based on heating two specimens with a platinum wire placed between them. The thin

platinum wire serves not only as a heater, but also as a temperature sensor, since the variation of its electrical resistance during the test is converted into variation of temperature. Thermal conductivity is calculated based on the rate of temperature increase of the wire and power input.

Laboratory A reported that substantial shrinkage occurred during the measurements for the three

materials. The two MK-5 specimens shrunk, exposing the platinum wire positioned between them. For

this reason, no thermal conductivity measurement could be performed for this material at 1,200 °C.

Table 6-4 summarizes thermal conductivity as a function of temperature. The results are plotted in

Fig. 6-4, which also shows the results for BLAZE-SHIELD DC/F from Harmathy, which were obtained

using a variable-state method (Harmathy 1983). The results show similar trends of increased thermal

conductivity with increasing temperature; however, the Monokote MK-5 specimens had a different

behavior than BLAZE-SHIELD Type DC/F and Type II at temperatures above 500 °C.

NISTNCSTAR 1-6A, WTC Investigation 67
Chapter 6

Table 6-4. Measured thermal conductivity as a function of temperature.

Thermal Conductivity (W/(m • K))

a

Temperature (°C) BLAZE-SHIELD DC/F BLAZE-SHIELD 11 Monokote MK-5

25 0.0460 0.0534 0.0954

50 0.0687 0.0745 0.0926

100 0.0628 0.0921 0.1252

200 0.0810 0.0895 0.0919

300 0.1106 0.1057 0.1214

400 0.1286 0.1362 0.1352

500 0.1651 0.1689 0.1504

600 0.2142 0.2156 0.1622

800 0.3380 0.2763 0.1895

1000 0.5010 0.3708 0.2618

1200 0.5329 0.4081

a. SI units are used because this system was used to make the measurements. To convert to Btu-in./(h ft2 • °F) divide by

0.1442279.

0.0 0 200 400 600 800 1000 1200

Temperature (°C)

Figure 6-4. Thermal conductivities of the three SFRMs as a function of temperature.

68 NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Properties

6.3.3 Specific Heat Capacity Measurements

For the specific heat capacity measurements, the same instrument (UnithermTM Model QL-3141) was

used with a slight modification. A thermocouple was added to the system and mounted on the specimen,

parallel with the platinum wire at a known distance from the wire. The test was performed in a similar manner as the thermal conductivity measurements, but from the thermocouple output the thermal

diffusivity of the material was derived. Knowing the thermal conductivity, the thermal diffusivity, and

the density calculated from the thermal expansion results and the thermogravimetric analysis (see

Section 6.3.4), the specific heat capacity of the material was calculated. Table 6-5 tabulates the

measurements. Figure 6-5 compares the present results for BLAZE-SHIELD DC/F with those from

Harmathy, which were obtained using a DuPont 910 differential scanning calorimeter with a heating rate of 5 °C/min (Harmathy 1983). It is clear from the figure that the inherently indirect nature of the technique used by Laboratory A precludes the direct measurements of specific heat capacity associated

with chemical reactions (peaks in the figure) when the SFRMs are subjected to heating.

Table 6-5. Calculated specific heat capacity of the three SFRMs.

Specific heat capacity (J/(kg K))a

Temperature (°C) BLAZE-SHIELD DC/F BLAZE-SHIELD II Monokote MK-5

25 826.4 801.6 841.0

50 941.5 868.4 1045.8

100 723.9 708.4 1005.7 200 897.2 925.4 1205.5 300 1020.2 1084.7 1253.9 400 1070.6 1147.5 1302.9 500 1097.6 1255.3 1331.6 600 1 189.7 1299.1 1400.8 soo 1258.6 1369.6 1468.2 1000 1325.3 1411.3 1520.8

1200 1391.7 1461.3

a. SI units are used because this system was used to make the measurements. To convert to Btu /(lb • °F) divide by 41 86.8.

NISTNCSTAR 1-6A, WTC Investigation 69
Chapter 6

4000

3500

3000

^ 2500

3

(j

2- 2000

1500

1000

500

0 200 400 600 800 1000 1200

Temperature (°C)

Figure 6-5. Comparison of BLAZE-SHIELD DC/F specific heat capacity measurements

from Harmathy (1983) with present results from Laboratory A.

To examine the chemical reactions associated with heating of SFRMs, samples were sent to another

laboratory (referred to as Laboratory B) to perform differential scanning calorimetry (DSC) because the

DSC in the Building and Fire Research Laboratory at NIST was not working at that time. The specimens

for DSC were prepared by removing small pieces from the bulk samples. The pieces were placed into small glass vials and sent to Laboratory B for analysis.

Specific heat capacity was measured in accordance with ASTM E 1269 (ASTM 2001) using a Perkin-Elmer Model DSC-2 Differential Scanning Calorimeter with sapphire as the reference material.

The standard and SFRM specimens were subjected to the same heat flux as a blank specimen, and the

differential powers required to heat the specimen and the standard at the same rate were determined using

the digital data acquisition system. The specific heat capacity of the specimen was computed from the masses of the sapphire standard and the SFRM specimen, the differential power, and the known specific

heat capacity of sapphire. The data were displayed visually as the test progressed. All measured

quantities were directly traceable to NIST standards.

Differential thermal analysis (DTA), which is a "fingerprinting" technique that provides information on

the chemical reactions, phase transformations and structural changes that occur in a specimen during a heat-up or a cool-down cycle, was used to locate the peaks and valleys during continuous heating to 600 °C at a rate of 10 °C/min. Once the peak and valley regions were identified, the sensitive DSC was

70 NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Properties

used to examine these regions further at a heating rate of 5 °C/min, first from room temperature to 350 °C

and then from 300 °C to 580 °C. It was noted by Laboratory B, however, that the DSC results at temperatures greater than 350 °C were of questionable quality and problematic. Only the results (up to 350 °C) are tabulated in Appendix B Table B-l and are displayed in Fig. 6-6, together with the results from Laboratory A for comparison.

Figure 6-7 shows a comparison of specific heat capacity data for BLAZE-SHIELD DC/F from

Harmathy (1983) with the results from Laboratory B. For temperatures up to 350 °C, both results exhibit

two peaks although their locations occur at different temperatures, and their magnitudes are different. In general, an increase in the heating rate results in a shift of the peaks toward higher temperatures and in increases of maxima or minima of peaks with narrowing peak widths. Both studies used the same heating

rate of 5 °C/min, however, other procedural and operational factors could have affected the

measurements. Since milligram quantities of SFRM are used in DSC, assurance of specimen

homogeneity and representativeness of the bulk sample in the specimen holder is essential to the validity

of the measurements, especially for inhomogeneous materials like SFRMs. In addition, mass loss from

the specimen holder during heating could interfere with the measurements.

Monokote MK-5 (Lab A)

Blazeshield II (Lab A)

Blazeshield DC/F (Lab A) Monokote MK-5 (Lab B) Blazeshield II (Lab B) Blazeshield DC/F (Lab B)

0 100 200 300 400 500 600

Temperature (°C)

Figure 6-6. Comparison of specific heat capacity measurements from Laboratory B with

results from Laboratory A.

NIST NCSTAR 1-6A. WTC Investigation 71
Chapter 6

o

1 , , i i , , i I 0 100 200 300 400 500 600 700

Temperature (°C)

Figure 6-7. Comparison of specific heat capacity measurements for BLAZE-SHIELD

DC/F from Laboratory B with the results from Harmathy (1983).

6.3.4 Density Measurements

Bulk densities of the SFRMs were not measured directly (except at room temperature) but were

calculated from thermal gravimetric analysis (TGA) and thermal expansion measurements. The TGA

tests were performed according to ASTM E 1 131 (ASTM 1998) using an Orton Model ST-736 TGA.

The resulting mass changes are shown in Table 6-6. The thermal expansion measurements were

performed according to ASTM E 228 (ASTM 1995) using a UnithermTM Model 1161 pushrod

dilatometer. Since the materials were not isotropic, separate measurements had to be performed for the X

and Z orientations. It was assumed that the X and Y directions had the same thermal expansion. The Z

direction was defined as the direction perpendicular to the fibrous strands in the samples. The specimens were tested from room temperature to 1 ,200 °C at a heating rate of 2 °C/min. All of the specimens shrunk

during the tests and in all cases lost contact with the pushrod at temperature about 1 , 1 00 °C before

reaching the maximum test temperature. Table 6-7 shows the results of the thermal expansion

measurements.

From the thermal expansion measurements, the change in volume for each material was calculated at each

temperature. The density values were calculated from the results of the TGA and thermal expansion.

Table 6-8 summarizes the calculations, and Fig. 6-8 displays the results. The shrinkage of the material

and the specimen mass loss both contribute to the unrealistic variation in density at high temperatures.

Thus, the density values are only valid up to 600 °C.

72 NIST NCSTAR 1-6A, WTC Investigation
Thermophysical Properties

Table 6-6. Mass loss of SFRMs with increasing temperature.

Mass Change (percent)

Temperature (°C) BLAZE-SHIELD DC/F BLAZE-SHIELD 11 Monokote MK-5

25 0.0 0.0 0.0 50 -0.2 -0.6 -0.5 100 -2.7 -3.9 -2.7

200 -5.1 -7.4 -15.0

300 -6.0 -8.7 -19.0

400 -6.7 -9.9 -22.0

500 -7.5 -11.0 -23.0

600 -8.6 -12.0 -24.0

800 -11.0 -16.0 -25.0

1000 -11.0 -16.0 -27.0

1200 -14.0 -20.0 -42.0

Table 6-7. Thermal expansion results of SFRMs.

Thermal Expansion (percent)

Temperature (°C) BLAZE-SHIELD DC/F BLAZE-SHIELD 11 Monokote MK-5

X and Y

Direction

Z direction Xand Y

Direction

Z direction X and Y

Direction

Z direction

25 0.00 0.00 0.00 0.00 0.00 0.00 50 0.02 0.02 0.02 0.02 0.03 0.03

100 0.05 0.03 0.04 -0.04 0.08 0.09 200 0.10 -0.13 0.04 -0.36 -0.06 -0.13

300 0.17 -0.12 0.09 -0.48 -0.23 -0.23

400 0.23 -0.16 0.11 -0.63 -0.65 -0.92

500 0.19 -0.38 0.08 -0.98 -0.69 -0.97

600 0.06 -0.93 -0.07 -1.45 -0.69 -0.47

800 -10.95 -26.40 -12.56 -12.42 1.22 -2.13

1000 -11.83 -27.86 -12.80 -13.63 -7.03 -8.32

NISTNCSTAR 1-6A, WTC Investigation 73
Chapter 6

Table 6-8. Calculated densities of SFRMs.

Density (kg/m3

)

a

Temperature (°C) BLAZE-SHIELD DL/b BLAZ.E-SHIELD 11 Monokote MK-5

25 236.8 313.7 292.4

50 236.1 31 1.5 290.5

100 230.1 301.3 283.8

200 224.6 291.3 249.1 300 222.

287.2 238.5

400 220.3 283.7 233.2

500 219.0 281.5 230.5

600 218.2 280.5 227.5

800 361.1 393.4 229.6

]000 375.8 401.1 269.3

1200 432.1 436.7 369.4

a. To convert to pcf multiply by 0.062428.

200

• - Monokote MK-5 • Blazeshield II Blazeshield DC/F

o

Q.

C

Q

0 200 400 600 800 1000 1200

Temperature (°C)

Figure 6-8. Bulk densities of the three SFRMs as a function of temperature.

6.3.5 Concluding Remarks

It should be noted that the thermal conductivity and bulk density depend on how the SFRM is sprayed or

applied; therefore, it is expected that the results will vary from sample to sample. In general, the thermal

conductivity of a porous material is a complex function of bulk density, porosity, and other material

74 NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Properties

properties (e.g. , Stephenson and Mark 1961). Recent attempts to use existing predictive methods to estimate thermal conductivities of porous media for SFRMs show some promise, and alternative

approaches have also been proposed for future research.

17

6.4 THERMOPHYSICAL PROPERTIES OF GYPSUM PANELS

In this section, measurement results of the thermophysical properties of four gypsum materials will be

presented. Unless stated otherwise, measurements were performed by Laboratory B. Four representative

types of gypsum materials were examined. They were:

1 . 5/8 in. thick gypsum panel A,

2. Vj in. thick gypsum panel,

3. 5/8 in. thick gypsum panel B, and

4. 1 in. gypsum liner panel.

6.4.1 Samples

The gypsum materials were all commercially available and were purchased from a local building supply

store in Gaithersburg, Maryland. Samples were cut from the gypsum panel using a box cutter and then

sent to the testing laboratory.

6.4.2 Thermal Conductivity Measurements

Thermal conductivity was measured using the heated probe technique described in ASTM D 5334

(ASTM 2000h). The following description of the heated probe method is provided by Laboratory B:

lH

"In the heated probe method, which may be considered as a variant of the

line source method, the line source and temperature sensor are combined

in one small diameter probe. This probe is inserted into the sample and

the heater turned on for a preselected time interval. During this time

interval, the rate of heating of the probe is measured. This heating rate quickly becomes semi-logarithmic and from this semi-logarithmic rate, the thermal conductivity of the sample is calculated. The probe may be

inserted into powders, fluids, small holes drilled into rocks, biological

materials, etc. A variety of probe sizes, ranging from needle-shaped to rods are available. The data is collected by the PC based digital data

acquisition system and the heating rate displayed visually. A semilogarithmic portion of the heating curve is chosen using the mouse and

the conductivity calculated based on this portion of the curve."

The measurement results are summarized in Table 6-9, and the results are plotted in Fig. 6-9.

17 Bentz. D. P., Prasad, K. R. and Yang, J.C. 2004. Towards a Methodology for the Characterization of Fire Protection Materials with Respect to Thermal Performance Models. Fire and Materials ^accepted for publication).

18 www.tpfrl.com/heatprb.html

NIST NCSTAR 1-6A, WTC Investigation 75
Chapter 6

Table 6-9. Thermal conductivities of gypsum materials

5/8 in. Panel A Vi in. Panel 5/8 in. Panel B 1 in. Liner Panel

(°C) (W/(m K))a (°C) (W/(m K) (°C) (W/(m K) (°C) (W/(m K)

23 0.156 23 0.194 23 0.154 23 0.133

45 0.1533 47 0.184 56 0.148 48 0.135

100 0.1558 97 0.188 103 0.156 97 0.136

222 0.0963 200 0.100 230 0.090 200 0.093

296 0.0976 299 0.097 3 IS 0.105 293 0.089

384 0.0987 406 0.106 428 0.113 413 0.107

4N2 0.1102 496 0.113 508 0.113 508 0.116

591 0.1276 603 0.121 609 0.131 598 0.134

a. To convert to Btu in./(h ft- °F) divide by 0.1442279.

0.20 • 5/8" Panel A

o 1/2" Panel

5/8" Panel B v

1" Liner Panel

0.08 i , ,

i i i 0 100 200 300 400 500 600 700 Temperature (°C)

Figure 6-9. Thermal conductivities of the four gypsum materials as a function of

temperature.

76 NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Properties

Figure 6-10 shows a comparison of the current thermal conductivity measurements with data from

Mehaffey et al. (1994) for Firecode Core Type X gypsum panel. The data from Mehaffey et al. were

obtained using a commercially available thermal conductivity meter. Both sets of data exhibit similar

trends, although, in general, the values from Mehaffey et al. are higher.

A comparison of the current thermal conductivity results with the data obtained from Harmathy (1983)

and Mehaffey et al. (1994) for Firecode C Core gypsum panel is shown in Fig. 6-11. The conductivities

from Harmathy (1983) are higher than those obtained from other studies. In general, the thermal

conductivity initially decreases and then increases with increasing temperature.

0.35

0.30 -

0.25

0.05

0.00

5/8" Panel A

-•— Laboratory B O- from Mehaffey etal. (1994)

O-O

O

200 400 600 800 1000

Temperature (°C)

Figure 6-10. Comparison of the thermal conductivity measurements from Laboratory B

with the data from Mehaffey et al. (1994) for 5/8 in. thick gypsum panel A.

NISTNCSTAR 1-6A, WTC Investigation 77
Chapter 6

0.30

E

>

o

~oco

u

TOE

<D .C

h0.25

0.20

0.15

0.10

0.05

0.00

^-4

—• Laboratory B (1/2" Panel) O Laboratory B (5/8" Panel B) -- from Harmathy (1983) -V from Mehaffey et al. (1994)

200 400 600 800 1000 Temperature (°C)

Figure 6-11. Comparison of thermal conductivity measurements from Laboratory B with

other literature values for Y2 in. thick gypsum panel and 5/8 in. thick gypsum panel B.

6.4.3 Specific Heat Capacity Measurements

Specific heat capacities of the cores of the four gypsum panel samples were measured using a TA

Instruments DSC 2910 differential scanning calorimeter at NIST. Tests were conducted according to the

procedure described in ASTM E 1269 (2001). Specimens of approximately 8.4 mg ± 0.1 mg in mass

were held isothermally at 30 °C for 5 minutes. The temperatures were then increased at a rate of

20 °C/min to a maximum temperature of 600 °C, the operating limit of this instrument. The specimens were held isothermally at 600 °C for an additional 5 minutes. Single scans of both an empty pan and a pan containing standard reference material SRM 720 (sapphire or a-A^O^) were conducted prior to testing and used to determine calorimetric sensitivity. The apparent specific heat capacity was calculated

according to the formulas presented in the ASTM standard.

An additional modification to the ASTM test procedure was necessitated by the chemical nature of the

material comprising the cores of the boards. The dominant material in the cores is gypsum, a naturally

occurring mineral composed of calcium sulfate chemically bound to hydrated water (calcium sulfate dihydrate or CaS04 -2H2 0). As gypsum is heated, the hydrated water is liberated in two endothermic

chemical reactions. If the core materials were contained within sealed hermetic pans, out-gassing of the

liberated water would eventually increase the pressure beyond the accepted limits of the pans. Use of an

7S NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Properties

open pan is undesirable, however, as the dehydration reactions also depend on the partial pressure of

water vapor in the gas surrounding the material. Therefore, aluminum hermetic pans with 50 um

diameter pinholes in the lids were used. The small diameter hole allowed pressure to dissipate from the

pan. maintaining structural integrity, but retained sufficient water vapor to resolve the two dehydration

processes. As the core of the gypsum panel is porous, having a porosity of approximately 0.3 (Blondeau

et al. 2003), it is further expected that the liberated water will remain locally in the form of vapor even as pressure diffuses across the porous matrix. The procedure used should, therefore, provide a better estimate of the response of gypsum panel cores to the rapid heating observed in fires.

Results are presented as apparent specific heat capacity of the material with respect to the initial mass of

the specimen. Clearly, as the water is driven from the samples and bleeds through the pinhole, the mass

of the sample will decrease. Results of thermal gravimetric tests should also be used if the true specific

heat capacity of the material is desired. The data are presented in Tables B-2, B-3, B-4 and B-5 and are plotted in Figs. B-l. B-2. B-3. and B-4 in Appendix B. Peaks and valleys attributed to chemical changes

are labeled on each graph with the corresponding chemical reaction. Figure 6-12 is a plot of the results for all four gypsum materials. It is seen that the four panels had similar specific heat capacities as a function of temperature.

Q.

o

25000

20000

15000

10000

5000

— 5/8" Panel A — 1/2" Panel •- 5/8" Panel B •— 1" Liner Panel

0 100 200 300 400 500 600 700

Temperature (°C)

Figure 6-12. Comparison of specific heat capacities for the four gypsum materials.

NISTNCSTAR 1-6A. WTC Investigation 79
Chapter 6

6.4.4 Density Measurements

Laboratory B used a Netzsch Model 409 Simultaneous Thermal Analyzer (STA) equipped with both high

and low temperature furnaces was used to determine mass changes as a function of temperature. The

STA is vacuum tight, allowing specimens to be tested in pure inert, reducing, or oxidizing atmospheres as well as under vacuum. The unit can be operated in the differential scanning calorimetric (DSC) or thermogravimetric analysis (TGA) mode.

A dual push-rod dilatometer (Theta Dilatronics II) was used to measure linear thermal expansion

following the procedure in ASTM E 228 (ATM 1995). The differential expansion between the gypsum

specimen and a known standard reference material was measured as a function of temperature. The

expansion of the specimen is computed from this differential expansion and the expansion of the standard.

The measurements are made under computer control, and linear expansion is calculated at pre-selected

temperatures. Six standard reference materials for expansion were obtained from NIST and these include

materials with low, moderate, and large expansions. For the purposes of calibration and checkout, one NIST standard was measured against another NIST standard.

Densities were calculated from the TGA results and linear thermal expansion measurements. Table 6-10

summarizes the calculated results, which are also plotted in Fig. 6-13. All four materials show the same

trend as a function of temperature. The variation of density with temperature is associated with the mass

loss and the change in volume of the gypsum material.

Table 6-10. Bulk densities of the four gypsum materials.

Density (kg/m3

)

a

Temperature

(°C)

5/8 in. Panel A Vi in. Panel 5/8 in. Panel B 1 in. Liner Panel

23 709 760 787 770

50 706 759 785 767

100 680 754 780 759

150 629 725 752 721 200 586 66X 691 664

250 580 636 656 638

300 581 634 654 636

350 582 634 654 638

400 597 659 679 659

450 600 665 684 663

500 600 664 682 664

550 599 663 681 664

600 605 663 6S2 664

a. To convert to pcf multiply by 0.062428.

80 NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Properties

800

550

• 5/8" Panel A o 1/2" Panel

5/8" Panel B v

1" Liner Panel

100 200 300 400 500

Temperature (°C)

600

50

48

46

44 ^X!

42 £

CD

40 en

38

36

700

Figure 6-13. Bulk densities of the four gypsum materials as a function of temperature.

NISTNCSTAR 1-6A, WTC Investigation 81
Chapter 6

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82 NISTNCSTAR 1-6A, WTC Investigation
Chapter 7

Adhesive and Cohesive Strength

In order to analyze the thermo- structural response of the WTC towers during the fires after the aircraft impacts, it was necessary to estimate the extent of dislodged thermal insulation on structural members.

Dislodgement could occur as a result of:

• Direct impact by debris resulting from breakup of the aircraft and its contents and breakup of

structural elements, or

• Inertial forces due to vibration of members excited by the impact events.

For a given level of vibration, the magnitude of the inertial forces acting on the insulation depends on the

density and thickness of the thermal insulation. The insulation would dislodge if the stresses resulting

from inertial forces exceeded the strength of the insulation. The focus of the investigation reported in this chapter was to determine tensile strength characteristics of the thermal insulation. Information on in- place measurements provide by the Port Authority are reviewed. The experimental approach used to obtain additional information is presented along with test results. Finally, a simplified approach is presented for estimating the accelerations required to dislodge the thermal insulation.

7.1 REPORTED IN-PLACE DENSITY AND BOND STRENGTH

As was mentioned in Section 4.3, the Port Authority provided data on in-place density and tensile strength characteristics of the thermal insulation applied to the floor trusses during tenant alterations. Figure A-60 in Appendix A shows an example of such test reports. The reports indicated that tests were

done in accordance with ASTM E 605 (density) and ASTM E 736 (cohesion/adhesion strength). As

mentioned in Chapter 4, BLAZE-SHIELD II was used in the upgrade, and as noted previously in Table 6-3, the manufacturer indicated that BLAZE-SHIELD II is about 20 percent denser and has about

20 percent higher adhesive/cohesive strength compared with BLAZE-SHIELD DC/F.

According to ASTM E 605 (ASTM 2000a), density is determined by removing a rectangular portion of

the insulation after taking 12 thickness measurements to obtain the average thickness. The length and

width of the removed specimen are measured, and the volume is calculated. The equilibrium mass of the

specimen is determined, and density is calculated by dividing the mass by the volume. The test reports

provided by the Port Authority provided no notes to indicate deviations from the standard procedure.

The technique described in ASTM E 736 (ASTM 2000b) is illustrated in Fig. 7-1. A bottle screw cap is glued to the surface of the thermal insulation, and after the glue has cured, the cap is pulled. The force

required to pull off the cap is divided by the area of the cap, and reported as the "cohesive/adhesive

strength." Failure is described as "cohesive" if it occurs within the insulation and is defined as "adhesive"

if it occurs at the interface with the substrate. Figure 7-2 shows an example of a cohesive failure.

NISTNCSTAR 1-6A, WTC Investigation 83
Chapter 7

Tensile Load

Figure 7-1. Bond strength test using screw cap in accordance with ASTM E 736.

Source: NIST. Figure 7-2. Cohesive failure of SFRM using ASTM E 736 test (dashed circle is approximate location of cap before being pulled off.

Table 7-1 summarizes the density and strength data provided by the Port Authority (see also Table 4-2).

The results of the tests are labeled as "bond strength." Test method ASTM E 736 calls for reporting the

failure mode, but the Port Authority test reports did not include information on the nature of the failure associated with the reported strengths. The density values in Table 7-1 are plotted in Fig. 7-3 and the

bond strength values are plotted in Fig. 7-4. Analysis of the density values indicated no statistically

significant differences between the reported densities of the upgrade thermal insulation on floor trusses in the two towers. The overall average density was 18.9 pcf with a standard deviation of 3.2 pcf, giving a

coefficient of variation of 16 percent.

S4 NISTNCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

Table 7-1. Density and bond strength of SFRM on floor trusses reported by the Port

Authority of New York and New Jersey (30-P).

Tower Floor Density, pcf

Bond

Strength, psf Tower Floor Density, pcf

Bond

Strength, psf

1

79 16.6 333

1

98

31.3 407

81

19.0 270 16.8 351

17.4 352 19.6 518

17.6 463

99

18.8 204

17.4 315 16.6 222

83 16.0 259 18.4 204

85

28.7 162

100

16.4 278

23.7 180 17.3 278

18.6 288 19.9 333

15.8 278

102

16.5 333

16.4 259 16.9 333

92

20.3 360 15.9 315

15.4 324

2

77

19.4 351

18.0 360 19.4 198

93

14.3 153 17.2 297

16.6 207

78

17.0 288

16.1 216 18.1 270

18.4 234

88

18.0 167

15.1 162 16.0 333

17.4 180 15.0 157

21.3 216

89

22.4 370

94

21 2 486 15.8 333

20.5 504 15.3 270

20.1 288

92

19.7 342

95

18.0 270 21.1 360

20.1 306 19.7 297

20.4 198

99

19.5 315

96

20.5 486 22.7 252

14.X 288 21.9 306

19.9 324 19.5 270

97 26.5 360

NISTNCSTAR 1-6A, WTC Investigation 85
Chapter 7

o

Cl

w

c

CD Q

35

30

25

20

15

10

• WTC 1 WTC 2 •

• ri.

• 1

>•••-< -s. A

• i j • * 9 j

75 80 85 90

Floor

95 100 105

Figure 7-3. In-place density of BLAZE-SHIELD Type II on floor trusses from Port

Authority test reports during the period 1997-1999.

600

500

C/J Cl 400

siC

CD 300

i_ CO

"Dc 200 o

CD 100

0

i i . t

i

s WTC 1 WTC 2

75 80 85 90 95

Floor

100 105

Figure 7-4. In-place bond strength of BLAZE-SHIELD Type II using ASTM E 736 from

Port Authority test reports during the period 1997-1999.

Analysis of the bond strength values indicated that there were statistically significant differences between

the average bond strengths for the different floors, but here was no statistically significant difference

between the average bond strengths for the two towers. The overall average bond strength was 302 psf,

with a standard deviation of 91 psf, giving a coefficient of variation of 30 percent. This value is less than

the value of 360 psf indicated in Table 6-3, but the tabulated values is for tests under controlled

conditions (referred to as "tested performance

,, in the manufacturer's literature) and is not representative

of field strengths. ISOLATEK product literature dated February 2002 refers to an average bond strength

86 NISTNCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

of 150 psf as "standard performance'" and this same value is used in its guide specification for BLAZESHEILD II.

19 Thus, the reported bond strengths shown in Fig. 7-4 are consistent with expectations.

7.2 SPECIMEN PREPARATION AND TEST PROCEDURES

While the in-place bond strength data of BLAZE-SHIELD II reported by the Port Authority appear to indicate acceptable performance, results of ASTM E 736 tests do not provide sufficient information for predicting whether insulation would be dislodged from structural members under various impact

conditions. The standard test does not provide unambiguous values of cohesive and adhesive strengths,

and it does not provide tensile properties in a direction parallel to the surface, that is, in-plane cohesive

strength. As was mentioned in Section 6.3.4, because of the way a fibrous SFRM is installed, the

resulting material is not isotropic. Layers of fiber bundles are deposited parallel to the surface of the

substrate. It is expected that the strength perpendicular to the planes of the layers would be less than the

strength parallel to the layers. Thus, a series of tests were conducted that would allow different strength

properties to be determined. In addition, it was decided to test BLAZE-SHIELD DOT because the Port Authority data did not include tests of this material.

7.2.1 Preparation of Test Plates

Test specimens were made by applying the SFRM to % in. steel plates measuring 8 in. by 16 in. One half

of the plates were coated with Series 10 Tnemec Primer (99 red)

20

, which is the primer that was specified

for the exterior columns (see Appendix A Fig. A-63). Nominal SFRM thicknesses of 3A in. and VA in. were applied. Thickness was controlled by surrounding the steel plates with wood strips to form molds of

the desired depth. Figure 7-5 shows the application of BLAZE-SHIELD DC/F to the steel plates

positioned on the floor of the laboratory. Thickness was built up in several passes of the spray nozzle.

Gentle hand rubbing was used to reduce local high spots and produce reasonably uniform thicknesses.

The average thickness of SFRM for the 3A in. plates was 0.85 in. with a standard deviation of 0.08 in. For

the VA in. plates, the average thickness was 1.62 in. with a standard deviation of 0.16 in. The plate

specimens were allowed to dry for over five months in the laboratory before testing. Companion

specimens were weighed periodically for loss of water, and it was found that the VA in. thick specimen

reached equilibrium in about one month.

7.2.2 Test Methods

It was desired to determine adhesive strength, cohesive strength normal to the surface, and cohesive

strength parallel to the surface of the SFRM. Figure 7-6 is a schematic of the method used to measure the

first two properties. This approach is based on the standard pull-off test method used in concrete technology to measure the bond strength of overlays applied to concrete substrates (ASTM 2004b). The

SFRM layer was cut carefully in two directions, and a 3/8 in. by 2.7 in. by 2.7 in. aluminum plate was

glued to the surface. After the adhesive had cured, a tensile load was applied to the plate, and the force

required to pull off the SFRM was measured. The advantages of this approach over the ASTM 736

19 Product Manual, Isolatek International. Stanhope. NJ. February, 2002. Purchased from Tnemec Company Inc., 6800 Corporate Drive. Kansas City, Missouri 64120-1372.

NISTNCSTAR 1-6A, WTC Investigation 87
Chapter 7

technique are that the resisting area is easily determined and it offers the ability to measure both adhesive

and cohesive strengths.

4. Aluminum Plate

/

CSN>XVVX\NXV\XVSX y Saw cut

/

Figure 7-6. Schematic of "pull-off' test method used to measure cohesive and adhesive

strengths.

In using the method shown in Fig. 7-6, one does not know beforehand what type of failure will occur, that

is, whether it will be adhesive failure at the SFRM/steel interface or cohesive failure in the bulk SFRM.

Failure occurs at the weakest link. It is possible, however, by a simple modification of the usual

procedure to measure both strengths in the same specimen. This is accomplished by bonding together the

failed specimen after the first test, and performing a second test on the repaired specimen. This approach

is illustrated in Fig. 7-7, where the schematics on the left represent the first test and those on the right

represent the re-test. Two cases are illustrated:

• Case 1: The initial failure is an adhesive failure near the SFRM/steel interface, and after repairing

the specimen the second failure is a cohesive failure in the bulk SFRM.

• Case 2: The initial failure is a cohesive failure in the bulk SFRM, and after specimen repair the

second failure is an adhesive failure near the SFRM/steel interface.

88 NISTNCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

As will be seen, this approach works because adhesive and cohesive strengths are similar in magnitude.

First Test Re-Test

t

Adhesive failure

Case 1 k\\\\\\\\\\\\\N

t

Cohesive failure

t

Case 2

Cohesive failure

t

[\\\\\\\\\\\\N\1

.TO

Adhesive failure

Failure plane Adhesive

Figure 7-7. Technique used to measure both "adhesive" and "cohesive" strength in the

same specimen.

The cohesive strength parallel to the surface was determined on specimens obtained by carefully

removing the SFRM layer from the steel and preparing a prism that could be loaded as shown in Fig. 7-8. The following section describes how the test specimens were prepared.

7.2.3 Preparation of Test Specimens

From each plate, three specimens were prepared for measuring both density and in-plane cohesive

strength, and two specimens were prepared for measuring adhesive strength and cohesive strength normal

to the surface. The first step was to cut the SFRM layer into five 2.7 in. wide strips. A fine-toothed saw

blade was used, and the sawing motion was done carefully so as to minimize damage to the SFRM (see

Fig. 7-9). The two outer strips and the middle strip were debonded from the steel plate by using a sharpened putty knife. Care was taken to ensure that the two strips for adhesive/cohesive strength testing were not disturbed (see Fig. 7-10).

NIST NCSTAR 1-6A, WTC Investigation 89
Chapter 7 L

Steel plate

Aluminum plate

Adhesive

Adhesive

I

Figure 7-8. Method to measure cohesive strength parallel to SFRM surface (in-plane

cohesive strength).

Source: NIST. Figure 7-9. Cutting the SFRM layer into five strips.

90 NISTNCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

Source: NIST. Figure 7-10. Five specimens obtained from single plate; top three specimens are used for density and in-plane cohesive strength, bottom specimens are used

for adhesion/cohesion tests.

For the adhesive/cohesive strength tests, an aluminum plate was bonded to the top surface using a fast curing, two-component urethane foam adhesive. Fixtures were used to ensure that the bonded plate was

parallel to the steel plate (see Fig. 7-11). After the adhesive had cured, the SFRM layer was cut as shown

in Fig. 7-12 so as to produce a prismatic test specimen. A hook was screwed into the aluminum plate and

a load was applied by hand using a 50 lb digital force gauge (see Fig. 7-13). The force gauge was able to store the peak load attained during the test. During loading, the steel plate was placed on the floor, and a

foot was placed at each end of the plate to provide resistance to the applied tensile load. The average

length and width of the failure area was measured and used to compute the adhesive or cohesive strength.

After the first test, the specimen was repaired with the same polyurethane adhesive, and the test was

repeated as discussed in Section 7.2.2. Figure 7-14 shows two specimens after the first test. The

specimen on the left failed in the bulk material, thereby giving a measure of the cohesive strength normal

to the surface. The specimen on the right failed near the SFRM/steel interface, which is taken to be the

adhesive strength. Figure 7-15 shows the same two specimens after they had been repaired and subjected

to the second loading. Now the specimen on the right shows a crack in the bulk material, and the

specimen on the left shows separation near the SFRM/steel interface. Note that for the specimen on the

right, which had an adhesive failure during the first loading, the failed specimen was bonded to a bare

steel plate (not shown) for the second test to measure cohesive strength. In some cases where the first

failure was cohesive, the repeated test also resulted in cohesive failure. In these cases, the specimen was

repaired as often as needed until an adhesive failure occurred.

NIST NCSTAR 1-6A, WTC Investigation 91
Chapter 7

Source: NIST. Figure 7-11. Aluminum plate being bonded to the top surface of SFRM specimen; the

wooden fixture is used to maintain the correct alignment of the plate.

Source: NIST. Figure 7-12. Preparing the SFRM specimen for adhesion/cohesion test.

92 NIST NCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

Source: NIST. Figure 7-13. Manual application of tensile load using digital force gauge.

Source: NIST. Figure 7-14. Results of first loading: specimen on left had a cohesive failure in the bulk SFRM, specimen on right failed near the

SFRM/steel interface.

NISTNCSTAR 1-6A, WTC Investigation 93
Chapter 7

Source: NIST. Figure 7-15. Results of second tests after repair: specimen on left had adhesive failure and specimen on right had cohesive failure.

The other three strips (see Fig. 7-10) were used for determining density and in-plane cohesive strength.

First, the top surfaces of the debonded strips were sanded on a belt sander to obtain prismatic specimens.

About 0.2 in. was removed from the 3A in. plates, and about 0.4 in. was removed from the 1

lA in. plates.

The prisms were weighed and their average dimensions determined. The densities were obtained from

the masses and computed volumes. Each prism was then bonded to a steel plate with the polyurethane

adhesive. An aluminum plate was bonded to the other end of the specimen. After the adhesive had cured,

a tensile load was applied to the aluminum plate until the SFRM failed (see Fig. 7-16). The area of the

fracture plane was determined and the in-plane cohesive strength calculated from the recorded maximum

load.

Source: NIST.

94

Figure 7-16. SFRM specimen after measuring in-plane cohesive strength.

NISTNCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

7.3 TEST RESULTS

Table 7-2 summarizes the properties that were measured and the types of SFRM plates that were tested.

It was assumed that the presence or absence of primer on the steel plates would not affect density or in- plane cohesive strength. Thus, only primed plates were used for these properties. The following sections

summarize the test results.

Table 7-2. Test matrix.

Property Va in. Nominal Thickness VA in. Nominal Thickness

With Primer Bare Steel With Primer Bare Steel Density X X

In-plane cohesive strength X X

Adhesive/Cohesive (N)* strength X X X X

*N indicates normal to surface of SFRM

7.3.1 Density

As mentioned in Section 7.2.3, density was determined by weighing prismatic specimens prepared by

sanding the irregular exposed surface of the SFRM. The specimens were about 5 months old when tested

and had attained equilibrium water contents. Five plates with primed steel were chosen at random for

each SFRM thickness. Table 7-3 lists the individual determinations, and Fig. 7-17 is a plot of the data. The average density of the Va in. thick specimens is 27.2 pcf, with a standard deviation of 0.8 pcf; and for the 1/4 in. thick specimens the average density is 29.7 pcf with a standard deviation of 1.3 pcf. The

difference in average values for the two thicknesses was found to be statistically significant.

Table 7-3. Density of BLAZE-SHIELD DC/F specimens.

Nominal Density, Nominal Density,

Thickness Specimen pcf Thickness Specimen pcf

7-a 26.1 24-a 29.5

7-b 26.0 24-b 29.2

7-c 26.6 24-c 29.3 6-a 27.2 29-a 30.0 6-b 27.2 29-b 29.0

6-c 26.7 29-c 29.6

18-a 26.2 10-a 31.2

Va in. 18-b 28.1 1

lA in. 10-b 31.4

18-c 27.2 10-c 29.9

16-a 27.0 30-a 26.9

16-b 28.2 30-b 27.7

16-c 28.3 30-c 29.5 2-a 27.9 11-a 31.5 2-b 26.7 11-b 30.5

2-c 28.0 11-c 29.7

NISTNCSTAR 1-6A, WTC Investigation 95
Chapter 7

o

CL

c/) c

<r> Q

32

31

30

29

28

27

26

25

*

1

1

1

"3/4 in. ^ w 1-1/2 in. < ^

• * .

1 •

• < •

•

4 6 Specimen10 12

Figure 7-17. Density of BLAZE-SHIELD DC/F specimens.

These measured densities are unexpectedly high compared with published values and the values reported

in Table 6-8, which indicates a room temperature density of 14.8 pcf. The 2001 ICBO Evaluation Service

report E-R 1244, refers to a minimum average density of 13 pcf for BLAZE-SHIELD DC/F

(ICBO 2001). The air-dry densities obtained in the NIST/UL fire endurance tests of floor truss assemblies (NIST NCSTAR 1-6B) are shown in Fig. 7-18. Again, those densities are lower than obtained

in this study. The exact reason for the higher density in this study is not known, but possible reasons

include the following:

• The use of forms, as opposed to only a piece of sheet metal (as in ASTM E 605), may have

provided confinement during spraying leading to more consolidation of the SFRM.

• The smoothing of the top surface by sanding removed the less dense material. Recall that about

0.2 in. and 0.4 in. were removed from the 3A in. and 1

lA in. plates, respectively.

• The hand screening that was done to remove local high spots may have resulted in additional

consolidation.

96 NIST NCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

CD Q

26-

24-

22-

20-

18

16-

14-

Test Asssembly

Figure 7-1 8. Air-dry density of BLAZE-SHIELD DC/F from NIST/UL floor truss fire

endurance tests (NIST NCSTAR 1-6B).

7.3.2 In-Plane Cohesive Strength

After completing the density determinations the prismatic specimens of SFRM were bonded to a bare

steel plate, and an aluminum plate was bonded to the other end (see Fig. 7-8). The steel plate was placed on the floor, and a tensile load was applied to the aluminum plate until the SFRM failed. The width and

thickness of the specimen adjacent to the failure plane was measured, and the in-place cohesive strength was calculated.

Table 7-4 lists the individual values on in-plane cohesive strength, and Fig. 7-19 is a plot of the results. The average strength for the 3A in. specimens is 1,120 psf with a standard deviation of 390 psf. For the

1 /4 in. specimens the average is 1,740 psf with a standard deviation of 540 psf. The difference in average

strength is statistically significant. The relative strengths are consistent with the differences in density for the two thicknesses.

NIST NCSTAR 1-6A, WTC Investigation 97
Chapter 7

7-4. In-plane cohesive strength for BLAZ z-onlcLU DC/F spec

Cohesive Cohesive

1\ t b ni i n 'A B 1 ' Ullllllul on ^112^111, |\nmi n a 1 Strength,

Thickness Specimen psf Thickness Snecimen psf

/-d lV7J 1/1 22 /9

7/ -0h 24-b 1 607

7-c 689 24-c 1 Z O "7 1687

O-d Q 1 Q z y-ci 1 *T / J D-D 7Q 1 ly i 29-b 1 AO Z 1986

o-c 1 ^ 1 7 1 A 29-c

T 1 Al 3101

1 8 Q 1 o-d 1 fH7 i a

10-a 1 AA/ 2006

3A in. 1 o-D 70 1 r/2 in.

1 A U. lU-b 1 8 /o

I o-C Q^l 7 J J

1 A

10-c 1304

16-a 575 1 A 30-a 1579

16-b 1500 30-b 636

16-c 1254 30-c 1630

2-a 1065 11-a 1902

2-b 1875 11-b 1226

2-c 1773 11-c 1861

If) Cl

_0

76

CO CL

c

0)

i—

CD>

c/) CD C

oO

3500

3000 -

2500

2000

1000

500

~i r ~i r

3/4 in.

"

: > 1-1/2 in. >

4> i

1 •

•

«

i

i...... •

•

4 6 8 Specimen10 12

Figure 7-19. In-plane cohesive strength for BLAZE-SHIELD DC/F specimens.

7.3.3 Adhesive Strength

Adhesive failure is defined as failure near the SFRM/steel plate interface. In all cases where there was

measurable adhesive strength a thin layer of cement paste and mineral fibers remained on the steel plate

when the specimen separated. Figure 7-20 shows one of the 3A in. specimens (with primed steel) after testing and illustrates "adhesive" failure. The photo on the left is a magnified view of about a

0.4 diameter region and shows the thin layer of mineral fibers and paste. Note in the in the right

photograph that there are regions on the steel with no adhering paste, indicating essentially zero adhesive

strength. The locations of the specimens for the adhesion/cohesion tests were chosen based on the

98 NISTNCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

location of the regions with adhesive failure when the three strips used for density determination were

removed. This is illustrated in Fig. 7-20, where the specimen on the right was located toward the top of

the plate and the one on the left was located at the center.

The plan was to select five plates at random for each combination of SFRM thickness and condition of

steel plate (bare versus primed). It was found that for the 1 Vi in. plates with primed steel two of the first three specimens had essentially zero bond strength because the SFRM strips were loose after cutting with

the saw. Figure 7-21 shows an example of a plate with essentially zero adhesion strength. At this point

in the testing, the remaining plates were examined by applying a small force by hand to the SFRM to check whether there was any significant adhesion. Ten of the 15 plates had no adhesion. Plates 30 and 1

appeared to have some adhesion, so these were selected to complete the 5 replicate plates for this group.

Source: NIST. Figure 7-20. Example of "adhesive" failure of SFRM (original location of test specimens

are the gaps in the two strips); photo on left is magnified view of thin layer of paste and

fibers (the marks around the perimeter is red ink used to locate field of view).

NISTNCSTAR 1-6A, WTC Investigation 99
Chapter 7

Source: NIST. Figure 7-21. Example of lack of adhesion in 1V2 in. SFRM on steel plate with primer.

There were no adhesion problems in the specimens made with bare steel. Figure 7-22 shows examples of

specimens with bare steel. The top photograph shows the appearance of a

3A in. SFRM plate after removal of the three strips to be used for density testing. The regions of the plates with bare steel are due

to the action of the putty knife used to debond the three strips. The lower photograph shows the

appearance after completion of the adhesion tests on a 1

lA in. SFRM specimen. Again the bare spots are due to scraping by the putty knife.

Table 7-5 shows the adhesive strength results and Fig. 7-23 is a plot of the data. Only four plates were

selected for the 3A in. SFRM with bare steel and only three were selected for the 1 Vi in. SFRM with bare

steel. Table 7-6 summarizes the adhesive strength test results. As a point of reference, the manufacturer

of BLAZE-SHIELD DC/F indicates an adhesion/cohesion value under controlled conditions in accordance with ASTM E 736 of 295 psf (see Appendix A Fig. A-63). In the ASTM standard procedure,

the SFRM is applied to a 12 in. square galvanized steel sheet (0.060 in. thick) at a thickness of *A in. to

1 in. Note however, that in the ASTM test method, failure can be cohesive (in the bulk SFRM) as well as combination of adhesive and cohesive failure.

It is clear that the condition of the steel has a significant effect on the SFRM adhesive strength.

Typically, manufacturers require that compatibility with primed steel be evaluated to ensure that proper

materials are used for adequate adhesion. For example, the following text is taken from the ICBO

evaluation of different BLAZE-SHIELD products (ICBO 2001):

"2.2.5 Primed or Painted Surfaces: CAFCO BLAZE-SHIELD

materials are permitted to cover primed or painted wide flange shapes,

subject to the following requirements:

1. Beam flange width is 12 inches (305 mm), maximum.

2. Column flange width is 16 inches (406 mm), maximum.

100 NISTNCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

3. Beam or column web depth is 16 inches (406 mm), maximum.

4. Bond tests of five specimens in accordance with ASTM E 736 are used to verify the bond strength of the fire -protection material to a painted or primed steel beam or column at the jobsite. Condition of

acceptance is that the average bond strength is 20 times the weight of

in-place fire -protection material but not less than 150 psf (7.2 kN/m: ), or the minimum average bond strength is 80 percent, with a minimum

individual bond strength of 50 percent of the bond strength of fire- protection material applied to bare, clean, i/s inch-thick (3.2 mm) steel plate, whichever is greater. Where bond-strength values are less than

these minimums, CAFCO BOND-SEAL Type E.B.S. adhesive is applied to the primed or painted surfaces, and the bond-strength tests are repeated."

The results of these tests show that BLAZE-SHIELD DC/F is not compatible, from an adhesion point of

view, with the Tnemec 99 Red Metal Primer used in this study and that was specified for the exterior

columns of the WTC towers.

NISTNCSTAR 1-6A, WTC Investigation 101
Chapter 7

Source: NIST. Figure 7-22. Examples of good adhesion in specimens with unprimed

steel plates: (top) 3A in. SFRM specimen before testing; (bottom)

V/2 in. SFRM specimen after completion of tests.

102 NIST NCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

Table 7-5. Ad iesive strength of RI A7F.^ HIELD DC/F specimens.

Adhesive /\onesive

Nominal Strength, \" t\ mjnnl

1 > UII111H til Strength,

Thickness Primer Specimen psf Thickness Primer Specimen psf

7-1 175 24-1 o

7-2 934 94-9 o

6-1 1i 97y i ">9-1 378

fi-9 lf\l Ly-L

18-1 276 10-1 0

Yes 18-2 164 Yes 10-2 0

16-1 257 30-l

a 501

16-2 246 30-2a 253

2-1 5 ll-l

a 130

3A in. 9 9 32 1lA in. 11 -2

a 44

4-1 389 1-1 703

4-2 493 1-2 651

5-1 488 2-1 543

5-2 493 2-2 767

No

365

No

6-1 3-1 459

6-2 552 3-2 876

7-1 425

7-2 472

a. Not selected randomly.

1000

C/5 Q. 800 - • With Primer

No Primer

3/4

CDL. CO« 400

0) < 200

I— 11/2

—

10 Specimen

15 20

Figure 7-23. Adhesive strength of BLAZE-SHIELD DC/F specimens for primed and

unprimed steel plates.

NISTNCSTAR 1-6A, WTC Investigation 103
Chapter 7

Table 7-6. Summary of adhesive strengt

Nominal

1 II It t\ 1 1 1 I> .> Primer \ vp1*51 op n^f

Standard

Dpvintinn l/l * lallUII^ ncf LI9I

Coefficient of

Variation,

percent

Va in. Yes 185 96 52

No 450 63 14

1 '/2 in. Yes 171

a 196 115

No 666 151 23

a. For selected specimens

7.3.4 Cohesive Strength Normal to Surface

As discussed in Section 7.2.3, the same specimens were tested twice (in some cases three times) so as to determine the adhesive and cohesive strength normal to the surface. Figure 7-24 shows examples of

cohesive failures in 1/4 in. SFRM specimens. These specimens were subsequently repaired with the

polyurethane foam adhesive, and the adhesive strength was then determined. In general, cohesive failures tended to occur close to the surface of the SFRM layer. This is logical because less compaction would be

expected near the surface and perhaps less hydration of cement due to drying.

Source: NIST. Figure 7-24. Examples of cohesive failure in VA in. SFRM specimens.

To compare the results from the current test method, one of the 2A in. plates with bare steel was also

subjected to an ASTM E 736 type test with round screw cap bonded to the top surface. First, a screw-cap

test was conducted at the center of the plate, and then three strips were cut as shown in top photo of

Fig. 7-25. Another screw cap test was conducted on the right side of the plate, as shown in the bottom

photo of Fig. 7-25. Finally, two tests with the current procedure were done on the strip on the left side of

the plate. In the bottom photograph it is seen that the screw-cap pulled away in the bulk material near the

top surface.

104 NIST NCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

Source: NIST. Figure 7-25. Comparative testing: current method versus ASTM E 736 method: (top) locations of two screw cap tests;

(bottom) after completion of tests.

Table 7-7 shows the individual cohesive strengths normal to the surface, and Fig. 7-26 is a plot of the

data. Table 7-8 summarizes the average strength and variability of test results.

NISTNCSTAR 1-6A, WTC Investigation 105
Chapter 7

Table 7-7. Cohesive strength normal to surface for BLAZE-SHIELD DC/F specimens Nominal

Thickness Primer Specimen

Cohesive

Strength psf Thickness Primer Specimen

Cohesive

Strength psf

Yes

3/4 in.

No

7-1 7-2

6-1 6-2

18-1 18-2

16-1 16-2

2-1 9-9

4-1 4-2

5- 1 5-2

6- 1 6-2

7- 1 7-2

7-3 7-4

318

324

507

381

503

416

401

548

340

595

412

373

349

366

373

264

372

430

419 a

369 a

Yes

Vi in.

No

24-1 24-2

29-1 29-2

10-1

10-2 30- 1 30-2

11- 1 11-2

1-1

1-2 2-la

2-2a

2-lb

2-2b

3- la 3-2a

3-2a

3-2b

538

709

463

592

680

834

458

403

755

667

464

574

372

354

661

740

700

530

836

722

a. Using screw cap in accordance with ASTM E 736.

IDCl

CDc

CD

i— CO

CD>

in

CD JZoO

900

800

700

600

500

400

300

200

• With Primer

No Primer a ASTM Cap

f

< ®

*

: c

i

3/4 m. 1-1/2 in.

10 Specimen15 20

Figure 7-26. Cohesive strength normal to surface for BLAZE-SHIELD DC/F specimens

for primed and unprimed steel plates.

106 NISTNCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

able 7-8. Summary of cohesive strengths normal to surface.

Nominal

Thickness Primer Average, psf

Standard

Deviation, psf

Coefficient of

Variation,

percent

3/4 in. Yes 433 99 23

No 367 79 13

VAin.

Yes 610 142 23

No 595 163 27

Analysis of the results indicated that there was no statistically significant effect due to the presence or absence of primer. This is logical, because the condition of the steel surface is not expected to influence

the properties of the bulk SFRM. There was a statistically significant difference in the average strengths

for the two thicknesses, with the 1 V2 in. SFRM having higher strength. This difference is likely related to the observed difference in density.

Examination of Fig. 7-26, shows that the two results using the screw caps resulted in values similar to those obtained with the current test method. This agrees with the view that the ASTM E 736 procedure

probably provides a measure of cohesive strength.

7.3.5 Adhesive Strength Versus Cohesive Strength Normal to Surface

A comparison was made of the adhesive strength and cohesive strength normal to the surface. The

individual results previously shown in Fig. 7-23 and Fig. 7-26 are shown as "dotplots" in Fig. 7-27, and

the average values from Tables 7-6 and 7-8 are shown in Table 7-9. In Fig. 7-27, the circles indicate

results with bare steel plates, and the blue points (darker shade) indicate adhesive strength. For the

specimens with primed steel, the average cohesive strength was much greater than the average adhesive

strength. For the specimens made with bare steel the difference between the averages for the two types of

strength was much smaller. Because of the high variability in individual test results, a formal analysis of

variance indicates that there is an 8 percent probability that the difference could be the result of

randomness. Generally, if this probability is greater than 5 percent, it can be concluded that the difference

is not statistically significant. Thus, for the case of good adhesion, the test results do not contradict the

assumption that the adhesive strength and cohesive strength normal to the surface are equal. If this assumption is accepted, the average of the adhesive and cohesive strengths is 409 psf for the % in. SFRM,

and the average is 622 psf for the 1

'/> in. SFRM.

From the measured strength properties, estimates were made of the local accelerations required to damage

or dislodge the SFRM, as described in Section 7.4.

NISTNCSTAR 1-6A. WTC Investigation 107
Chapter 7

1000

800

Q- 600

CT>

CD 400-

CO

200

3/4 in.

• Adhesive-NP

c Cohesive-NP X Adhesive-P X Cohesive-P

1 1/2 in.

Figure 7-27. Comparison of adhesive strength with cohesive strength normal to surface

(P = primed steel, NP = bare steel).

Table 7-9. Comparison of average adhesive strength and average cohesive strength

normal to surface.

Primer

Nominal

Thickness, in.

Average

Adhesive

Strength, psf

Standard

Deviation, psf

Average

Cohesive

Strength, psf

Standard

Deviation, psf

Yes

3/4 in. 185 96 433 99

1 V2 in. 171 196 610 142

No

3A in. 450 63 367 79

1 Vi in. 666 151 595 163

7.4 SIMPLIFIED APPROACH TO PREDICT DISLODGING OF SFRM

This section presents a simplified approach for estimating the acceleration required to dislodge SFRM

from a structural element. When a member is subjected to an impact, it will undergo various modes of

vibration. The vibrations result in local cyclic accelerations. These accelerations are transferred to the

SFRM by forces applied at the interface between the steel and the SFRM. Two limiting cases are considered:

• Case 1 is a planar element with SFRM applied to one face of the element. This would be

representative of SFRM applied to large webs and flanges of beams and columns. In this case, adhesive strength or cohesive strength normal to the surface would be the controlling SFRM

properties.

• Case 2 is a slender bar encased with SFRM. This would be representative of SFRM applied to elements of the floor trusses. In this case, in-plane tensile strength and bond strength are the

controlling SFRM properties.

108 NISTNCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

CASE 1: Planar Element

The simplified model considers the substrate and SFRM as rigid bodies. The SFRM would dislodge

when the inertial force exceeds the smaller of the adhesive bond strength or cohesive strength normal to the surface. Figure 7-28, shows the free body of the thermal insulation being acted upon by its inertial force and the adhesive force. The acceleration to dislodge the SFRM from the substrate is:

where:

fb = cohesive strength normal to surface or adhesive strength, whichever is smaller

t = thickness of SFRM

p = mass density of SFRM.

This equation shows that the acceleration to dislodge the SFRM from a planar surface is directly

proportional to the smaller of adhesive or cohesive strength (normal to surface) and inversely proportional

to the thickness and density.

To arrive at the ranges of accelerations that could be expected to dislodge SFRM from a planar surface,

the following plausible ranges of values were assumed:

• SFRM thickness: 0.75 in. and 2.25 in.;

• SFRM density: 15 pcf and 25 pcf21

;

• SFRM bond strength: 1 00 psf and 500 psf

Table 7-10 shows the resulting accelerations expressed as a multiple of g, which is the gravitational

acceleration. For the combination of low thickness, low density, and high bond strength, the required

acceleration is about 530 g. For the other extreme combination of high thickness, high density, and low

strength, the required acceleration is about 20 g. This simplified model, thus, gives an approximate range

of the amplitude of accelerations required to dislodge the SFRM from a planar surface, depending on the

actual values of the key parameters. For example, using the average values of in-place measurements for BLAZE-SHIELD II summarized in Section 7.1, for SFRM with a thickness of 2.5 in., a density of 19 pcf,

and an adhesive strength of 300 psf, the SFRM would dislodge from a planar surface at an acceleration of

about 80 g.

21 These numbers need to be converted to units of mass by dividing by the gravitational acceleration.

NISTNCSTAR 1-6A, WTC Investigation 109
Chapter 7

A

TsT Inertial Force Equilibrium

f *

•VSFRM .. F - m a — fb A=pAt amax ^ amax -fbHP *) Substrate

A = cross-sectional area

Figure 7-28. Derivation of acceleration to dislodge SFRM from planar substrate.

Table 7-10. Acceleration required to dislodge SFRM from planar surface for different

Density, pcf

Bond

Strength, psf

Thickness,

in. Acceleration/g

15 100 0.75 107

15 100 2.25 32

15 500 0.75 533

15 500 2.25 160

25 100 0.75 64

25 100 2.25 19

25 500 0.75 320

25 500 2.25 96

19 300 2.5 76

Case 2: Encased Bar

The second case is representative of slender elements that would be surrounded by SFRM, such as the

chords and diagonals of the floor trusses. In this case, adhesive strength is of minor importance, and the

in-plane cohesive strength is of major importance. Figure 7-29 shows the derivation for the relationship

between material strengths and acceleration to dislodge the SFRM from a round bar. The required

acceleration is as follows:

j= 4ft (d0 +(a-\)di ) {dl-df)p7t

where:

ft = in-plane cohesive strength of SFRM

do = outside diameter of SFRM

dj = steel bar diameter

110 NISTNCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

a = ratio of adhesive strength to in-plane cohesive strength of SFRM

p = density of SFRM

Inertial Force Equilibrium 2 2

TV/T ("O ~dj ) Mass = m = 7i — — p

4

F = ft (dQ -di ) + fbdi Let fb =ccft 2 2 F = ft {d0 +{a-\)dl ) = 7r {d

° ~ di ) pa

a

4/, (rfQ +(<*-!)</,-)

2 2

do

Figure 7-29. Derivation of acceleration to dislodge SFRM surrounding a round bar.

To arrive at the ranges of accelerations that could be expected to dislodge SFRM from a round bar, the

following ranges of values were assumed:

• Bar diameter: 0.9 in. and 1.2 in;

• Thickness [(d0 - dj)/2]: 0.75 in and 2.5 in.;

• Density: 15 pcf and 25 pcf;

• In-plane cohesive strength: 500 psf and 2000 psf; and

• Strength ratio (a): 0 and 0.3.

Table 7-11 shows the results of using these limiting values in Eq. (3). The smallest required acceleration

is about 40g, which corresponds to a large bar having a thick layer of the higher density SFRM with low

strength. At the other extreme, the required acceleration is about 730g. For a 1.2 in. diameter bar with

2.5 in. thickness of SFRM and density of 19 pcf, the acceleration required to dislodge the SFRM would

vary from 55g to 230g. depending on the strength characteristics within the assumed ranges given above.

These simplified models are intended to provide insight into the important variables that affect the

magnitude of the disturbance (that is, acceleration) required to dislodge SFRM from different kinds of

structural members. These models do not consider the fact that the applied acceleration in an actual

structure subjected to impact would vary with time. Also, these models apply to members not directly

impacted by debris. As discussed in NIST NCSTAR 1-3C, there was photographic evidence to suggest

that thermal insulation was dislodged from exterior columns in regions not likely to have been impacted

directly by debris.

NIST NCSTAR 1-6A. WTC Investigation 111
Chapter 7

Table 7-11. Acceleration required to dislodge SFRM from encased bar for different

values of bar diameter, SFRM thickness, SFRM in-plane cohesive strength,

and strength ratio (alpha).

Bar Diameter, Outer Cohesive

in Diameter, in. Density, pcf Strength, psf Alpha Acceleration/g

500

0 154

0.3 182

2000

0 617

? 4

0.3 728

500

0 93

0.3 109

2000

0 370

yj.y 0.3 437

500

0 75

1 J 0.3 79

2000

0 300

jS .yQ

0.3 316

500

0 45

0.3 47

2000

0 186

0.3 189

500

0 131

1 J 0.3 162

2000

0 522

1 7 0.3 648

500

0 78

0.3 97

2000

0 313

0.3 389

500

0 69

1 0.3 74

2000

0 275

6.2

0.3 295

500

0 41

25

0.3 44

2000

0 165

0.3 177

112 NISTNCSTAR 1-6A, WTC Investigation
Adhesive and Cohesive Strength

7.4.1 Debris Impact Study

A series of simulated debris impact tests were conducted using steel plates and bars covered with

BLAZE-SHIELD DC/F. The experimental techniques and results are summarized in Appendix C.

NISTNCSTAR 1-6A, WTC Investigation 113
Chapter 7

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114 NIST NCSTAR 1-6A, WTC Investigation
Chapter 8

Summary

This report focused on the passive fire protection used in the WTC towers. Specifically, it sought to establish the likely characteristic of the sprayed fire-resistive materials (SFRMs) applied to the structural system. This information was required for calculating the thermal histories of structural members in a conventional building fire and during the fires after the aircraft impact.

To provide context, a brief review of code provisions related to structural fire protection was provided.

An effort was made to document key decisions and actions related to passive fire protection during the

design, construction, and subsequent occupancy of the towers. Copies of documents that support the

findings are provided in Appendix A.

The NIST investigation sought available information on the in-place condition of the SFRM in the WTC

towers. Some information was provided by the Port Authority in the form of thickness, density, and bond

strength measurements on floor trusses taken at various times during the 1990s. Additional information was obtained from photographs of floor trusses provided to NIST. Analyses of the data indicated that

fire-resistive material thickness was variable, as would be expected for application to floor truss members

with small cross sections.

Results of simplified finite-element simulations of heat transfer under fire conditions showed that variability in thickness of SFRM reduced the effectiveness of the insulation so that protection was less than implied by the average thickness of the SFRM. A procedure was developed for estimating the

equivalent uniform thickness of the variable thickness SFRM.

Tests were done on samples of SFRMs to establish the temperature dependencies of key thermophysical

properties that were needed for calculating the thermal-structural response of the towers.

Tests were also done to establish basic tensile strength properties of SFRM, which are necessary to estimate the extent of dislodgement due to aircraft impact. Photographic evidence, documented in another phase of the investigations (see NIST NCSTAR 1-3C), suggested that thermal insulation was

dislodged from visible portions of the exterior columns of WTC 1 and WTC 2 that were not impacted

directly by debris.

8.1 FINDINGS

The following are the key findings based on the information discussed in this report.

• The reviewed documents appear to indicate that the initial design of the towers was based on the

1938 New York City Building Code and predicated on a Class 1A classification, which required a 4 h fire rating for columns and 3 h for the floor system. The WTC towers were classified

subsequently as Class IB, as defined by the 1968 New York City Building Code. This required a

3 h fire rating for columns and 2 h for the floor system. A condition assessment conducted in

NIST NCSTAR 1-6A, WTC Investigation 115
Chapter 8

2000 reported that the WTC towers were classified as Class- IB—noncombustible, fire-protected,

retrofitted with sprinklers in accordance with Local Law 5/1973.

• The use of sprayed fire protection for floor trusses was innovative at the time of the design of the

WTC and not consistent with prevailing practice, which used enclosures of fire-resistive materials

to surround the floor trusses. Trial applications were performed to demonstrate that is was

feasible and practicable to use this fire protection method for the composite floor truss system.

Correspondence revealed that adhesion problems were encountered during application of the

SFRM to the exterior columns.

• The 1968 New York City Building Code required testing of assemblies to establish that their fire rating conformed to Code requirements. The manufacturer of the floor trusses, the Architect of

Record, and the Structural Engineer of Record recognized the need for such fire endurance testing

of the composite floor system. There were no records of a fire endurance test of the WTC floor

system.

• Fire protection of the exterior columns was the responsibility of Alcoa, which sub-contracted the

work to Mario & Di Bono Plastering Co. (Mario & Di Bono) The sprayed fire protection of the

floor trusses and core members was performed under a separate contract awarded to Mario & Di

Bono. The project specifications for sprayed fire protection of the interior portions of the towers

did not specify the type of material or thickness to be applied. Correspondence in 1969, from the

construction manager to Mario & Di Bono, stated (see Appendix A Fig. A-23) that those portions

of the floor system requiring thermal protection were "to have a

lA in. covering of 'Cafco.'" The

product known as "Cafco" was BLAZE-SHIELD Type D supplied by U. S. Mineral Products

Co., and was composed of asbestos fibers with a portland cement binder. No evidence was

available to provide the technical basis for the value of Vi in. thickness indicated in the

correspondence. Correspondence indicated that economics was an important factor in the Port Authority's decisions related to passive fire protection.

• Because of the asbestos fibers, the use of BLAZE-SHIELD Type D, was discontinued in 1970 at the 38th floor of WTC 1. The existing thermal insulation was encapsulated with a coating to contain the asbestos fibers. BLAZE-SHIELD Type DC/F was used as its replacement. This

material contained mineral fibers instead of asbestos. Tests conducted by Underwriters

Laboratories in 1 970 indicated that BLAZE-SHIELD Type DC/F was at least as good as BLAZESHIELD Type D in terms of fire resistance."

• In 1975, the Structural Engineer of Record reported that in March of 1975 he was made aware of

a fire endurance test of a floor assembly consisting of composite floor trusses with a normal

weight concrete slab on a corrugated steel deck. The trusses were protected with "Mono-Kote,"

which was described as a "cementitious spray-applied fireproofing" (see Appendix A Fig. A-45).

The members of the trusses were coated with 1 Vi in. of the insulation and the sheet metal deck

had lA in. The results of the fire endurance test assigned a 3 h rating to the floor system. It is noted that this test was not related in any way to the floor system in the WTC towers. The

Structural Engineer of Record used this test result "with many simplifying assumptions" to demonstrate that lA in. of BLAZE-SHIELD would provide the same 3 h rating when applied to 1

in. web bars (see Appendix A Fig. A-46). The calculations were said to be based on the

differences in the room temperature thermal conductivity of the two insulation materials, with the

116 NISTNCSTAR 1-6A, WTC Investigation
Summary

Mono-Kote product having about twice the thermal conductivity of the BLAZE-SHIELD

product. He noted: "however, that theoretical extrapolations of fire endurance tests must the

viewed with caution." He stated further that: "Without benefit of a full-scale fire test we cannot

establish a rating for the floor assembly."

• In 1975, the Structural Engineer of Record reported that certain elements of the floor system did not require fire protection because those elements were not critical in supporting gravity loads. These included the bridging trusses and the top chords in the one-way portion of the floor system.

• Based on data provided by the Port Authority of insulation thickness on 16 trusses on each of

floors 23 and 24 of WTC 1, the average thickness of the original thermal insulation on the floor

trusses was estimated to be 0.75 in. with a standard deviation of 0.3 in. (coefficient of variation = 0.40). The reported average thicknesses ranged from 0.52 in. to 1.17 in.

• In 1995, the Port Authority performed a study to establish the thickness of fire protection to be

applied to the floor trusses during major tenant renovations. On the basis of Design G805 listed

in the UL Fire Resistance Directory, the thickness to achieve a 2 h fire rating was estimated to be

1 Vi in. At the time of the WTC disaster, fire protection had been upgraded on floors affected by

the aircraft impact. According to information provided by the Port Authority, upgrading had

occurred on floors 92 through 100 and 102 of WTC 1 and on floors 77, 78, 88, 89, 92, 96 and 97

of WTC 2.

• Based on analyses of insulation thickness data contained in Construction Audit Reports provided

by the Port Authority, the average thickness of the upgraded thermal insulation (BLAZESHEILD II) on the floor trusses was estimated to be 2.5 in. with a standard deviation of 0.6 in. (coefficient of variation = 0.24). The reported average thicknesses ranged from 1.7 in. to 4.3 in.

• Based on finite element simulations of a 1 in. round bar covered with SFRM having lognormal

distributions for thickness that were consistent with the average values and standard deviations

noted above, it was concluded that the original thermal protection on the floor trusses was

equivalent to a uniform thickness of 0.6 in. and that the upgraded insulation was equivalent to a uniform thickness of 2.2 in.

• No information is available on in-place conditions of the thermal protection on the exterior

columns and spandrel beams, and little information is available on the conditions of fire-resistive material on core beams and columns. For thermal analyses of the towers, the thermal protection on these elements was taken to have uniform thicknesses equal to the specified values. This

assumption is justified by the offsetting factors of measured average thicknesses tending to be

greater than specified thicknesses and the reduced effectiveness of a given average thickness of

SFRM due to thickness variability. These were lA in. for beams and spandrels, 2 1/16 in. for

columns lighter than 14WF228, and 1 3/16 in. for columns heavier than 14WF228.

• Data provided by the Port Authority on the thickness and density of the upgraded thermal

insulation for floor trusses indicated that the average thicknesses exceeded the design thickness of

1 Vi in. and the bond strength measured according to ASTM E 736 exceeded 150 psf, which was

stated to be the "standard performance" of BLAZE-SHIELD II.

NISTNCSTAR 1-6A, WTC Investigation 117
Chapter 8

• Results of NIST tests indicated that the thermal conductivity of SFRMs increased significantly at higher temperatures.

• Results of NIST tests indicated that the presence of primer paint caused significant reductions in the adhesive strength of BLAZE-SHIELD DC/F. Good adhesion was found with bare steel, in which case there was not a statistically significant difference between adhesive strength and

cohesive strength normal to the surface.

• Results of NIST tests indicated that the in-plane cohesive strength of BLAZE-SHIELD DC/F was

almost three times the cohesive strength normal to the surface.

• The density of BLAZE-SHIELD DC/F in the NIST tests for strength properties was greater than

the densities in the Port Authority reports or in the manufacturer's catalogs. This may have

accounted for the higher strength values obtained by NIST compared with the manufacturer's

published values.

• Based on simplified models, the acceleration required to dislodge SFRM from planar surfaces

might range from 20 g to 530 g, depending on the in-place density, thickness, and bond strength.

For density of 19 pcf, thickness of 2.5 in., and bond strength of 300 psf, which are representative

of the upgraded insulation on the floor trusses, an acceleration of about 40 g would dislodge the

SFRM from a planar surface. For a round bar encased in SFRM, the estimates are 40 g to 730 g, depending on the bar diameter, insulation thickness, in-plane cohesive strength, and adhesive

strength. For a 1.2 in. diameter bar, with 2.5 in. thickness of insulation, having a density of 19

pcf, the acceleration required to dislodge the SFRM was estimated to be between 55 g and 230 g, depending on the strength characteristics of the SFRM. These models provide insight into the

factors that affect SFRM dislodgment due impact-induced vibration.

118 NISTNCSTAR 1-6A, WTC Investigation
Chapter 9

References

ASTM 1961. Standard Test Methods for Fire Tests of Building Construction and Materials.

ASTM E 1 19-61. ASTM International, West Conshohocken, PA.

ASTM 1973. Standard Test Methods for Fire Tests of Building Construction and Materials,

ASTM E 1 19-73. ASTM International, West Conshohocken, PA.

ASTM 1992. Standard Test Method for Cohesion/ Adhesion of Sprayed Fire Resistance Materials

Applied to Structural Members, ASTM E 736-92, ASTM International, West Conshohocken, PA.

ASTM 1993. Standard Test Methods for Thickness and Density of Sprayed Fire-Resistive Material

(SFRM) Applied to Structural Members, ASTM E 605-93. ASTM International, West

Conshohocken, PA.

ASTM 1 995. Standard Test Method for Linear Thermal Expansion of Solid Materials With a Vitreous

Silica Dilatometer. ASTM E 228-95, ASTM International, West Conshohocken, PA.

ASTM 1998. Standard Test Method for Compositional Analysis by Thermogravimetry, ASTM E 1131-

98, ASTM International, West Conshohocken, PA.

ASTM 1999. Standard Test Method for Thermal Conductivity of Refractories by Hot Wire (Platinum

Resistance Thermometer Technique). ASTM C 1 1 13-99. ASTM International, West Conshohocken,

PA.

ASTM 2000a. Standard Test Method for Thickness and Density of Sprayed Fire-Resistive Material

(SFRM) Applied to Structural Members, ASTM E 605-93 (Reapproved 2000), ASTM International.

West Conshohocken. PA.

ASTM 2000b. Standard Test Method for Cohesion/Adhesion of Sprayed Fire-Resistive Materials

Applied to Structural Members, ASTM E 736-00, ASTM International, West Conshohocken, PA.

ASTM 2000c. Standard Test Method for Effect of Deflection on Sprayed Fire-Resistive Material Applied

to Structural Members, ASTM E 759-92 (Reapproved 2000), ASTM International, West

Conshohocken, PA.

ASTM 2000d. Standard Test Method for Effect of Impact on Bonding of Sprayed Fire-Resistive Material

Applied to Structural Members, ASTM E 760-92 (Reapproved 2000). ASTM International, West

Conshohocken, PA.

ASTM 2000e. Standard Test Method for Compressive Strength of Sprayed Fire-Resistive Material

Applied to Structural Members, ASTM E 761-92 (Reapproved 2000), ASTM International, West

Conshohocken. PA.

NIST NCSTAR 1-6A, WTC Investigation 119
Chapter 9

ASTM 2000f. Standard Test Method for Air Erosion of Sprayed Fire-Resistive Materials (SFRMs)

Applied to Structural Members, ASTM E 859-93 (Reapproved 2000), ASTM International, West

Conshohocken, PA.

ASTM 2000g. Standard Test Method for Corrosion of Steel by Sprayed Fire-Resistive Material (SFRM)

Applied to Structural Members, ASTM E 937-93 (Reapproved 2000), ASTM International, West

Conshohocken, PA.

ASTM 2000h. Standard Test Method for Determination of Thermal Conductivity of Soil and Soft Rock

by Thermal Needle Probe Procedure, ASTM D 5334-00, ASTM International, West Conshohocken,

PA.

ASTM 2001 . Standard Test Method for Determining Specific Heat Capacity by Differential Scanning

Calorimetry, ASTM E 1269-01, ASTM International, West Conshohocken, PA.

ASTM 2004a. Standard Test Method for Behavior of Materials in a Vertical Tube Furnace at 750 °C,

ASTM E 136-04. ASTM International, West Conshohocken, PA.

ASTM 2004b. Standard Test Method for Tensile Strength of Concrete Surfaces and the Bond Strength or Tensile Strength of Concrete Repair and Overlay Materials by Direct Tension (Pull-off Method),

ASTM C 1583-04. ASTM International, West Conshohocken, PA.

Blondeau P., A. L. Tiffonnet, A. Damian, O. Amiri, and J. L. Molina. 2003. Assessment of contaminant

diffusivities in building materials from porosimetry tests. Indoor Air, 13, 302-310.

Buchanan, A. H. 2001, Structural Design for Fire Safety, John Wiley & Sons Ltd. West Sussex, England.

Bukowski, R. W. 2003. Prediction of the structural fire performance of buildings, Proceedings, Fire and

Materials 2003, 8

th International conference, Jan 27-28, 2003, San Francisco, CA Interscience

Communications Limited, 8 pp. http://fire.nist.gov/bfrlpubs/fire03/art028.html

Bukowski, R.W. 1997. Progress toward a performance-based code system for the United States, Proc

FORUM Symposium on Fire Safety Engineering, Tianjin China, 6-7 October 1997.

Gewain, R.G., Iwankiw, N.R. and Alfawakhiri, F., Factsfor Steel Buildings—Fire, American Institute of

Steel Construction, Chicago, IL, October 2003. 51 pp.

Harmathy, T. Z. 1983. Properties ofBuilding Materials at Elevated Temperatures. DBR Paper No.

1080. National Research Council of Canada, Division of Building Research. Ottawa, March.

ICBO 2001. ES Report ER-1244, June 1, 2002, ICBO Evaluation Services, Inc., Whittier, CA.

ICC. 2003. International Building Code 2003. International Code Council, Alexandria, VA.

Mehaffey J. R., P. Cuerrier, and G. Carisse. 1994. A Model for Predicting Heat Transfer through

Gypsum-Board/Wood-Stud Walls Exposed to Fire. Fire and Materials, 18, 297-305.

120 NISTNCSTAR 1-6A, WTC Investigation
References

Melchers, R. E., 1999. Structural Reliability Analysis and Prediction. John Wiley & Sons, New York,

NY.

Messersmith. J. J. 2002. Unwarranted relaxation. Concrete Products, September 1, 2002.

http://concreteproducts.com/issue_20020901/

Miller, I. and Freund, J. E., 1965. Probability and Statistics for Engineers, Prentice-Hall, Inc., Englewood

Cliffs, NJ.

NFPA 5000. 2003. Building Construction and Safety Code, NFPA 5000. National Fire Protection Assn.,

Quincy, MA.

NFPA.220, 1999. Types ofBuilding Construction, NFPA 220(99), National Fire Protection Assn.,

Quincy, MA.

NYCBC 1961-1962. Administrative Building Code of the City of New York.

NYCBC 1968. Building Code—Local Law No. 76 of the City of New York. New York, NY.

NYCBC 2001. Building Code of the City of New York, 2001 Edition. Gould Publications, Binghamton,

NY.

NYCLL5/73 1973. Local Laws of the City of New York for the year 1973, No.5. New York City Council,

December 22, 1972. www.nyc.gov/html/dob/downloads/pdf/ll_0573.pdf

Powers, W. R. 1975. One World Trade Center Fire. Report of The New York Board of Fire Underwriters,

New York. NY.

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UL 2002, "Design No. G805," Fire Resistance Directoiy, Volume 1, Underwriters Laboratories, Inc., pp.287-288.

NIST NCSTAR 1-6A, WTC Investigation 121
Chapter 9

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122 NISTNCSTAR 1-6A, WTC Investigation
Appendix A

Referenced Documents

CHt£». PLANNING Oivisto

AUonouin 3-IOOO WORLD TRADE CENTER

Mr. Minoru Yamasaki

Minoru Yamasaki & Associates

1025 East Maple Road

Birmingham, Michigan

Dear Yana:

At a recent meeting with Mr. John Kyle, Chief Engineer, the subject of New York City Code compliance was further amended as follows:

"All consulting engineers and architects working on the World

Trade Center have been instructed to comply with the Code in preparing

their designs. Questions have arisen, however, in areas where the Code

is not explicit. It was agreed that in such cases and, where technological advances make portions of the Code obsolete, the consultants

may propose designs based on acceptable engineering practice. All such instances will be called to the attention of The World Trade Center

Planning Division. When preliminary designs have been completed, the Chief Engineer will review all design concepts with the appropriate

municipal agencies before the consultants proceed with the final design",

Sincerely,

LF :db

cc: Mr. J. Roth (ERS)

Malcolm P. Levy

Chief, Planning Division

Figure A-1. Port Authority letter instructing consultants to follow New York City Building

Code (3-P).

NISTNCSTAR 1-6A, WTC Investigation 123
Appendix A

\ hp.- 4*

CHIEF, FUNNINO DIVIffON

620.B233 WORLD TRADE CENTER

DIRCCTT3R September 29, 1965

Mr. Minoru Yaraasaki

Minoru Yamasaki & Associates

1025 East Maple Road

Birmingham, Michigan 48011

Dear Yama:

We have decided to adopt the new Building Code presently

existing in second and third draft form for The World Trade Center.

The Roth office is requested to revise floor plans as quickly as possible and on an accelerated basis to comply with

the provisions of this code. It is my understanding that the present drawings have been prepared to permit rapid conversion to the new code. Generally the tower core should be redesigned to eliminate the fire towers and to take advantage of the more lenient

provisions regarding exit stairs. No other major change to the core should be undertaken -without review by this office.

The structural consultants are instructed, by copy of this

letter, to revise structural design in accordance with the more

realistic criteria for partition weight allowance. The majority

of interior partitions, as noted in a previous letter, will consist

of reinforced gypsum plank.

The Roth office is requested to provide me with the dates on which we can expect revised floor plans and also to indicate any changes in design schedule caused by these instructions.

Sincerely

alcolm P. Levy

cc: R. P.aum (JBB) , J. Loring (JRLA) , J. Roth (ERS), J. Skilling

and L. Robertson (WSHJ)

| Similar letter sent to Mr. Julian Roth (ERS)

Figure A-2. Port Authority letter instructing consultant to follow New York City Building

Code under development (3-P).

22

Designation in parentheses refers to NIST catalog number for document or group of documents.

124 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

MEMORANDUM OF UNDERSTANDING BETWEEN THE NEW YORK CITY DEPARTMENT

OF BUILDINGS AND THE PORT AUTHORITY OF NEW YORK AND NEW JERSEY

This Memorandum shall govern the relationship between the New

York City Department of Buildings (the 'Department") and the Port Authority of

New York and New Jersey (the "Port Authority"), both parties entering into this agreement with the intention to establish procedures to be followed by the

Port Authority for any building construction project (" Project") , to be undertaken

by the Port Authority or any of its tenants at buildings owned or operated by

the Port Authority and located in the City of New York (the "City), to assure conformance of Projects at such buildings with the standards set forth in the

New York City Building Code (the "Code").

While the facilities of the Port Authority, an agency of the States of New York and New Jersey, are not technically subject to the requirements

of local building codes, the long-standing policy of the Port Authority has -been

to assure that its facilities meet and, where appropriate, exceed Code

requirements.

The purpose of this Memorandum is not only to restate that longstanding policy as part of an understanding with the City but to provide

specific commitments to the Department, as the agency of the City responsible

for assuring compliance with the Code, regarding procedures to be undertaken

by the Port Authority for any Project at its facilities in the City to assure that the

buildings owned or operated by the Port Authority within the City are in conformance with the Building Standards contained in the Code.

Accordingly, the Department and the Port Authority hereby agree

as follows:

1 . Port Authority Review. To assure conformance with the building

standards set forth in the Code at the time of the design and construction of

any Project, the Port Authority shall, in the case of each Project, thoroughly

review and examine all plans in connection with such Project for conformance

with the building standards set forth in the Code. Plans prepared for Projects

to be undertaken by Port Authority tenants shall be prepared and sealed by a New York State licensed professional engineer or architect retained or employed by tenant; plans prepared for Projects to be undertaken by the

Port Authority shall be prepared by a New York State licensed professional

engineer or architect employed or retained by the Port Authority. The Port Authority's examination of plans shall be conducted by New York State

licensed architects and engineers retained or employed by the Port Authority.

The Port Authority engineer or architect approving the plans for any Project

from the standpoint of Code conformance shall be a New York State licensed

architect or engineer who shall not have assisted in the actual preparation of

such plans.

2. Project File . The Port Authority shall maintain a file (the Project

File") for each Project which file shall at all times contain the most recently

1

Figure A-3. 1993 Memorandum of Understanding between Port Authority and New York

City Department of Buildings (113-P).

NISTNCSTAR 1-6A, WTC Investigation 125
Appendix A

prepared drawings, plans and any other documents required in connection

with the review of the Project from the standpoint of Code conformance. In the case of any Project being effectuated by a tenant of the Port Authority

(a "Tenant Project") such file shall also include the Tenant Alteration Application

prepared by the Tenant. In the case of any project administered by a line department of the Port Authority, such file shall include any construction

application prepared in connection with such Project. The Line Departments

of the Port Authority are currently its World Trade, Aviation, Interstate Transportation, Port, and Regional Development Departments.

3. Project Certification. For each Tenant Project, the Port Authority

shall require the Tenant to obtain the certification of a New York State licensed

architect or engineer that such Project was constructed in accordance with

the approved plans and specifications for such Project. For any Project

effectuated by the Port Authority, the Chief Engineer or his successor in duties

shall certify that the Project was constructed in accordance with the approved

plans and specifications for the Project. Certifications for each Project shall be

maintained in the Project File.

4. Copies of Project File. The Department • may at any time

request the Port Authority to provide it with a copy of any Project File and the

Port Authority shall promptly provide a copy of the Project File to it.

5. Variances. The Port Authority shall promptly advise the

Department of any Project approved by the Chief Engineer of the Port Authority which involves, in the judgment of the Chief Engineer of the Port Authority or his successor in duties, a variance from the clear requirements of

the Code. In the event that the Department disagrees with the manner in which questions of Code conformance have been or are proposed to be

dealt with in connection with such Project, it may so advise the Authority. The

Port Authority shall seek expeditiously to resolve the matter. Any matter of

Code conformance in connection with such Project which the Department

believes involves an unacceptable variance from the requirements of the

Code shall be subject to the further review of the Port Authority Board of

Commissioners. The Commissioners shall be advised of the Department's views

on the matter.

6. Inspections and Surveys. The Port Authority shall continue to

conduct or cause to be conducted all building inspections, during both

construction and post-construction periods, required under the Code. In addition, the Port Authority will continue to perform structural integrity

inspections on a cyclical basis for all of its structures located in the City.

7. Port Authority Responsibility. As indicated above, the purpose

of this Agreement is to set forth certain basic understandings between the

Department and the Port Authority. It is understood, however, that the Port Authority with its tenants shall continue to bear the responsibility for life safety

in buildings at its facilities and nothing in this Agreement is intended to impose

any obligations of inspection or review on the Department. The Department

shall refer back to the Chief Engineer of the Port Authority any requests for

2

Figure A-3 (Contd.). 1993 Memorandum of Understanding between Port Authority and

New York City Department of Buildings (113-P).

126 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

information or interpretation which it may receive from tenants of the Port Authority with respect to any Project.

8. No Personal Liability. No Commissioner, officer, agent or employee of the Port Authority or the Department shall be held personally

liable under any provision of this Agreement or because of its execution or attempted execution or because of any breach or alleged breach thereof.

IN WITNESS WHEREOF, the parties hereto have caused this instrument to be signed, sealed and attested.

ATTEST: THE PORT AUTHORITY OF NEW YORK

AND NEW JERSEY

Secretary Stanley Brezenoff

Executive Director

DATE: Ilj^>jl3>

ATTEST:

FRANK M/SCHWAKTZ

Notary PuW^SWMtf***

4M633566

QuaHteS m O-jtcns CoWfff Commission E*p«tS J?"^ *»• 1 DATE: JO

THE NEW YORK CITY DEPARTMENT

BUILDINGS

By: ^ Stewart D. O'ftrien

Acting Commissioner

3

Figure A-3 (Contd.). 1993 Memorandum of Understanding between Port Authority and

New York City Department of Buildings (113-P).

NISTNCSTAR 1-6A, WTC Investigation 127
Appendix A

SUPPLEMENT TO MEMORANDUM OF UNDERSTANDING

BETWEEN THE NEW YORK CITY DEPARTMENT OF

BUILDINGS AND THE PORT AUTHORITY OF NEW

YORK AND NEW JERSEY

In November. 1993 the New York City Department of Buildings (the

'Deportment") and the Port Authority of New York and New Jersey (the 'Port Authority*) entered into the attached Memorandum of Understanding (the

'Memorandum*) establishing certain procedures for the purpose of helping to assure conformance of construction projects to be undertaken at buildings

owned or operated by the Port Authority in New York City with the standards

set forth In the New York City Building Code.

Recently, the Department Implemented Its own optional plan,

review system providing for professional certifications of applications and plans

and subsequent construction work falling under Its jurisdiction.

The purpose of this Supplement to the Memorandum Is to provide

under the Memorandum for the adoption by the Post Authority of a procedure

under which any Port Authority tenants at the World Trade Center may utilize New York State licensed architects or engineers to certify. In lieu of any review

by the Port Authority, that CO the tenant's construction plans are in conformance with the standards set forth in the New York City Building Code,

and (H) construction has been performed in accordance with such plans. It being understood that the persons making the certifications described In (0

and 00 shall not be the same.

Accordingly, the Department and the Port Authority hereby agree

that the Memorandum is amended as follows:

1. Professional Certification. Notwithstanding anything to the

contrary In the Memorandum, the Port Authority may. in Beu of any reviews or

certifications by the Port Authority provided for In the Memorandum, provide

procedures pursuant to which Its tenants at the World Trade Center may utilize New York State licensed architects or engineers meeting qualifications to be

established by the Port Authority to (A) prepare and review such tenant's plans

for the construction of any project and certify that such plans conform with the

building standards set forth in the New York City Building Code and (B) certify

that such project has been constructed in accordance with the approved

plans and specifications for such project. The person or firm performing the

review and certification described in (A) above shall not be the same person

or firm providing the certification described "m (B) above.

2. Other Provisions. Except as provided herein, all the terms and

conditions of the Memorandum shall remain in full force and effect.

3. No Personal Liability. No Commissioner, officer, agent or employee of the Port Authority or the Department shall be held personalty

Figure A-4. 1995 Supplement to Memorandum of Understanding between Port Authority

and New York City Department of Buildings (113-P).

128 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

liable under any provision of this Supplement or because of its execution or attempted execution or because of any breach or alleged breach thereof.

IN WITNESS WHEREOF, the partfes hereto have caused this Instrument to be signed, sealed and attested.

ATTEST: THE PORT AUTHORITY OF NEW YORK AND

WrTNESS: frank u. schwariz THE NEW YORK CITY DEPARTMENT OF n.kif. f.^i. .< kJ»_ Vult _ . ...

Figure A-4(Contd.). 1995 Supplement to Memorandum of Understanding between Port

Authority and New York City Department of Buildings (113-P).

NISTNCSTAR 1-6A, WTC Investigation 129
Appendix A

THE TOOTAimORnY(oF[OT©M One World Trade Center New York. N Y 10048

September 15. 1995

William H Goldstein Deputy Executive Director/ Capital Programs

(212)435-8415

(201)961-6000 x8415 Honorable Joel A. Mlele, Sr., Commissioner

Department of Buildings

City of New York

60 Hudson Street New York, New York 10013

Dear Commissioner Mlele:

As you know, the Port Authority of New York and New Jersey (the "Port Authority*) and the New York City Department of Buildings (the •Department*) recently

executed a supplement (the "Supplement*) to the Memorandum of Understanding

between the Department and the Port Authority to provide that the Port Authority's

tenant at the World Trade Center could. In lieu of any review by the Port Authority, use New York State licensed architects or engineers meeting qualifications to be

established by the Port Authority to: (A) prepare and review such tenant's plans for the construction of any project and certify that such plans conform with the building

standards set forth in the New York City Building Code and (B) certify that such project

has been constructed In accordance with the approved plans and specifications for such project.

As you also know, the Supplement provides that the person or firm performing the review and certification described In (A) above shall not be the same

person or firm providing the certification described In (B) above. A copy of the

Supplement Is attached.

This letter win -confirm the agreement of the Port Authority and the

Department that, notwithstanding the last sentence of paragraph 1 of the Supplement, a single licensed consultant may make both certifications described In (A) and (B) of

such paragraph, except where the alteration would change the character of the

occupancy group under paragraph 27-237 of the New York City Building Code which

would have been applicable to such space had such space been located In a

privately owned building.

If the foregoing meets with your approval, please be good enough to

sign this letter on behalf of the Department where Indicated below and return one of

the originals to me. In light of the fact that three originals of the Supplement were

furnished to the Department, we have, for your record purposes, executed In total four

originals of this letter.

Figure A-4 (Contd.). 1995 Supplement to Memorandum of Understanding between Port

Authority and New York City Department of Buildings (113-P).

Very truty_yours.

WHBam H. Goldstein

Deputy Executive Director

Capital Programs

OF BUILDINGS

130 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

MEMORANDUM OF UNDERSTANDING BETWEEN THE FIRE DEPARTMENT

(IF THE CITY OF NEW YORK AND THE PORT AUTHORITY OF NEW YORK AND NEW JERSEY

EXECUTED AS OF DECEMBER 30, 1993

On April 15, 1993, the Port Authority, in order to maintain and enhance the

safety of Port Authority facilities, adopted a policy providing for the

implementation of fire safety recommendations made by local government fire

departments after a fire safety inspection of a Port Authority facility and for

the prior reviev by local fire safety agencies of fire safety systems to be

introduced or added to a facility.

The purpose of this Memorandum of Understanding is to reiterate the Port

Authority's commitment to this policy and to set forth certain procedures to facilitate the implementation of this policy for buildings at Port Authority

facilities located in Nev York City.

Specifically, the Fire Department of the City of Nev York ("FDNY") and the Port

Authority hereby agree as follovs:

1. FDNY, acting through its Bureau of Fire Prevention ("BFP") , shall have the

right to conduct fire safety inspections at any Port Authority facility

located in the City of Nev York- These inspections vill generally be

coordinated vith the Port Authority's General Manager of Risk Management

operations, but the BFP, at its option, may conduct inspections vithout

prior notice to the Port Authority.

2. BFP vill issue a letterhead report of its fire safety findings and

recommendations for corrective action vith respect to any deficiencies

forming a part of such findings addressed to the Port Authority's General

Manager of Risk Management operations. The Port Authority vill promptly

undertake the implementation of such findings (including undertaking

corrective action vith respect to any deficiencies) and shall notify BFP of

the actions taken to implement such findings. BFP may at any time conduct

follov-up inspections vith respect to any matters recommended to the Port

Authority for corrective action.

3. Prior to the introduction of a nev fire safety system or the introduction

of modifications to an existing fire safety system at any building located

at a Port Authority facility in the City of Nev York, the Port Authority

shall provide BFP vith copies of the dravings and specifications or other

appropriate description of such system or modification for reviev and

approval. The Port Authority policy is and vill continue to be to assure

that such nev or modified fire safety systems are in compliance vith local

codes and regulations. When circumstances or conditions are unusual, the

Port Authority shall have the right to petition the Bureau of Fire

Prevention for a variance in specific cases.

Figure A-5. 1993 Memorandum of Understanding between Port Authority and The Fire

Department of New York City and 1995 amendment (160-P).

NISTNCSTAR 1-6A, WTC Investigation 131
Appendix A

4. The Port Authority and BFP vill seek to expeditiously resolve any issues

arising out of matters covered by this Memorandum of Understanding.

5. Nothing in this Memorandum of Understanding is intended to limit or modify

in any way any arrangements vhich the Port Authority currently has vith

local fire companies in Nev York City regarding either facility inspections

or joint training exercises or any other matters.

6- The Port Authority shall continue to be exempt from all inspection and

permit fees for FDNY inspections at its facilities.

7. No Commissioner, officer, agent or employee of the Port Authority or FDNY

shall be held personally liable under any provision of this Memorandum

or because of its execution or attempted execution or because of any breach

or alleged breach thereof.

IN WITNESS VHEREOF, the parties hereto have caused this instrument to be signed

and sealed by duly authorized officers thereof.

THE PORT AUTHORITY OF NEV YORK AND NEV JERSEY

FIRE DEPARTMENT - CITY OF NEV YORK

Fire Commissioner

City of New York

Figure A-5 (Contd.). 1993 Memorandum of Understanding between Port Authority and

The Fire Department of New York City and 1995 amendment (160-P).

132 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

FIRST AMENDMENT TO MEMORANDUM OF UNDERSTANDING BETWEEN THE FIRE

DEPARTMENT OF THE CITY OF NEW YORK AND THE PORT AUTHORITY OF

NEW YORK AND NEW JERSEY EXECUTED AS OF DECEMBER 30, 1993

On December 30, 1993, the Port Authority of New York and New Jersey (the

"Port Authority") and the Fire Department of the City of New York ("FDNY")

entered into a Memorandum of Understanding ("MOU") with respect to certain

matters relating to the implementation of the policy adopted by the Port

Authority on April 15, 1993 regarding the maintenance and enhancement of fire

safety at Port Authority facilities.

Under paragraph 3 of the MOU, the FDNY, acting through its Bureau of Fire

Prevention ("BFP") was to receive copies of the drawings and specifications of

proposed new or modified fire safety systems for BFP's review and approval.

FDNY has requested, and the Port Authority is agreeable, to the following

changes to paragraph 3 of the MOU. Accordingly, effective January 1, 1995, FDNY

and the Port Authority agree that paragraph 3 of the MOU shall be amended to

read as follows:

3. The Port Authority shall notify the BFP in writing prior to the

introduction of a new fire safety system or the introduction of modifications*to

an existing fire safety system at any building located at a Port Authority

facility in the City of New York.

a. P ort Authority Review : To assure conformance with the standards set

forth in local codes and regulations at the time of the design and construction

of any new or modified fire safety system, the Port Authority shall, in the case

of each system, thoroughly review and examine all plans in connection with such

system for conformance with the standards set forth in all applicable local

codes and regulations. Plans prepared for new or modified systems to be

undertaken by Port Authority tenants shall be prepared and sealed by a New York

State licensed professional engineer or architect retained or employed by

tenant; plans prepared for new or modified systems to be undertaken by the Port

Authority shall be prepared by a New York- State licensed professional engineer

or architect employed or retained by the Port Authority. The Port Authority's

examination of plans shall be conducted by New York State licensed architects

and engineers retained or employed by the Port Authority. The Port Authority

engineer or architect approving the plans for any new or modified system from

the standpoint of Code conformance shall be a New York State licensed architect or engineer who shall not have assisted in the actual preparation of such plans.

b. N ew and/or Modified Fire Safety System File : The Port Authority

shall maintain a file for each new or modified system which file shall at all

times contain the most recently prepared drawings, plans and any other documents

required in connection with the review of the systems from "the standpoint of

Code conformance". In the case of any new or modified system being effectuated

by a tenant of the Port Authority, such file shall also include the Tenant

Alteration Application prepared by the tenant. In the case of any new or modified system administered by a line department of the Port Authority, such

file shall include any application prepared in connection with such new or modified system. The Line Departments of the Port Authority are currently its

World Trade, Aviation, Interstate Transportation, Port and Regional Development

Departments

Figure A-5 (Contd.). 1993 Memorandum of Understanding between Port Authority a The Fire Department of New York City and 1995 amendment (160-P).

NIST NCSTAR 1-6A, WTC Investigation 133
Appendix A

c. Fire Safety System Certification : For each Tenant System, the Port

Authority shall, require the Tenant to obtain the certification of a New York

State licensed architect or engineer that such system was constructed in

accordance with the approved plans and specifications. For any system

effectuated by the Port Authority, Risk Management shall certify that the system

was constructed in accordance with the approved plans and specifications.

Certifications for each System shall be maintained in the New and/or Modified

Fire Safety System File.

d. Copies of New and/or Modified Fire Safety System File : The BFP may

at any time request the Port Authority to provide it with a copy of any Fire

Safety System File and the Port Authority shall promptly provide a copy of the

File as requested. The BFP reserves the right to audit any new or modified fire

safety system to assure conformance with the standards set forth in local codes

and regulations.

e. Variance : The Port Authority policy is and will continue to be to assure that such new or modified fire safety systems are in conformance with the

local codes and regulations. When circumstances or conditions are unusual, the

Port Authority shall have the right to petition the BFP for a variance in

specific cases.

IN WITNESS WHEREOF, the Port Authority and FDNY have caused this First

Amendment to the MOU to be signed by duly authorized officers thereof.

THE PORT AUTHORITY OF NEW YORK AND NEW JERSEY

Dated : ^ 1 A ) 2

Dated: (JJj/W

Bv: VP^7

Stanley Breitei§ ifTT

Executive Director

FIRE DEPARTMENT - CITY OF NEW YORK

By:

Howard Safir

Fire Commissioner

City of New York

Figure A-5 (Contd.). 1993 Memorandum of Understanding between Port Authority and

The Fire Department of New York City and 1995 amendment (160-P).

134 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

.'ay 14, 1969

.\r. .\i;tort oerscnian

Tisr.:aan Rc-icy & Construction Co., Inc. 30 Church Street - 11th Floor Kew York, New York 10007

Re: THE i-.'ORU TRADE CENTER - Sevi York City Building Code

D-jar Milt:

A co..?>:risor. of the recently revised Mew York City

2uiiuing Code effective December 6, 196S and The World Trade Center Design Standards, with respect to tenant demising

walls, leads to soae interesting questions.

The Code s^er-.s to indicate that the demising walls

between tenant spaces in the Towers co-Id be non-combustible

and not fire-rated if the Code were applicable.

?r -;e 39 - C2S - 301.1 M y)

The Verio Trade Center Towers would be classified

as Occupancy Group "E" (Business) with a fire

index of 2 hours.

?a?.s 39 - C26 - 301.4 (B)

In Occupancy Group "E", tenants shall be separated

frees each other by construction neeting the fire

resistance rating recuireaent for a "Fire Separation".

d'0

Tne miniiaeu requirement for a "Fire Separation" is that it be non-combustible. -J \j\ OS"*

^£>^ ' TiSHMAft

5 MAY A D

Figure A-6. Letter from Port Authority to Tishman Realty & Construction Co. regarding

Occupancy Group for WTC towers (3-P).

135

NIST NCSTAR 1-6A, WTC Investigation
Appendix A

11

2 - May 14, 1969

If we Ej'l'Iy these ir.terpretaticr.s to the V.orld Trade

Center, ci-.jrc would be savings in cons.tri-c tion costs with

respect co ur.o following ite.r.s:

ti . C-'cinary ;-.on-ccnibus;ibie p^rtitions could be

used ir. lieu of the or.e-hour rated tenant demising walls.

b. Standard nor.- combustible ceiling s?\ ste-i could

be used in lieu of the one-hour rated acoustical

tile ceiling.

c. The deletion of all insulating batt fire

protection at all air handling lighting fixtures

in ceiiings as well :s the deletion of damper

equipped return air troffers. Tnese are

p-.reser.tly proposed for iixcures within 10 ' -0"

of a de-.ising partition.

V.e v.'oulC appreciate your opinion as to whether it

would be appropriate to nake the changes to che design noted

in paragraphs a, b and c. By copy of this letter, the

office of Emery Roth & Sons is also requested to cossnent.

Sincerely,

Malcoln P.. Levy

cc: Xr. Joseph Soloaon (ER&S)

Figure A-6 (Contd.). Letter from Port Authority to Tishman Realty and Construction Co.

regarding Occupancy Group for WTC towers (3-P).

136 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

MEMORANDUM

J*~V OF N & ,

TO: Robert J. Linn, Deputy Director for Physical Facilities, WTD ^

' '•" FROM: Lester S. Feld

DATE: January 15, 1987 11 £ C != i \/ c n

SUBJECT: THE WORLD TRADE CENTER - TOWERS & PLAZA BUILDINGS f¥AM^'^1HI__„. _

PER NYC BUILDING CODE REVISION EFFECTIVE 12-6-68.-

REFERENCE:

COPY TO:

2.

(1) - Memo - M. Levy to File - dated 4-20-65

(2) - Letter - L. Robertson (WSHJ) to M. Levy - dated 4-26-65

(3) - Letter - M. Levy to M. Gerstman (TRCC) - dated 5-14-69

(4) - Office Memo - W. Bracco (TRCC) to J. Endler (TRCC) - dated 5-26-69

(5) - UL Fire Test Report from T. P. Feit - dated 7-26-69

(6) - Letter - A. F. Abbasi (UL) to T. P. Feit (Zonolite) - dated

3-26-70

(7) - Buckslip - V, Dovletian to D. Bais - dated 1-9-87

(8) - Page 4 - Item 1C of Issue A entitled "Office Space Design

Guide"

D. Bais, J. Carlock, A. Cracchiolo, V. Dovletian, P. Martinez

D. Montalbano, A. Preschle, J. Pugh (LERA) , L. Robertson (LERA)

A. Vaccaro - All w/Reference 1-8 attached.

j/Z.f fa"

On January 13, 198Z I contacted Richard Roth, Jr. (ER&S) regarding the i subject fire ratings, normally established by the Architect. Mr. Roth

referred me to Phil Martinez for the required information.

Planning Division) was as follows:

A. The egress requirement and fire ratings used to design the

WTC Towers & Plaza Buildings were in accordance with the

provisions of the planned NYC Building Code revisions effective December 8, 1968. Normally fire ratings are not shown on the Architectural Working Drawings or in the General Notes

The fire ratings are given only on the application forms

filed with the plans for NYC Building Department Approval.

Since the Port Authority is not subject to the NYC Building

Code Requirements, no plans or forms were filed.

B. For office buildings there is no economic advantage in using

Class 1A Construction, and ER&S used Class IB Construction

for the WTC Towers and Plaza Buildings which are Occupancy

Group "E" (Business) with a fire index of 2 hours. As such,

columns must have 3 hour fire rating and floor construction

with a 2 hour rating.

Please note that Reference #3 by Mai Levy was concurred in by W. Bra< (TRCC) in Reference #4, with regard to Class 1-B Construction cited by

Mr. Martinez. In addition, References #1 & $2 (written in 1965) are superseded by References #3 & #4 (written in 1969).

i -

"'.

i '-

t

j if—

j

ir~

h

! I—

! rvn~-B !

r; ^G

'A GEN

RETURN

POST

Figure A-7. Port Authority memorandum indicating that WTC towers were classified as Class 1B Construction (3-P).

NISTNCSTAR 1-6A, WTC Investigation

137
Appendix A

4. For your information and use I have also attached References #5 & #6 on the UL Test of floor construction showing a 3 hour rating. Please

note that the UL Test is based on the use of lSg" thick Monokote

Fireproof ing on joists and %" thick Monokote on steel deck. Actually - Cafco- Type "D" spray-on was used at the WTC on joists only, in lieu of

Monokote. In addition, the UL Test used stone-concrete slab with a thickness of 2 3/4" over top of corrugated deck, as compared to the 4" lightweight concrete slab used at the WTC.

5. With regard to Reference #7, no joists were used in the floor construction of 3 WTC, 4 WTC, or 5 WTC - rolled beam are used in all Plaza

Buildings. Mr. Martinez (ER&S) Mai Levy (Reference #3) & TRCC

(Reference #4) all concur that the Plaza Buildings are Class IB Construction.

6. In addition, Issue "A" of the "Tower Office Space Design Guide" prepared

by the WTC Planning and Construction Division (with Errata Sheet #1 to Issue A - dated March 23, 1970) - Page 4 - Item CI (attached as Reference

#8) verifies that the towers are class IB Construction.

Figure A-7 (Contd.). Port Authority memorandum indicating that WTC towers were

classified as Class 1B Construction (3-P).

138 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

^ .p. EMERY ROTH & SONS

J; J

850 THIRD AVENUE

NEW YORK, N. Y. 10022

February 11, 1969

Mr. Joseph A. Schwartzraan

The Port of New York Authority

111 Eighth Avenue

New York, N. Y. 10011

RE: WORLD TRADE CENTER

TOI/ERS "A" and "B"

SPRAY-ON FZRFFROOFING

Dear Joe:

In checking out your printed copy of the "Spray-On,

Fireproof ing' specification," it has been noticed that someone in your office has taken the liberty of rewriting

the original specification, asking it almost totally un~ recognizable. In the process of rewriting i;he specifics = ticn , a key paragraph seeing to have been . omitted in its

entirety, reading as follows:

'Finished thicknesses of applied material over the

various component .steel parts- requiring fireproof ing

shall be great enough to qualify the fireproofcd p3rts

for a three (3) hour rating (support bearas, steel deck

vjork) and a four (4) hour rating for all pick-up girders,

if any, and columns'

We cannot be expected to accept responsibility for specifications v;hich have been revised in such a manner; that which

originally stated clearly and simply, has become a meaningless

document.

Very truly yours,

EMERY ROTH & SONS

" — '

i

DF

BY ______ : er f *"I)0LrGLAS FERNANDEZ

Figure A-8. Letter from Emery Roth & Sons to Port Authority regarding specification for

sprayed thermal insulation (3-P).

NISTNCSTAR 1-6A, WTC Investigation 139
Appendix A

ATTACHMENT A PAGE 3

Standpipe Hose Stations

6. Several standpipe and auxiliary hose stations do not provide coverage of all portions of all floor areas within the required 145 feet of any given hose's effective reach. Further, some

hose racks are equipped with 1 50 feet of hose in lieu of the standard 1 25 feet, and

provide coverage for 170 feet.

It is recommended that the Port Authority establish a program to survey all tenanted

floors to identify areas inadequately covered, and to remediate such inadequacies as quickly as possible.

Also, it is recommended that approval be obtained from the New York City Fire

Department for the existing 150 foot long hoses.

Standpipe Telephone Jacks

7. The requirement that permanent telephone jacks be installed on each floor near standpipe risers has been addressed. Permanent standpipe telephone jacks

have been installed and activated on each floor level of all fire stairways in both towers. Smoke Vents

8. All closed shafts having a cross-section area exceeding four (4) square feet are required

to be equipped with a smoke vent. Although the return air shafts currently have the means to exhaust smoke-laden air directly to the outside by mechanical means, it is recommended that the Port Authority investigate methods by which this

overall requirement maybe satisfied.

Sprinkler Protection

9. At this writing, only four (4) tenanted floors (all in 1 WTC ) have not been sprinklered.

Of those floors, the sprinklerization of floors 17, 30, and 33 will be completed by the end of

this year (1997).

Additionally, as referenced in Item ! above, plans will be made to sprinkler the MER's and

the skylobbies in both towers.

All four (4) floors noted above (floor 19 was not mentioned by Mr. Cory of Rolf

Jensen) have been completed at this time. Also, the Sky Lobbies sprinklerization are currently underway.

Return Air Smoke Detectors

10. Although smoke detectors or combination smoke/heat detectors are required at each inlet to a return air shaft on each floor, our survey indicated that such detectors may not have

been installed at all required locations.

This has been addressed via a Port Authority contract which will be handling new,

addressable smoke detectors at each return air intake above the suspended ceilings

beginning July 1997 and completed by December 1999.

Figure A-9. Excerpt from 1999 code compliance evaluation indicating progress since a

similar 1997 evaluation (1999 evaluation is shown in bold-italic text) (161-P).

140 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

Ooe World Trade Cento Wodd Trade Center New York, New York

The ADA sets forth "recommended priorities for public

accommodations" to be accessible to the disabled. In

general, the three priorities are as follows:

1. Access from public sidewalks, parking, or public

transportation to a building entrance;

2. Access to any areas of goods and services that are made

available to the public; and, 3 . Access to rest room facilities. During our tour of the project, we noted the following:

The building's primary entrance is from West Street into the Tower lobby through automatic power operated entrance

doors. The path to the elevators is accessible. The

Concourse entrance also has 2 sets of automatic doors.

The Plaza Level main entrance has 2 sets of swing doors, without automatic door opening hardware. Provide door- opening hardware on 1 set of swing doors to make the entrance accessible.

The banks of local elevators and mid-zone express elevators are equipped with car control panels that comply

substantially with ADAAG. Two upper zone elevators (19

and 19) are not equipped with complying car controls. Some (approximately 25%) toilet rooms have had upgrades

for ADA requirements, but in most rooms observed, there were noncompliant items such as lack of full size ADA toilet

stalls, and ADA compliant urinals. ADA compliance on

most full tenant floors is reportedly the responsibility of the tenant under terms of the lease.

12. Code Compliance

Applicable Code 1968 NYC Building Code as Administered by the Port Authority of New York and New Jersey

Building Construction

Classification Class 1-B - noncombustible, fire-protected, retrofitted with

sprinklers in accordance with Local Law 5/1973

Occupancy Type Group E - Business

December 6, 2000 20-251E - Section V-l - Page 24

Figure A-10. Excerpt from 2000 property condition assessment of the WTC towers

indicating construction classification (7-P).

NISTNCSTAR 1-6A. WTC Investigation 141
Appendix A

Truss Fi reproofing Systems

Early discussions for fireproofing systems for the floor truss work

covered nearly every conceivable method. Port Authority staff

as well as the architectural and structural consultants sought

efficient and economical systems; the structural steel industry

proposed alternative methods.

In early 1963 project estimates carried an allowance for a "demountable ceiling" providing the needed fire protection for

the steel floor trusses. The problems of fire dampers for such

a ceiling were discussed at length.

By late 1964 a series of alternate contact fireproofing systems

had been investigated with some cost data assembled.

By late 1965 the use of a spray-on material similar to Cafco or Mono-Kote appears to have been selected. The ERS letters of

December 14 and 23, 1965 are clear on this point. Only the

required thickness appears to have been in doubt, (see pages

5.1 and 5.2).

"Demonstrations" of fireproofing systems were carried out by various

vendors. For example, on Aug. 7 and 8, 1967, the application on Laclede trusses Mono-Kote fireproofing was demonstrated to Mr. Feld

and others (l"thickness) . In September of 1967 Messrs. Monti

and Solomon appear to have wittnessed spray tests making use of

U.S. Mineral Products Co. "Cafco".

-5- SKILLINC. HELLE, CHRISTIANSEN. ROBERTSON

Figure A-11. Excerpt from April 1, 1975 post-fire report prepared by Skilling, Helle,

Christiansen, Robertson (3-P).

142 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

CC: W. M

P. E. H. R

A. C,

R. D

J. R,

Akin

Akin

Kilpatrick

Weber

Bay

Paul

OFFICE KEMORANDUii

August 10, 1567

BLOWN ON FIREFROOFING

LACLEDE STEEL JOISTS

During the past week two test applications of blown on fireproofing

on Laclede joists and trusses have been accomplished by the U. S.

Gypsum Company and the Zonolite Division of W. F. . Grace and Company.

This testing, primarily concerned with the floor trusses of the

World Trade Center, has been necessary to provide information tc

the Fort of Hew Fork Authority engineers on the amount cf Ices they

might expect from a spraying operation cr, open wee structures

The U. S. Gypsum Company materials, primarily a gypsum and ascestcs • combination of fibrous material, was applied at the Cupples Company

plant cf the Aluminum Company cf America on Hanley Read cr. the v/all

structure that is currently being tested for wind and temperature

variations

The Zonolite Company material made up primarily of vermiculite and

gypsum plaster is a much harder cementaecous coating that seems to

apply better than the so-called Cafco (U. S. Gypsum material). "

A set cf 2^H8 joists electro coated in the same fashion that the

World Trade Center joists will be painted were set up at ."-iadison and with 1/2" anc 3/S" nozzles, the Leroy Thompson Plaster Company

of Belleville, Illinois coated six joists, two of them with only

a single coat to demonstrate the material adherence.

It is apparent that a single coating or scratch coat can be applied

as quickly as a man can pass across web and chord sections of the

joists leaving a thickness of 3/6" to 1/2" completely incasing all

metal.

With a one to two day drying time, depending on the humidity, a second and final coat to a 1" thickness can be easily applied, and

according to figures from the Zonolite engineers, a remarkably low- percentage cf material loss results. Less than 15% material was shot through the joists and lost. With this low material loss it

has been pointed- out that the use of material is far less than

would be required for solid section beams previously considered

for spray insulation and is no more than would be experienced with

angle and flat section trusses.

Figure A-12. Intra-office correspondence at Laclede Steel Co. regarding 1967

demonstration of sprayed application of thermal insulation to floor trusses (70-I).

NISTNCSTAR 1-6A, WTC Investigation 143
Appendix A

- 2 -

With the successful application of spray-on insulation an entire

new scheme of fire safe building construction is possiDle for steel

joists in tnat the fire protection of the joists would permit the

installation of low cost acoustical ceilings with access to utility

lines that have not be possible in the two hour rated buildings

before

It is anticipated that the U. S„ Gypsum Company will oe doing further

testing on small web trusses at their plant in Stanhope, New Jersey

since Ray Monti the general superintendent cf the World Trade

Center called yesterday to asx if we would provide joists similar

to these used by Zcnolite for u. S. Gypsum. A Mew York plastering

contractor that is normally the applicator for Li. S. Gypsum

products in hew York, Mario DeBono, is the contractor with whom we would be working if U. S. Gypsum material would be specified.

Mr. DeEono is to call us with an order for electro coated 2 V

trusses, and according tc the Port Authority, will be paying for

them since this is a research tnat U. S. Gypsum is intending to

perform without others observing the results. From what I gather,

various types of surrounding: nozzles are proposed by tne DeBono

people and they are not anxious to have their competitors learn

of their application plans.

In any event, tne fireproof ing of joists seems tc be a problem now

solved, and in the World Trade Center as well as in otner steel

joist structures, we may be sure tnat an economical fireproofing

can De effected in the field without the expense of a heavy ceiling

construction

A. C. Weber

ACW : p j z

Figure A-12 (Contd.). Intra-office correspondence at Laclede Steel Co. regarding 1967

demonstration of sprayed application of thermal insulation to floor trusses (70-I).

144 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

Q^paiE IP©BT ©IT BEWTOaK JWnrEOBaiTT

Tn Malcolm P. Levy

R. M. MONTI (Ext. 7918 cc: Mr. H. Tessler

Attached brochure was given to me and

J. Solomon, by U.S. Mineral Products Co.,

during inspection of spray tests on 9-13-67,

arranged by U.S. Mineral Products and Mario and

DiBono.

U.S. Mineral Products will send a sample

spec to Joe Solomon of their Mark II asbestos

cement overspray for possible use in elevator

shafts. The Mark II samples appeared to have

a well sealed surface, which would prevent

dusting.

/In

Att.

Figure A-13. Port Authority intra-office memorandum indicating demonstration of the

application of thermal insulation from U.S. Mineral Products Co. was completed in August 1967 (176-ITK).

NIST NCSTAR 1-6A, WTC Investigation 145
Appendix A

AGENDA

COMMITTEE ON CONSTRUCTION IfimRfr^G

January 29, 19 6» ""•W>579

TITLE MO. THE WORLD TRADE CENTER x^5RT?*Afer>€0UTH TOWER BUILDINCS - SPRAY

' flKEPROOriNC , - CONTRACT. WTC-113.00- ^SUPPLEMENTAL AGREEMENT

RECOMMENDATION ; That the Committee authorise a Supplemental Agreement to Contract ~ WTO113. 00 - Spray Fireproofing, North and South Tower Building*,

The World Trade Center - with Mario and DIBono Plastering Company,

Inc., providing for fireproofLog isolated steal box columns in the North and South Tower* , at • cost of $65,000.

REPORT; The Board, at its meeting on November 14, 1968, authorized the award of Contract WTC-113.00 to Mario and DIBono Plastering Company,

Inc., at a price of $1,725,000, and Including an allowance of

$60,000 for extra work and extra materials. Contract WTC-113.00

provides for the spray fireproofing of Interior steel work in the North and South Tower Buildings.

AC the time or award of Contract WTC-113.00, It was planned to fireproof, certain interior column* by 'enclosing them, with gypsuqu

plank. partitioning and wall board.. These columns form- the framework for the elevator shafts. Tale.work.V** tft._be_ performed under

Contract WTO110.00 - Carpentry, North and South Towers and Below

Grade - which was awarded to Star Circle Vail Systems, Inc. by the Board at Its meeting on November 27,. 1968.

During_the_contract discussions with_Star Circle,, evaluation of

the fireproofing. requirements^ shoved that sufficient protection

would be provided by spray fireproofing these columns' and that

this method would be more economical. Therefore, applying gypsum plank and wall board fireproofing to the columns was deleted from

Contract WTC-110.00, resulting in a reduction in their proposal.

Mario, and DIBono Plastering. Company^. Inc. has agreed to spray, fireproof"" the columns at a price of $85,000 which is considered

reasonable. It is, therefore, proposed to include this work in

a supplemental agreement to Contract WTC-113.00.

f

4

Figure A-14. Agenda item for January 29, 1969 meeting of Committee on Construction

regarding modification to sprayed fire protection contract (120-ITK).

146 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

j w The World Trade Center - North and South Tower Buildings - Spray Fireproofing - ~ Contract WTC-113.00

It was reported to the Committee that Contract WTC-113.00 requires the :ontractor to spray the structural steel of the North and South Tower Buildings of The

Jorld Trade Center with a mixture of asbestos, cement and water, which, when hardened,

tfill provide the necessary fire protection for the structure.

The Board, at its meeting on January 12, 1967, authorized the award of Contract WTC-400.00 - North and South Tower Buildings, Curtain Wall, The World Trade

Center - to Aluminum Company of America. Under this contract, Alcoa will provide

spray-on fireproof ing and plastering to the exterior columns of the North and South

Tower Buildings. Alcoa sub-contracted this work to Mario and DiBono Plastering Company,

Inc., who performed extensive tests of various methods of providing fireproofing which

would meet specifications.

The fireproofing mixture will be applied to the erected steel on each

floor and must be completed before any other work on a floor can proceed. In view of

this, it was evident that the interior and exterior fireproofing applications would

have to be closely coordinated. Staff determined that contract administration problems

would be minimized and coordination between the fireproofing work on the interior

structural steel and the exterior columns would be facilitated if a single contractor

i to perform such work. Therefore, discussions were held with Mario and Di Bono on

tiie interior fireproofing work and resulted in the submission of a proposal of $1,725,000,

including $925,000 for work and $800,000 for sale.

The Project Estimate for Contract WTC-113.00 is $1,625,000, exclusive of an allowance of 57. for extra work and extra materials.

Mario and DiBono Plastering Company, Inc., is qualified to perform the work

under Contract WTC-113.00. In the past, they have provided all interior finish plastering,

exterior cement plastering and interior and exterior fireproofing for such projects as the International Arrivals Building at Kennedy International Airport; Madison Square

Garden; Two Penn Plaza; Rochdale Village, Jamaica, Long Island, consisting of twenty

lA-atory buildings; and Co-op City in the Bronx, New York.

Recommendation was made that the Committee recommend to the Board that the Board authorize the award of Contract WTC-113.00 - Spray Fireproofing, North and South

Tower Buildings, The World Trade Center - to Mario and DiBono Plastering Company, Inc.,

•t a price of $1,725,000 and an allowance of $80,000 for extra work and extra materials.

Approved and recommended to the Board.

Figure A-15. Excerpt from October 30, 1968 minutes of the Committee on Construction

regarding the sprayed fire protection contract (123-ITK).

NISTNCSTAR 1-6A, WTC Investigation 147
Appendix A

Tishman Realty X Construction Co., inc.

666 FIFTH AVENUE

NEW YORK. N.Y. IOOI9

OWNERS AND BUILDERS SINCE 1696

March 30, 1 966

JUDSON 2-6700

THE PORT OF NEW YOnK «iMN'.i!i y RECtlVLU

1 \m

WO*Ll> r ««*.!}(: .;t'-'i;.p PLANNING DIVISION

Port of New York Authority

1 1 1 Eighth Avenue

New York, New York 1001

Attention: Mr. R. M. Monti, Res. Engineer - World Trade Center

Re: Fireproofing Cost Comparison

World Trade Center

Dear Ray:

We are transmitting herewith our Cost Comparison and Recommendations

tor Sprayeo Fireproofing. This Analysis compares the costs and merits

of Vonco 2, Cafco Type D, Spray-craft, Firecode V and Monocoat Spray

materials. We have selected for comparison, only those systems for which Underwriters' Laboratories Inc. and/or New York Board or Standards

and Appeals approvals already exist or arc imminently expected.

The Analysis shows authority, structural member si2e and functional

fireproofing thickncss required, firl rating in hours, as well as cost

per souarc foot for material and labor at the indicated thickness. we

have also interjected by note, information which wc feel is pertinent

to performance as well as possible, hidden economies or expenses.

Very truly yours,

Ti shman Realty &/Cpi<fS7R^CT i on Co., Inc.

&/O^mes R. EndlCK

/] Assistant Vice President ' 1

Encl.

DU

USM-002657

DEFENDANT'S

EXHIBIT

OX 282

Figure A-16. Correspondence related to economic study of alternative thermal

insulation materials (432-P).

148 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

WORLD TRADE CENTER FIREPROOF I NG COST ANALYSIS

Labor and Material costs reflect sprayed square foot contact area, including

overhead and profit and n.y.c. sales tax for the indicated thickness and assume large uncluttered areas where full proooction is assured, but does not provide

FC R EXCESSIVE CLEAN-UP OR SCAFFOLDING. ThESE COSTS SHOULD NOT BE USED FOR SPRAY

REOU I REMENTS BETWEEN EXTERIOR COLUMN OR SPANDRELS AND THE CURTAIN WALL, SINCE ACTUAL PRODUCTION CANNOT BE DETERMINED.

MATERIAL DESCRIPTION AUTHOR 1 TY size or 1 NCHES FIRE MAT. LABOR TOTAL

(U.L.I.) MEMBER REG. RATING $/SQ.FT. $/SQ.FT. $/SQ.FT.

(B.S.A.) TESTED IN HOURS

"VON CO 2 and li W uli -48-3 8"Beam 9/1.6" 5 .225* .057** .282

Magnesium OxYchloride uli -25-1; IOWF49 Ccl . 2 5/16" h .925* .210 1.135 Spray Mater i al as MANUFACTURED EY THE ULI -2-I5 lowrtj cc. . 1" .400* .09! .491 MO Corp. of 101 Emp taz IOWF49 Ccl 1 3/^': Building, Springfield, Unl 1 STED*** .859 h .700* •159

Ml SSOUR 1

UNL 1 ST ED*** IOWF49 Col • 4" .600* .136 736

Unl 1ST ED*** I0WF49 Col • li" 2 .500* .113 .613

* Material COSTS KAY EE REDUCED T ROM .05 TO .Cc PER e^ard ft. if a VONCO Plant

- .S LOCAT ed in the East as indic AT ED EY Mr . Harvey Davis of the MD Corp.

** Laboa costs were assumed the same as those used for Sprayed Cementatious

.'.ATEK:ALS since no actual application costs ARE AVAILABLE FOR VOiMCC.

JLI Firc Tests were conducted and approved, sut were not included in the i960 UL! Building Materials' list or the Feer.jary 5i-Kgnthly Supplement.

NOTE Nc.i - This Company has also conducted the following ULI Fire Tests on a I0WF-I9 Column.

These approvals are not listed to date. A) 5" thickness "ailed § 50 minutes

B) I" THICKNESS FAILED @ I HOUR AND 55 MINUTES

C) 2t"THlCKNESS FAILED 2 6 HOURS AND 14 MINUTES

NOTE 'AZ.C. - TrMS MATERIAL IS REPORTED ACCEPTABLE FOR EXTERIOR APPLICATION AT OUTSIDE

TEMPERA".-,!! ZF 0°F.

CAFCO 7YCI

"2' ULI -86-3

I 05.65 -SM 8" Beam CRYSOTiLE AS3EST0S

AND Mi l.-ERAL F I SER FlREP ROOFING AS MANUFACTURED BY THE United States Mineral UL1-20-4

Products Co.,

Stanhope, N.J. and called "Blaze Shield

ULI -1 9-3

195-65-SK I4V/F22G Col. I I /£"

195-65-SK 14WF22& Col. I

.075

.169

.262

.041

.092

144

.261

.406

NOTE Nc.i - as per CAFCO file No. C-409, field painting of structural steel may be eliminated

when "CAFCC" is applied direct.

NOiL No. 2 - No TAMPING OR ADsESIVE IS REOUIREC

USM-002658

Figure A-16 (Contd.). Correspondence related to economic study of alternative thermal

insulation materials (432-P).

NISTNCSTAR 1-6A, WTC Investigation 149
Appendix A

NOTE No . 3

- May 3E sprayed ey pole-f i eer-gu.n wkick should effect scaffolding costs.

TERIAL DESCRIPTION AUTHORITY SIZE OF (U.L.I.) MEMBER

(d.S.a. TESTED

INCHES FIRE

REQ. RATING

IN HOURS

MAT . LABOR TOTAL

$/SG.FT. $/SQ.FT. $/SQ.FT

SPRAY CRAFT ULI -203-2

Asbestos Fiber 502-53-SM 10" Beam 1 16 1

-

• u O oh 1 MANUFACTURED 3Y THE

1

ll Smith &. Kanzler Corp., ULI -8l -5 IOWF25 Beam

-7 /On 7/0" .131 .072 .203

1414 East Linden Avenue

Linden, N.J. ULI -76-3

502-53-SM 10" 3eam 4 •113 .062 .175

ULI-25-5 8" Beak 1 7/8" .281 .15* .435 R2923-I2

(OasOLETE .246

)

Column l\ .4 5 0

• .696

UNL 1 STED* I4WF228 Col. 1 3/4" J .265 .144 .407

UNL 1 STED* 14WF22& Col. 1 3/16" h .178 .097 .275

UNL 1 STED* I4WF22& Col. 7/6" •131 .072 .203

NOTi

NOT

* ULI Fire Fests' were conducted and approved but v/ere not- included in the 1 966

ULI Building Materials List or the February Bi-Monthly Supplement.

kc. 1 - No T A v. ping or adhesive is reouirec.

is'c . 2 - May be applied with pole-fiber-gun, which should effect scaffolding costs.

Spray Ccmentatious a; kam>f actus ED Sy The

Um:ted States Gypsum

Co., Cn.CAGC, III.

uli -37-5 8"Beam only . 108 .119 .227

ULI -22-3 8" Be am 1 k . 108 . 1 l'9 .227

ULI -24-3 8"Beam ' 2 4 . I2*i

_ .136 .260

'ULI -32-3 I2"Beam 1

1 "

I L 5. 108 .119 .227

ULI -67-3 8"Beam only .077 .091 . 168

ULI -70-3 8" Be ax 1

1 11

. 124 .13.6 . 260

ULI -30-4 I0WF49 Col. 2i" . 186 .204 .39c

ULI - 1 3-3 Column 2 1/8" • 175 • 193 .368

ULI -23-3 I4WF228 Col. .7/8" .072 .079 • 151

ULI -25-3 I0WF4O Col. 1 7/8' : • 15* . 170 .324

ULI -229-2 8 WF Beam 3/1,- .062 .066 . 130

USM _002659

Figure A-16 (Contd.). Correspondence related to economic study of alternative thermal

insulation materials (432-P).

150 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

MATERIAL DESCRIPTION AUTHORITY

<U..L.!.)

(B.S.A.

)

size or MEMBER TESTED

1 NCKES

REQ. FIRE RAT 1 NG

IN HOURS

MAT.

&/SQ.FT. LABOR

ii/SQ.FT. TOTAL$/SQ.FT

ul; -31 -4 UNL 1 S7ED* IOWF226 Col. 1; .108 .113 .221

UNL 1 ST ED''' IOWF228 Col. i i/6: ' t .092 .102

L'.NL 1 ST ED"*" IO.VF228 Col. 13/16" 5 .066 .075

* UL I Fire Tests were conducted and approved but were mot included in the 1966

- ULI Building Ma7 e r 1 a l s

1 List cr the February Bi-Monthly Supplement.

NOTE Nic. . - Costs indicated do not include possible required scaffolding or excessive

clean-up and/or protection for overspray.

NOTE Nc . 2 - Material costs were indicated by the N.Y.C Representative of U.S. Gypsum Co. (rev I sec PR 1 ces) .

MONCC

Ceme.ntat : ous Spray

F 1 s epr oof 1 AS v.anufa ct ui" ed iY Th:

Zo.\ol:te Division of the v.'.R. Grace & Co.

r -ago, 111.

UL!-2^-2* OWF26 Beak 3/I5" k

UL 1-23-3"

ULI-27- 1***

|i}WF228 Col. 7/6"

|i!WF220 Col. \~"

.0o2

.070

.108

.066

.079

.115

.130

.227

* ULI F.'RE Tests were conducted and approved eu~ *r v.'ERE NOT INCLUDED IN THE 1 966 ULI BUILDING MATERIALS 1 L I ST OR THE FEBRUARY

E

-Monthly Supplement. (3/^!' thickness failed % k hours and 10 minutes.)

NC".*£ '.kg. ' - Costs indicated dc not include possible required scaffolding or excessive CLEAN-UP AND/oR PROTECTION FOR OVERSPRAY.

NOTE Ko. 2 - Material costs were indicated by the W.R. Grace &. Co.

USM-00266C

Figure A-16 (Contd.). Correspondence related to economic study of alternative thermal

insulation materials (432-P).

NISTNCSTAR 1-6A, WTC Investigation 151
Appendix A

WORLD TRADE CENTER - Fl REPROOFING ANALYSIS

RECOMMENDATIONS

Presently, it appears that the sprayed fiber materials (Cafco and Spray Craft)

enjoy a slightly more economical applied cost per square foot than the sprayed

cement i t i ous (flrecode v and monccoat / materials but not enough to preclude

keeping 30th in competition until a final buy is made. note that the fiber

suppliers kav£ not conducted as extensive a fire testing program as have the cement i t i ous material manufacturers. slnce more data is available in the latter

instance, more accurate interpolation is possible here without expensive addition... testing.

Th£ REMOVAL OF BOTH THE TAMPING and ADHESIVE REQUIREMENTS (3Y ACTUAL U.L.I. Author ; ty } from the fiber applications, the apparent adility to spray fiber with

accuracy from the tloor using ti-le newly developed pole-fiber-gun and the relative

ease of clean-up without scraping of over sprayed material, generally contributes

to the edge in economy of the fiber materials.

The possible requirement (assuming that an exterior gypsum board assembly proves

itself; of confined spraying between the curtain wall and exterior sox columns

as y ell as between the curtain wall and exterior spandrel members, could give

the fiber matekjal an added advantage over cement it i ous, since fiber equipment

appeals mor - versatile and easily adaptable to fan sprays, nozzle mixing or

sll":rv mixixg. (grout), simply by changing existing spray heads or adapting new

h_ r.3 configurations if existing equipment cannot be satisfactorily controlled.

t.-;r_ ai.lltv of the cementltious material to harden or crust after application l£ a ,-_o's for this material since duct work generally is scheduled for installation

(eLVV.'EEN TRUSSES) AFTER THE FIREPROOF 1NG OF STEEL, WITH RESULTING DAMAGE TO FIRE-

?,;,;• . \g being minimized. material costs have seen dropping and may not have

.-:eac:.id bottom.

!t is recommended that both sprayed fiber and sprayed cementltious subcontractors

be placed i n a competition with each other with instructions for logical interpolation of required thickness of their respective materials based on actual or unpublished Underwriters' Laboratories approvals.

We a::- in the process of evaluating the economics of Vonco Mag'nes i um spray versus

a s°ec;al waterproofed laminated assembly of gypsum board sheets for the exterior

of t.-.z columns and spandrels only ( where moisture or temperature precludes other

MATERIALS, IN OUR OPINION, WITHOUT EXCESSIVE RE-WCRk).

Vonco is tco costly for further consideration for interior fireproofing application.

When 7 r:;s analysis is complete, we will recommend the most economical approach

TO 7:-.: PROJECT'S EXTERIOR FIREPROOFING REQUIREMENTS. AT THIS TIME, THERE AP- PEALS JUSTIFICATION TO PURSUE THE INVESTIGATION OF THIS PREFABRICATED LAMINATED

ASSEMBLY OF EITHER THE STANDARD J /&" FlRECODE GYPSUM BOARD OR A SPECIAL BOARD

MADE C 7 FlRECODE V MATERIAL WHICH CONCEIVABLY V/ i L L PERMIT A k HOUR RATING WIT:-: A SINGLE ! 1 /o" THICK SOARO (U.L.I. 3 ' ~ ^

' R Z v 1 s E 0 ) F0R APPLICATION" TO THE EXTERIOR

FACE OF THE EXTERIOR SOX COLUMNS, PERMITTING THE ERECTION OF CURTAIN WALL AND THE CLOSING IN OF THE TOWER STRUCTURE PRIOR TO APPLICATION OF THE INTERIOR SPRAYED

USM-00266]

Figure A-16 (Contd.). Correspondence related to economic study of alternative thermal

insulation materials (432-P).

152 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

firep roofing. If the suilding can be enclosed early in the construction cycle,

interior f i reproof i ng with e i t t-i z r f i £ er or c em e nt i t i 0 u s material will ee more efficient and thus more economical.

Figure A-16 (Contd.). Correspondence related to economic study of alternative thermal

insulation materials (432-P).

NISTNCSTAR 1-6A, WTC Investigation 153
Appendix A

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Figure A-17. Thermal conductivity and heat transfer coefficients used in 1966 study of

candidate thermal insulation materials for exterior columns (437-P).

154 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

•THERMAL INSULATION

The insulation materials applied to the structural steel components ol the wall (columns and spandrels) must serve to control column

temperature to a minimum of 50° wiih 70°

inside and 0° outside, provide fireproofing

to meet a four hour test on a heavy column, and minimize heat loss and gain to satisfy HVAC requirement. After extensive testing of many insulating and fireprcoling materials, a sprayed mineral fibre has been selected to meet all requirements of the three purposes

above. It will be used on the three exterior sides of the column and both sides of the spandrel plate. The rcom side of the column will be

covered with gypsum plaster to meet lireproof- ing requirements with a relatively high "K"

value to permit heat migration to the steel. This migration is necessary to hold steel lemperatures above specified minimum during extreme and prolonged cold periods- Thermal Testing The minimum column steel temperatures of 50°F requires strategic use of both high "K"

and low "K" fireproofing. Since the required therma! balance results from a combination of many factors, calculations can be only a rough

guide to design and true performance can be determined only by actual test. Such tests have been performed at Cupples

on three 5' sections of columns completed in

full detail typical of the 100th floor. Two units were assembled in a dividing panition of the thermal chamber at Cupples with thermocouples mounted on the steel, top ana bottom and

inside to outstde. "Outside" temperature on

one side of the partition was reduced to 0

3 F and "inside" temperature was controlled at 70°F until steel had reached therr.3l balance when results were recorded. A thud unit was

tested similarly at Pennsylvania Stale University in the thermal chambers of the Institute lor Building Research. Complete details ol tests and results are in- cluded in the pecket at the back cf this book.

Low Conductance

Spray Fibre Fireproofing

Moil Flow C.iOf*c;c*'it'Ci of column, loanoiei and fuep'ooftnc.

Therm;! tcs'.s In progress at the Ins! Pennsylvania Slate University.

Building Researcr*.

Figure A-18 Excerpts from December 1996 Alcoa proposal for exterior wall of WTC

(448-P).

NISTNCSTAR 1-6A, WTC Investigation 15
Appendix A

• Hoisting—All hoisting would be done after

regU i ar working hours from 4 P.M. to approxi- mately 8 P.M. Assuming the inside dimension

of the hoist platform to be TV % 12'3", each

lift will include one mobile cart carrying two 1800= packages.

Distribution and Floor Storage—On the designated floor the mobile carts would be moved to storage areas allotted for the pur- pose. A minimum of six and as many as ten

floors of material would be so stored ahead of the actual erection. Glass would be handled on the inside job hoist in cases weighing

3.600 lb. The cases would be handled, moved

and stored on the floors in the same manner

as the metal components.

FiREPROOFING

Sprayed fiber material as manufactured by CAFCO and of a type described in Underwriters Laboratories report R 3749-10 will be

applied to three sides of the exterior columns

thick enough to provide four hour fire protection and lo maintain the proper thermal insulations. The required thicknesses to meet fire- proofing requirements are 1'/u" for exterior columns and Vi" for spandrels. As space permits, the thickness can be increasecLto obtain

the required thermal characteristics. On the inner side of the columns, a high "K"

value material will be applied to provide fire- prooling while also permitting heat migration from room air to column steel.

The sprayed liber will r esist the elements

during construction of the curtain wall, remain

7i rm to Ihe touch and will not reduce in t hick- ness with time. jSee copy of CAFCO Bulletin C-940 i n pocket at rear of book). Application would be accomplished with a special nozzle and a transportable cage to safely proiect the applicator to the exterior of the

building. Adjustable vertically, the cage would

permit complete coverage of the outer faces

of columns and spandrel beams. A screen would be provided around the spray zone to prevent the "blow-by" of fiber material to the

exterior of the building and the street below.

Fireproofing in progress would be approxi- mately ten floors above the aluminum wall,

Sketch illustration of ipra}inp. of fireproofing :tom enc:oseO cac? sr.cj screen

Figure A-18 (Contd.). Excerpts from December 1996 Alcoa proposal for exterior wall of

WTC (448-P).

156 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

TO:

FRO.M: DATE: SUBJECT:

REFERENCE:

COPY TO:

MEMORANDUM

0011788

Mr. R. M. Monti

A. J. Calabrese

August 8, 1967 COLUMN AND SPANDREL FIREPROOFING OBSERVED AT -ALCOA PLAN"

2036-

' REFER NO 'ED

to" DATE BY CATE

RETURN TO File

I went Co Alcoa-Cupples plant in St. Louis on August 3, 1967 on an inspection of colirm and spandrel fireproofing of mock-up.

Mar~io and DTiono - plasterer - contractor representative was

a Mr. Louis D'Bono and Cafco representative was a Mr. A. Bessemer.

The above mentioned ar.d I were present when columns and span- drels were sprayed with Cafco Blaze Shield Fireproofing Type "D" on August 3 and 4, 1967.

It is my opinion that the method of applying was done in a workmanship like manner. Ic is also my opinion that the method of applying was done with ease and very little spillage.

AJC/eam

A. J. Calabrese

THE POST OF N F_W YOSK AUTHOHI fY RECEIVED

At 8 1257

WORLD TRADE DEPARTMENT WORLD TRADE CENTER

PLANNING DIVISION

PLAINTIFF'S

EXHIBIT

(-<(,- SP-Sb . JU- 57< -\a-7-t

<f- /oA-'V^

Figure A-19. Port Authority correspondence related to demonstration of application of

BLAZE-SHIELD Type D to mockup of exterior columns and spandrels (384-P).

NISTNCSTAR 1-6A, WTC Investigation 157
Appendix A

75

Deoember 14, 1G33

1*7 » T^COlD P. Sroxry :o o2 r:^ Vcrk Authority

Ro: Spraycd-on Fireproof iarj

V/orld Trado Center

r:r^ Mi

Ci" r:?±C3y, Dcecnber 10, 3iCS5, a nootins \?aa held in our

Cj;"£C-) to tUC0u23 tho £ircrroo£±r.s requirements oi tho

^:V;:r tL"crrr..i. TIso cootin^ eas at vended by IZszora. Ce2.cz^a,

L^.^r;;ol, Cc2£cr c;id Brcner. Tliio letter ccztfim3 ufcat raa

•Olccucccd nt tlio eeotiDs.

C:~' rrcDcnt eeeicna concept, and tho end ^h&eh v?o ore ce?s-

§2*:;2lv.3 t?ith, io fosed iigoa tlio noo of a reasicua tbicUacsa

CU <:r.o zzza e^raye-J-oa jiircprcoiin^ caxeriral uruuad tucs

£z.:.'s.?lCz?& eerpsscata oi? tho fleer trusses, ¥h±o ceiscest

<-;-.r.;-] isscn t£ao criciiual otas^ardo £o? the protest therein

£3 V-JiHd olthcr coot tbo Ilo-ar Ycr>; City codo or tTneerpritcr 1, o

^o c^to» thG ono inch thiol; cn^orial imsots tho 3-hour

VC'z^czz^Zd c2 eeth tha dq code and Uncleiwiter *o uains

jT-yVic-jz;^ approved Gsse^blica tested by tho "lead criteria"

L*ju a^nc^irrs tho ccro atric^ont tiuio-teztpcraturo-rate»o£«

l?£r;o c:?£vcs, £ri tlaieu io an aatc>nato teatier; procedure tsst

. re re- ire:! by tto Eicn cede or by Und^rtyriter^o, end *;h±ch v?o

On Friday, December 10, 1965, a meeting was held in our office to discuss the

fireproofing requirements of the floor trusses. The meeting was attended by Messrs. Solomon, ??????, Softer, and Brewer. This letter confirms what was discussed at the meeting. Our present design concept, and the one we are continuing with, is based upon the use of a maximum thickness of one inch sprayed-on fireproofing material around the individual components of the floor trusses. This concept is based upon the original standards for the

project where in we would either meet the New York City code or Underwriter's requirements. To date, the one inch thick material meets the 3 hour requirements of both the new code and Underwriter's using previously approved assemblies tested by the "load criteria" but

ignoring the more stringent time-temperature-rate-of-rise criteria which is an alternate

testing procedure not required by the new code or by Underwriter's, and which we do not consider necessary.

tan uo&i

Figure A-20. Correspondence from Emery Roth & Sons to Port Authority related to

thickness of thermal insulation for floor trusses (text in box was typed by NIST since

copy of document is of poor quality) (3-P).

158 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

COPY EMERY DOTH £ SONS, ARCHITECTS

050 THIRD AVENUE

NEW YORK 22, N. Y.

.>;!, !> '; Co L II iltlW?-- .

Dacanoar .23, 1065

.ir. 2-iiilcoi-;-.; ?. Lavy

TIj-j ?ort of .ietv '/erk Authority Hi li^htb Avenue

S.a: Spraysd-on Fireproofisg

... i'orlc Trade Caatar

Dear .-;a.l; This suppliants sy Dacember 14th letter to >ou. r-Ithough thi o:;s.Li:h thich spruyed-oci rireproofiu£ .aeets the J-^o-r ra.-,_iraniaiit3 ox" ooth tha proposed 3 iiidin0 Code and

iidervjritsrs; adv^r.cj i:-.xor.^d£ioi- from rsaa..:f*ii. errors .uadicatas

that if the- tr^-ss -..ora r._- s virad to ~-s tire- tested, then two

i-schas or material -oulu be re s irod iur chs lijht anjjle asiaoers.

v. a iira tharafora ravisi::-^ o_r •,.or.;i.n=J driwio&s to ^lidiccita a

o:-.^-i--.-.h ?:-a?r? of spraya-3-ou fireproofing aro_ud the top a::c ~tt-_ chords of thi cr^ssas, fc;;d - tvo-isui! thic^ss for ail

other us^'ivrs ol tha trasses.

-'•> iniorsottonii! copy or this letter, oil consul exists ara re- V-astad to review chair designs and drat.iii.js, tJac; co r^ice oil

oecassary chiisiges to u,eet this nov- writer iu.

Sincerely

,

EiiEIW RoTH i; 3UX3

cc: Leslie Robert

Aiiroii ifchraic

Joseph !

:.- Los

J^ruo, jiaira J. i'o;.o.:o;.

This supplements my December 14

th letter to you.

Although the one-inch thick sprayed fireproofing meets the 3 hour requirements of the proposed building code and Underwriters, advance information form the manufacturers

indicates that if the truss were required to be fire-tested, the two inches of material would

be required for the light angle members. We are therefore revising our working drawings

to indicate a one-inch thickness of sprayed-on fireproofing around the top and bottom

chords of the trusses, and a two-inch thickness for all other members of the trusses.

By informational copy of this letter, all consultants are requested to review their designs and drawings, and to make all necessary changes to meet his new criteria.

(5.2)

Figure A-21. Correspondence from Emery Roth & Sons, to Port Authority on thickness

of thermal insulation for floor trusses (text in box was typed by NIST since copy of

document is of poor quality) (3-P).

NISTNCSTAR 1-6A, WTC Investigation 159
Appendix A

•'32-5222-3-4 2k3§cZ>/lO

Plastering Co.. Inc. 136 LIBERTY STREET NEW YORK. N. Y. 10006

September 15, 1969

Mr. Milt Gerstman

Tishman Realty h. Construction Co., Inc. 30 Church Street New York, New York

RE: Fireproofing thickness 1 to be sprayed on steel

Dear Mr. Gerstman:

This list is being submitted for your approval.

1. Beams throughout buildings - 1/2 inch. No tamping or shaping of Cafco type D.

2. Columns 1 3/16 inches. No tamping or shaping of Cafco

type D.

3. Elevator columns - 1 inch total including overspray. No

tamping or shaping of Cafco type D.

4. Bar joist - 1 inch overall thickness. No tamping or shaping

of Cafco type D.

Very truly yours, MARIO & Dl BONO PLASTERING CO., INC.

8

ld/cz 7ISSKAM REALTY I CONST. CO., INC.

15 1969

Louis Di Bono

USM-002883

DEFENDANT'S

EXHIBIT

DX 434

Figure A-22. Correspondence from thermal insulation contractor to Tishman Realty &

Construction Co. related to insulation thickness (255-ITK).

160 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

732-5222-3-4

Plastering Co., Inc. 136 LIBERTY STREET NEW YORK, N . Y. 10006

September 18, 1969

A-fi

Mr. Milt Gerstman

Tishman Realty & Construction Co., Inc. 30 Church Street

New York, New York

RE: Fireproofing thickness' to be sprayed on steel

Dear Mr. Gerstman:

In regard to our letter dated September 15, 1969 concerning the

thickness of fireproofing material, please add the following

paragraph:

5. All beams in MER rooms and utility rooms will be 1/2 inch thickness

with overspray. No tamping or shaping of Cafco type D.

Very truly yours,

MARIO & DI BONO PLASTERING CO., INC.

Louis DiBono

LD/cz

TISHMAN REALTY & CONST. CO.. IMC.

SEP 22 1969

USM-002884

Figure A-22 (Contd.). Correspondence from thermal insulation contractor to Tishman

Realty & Construction Co. related to insulation thickness (255-ITK).

NISTNCSTAR 1-6A, WTC Investigation 161
Appendix A

> r. Louis DiDono

Hirio & DiBono Plastering Co., Inc.

3.0 Northern noi.iU-v.nrd

Great Keck, Long. J.slcnd, New York 11021

Re: THE WORLD TRADE CENTER - Com;: net KTC 113.00-

Spray-On Fireproof in?, - Towers A '< D

Dca Lou:

As a result of your is»oel.infl \ ilh Mr. Levy on October 21, 1969

I am enclosing a list of T"\:er "A" coJuii-n.s tli.it ore less thru

14VF1 28 which will n quire' 2 3/if-" thick of "Cafee G Lo:-.e - S!> i e Id •fypeD'""

spra\-on f ireproo f inj- . All Tower columns o-;ual L>> or f;reatvr than

lHv.r.: . '" V.~J.li :

:.: Lj^; j. :V i J/ i"" ' ! L i. reprt'O I inj-.,, inn ii Oi i in- .inuvi: thicki. ",.5S-i">s develop (he required M-hour rr-Lin---..

All Tower l'-nms, spandrels and bar joists roquirin;',

spray- ^n r ireproofjnp «--ro to have a V

1 covering nf "Cafco". ^^^>J

T,\o above reqn i rcmon-t s must be adhered to in order to

maintain the Class 1-A Fire Rating of the New York City liuiLding Code.

Sincerely,

Robert J. Linn

• Manager, Project Planning

The World Trade Ccntcr

cc: Messrs. M. Gerstman (TRCC), J. Solomon (ER&S)

Figure A-23. Correspondence from World Trade Center Department to the thermal

insulation contractor specifying the required insulation thickness (3-P).

162 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

/ ri/tfip.tOO fiitfj STANDARD

ARCHITECTURAL SPECIFICATIONS

BLAZE-SHIELD STANDARD

is a mill quality control blend

ol virj:n asbestos fiber, hijhiy refined white mineral fiber and

pfopri-: i.ir / binders. Tested and listed by Underwriters' laborato/res. Ire. !ULI) and Underwriters' Laboratories of Camda (ULC)

lor firiprcofing applications, code acceptance has been registered by ma.or municipal buitdrc departments throughout the United

Slates and Canada and in many countries overseas. PRODUCT FEATURES

•

. c: A.- t!DAi — An improved BLAZE-SHIELD STANDARD

formation eliminates aprlication dustiness generally associ- ated .vith conventional sprayed fibc-r products. Respiratory

hazarc;. clean-up time and expenses are minimized. \ ' — 8LAZ£-SHiaD STAfiDAP.O out-performed

other fireproofing media when exposed to severe lire temperatures on major high rise structures. CAFCO applications have been credited with restricting fue spread and preventing serious damage.

'

' F-'

! '.T ' — Tested in accordance with ASTM

B-117 and federal Specification MJL-E-5272A, CAFCO protected, shop tainted steel evidenced no corrosion under severe exposure

conditions. Rust preventive properties are superior lo the combination of shop and held painting; costly held painting may be eliminated.

1-1.- — CAFCO treated spandrels, rcof decks

and foor units reduce heating and air conditioning costs; d :nsj!stion at root set backs may be etiminj'ed. BLAZE

,£L n STirl9ADr> prevdes a Uier.TOl ccniuct-Yty ft) vjtve

i.-.l ml

ALL-WEATHER APPLICATION REDUCTION IN DEAD LOAD PERMANENCE Of PROTECTION

ACOUSTICAL ABSORPTION

GENERAL

S? : . — See BLAZE-SHIELD Type D specification

F

" :i c:'. .if.C/".: - — See BLAZE SHIELD lype 0 specification C--V ..:•>{.:• — See BLAZE-SHIELD Typ» D specification MATERIALS — Bonding adhesive .-/here required, shall be a milky while, latex type waier emulsion which shall be unafieclrd by water, waler vapor, condensation, aging or freeziig once it has set. Shall be CAFCO ADHESIVE as supplied by the United Stales Mineral Products Company (Canadian subsidiary —Columbia Acoustics & Fireproolmg Co (Canada) Ltd.), or approved equal. — The liber sha'l be a factory quality controlled aai Ijrmulated mix

consisting of 100?i inorganic virgin Crysolne asbeslos fiber and small pellet, white mineral

fiber, combined with 1C0% inorganic binders. Fibers shall be CAFCO BLAZE SHIELO STANDARD

as manufactured by United States fViner.il Products Company (Canadian subsidiary— Columbia

Acoustics & fireproolmg Company -(Canada) Ltd.), or approved equal, and shall be supplied

to the job site in sealed bags, properly marked and labeled lo show Hie inspection ol Underwriters' Laboratories. Inc. or Underwriters' laboratories ol Canada lor the application

specified. v nvr-: — Overspray. where required, shall be transparent and unaffected by moisture; shall be CAFCO SEALER as supplied by United States Mineral Products Company

(Canadian subsidiary —Columbia Acoustics & Fireproofing Company (Canada) Ltd.), or approved

equal. WORK OF OTHER SECTIONS

' -.;;C:: PF " 7 . — See BLAZE-SHIELD Type D specification

!' . .1 — See BLAZE-SHIELD Type D specification

F-J.i -VL.r.K :.? TH'S r: .A .. — See BLAZE-SHIEiD Type 0 specification INSTALLATION

113 ;:.:(. > — See biAZE-SHitii) Type 0 specification

'-rr "-T't • ":.'.'; :-• — See El AZE SHIELD Type 0 specification — All surfaces to be treated shall be primed with CAFCO ADHESIVE, fibers

shall be applied and tamped to required thickness and oveisprayed, where required, with CAFCO SEALER. Cu — See BLAZE-SHIELD Type D specification

BEAMS - GIRDERS - SPANDRELS

SYSTEM HOURS

BEAMS. GIRDERS, SPANDRELS

THICK- NESS AUTHORITY

ULI=R3749-6

ULI=R3789-2 ULI-R3749-13 N^f X

BLAZE-SHIELD

lype 0 Standard CONSTRUCTION

CAPPED BEAMS. GIRDERS, SPANDRELS. JOISTSULI=R3749-18 ULC-60T9? COLUMNS

COLUMNS AND COLUMN CAPS

1"."

Wi"

Hi"

2'r,"

ULI-R3749 I0T x ,V7

. ULI-R3749-9* Jfifft? ULI=R3749 19 PS

Ull=R3749-19 \ Zif Ull=R3749-I9 JC Sol WALLS

w;lls

* fit application lo columns 14/;f/?8 or greafei IRC — UndttwfilW*' laojfdttf'ei ci Carina \ ULiAi: lens conducted in accoidan<e *-ln ASTM £-119

ULI-R3749-21

Unrjfnr/f iters' Laboratories, inc

1—

Figure A-24. Excerpt from 1966-67 U.S. Mineral Products Co. catalog for BLAZE-SHIELD

indicating thermal insulation thickness for various applications (3-P).

NISTNCSTAR 1-6A, WTC Investigation 163
Appendix A

Figure A-25. Portion of "General Notes" page of the Alcoa curtain wall drawings and

blow-up of Note 11 indicating the thermal insulation thickness for the exterior columns

and spandrels (116-LERA).

164 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

,r<c ,b 1 t-WM*"!

joe HUHBCIt SMttT.

'

THF WORtB^TRAD'E r.FMTTFJ*^

THE. PORT OF NEW YORK AUTHQgEW^jj CONTRACT' W-TC"4^0':C,'d

MINORU YAMASAKI ASSOC. EMERY SONS an isioms". -.qs^-

ALCOA

CUPPLES PRODUCTS

cu.STi.rN %jfA'IA.. TOWERs Aland "B

5- \'^.-UU \ t-.-t ~. ic

<s

| "»vl^..?5&q».y/.',y

Figure A-25 (Contd.). Portion of "General Notes" page of the Alcoa curtain wall drawings

and blow-up of Note 11 indicating the thermal insulation thickness for the exterior

columns and spandrels (title blocks of drawing are also shown) (116-LERA).

NISTNCSTAR 1-6A, WTC Investigation 165
Appendix A

f—. -p. , EMERY nO TH ft SONS. AHLI-II I r.v. . V^_/ 1 J

050 THIRD A.VENUE NEW YORK 22, N. Y. '

• . 7 c -

1 1

-

July 25, I9'66

Mr. Halcolsi P. Levy

The Port of tiew York Authority

111 Eighth Avenue

Mew York, New York IC011

Re: Itorld Trade Center

Dear Mai:

In accordance with your requirement that we inform you of any

proposed installation that night not conform to the Hew York

City Building Code, I would lilts to call your attention to the

floor construction in the tower buildings.

As you know, we propose to pour a 4" concrete slab over a metal

deck which serves only as a form and will have no structural

value but will remain in place at completion. Since the deck

is non-structural it will not be fire proofed.

The electrical contract drawings show 3" header ducts buried

in the slab with 1" concrete over the duct and removable aecal covers at the 5.ntarsection3 of racavay cells. Spray fireproof

ing will be applied to the under side of the deck in strips

where headers occur. The headers, in turn, feed into electric and teleohone raceways

which are 6' -8" cn centers having floor inserts 3' -4" o.c. and

knock-outs for lighting below spaced alternately. The deck

under the raceways will not be fireproof ad.

Obviously with so many penetrations of the floor system the fire

rating oj: the floor construction is of an indeterminate value

unless tested. It is doubtful if it will meet a 3-hour test.

However, I believa that this i3 still much better than the

"punch- through" system currently prevalent in jsany newly con- structed buildings in ilew York City.

If there is concern for fire rating perhaps spraying the under s of the entire deck nay be a solution. I would like to have your

thoughts on this.

Very truly yours,

EMERY ROTH a SONS

CC Aaron Schreier/HYA ^

Dick Humenn/JItLA /

HJH : mlk 11AR:U J. ia.uHAfl

Figure A-26. Letter from Emery Roth & Sons to Port Authority regarding the application

of thermal insulation to the bottom of the concrete floor slabs (3-P).

166 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

New York. N Y 10046

(212) 466 7000

(201) 622-6600

PORT AUTHORS OF N- V_ &

J - prCElVED

MAR 17 198?

WORl. i KAOt DEPARTMENT

DEP. DIR. PHYS. FAC.

March 14, 1983

Mr. Jerry Silecchia

National Cleaning Contractors, Inc.

60 Madison Avenue

New York, New York 10010

Dear Jerry:

As you know, during the construction of the World Trade Center the use of asbestos fireproofing was discontinued at the 38th

floor of the World Trade Center. Those areas were subsequently

encapsulated with a spray-on hardening material. The Port Authority

has, on occasion, reviewed the asbestos fiber count above the ceiling in these areas and found these counts to be well below the OSHA standards .

However, in the interest of safety for all, you should

direct your employees to use OSHA approved dust filter masks, pro- vided by the Port Authority, when working above the ceilings in these areas .

Kindly advise your employees as needed.

Sincerely,

Daniel J. Censullo

Manager, WTC Operations

The World Trade Center

bcc: T. Cancelliere, J. CrismerAR. Linn,)A. Rhome , J. Ritter, J. Verbist

Wiilci ; Uifoci d.al telephone 466 358 5

Figure A-27. Correspondence indicating that use of BLAZE-SHIELD Type D was

discontinued at the 38th floor of WTC 1 (229-ITK).

NISTNCSTAR 1-6A, WTC Investigation 167
Appendix A

TO: FROM: BATE:

SUBJECT:

REFERENCE:

MEMORANDUM

File

R. M. Monti

May 15, 1970 THE WORLD TRADE CENTER WTC 113.00, WTC 120. OP

-iV.-SREFER.' •<

• NOTED .

-TOVA '.DAT Em. •i BY':' DATE

. ". tj. s Kf ' «TU«« TO < r> - .

SPRAY FIREPROOFING - CONTRACTS WTC 400.00,

copy TO: Messrs. Levy, Tozzoli, Falvey, Werneke, .Raiola, DeConzo (AllW/Ref.)

At the '.present time -there Yarei- two '^contracts :ihvolvedHh'«spray

fireproofing: i')*WIC :406.00*vith ALCOAj«s and -.,2 ) Port .Authority-Contract VTC.:ll3.00Vfbr fireproofing *of floor-^trusses\ln the" towers, corejcolumn

in -the towers, below .grade.-areas io'f itne.?bathtub area; and the -Northeast Plaza Building. In^£he.iimmediate£future ..there^vili.-.be Mfrt2iird'.vsubcohtract '(WTCil20iOq;.. fbrjiireproof^gtlAeJCustoms building;:

ILCOA: Contract WTC &00.00

ft?-

From the inception of •ctudies.'ionJ^his' cbncractyALCOA^proposed

.tne jise .of catco \type.:D spray \f ireprbpfing^vhicli'iconforms tbithe fire, requirements, bu^more^iinportant to aLCOA,: eoniorms to the frequired 'K fact9r.;tor.if th'ermal conductivity; ALCOA is a^erformance<typej:contract

MO they ^proposed, to «use . this material .which met. their ?perfj)rmarice?reguir»'- ments and -containedfasbestos^.f ibers;; On ill mother xontracts'sthe 'Sari-- Authority -likewise ^specified .Caf co type D spray' fireprooting jwh'ich-xbntained

asbeitp.sa^ib'ers..

For the last six months there has been -a certain amount 01 interest developed in the New York City area on -the potential- health problems caused by asbestos fibers. This 6tudy vas conducted primarily

by Dr. I. Selikoff of Mt. Sinai School of Medicine in conjunction with

the New. York City Air Pollution Department. Early in April.'Nev York City

promulgated a 6et of emergency -instructions regarding the application and use of spray fireproofing containing asbestos fibers (Enclosure 1 is 'a. J copy of 6aid regulations). On the World Trade Center, the Port" Authority

complied to the best of its ability and vas praised as the best Job in the city in conforming with the regulations for the application of this material. However,' item' No.. 10 of Enclosure 1 indicates potential problems of exposed fireproofing containing asbestos which is installed !in- return air plenum ceilings. ', It" was. maintained by Dr. Selikoff that studies performed

by his staff .indicated that exposure overa considerable number of years, of people sitting in an office,- where the' return air passed by exposed spray fireproofing containing asbestos, could cause health problems. Item No. 10

.of Enclosure 1 specifies that such asbestos products in return plenums

should be sealed with -an appropriate sealant to prevent dusting of asbestos particles. At this point the Port Authority started studying possible sealants that could be applied, should it be decided to proceed in this

matter.'-: Enclosure Z is a letter from Mario A DiBono Plastering Company,

listing the components of a possible sealant manufactured by U. S. Mineral Products for areas already sprayed with -asbestos.^ Enclosure '3 is a letter

from. R. .M, Monti to Dr. Selikoff regarding the possible -use of a 6ealant and asking that.he >dvise\us-'of: his' opinion before we proceed further. (DEFENDANT'S,' EXHIBIT'

DX 589 f

{DEFENDANT'S,'!

>• -EXHIBIT"''.! DX 589

Figure A-28. Port Authority memorandum summarizing the factors considered in

choosing BLAZE-SHIELD Type DC/F as a replacement for the asbestos-fiber containing

Type D (185-ITK).

168 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

- 2 - May 15, 1970

Enclosure.4 is a letter from Dr. Selikoff, Mt. Sinai School of Medicine,

to R. M. Monti, dated April 16, 1970, indicating that our proposal to use

a 6ealant on areas sprayed with mineral fireproofing containing asbestos

is the be6t technical means available at thi6 time to prevent dusting,

and it has his concurrence.

On April 17, 1970 the spray fireproof contractor, Mario & DiBono

Plastering Co. who is a subcontractor to ALCOA under WTC 400.00 and .also the -Port Authority's contractor -under VTC 113.00, was served with five summonses /-one for each . day of the week of April 13th. These summonses stated that he was in violation -of the regulations listed in Enclosure 1. On . April *17 th,;_..Mario..,& .DiBono also ;received ? a -Show .-Cause.;order returnable

inYconhectibn with" the" -fireproof ing work being'^erformed at 'the World

Trade Center, as -to why .the job should not be sealed off. --On April. 20, 1970

I was advised by Mario & DiBono that he had received said Show Cause order

and asked my advice; . I imaed lately contacted :Pat Falvey,\Assl8tant -General

Counsel of the Port Authority, and discussed .it ;vith him;; A- meeting. regarding this (Show Cause order was held With Pat Falvey_;on April 21,;. 1970, at which'time Hr.- Falvey called Mr. Fabricant, General Counsel rof the New York

City Environmental Protection Administration, and requested that said

Show Cause order be indefinitely postponed. Mr. Fabricant agreed, .providing

he received 6aid request in writing from Mr. .Falvey.^ .^Enclosure 5j is a copy

of *Mr^Falv'ey '6*.rleYter

^

letter states that should -fee resume spraying with asbestos we would give

the City a two day notice, and should we resume spraying with non-asbestos

material we would give them a one day notice of our intentions.

As of April 20, 1970 all spray fireproofing operations at the World Trade Center site were suspended.

On April 20,. 1970 I also went to the office of U. S. Mineral

Products Company in Stanhope, New Jersey where I observed a test demonstration on Cafco type D which had, been sealed with a sealant to prevent its

dusting. Enclosure 6 is a copy of results of tests conducted on mineral

fiber fireproofing in accordance with GSA specifications regarding dusting.

I was advised by the Research Director of U. S. Mineral Products that the

application of a Eealant on top of the Cafco type D would reduce the dusting

to a negligible amount. Jests on Cafco type D for dusting, due to a*r

velocity without a sealant, have been conducted and documented as listed

in Enclosure 6. These tests indicated that the amount of asbestos particles

dusting off due to air velocity are well within the standards set by the

Environmental Health Department o/ the United States and also the British

standard. It is also concluded and concurred in by Dr. Selikoff as indicated

in the aforementioned Enclosure 4, that the use of a sealant is the best

way to control dusting for work already installed that contains asbestos.

While at Stanhope, New Jersey, I also inquired into their research

of an asbestos free material which would perform the 6ame functions as Cafco-D. I was advised that they have such a material which had passed

Figure A-28 (Contd.). Port Authority memorandum summarizing the factors considered

in choosing BLAZE-SHIELD Type DC/F as a replacement for the asbestos-fiber

containing Type D (185-ITK).

NISTNCSTAR 1-6A, WTC Investigation 169
File - 3 - May 15, 1970

preliminary tests and which they were working on final tests for all the

requirements. The tests that are required for approval of this material

are as follows:

1. A fire rating test.

2. An adhesion under fire test.

3. AT factor or thermal conductivity test.

4. A bonding strength test.

5. •Confirmation regarding the components of the material

that.' could possibly be alleged to have healthharards.

Cafco research lab advised me that they had performed allJof the above tests ^in their -'own ^.laboratory , vand that^

known as. Ca'fro <£ypet^

with asbestos"in -all 'aspects;! . 1 advised Cafco representatives H^at'-i xoul'd not accept only the findings of their own laboratory butf.nwst haye^independent

laboratory tests. They said they vbuld arrange for allfsuchltestsTand 'send reports directly tome. Oa April 23, . 1970 Cafco called meVand^. advised me

that the fire : rating tests being conducted by /Underwriter's Labora tory ^ in

Chicago had' passed all 'the requirements. I requested &a't*ttiis be'jput in

writing. • On -April .24; ' 1970 1 received a telephone call^from Kan! engineer

in Underwriters Laboratory, Inc., Mr. .S. Bell, who advised me that the fire

resistance teste on Cafco type D-CF were at least equivalent and/probably

57. _ better

( than Cafco ;.type

%>D. I requested confirmation

In ;writing.'^«.Attached

is' i: Enclosure ^~ffom: 'Underwriters 'Laboratory att^

Enclosure 8 is a letter from U. S. Mineral Products dated April 30,

1970 attaching a copy of a test made by Dynatech of Cambridge, Massachusetts

on the thermal conductivity of type D-CF. The test indicates that type D-CF

is equivalent or better to regular type D.

Cafco also advised that they had performed bonding .tests on type D-CF and these were successful. However, I requested independent

laboratory tests. Enclosure 9 is a report from International Testing

Laboratories, Inc. of Newark, New Jersey which reports the tensile strength

in pounds per square foot of type D-CF to be within a range of 19.9 to 22.40. This tensile strength Indicates that type D-CF is able to support

its own weight approximately 20 times. Regular type D Cafco is advertised

to support Its own -weight 10 to 12 times. Therefore, type D-CF results

indicated it to be better than regular type D for bond strength.

I had previously been advised by Cafco representatives that two

'samples of type D-CF had been sent to Dr. Sellkoff at Mt. Sinai for his

examination. On April 23, 1970 i called Dr. Sellkoff and asked him if ne ever had examined Type D-CF. He advised me that he had not, but he had

examined some similar material and he had found it to contain certain par- ticles of asbestos. He advised that if I were to deliver to him a sample

of this type, which I had taken personally Out of a bag, he would re-examine

same. I had a bag of -type. D-CF delivered to my office and one of my

inspectors removed from the bag a one gallon canister of this material

with rubber ' gloves,' sealed -it and delivered it to Mt. . Sinai Hospital.

:losure 10 Is a memorandum itq 'file from my Inspector, R. Kalenborn,

lfirming said delivery.

Figure A-28 (Contd.). Port Authority memorandum summarizing the factors considered

in choosing BLAZE-SHIELD Type DC/F as a replacement for the asbestos-fiber

containing Type D (185-ITK).

170 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

File . 4 _ May 15, 1970

On the afternoon of April 24, 1970 Dr. Nicholson, assistant to Dr. Selikoff at Mt. Sinai Hospital, called me and advised me that a preliminary analysis of the material indicated that it was free of asbestos

fibers except for possibly a few fibers that could have been picked up in

the production line of the previous Jype D material. Dr. Nicholson gave me a good report on the material and further stated that it appeared to be

much better in all respects to type D. I asked Dr. Nicholson if he would

put this in writing to me. He said he would and he further stated that In his opinion this material did not. present a health hazard due to asbestos,

but of course ve -should maintain tarpaulins during installation and thorough

cleanup as you would do "with any material. He even said that it would not

be necessary to comply -with the -City regulations listed in Enclosure 1 for

this material.;. . Dr. -.Nicholson did ;say. that he would do further analysis/ of

the'material.-tOiCheckifjo^ -1 received.-.ailetter

dated April 29, 1970 from'.Dr. -"Nicholson, Enclosure 11 hereto, regarding

the examination of this.raaterial,- which indicates the material is free from

asbestos and excellent in other .respects. However, Dr. Nicholson stated

that "while no direct 'evidence exists linking mineral wool fibers to disease its extensive -use has ;n'ot been -of sufficient duration to say that

there could not be suclr disease/1 This statement merely allows Mt; Sinai

to keep the. door open on research -of this material.

I have also received other preliminary verbal reports on extensive

previous research performed by independent outside agencies on any deleterious

health ""problems : due~' tb'ihVvmineral "wool fibers -.in Cafco

-, "D-CF.?rS.These^reports,

to date, are very encouraging in that they are all negative. When written

reports are received, copies will be sent to all interested parties.

On April 27, 1970 Mr. Sorrell and Mr. Roby of ALCOA requested my

acquiescence to allow them to resume spraying and/or patching on floors 16

to'" 19 with type D-CF to permit continued erection of aluminum column covers. At this time all the required test reports indicated above had not been

received by me and therefore I merely indicated my acquiescence" to their

request to proceed with the understanding that thi6 change in material for

these floors or for any subsequent change for their material under their

performance type contract would not entail any additional costs to the Port Authority. Mr. Sorrell agreed to no cost for floors 16 to 19 but

said "let's not talk about the rest." I repeated my statement that there

would be no consideration of additional costs under their performance type contract for changing the- materials. Enclosure 12 hereto is a copy \>f my

letter to ALCOA dated Appil 27, 1970, confirming the aforementioned discussions and restating the Port Authority's position on no additional compensation for change in material, should ALCOA desire to do 60. Enclosure 12 was reviewed by Tony Raiola and Bat Falvey of the Port Authority Law

Department ppior to its issuance.

Enclosure 13 attached hereto is a copy of a letter from ALCOA

to Mr, Tozzoli, dated April 23, 1970, requesting consideration of additional

compensation of $173,000 for their corporate decd.si6nntb change the material

to type D-CF. This letter "-was received in Mr. Tozzoli' s office on April 27. This is an attempt by ALCOA, as I discussed with Mr. Tozzoli, to see if

\ one letter they can possibly get consideration of $173,000. I underd that ALCOA has made a corporate decision to change this material on

Figure A—28 (Contd.). Port Authority memorandum summarizing the factors considered

in choosing BLAZE-SHIELD Type DC/F as a replacement for the asbestos-fiber

containing Type D (185-ITK).

NISTNCSTAR 1-6A, WTC Investigation 171
Appendix A

File 5 - May 15, 1970

on their own, regardless of the fact whether they get additional compensation, because they do not want to get involved with the bad public"

relations that would be associated with their continuing the two towers with an asbestos material, even if they were able to continue, by conforming

to the regulations in Enclosure 1. It is interesting to note that since

April 20 all jobs in New York City using asbestos material have been

stopped, and to the best of my knowledge, as of this date have not resumed

spraying. Enclosure 14 i6 a reply by Mr. Tozzoli to ALCOA dated May -8 substantiating the Fort Authority's position as stated in Mr. Monti's

letter to Mr. Sorrell of ALCOA, dated April 27, 1970, in that thejpdtt'

Authority does not accept any responsibility for any additional costs ALCOA may incur due to their -performance type contract. On May 1/ 1970

Mr. Sorrell of ALCOA hand delivered to '-me.; a letter tJated May 1, J.970

requesting :Fort Authority approval to -use ' type D-CF in lieu of "type U 'for the entire project. This is •Enclosure 15 "hereto. Since on May 1/.1970

I did not have in my hands all complete reports listed above annotated

said ALCOA letter and gave verbal approval to proceed with type D^CF- only

for Tower "A" floors 20 through 25 inclusive, pending receipt of final

reports. Mr. Sorrell concurred with this and advised that by the vtime/.-he reached the 25th floor, maybe all reports would be in and we could give "him an unqualified proceed for the entire two towers.

In the interim Tishman, Realty & Construction Co., Inc. • proceeded on a separate s course^-of.investigating '.other^sources of spray material fwhich

would be free from asbestos." "Enclosure T.6 is' a'"copy of a letter from" Tishman to ALCOA dated May 1, 1970, reporting on their investigations with

V. R. Grace Company on a material called Monacote and coming to the conclusions that the K factor of the material that they investigated did not meet

the requirements and therefore concluded that Monacote would not be considered

any further for application.

Contract WTC 113.00

Mario & DiBono Flasterinc Company includes the spraying for Towers "A" & "B" and below grade. This contract was awarded specifying

asbestos spray materials <Cafco type D) for floor trusses, columns and

beams. Certain specific columns In the elevator shafts are required, under

the original contract, to" be coated with Cafco Mark II hard finish coating

due to the high" 'velocity of air caused by the elevators. Thus, if we con- tinued spraying with Cafco type D, the elevator shafts specified to be hard

finished are already sealed and would not require a sealant on top of same. All other areas which were to be sprayed with type D asbestos material would

require a sealant.

During the week of April 13, 1970, I started discussions with the

contractor regarding the possibility of applying a sealant to all areas of

both Tower6 "A" & "B" and below grade which are not required to have Cafco

Mark II hard finish coating.-. The contractor originally indicated that the

going price for sealants .per .square foot would result in a total compensation of approximately ' $605,000 for .sealing the entire project. The contractor

'icated, however, -he was 'willing to ; cooperatei Using an estimated cost

9 en to me by -Dr. Neuman of Tishman Realty-d Construction Co., Inc. of

Figure A-28 (Contd.). Port Authority memorandum summarizing the factors considered

in choosing BLAZE-SHIELD Type DC/F as a replacement for the asbestos-fiber

containing Type D (185-ITK).

172 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

Tile - 6 - May 15, 1970

3^ cents per square foot as an equitable price, I vas able to convince the contractor to agree at a lump sum proposal of $350,000 for sealing all areas of Towers "A" & "B" and below grade. The contractor also agreed that he

would release the Port Authority of hi6 existing claim for excessive rust scaling on steel, which is outside of the scope of hi6 contract, and was estimated by him to run $160,000. My staff indicated to me that based on T&M slips submitted to date that this item of removing excessive rust could run as high as $200,000.

Subsequent to the above discussions, theproblem of continued use of asbestos material arose; therefore, I proceeded to discuss costs of substituting type D-CF fireproofing and only sealing the areas that had

previously been sprayed with the asbestos material, -plus continued release

of :the claims for excessive rusting -of /the -st'eei. ' .The -contractor's proposal

for this work, including xhanging the material 'oh the U. S. Customs Building

and the .Northeast Building, amounted to $442,425. .1 offered the contractor $296,500. After further review with the contractor and a review of the

numbers with Mr. Tozzoli, I made a final offer to the contractor of $320,000.

The contractor accepted same. This cost covers the following items of work

in *Towers : "A" & "B" and below grade, the Norhteast Plaza 'Building and the '." V. S. .Customs Building:

1. From the times that we allow him to proceed to resume spray operations he will use asbestos free Cafco type D-CF in all spray work.

2. He will apply a 6ealant to all areas that have previously been

sprayed with asbestos material, except for those areas which

receive Cafco Mark II hard finish, in both Tower "A" and below

grade, and should any be done in Tower "B", in that area also.

3. He releases the Port Authority by signed release from any further claim regarding Temoval of excessive rusting from the steel. Clause 13.03 subparagraph 2 on page 123 of Contract VTC 113.00 must be amended or deleted so that no further recourse to said statements can be made by the contractor.

R. M. Monti

Construction Manager

The World Trade Center

RMM:rd

Figure A-28 (Contd.). Port Authority memorandum summarizing the factors considered

in choosing BLAZE-SHIELD Type DC/F as a replacement for the asbestos-fiber

containing Type D (185-ITK).

NISTNCSTAR 1-6A, WTC Investigation 173
Appendix A

UNDERWRITERS' LABORATORIES, INC.

on indqxmltut.vul'fvr-jintjH ortjaukulion testingfur public safety

April 24, 1970

1.3749

Port of i:e\v York Authority

111 6th Avenue, I:oom 300

New York, I.'ew York

Attention: fc.r. K. Lcnti , Construction kanager

i'.'orld Ti-ade Center

Subject: 1'ire JieciBtnnce Evaluation of Cefco C> Type "U" vo Cafco Type 'O"

Gentlemen:

Confirming our telephone conversation of April 23, the

Subject investigation io npproximately 80 per cent completed.

All of our test results to date indicate that Cafco CJ Type "D" sprryed fibar is nt lonet eu good bo Cnfco Type •3)" in record

to fire resistance. The CJ-* Type "1)" nay even be slichtly better

from this standpoint.

Although our test results to date are not 100 per cent

conclusive, the indications are thot Cafco CF Type ,rJ

n will be

approved for all of the lloor and Ceiling Designs for which

Cafco Type "D " is currently Listed, particularly those incorporating

a 1 to 1 blend of cellular and fluted steel deck units and

.normal weight concrete.

If you should have any further questions regarding this

investigation, we would be happy to try to answer them for you

ao long as we have the permission of United States L'ineral

Producta Company to release our tooting information.

SWBAlr

cc: Kr. Frank X. Stumpf

USM-007234

Figure A-29. Correspondence indicating BLAZE-SHIELD Type DC/F as a suitable

replacement for Type D (180-ITK).

S. V7. SELL

Assistant Engineer

Fire Protection Department

174 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

SKILLIN6, HELLE, CHRISTIANSEN, ROBERTSON

Consulting Structural and Civil Engineers • 230 Park Avenue, New York, N. Y. J00J7 IWu. 9-8874

JohnB.Skilling • Helge }. Helle \ohn V'. Christiansen • Leslie E. R.bertson

vlmager

Wayne A b'ewer April 1, 1975

File: WTC-Fire

Mr. Malcolm P. Levy

Chief, Planning and Construction

Port Authority of New York § New Jersey

1 World Trade Center - 65rd floor New York, New York 10048

Dear Mai

Attached to this letter is a report dealing with the fire safety of specific

facets of the twin towers of the World Trade Center,

The report deals with the general topic of the fire resistivity of the floor

system. Questions of structural integrity and of heat transmission througl<

the floor are examined. The report is intended to provide background tc the reader as to the development of the fire-resistive standards for V\uiTu Trad'; Center and looks also at the adequacy of the existing systems.

In preparing these documents, SHCR holds itself out as a reporter of facts-

as they are presented in communications gleaned from the files of Port Authority, ERS, MYA and SHCR. It does not purport to have any special exper .ist not commonly held by other structural engineers. No new literature search or research was accomplished for purposes of this report.

Finally, the data contained in the report is based on logic and analysis and,

as such, is not definitive or conclusive. The only way to assure the existence

of the fire safety of floor systems is to.be found through the participation cf

a fire safety engineer and/or fire testing*

Please feel free to call on us should you have any questions.

Very truly yours,

SKILLING, HELLE, CHRISTIANSEN , ROBERTSON

Leslie E. Robertson

Enclosure

LER/amh

: .c. Mr. Julian Roth, ERS (End)

Mr. M. Yamasaki, MYA (End)

ARTHUR i, OARf.SMIRC MANACFH. ALASKA COWAAO R WOLFE -—' BUSINESS MANAGER SEATTLE OFFICE I 2 15 FOURTH AVENUE. SEATTLE WASHINGTON 98161

ALASKA Of FICt 601 WEST FIFTH A VENUE. ANCHORAGE* ALASKA 9 9 5 O 1

RICHARD W CHAUNER PAUL S. A. FOSTEP

PRANK MOlLltflHOff

E R N C S T T LIU KENT R. ROGERS

CHARLES A SANDUSKY WILLIAM D WARD

C . J . WHITE. J n

LOR ENTS. L. WIDINC PETER W. CHEN

ROBERT O FOv/Ltfi. JR V. A. PRISADSKV

MICHAEL B «ICO MAROLO D. RCCT

RODERT P. 9T. GERMAIN HICHARD C. TAYLOR

Figure A-30. Excerpts from April 1, 1975 post-fire report prepared by Skilling, Helle,

Christiansen, Robertson (3-P).

NISTNCSTAR 1-6A, WTC Investigation 175
Appendix A

MANUFACTURERS CATALOGUES

The fireproofing contract was accepted on the basis of the

Mario and DiBono Plastering Co., Inc. proposal dated March

17, 1969. While SHCR is not privy to the contents of that

proposal, it is likely that it contains only finanical and

catalogue information.

The only Cafco catalogue available to SHCR (excluding current

issues of 1975) is the one supplied by Mr. Monti to Mr. Levy

in September 20, 1967 (see -appendix). The catalogue cites

ULI #R3749-6, ULI R3789-2 and ULI #R3749-13 for the spray

fireproofing of beams. From the catalogue one can determine

that:

(1) The product has been subject to extensive ULI testing; and

(2) for "beams, girders and spandrels", a thickness of 1/2 inch of Blazc-Shicld Type D

(the product used in World Trade Center) provides

a 4 hour rating.

The catalogue does not report on fireproofing of trusses.

-11- SHILLING, HELLE, CHRISTIANSEN. ROBERTSON

Figure A-30 (Contd.). Excerpts from April, 1 1975 post-fire report prepared by Skilling,

Helle, Christiansen, Robertson (3-P).

176 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

LACLEDE COMPOSITE FLOOR TRUSSES

FIRE RESISTIVITY - TOP CHORD

Introduction

The Laclede trusses used in the construction of The World Trade Center are a standard product manufactured from specially-rolled angles used in conjunction

with round-bar webs. To achieve composite action the webs extend into the con- crete slab so as to effect the required shear transfer.

In The World Trade Center the top chords are not spray fireproofed for selected

areas of the work. Specifically, for the most of the one-way span areas directly out from the service core, the top chords are not always spray fireproofed.

Also bridging trusses are not spray fireproofed.

This paper addresses itself to reasons of structural engineering as to why

spray fireproofing may not be requiredStructural System - Top Chord

First, a discussion of the role of the steel "top chord in the overall structural

system:

1) Construction Period:

a) Acting in conjunction with the bottom chord and the web, the steel

top chord completes the trusswork providing primary structural

support for the concrete slab until such time as the slab has

achieved design strength.

FiTeproofing of the steel top chord is not required for reasons of

construction loading.

b) Acting as a beam, spanning from truss panel point to truss panel

point, the top chord supports a small amount of concrete until

such time as the concrete has attained design strength.

Fireproofing of the steel top chord is not required for reasons of

construction loading.

2) Supporting Gravity Loads:

a) Once concrete strength has been achieved, the capabilities cited

under 1) are modified. The concrete slab becomes the dominant

element of the top chord. So long as the shear knuckle, is maintained, the structural integrity of the steel top chord is not required.

-13-

SKILLING, HELLE, CHRISTIANSEN', ROBERTSON

Figure A-30 (Contd.). Excerpts from April, 1 1975 post-fire report prepared by Skitling,

Helle, Christiansen, Robertson (3-P).

NISTNCSTAR 1-6A, WTC Investigation 111
Appendix A

Since the top chord may be cut without loss of structural integrity, we

concur that fireproofing of the steel top chord is not required for

this purpose.

b) Where a given shear knuckle is not adequate to transfer panel point

loads directly into the slab, then an increment of the load must be taken down the steel top chord to the next knuckle. This condition exists only in the comer, two-way portion of the floor.

We concur that fireproofing of the steel top chord is required and

is provided for this purpose.

3) Assisting in Diaphragm Strength:

a) The concrete slab, with its mesh and bar reinforcing provides for

diaphragm strength within the building. As structure sway under

wind load increases, the need for diaphragm strength increases.

Structural steel top chords provide a kind of reinforcing steel

and add to diaphragm strength. While diaphragm strength is not required by Code, we know it to be essential to the proper behavior

of the structural system. We do not believe it to be proper to design for the combined circumstance of an extreme wind and an extreme fire with the same factor of safety as that associated with

the single event alone.

Since the structural steel Lup chord provides only a small increment

in the diaphragm strength, we concur that fireproofing may be omitted

for this purpose.

Structural System - Bridging

The bridging system is used only to provide for the reduction in floor "tremor"

and to reduce the effects of differential deflections associated with heavy

gravity loads.

Since it is not required as a part of the structural system, we concur that

fireproofing may be omitted for these members.

Conclusions

Fireproofing of the top chords of floor trusses is required and is provided in

the two-way portions of the floor systems.

A logical analysis indicates that fireproofing of the structural steel top

chord and of the bridging is not required so long as the risk of the joint occurrence of an extreme value wind storm and a fire is accepted. Over much

of the two buildings, fireproofing has been provided.

14-

SHILLING, HEULE, CHRISTIANSEN. ROBERTSON

Figure A-30 (Contd.). Excerpts from April 1, 1975 post-fire report prepared by Skilling,

Helle, Christiansen, Robertson (3-P).

178 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

PERFORMANCE IN SERVICE

The fire of February, while reported in the press to have been

very hot, did not damage a single primary, fireproofed element.

Some top chord members (not needed for structural integrity, some bridging members (used to reduce, floor tremor and the

like) and some deck support angles (used only as construction

devices) were buckled in the fire- -all were unfireproofed

steel

The SHCR report of fire damage, including all repairs, is

attached in the appendix.

As requeste by Port Authority Engineering Department and by

SHCR, shores were placed in the vicinity of repairwork. This was done, not because of concern for damaged structure, but

as a matter of prudence to avoid the accidental destruction

of needed structure by over- zealous steel workers.

It is likely that this fire did not provide the ultimate test of fire-resistivity. More severe fires will likely strike the

project. However, since only non-essential, non- fireproofed

elements of the floor assembly were damaged, some optimism

can be expressed.

SKILLING, HEULE. CHRISTIANSEN. ROBERTSON

Figure A-30 (Contd.). Excerpts from April, 1 1975 post-fire report prepared by Skilling,

Helle, Christiansen, Robertson (3-P).

NISTNCSTAR 1-6A, WTC Investigation 179
Appendix A

March 7, 2003

John L. Gross, Ph.D., P.E. Leader, Structures Group

National Institute of Standards and Technology

100 Bureau Drive, Stop 861

Gaithersburg, MD 20899-861

Re: Confidential and Pre-decisional Communication - Questions on Fire Resistance of

the WTC Floor System

Dear John:

Following are the Port Authority (PA) responses to your questions:

Questions to the Port Authority of New York & New Jersey, February 26, 2003

1 . In a letter from ERS (Julian Roth) to PoNYA (Malcolm Levy) dated December

14, 1965, it had apparently been decided that the fire protection of the WTC

floor system would involve "the use of a maximum thickness of one inch

spray-on fireproofing material around the individual components of the floor trusses." It was further stated that "one inch material meets the 3-hour

requirements of both the new code (New York City Building Code under

revision in 1965 and ultimately published in 1968) and Underwriter's

(Underwriter Laboratories, Inc.) using previously approved assemblies tested

by the 'load criteria' method but ignoring the more stringent time-temperaturerate-of-rise criteria which is an alternate testing procedure not required by the

new code or by Underwriter's, and which we do not consider necessary."

In a follow-up letter from ERS (Julian Roth) to PoNYA (Malcolm Levy) dated

December 22, 1965, the PA is advised that "advance information from

manufacturers indicates that if the truss were required to be fire-tested, then

two inches of material would be required for light angle members."

In a letter from ERS (Harry Harman) to PoNYA (Malcolm Levy) dated July 25,

1966, it is stated "Obviously, with so many penetrations of the floor system [4" concrete slab over a metal deck] the fire rating of the floor construction is of an indeterminate value unless tested."

1) Were tests performed on the fire resistance of the composite floor

system during the design or construction phase of the project?

PA Response: There are no test records in our files.

Figure A-31. Response from Port Authority regarding the applied thermal insulation

(678-P).

180 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

2. In a letter dated October 30, 1969, from PoNYA (Robert Linn) to Mario &

DiBono Plastering Co., Inc, the contractor is directed as follows: "bar joists

requiring spray-on fireproofmg are to have 1/2" covering of 'Cafco'."

2) Was 1A inch of Cafco Type-D fireproofmg specified for the floor

trusses requiring spray-on fireproofmg?

PA Response: Thickness was not specified on the drawings. PA is still trying

to locate the original specifications, which NIST is aware of. The letters you

reference and quote in your questions are snapshots in time. The culmination of

these written exchanges led to what was finally called for in the original

specifications that were part of the contract documents. In the absence of the

original specifications, we must rely on the actual measured thickness of the

fireproofing. Over the years, this has been documented to be a nominal 3A

inches.

It should be kept in mind that the fireproofmg determinations were made in the context of buildings that were to be constructed without a sprinkler system.

Following the enactment of Local Law 5 in New York City, a complete

sprinkler system was added to the towers over a period of years, thus reducing

the overall reliance on the truss joist fireproofmg for fire protection.

3. In a report by SHCR prepared for the PANYNJ dealing with "the fire safety of specific facets of the twin towers of the World Trade Center" following the

1975 fire, it is stated that the 4 inch slab exceeds the commonly used (and

therefore accepted by the NYC Building Dept.) 3-1/4 inch slab on metal deck

without fireproofing.

3) Was the underside of the floor slab (metal deck)

fireproofed?

PA Response: No.

4. In this same report by SHCR prepared for the PANYNJ, it is stated that,

fireproofing of the top chord of the floor trusses is not necessary (except for the two-way portion of the floor). Additionally, it is stated that fireproofing of the bridging system is not required.

4a) In the one-way portions of the floor system, were the top chords of

the composite floor trusses fireproofed?

PA Response: Yes.

4b) In the one-way portions of the floor system, were the bridging

trusses fireproofed?

Figure A-31 (Contd.). Response from Port Authority regarding the applied thermal

insulation.

NISTNCSTAR 1-6A, WTC Investigation 181
Appendix A

PA Response: Yes.

5. It is our understanding that initially the spray-on fireproofing contained

asbestos. We also understand that, at some point, asbestos was not permitted and a Cafco product that contained mineral wool instead of

asbestos was substituted.

5a) Is the situation stated here correct?

PA Response: Yes.

If so,

5b) What floors of which towers were fireproofed with the asbestoscontaining product?

PA Response: For the tower floor system, only steel trusses in Zone l(44

,h

floor and below) in Tower 1 were fireproofed with asbestos containing

product.

5c) Was the asbestos-containing "fireproofing" removed?

PA Response: Yes.

I hope these responses are helpful. If you have any further questions please send them to

us.

Sincerely,

o/s/b

Joseph M. Englot, P.E.

Asst. Chief Engineer/Design

CC: F. Lombardi

Figure A-31 (Contd.). Response from Port Authority regarding the applied thermal

insulation.

182

NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

• O: B . Weinstien. Project Manager (TRCC)

DATE: March 25, 1970

FROM: n. L. Brown

SUBJECT: THE VORLD TRADE CENTER CONTRACT 113.00 - MARIO DIBONO PLASTERING CO. SFRAY ON F1REPR00FINC - TOWER A & B - ^SPECTION

REFERENCE:

COPIES: p. Balduizi, R. Linn, M. Levy, R. Monti, T. Celabrese, F. Wernekc

During a routine inspection trip on March 19, 1970, I hod

occasion to dlecuss with Frank Tartemelle, superintendent, the stetus of

vork under the subject contract. In the course of this conversation 1 reminded Frank Tartaraella that Morio DiBono still had to complete the core columns spray-on fireproofing of Tover A core columns up to the 28th

floor as these columns are unsatisfactory having only V to 3/4" of fireproofing not the 1 3/16 inches required, lie stated that I should direct

this matter to his office as he did not plan to do any further v;ork on

these members. Please again remind the contractor that this work is not ecceptable to this office, also that they are to fireproof the under side

of the electrical header ducts.

D. L. Brown

Supervising Engineer

The World Trade Center

Figure A-32. Correspondence indicating that thickness of thermal insulation was being

checked during construction (256-P).

NISTNCSTAR 1-6A, WTC Investigation

183
Appendix A

M20 (212) 9C4 - D6«o

QTii&man deafly <^(5o/?Jtiudw}^a,Qfic. ^

AS AGENTS

SO CHURCH

FOR

WORLD

THE

STREET,

PORT

TRADE

NEW

Of

CENTER

NEW

YORK,

YORK

N . Y.

AUTHOR!

10007

-mm

Marchch 30, ju, 1970 • - x

Mario & DiBono Plastering

I36 Liberty Street

New York, New York 10006"

Attention: Mr. F. Tartamello Re: V/TCj/l^.OO J/ INSUFFICIENT THICKNESS

Gentlemen;

Reference is made to our letter dated January 9> '970

WITH rOLLOW-UP COPIES SENT DATED JANUARY I9TH AND FEBRUARY 6th,

in addition to phone calls on the subject, advising you op the

insufficient thickness of spray-on fireproof ing on core columns.

we are now in receipt of a communication from the port of New York Authority reiterating the same item.

Be advised that to continue to ignore these communications

will require us to advise the port of new york authority to seek

compensation amounts from your contract price, commensurate w 'th the work which is incomplete plus any costs involved in removing

and replacing work by others which may, due to this long delay, cover your work.

Very truly yours,

TISHMAN REALTY & CONSTRUCTION CO., INC.

Bert V/e instein

Project Manager

BW/bms

CC: Messrs. Monti, Werneke, P/A

Figure A-32 (Contd.). Correspondence indicating that thickness of thermal insulation

was being checked during construction (256-P).

184 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

ORIGINAL „ . Port Authority of N.Y and N.J. ^' '—

Litigation Sampling Program

JOB NUMBER \\5' 2*4 fi Sample Area Data Sheet

Facility: O*06" WorU Tft^bE CE<rt-f<- Building: "Bo.\A>r->^ One. Building No: 1 Floor: 2.°\* FLoor- Sample Size VvoJ t\0l.

Description of Sampling Area: 2*3 * h

P"loo<-

Sample Numbers: ado . + .ena.\ on VV»e

LL- 3*1 -wrc- A.B.c LL- 315- VJTC - A,6.c LL- cjtc - LLLL-310-urrt - V. A B.C. LL- 3*U>-• WTC- M.c LL- MP2 - urrc -\],(\fi,c LLLL- ~&\ i - u3tc - A . 6 . C LL- 311 - WTC- A,6,C LL- 4oi- U)TC- A.6.C LL- tx-sai- one- A ,6 c LL- 3=V?- \J-rC - A,e,c LL- - LOTC- LLLL-3^3-vJTC-V.A,6 C LL- 3<W-• VTC- V.A.B.C LL- LL-

^LL-31M - WTC- A.fc.C LL- <-JOC - \^nc - A,6,C LL- LLion of

Sprayed-On Support Beams/Columns

Troweled-On/Cementitious c-^ Concrete Slab/Metal Decking

Plaster Cable

Acoustical Plaster Duct/Breeching

Air Cell Floors

Molded Sections/Pads Heating/Cooling Eguiptment

VAT Ceilings

Ceiling Tile Piping/Fittings

Other: Other: rro^)«.l«i on oj^U s^per-l- &*><

Comments :( Indicate any unique characteristics of the material which may help

identify the manufacturer.)

Sample taken by:

^^

rw,brc „,lle , F?^W T^rooU Date: 03 ) \J~ bg_;

Persons Present Vro-oi i_ txt y, We. F<r«T\V "P-gn^elo- Chaz-lrS b-^Ao^kxis

Photographs Taken By: Fr»n^s tv~^U-<w.M<- T^-moV VefjoW .

Figure A-33. Example of "Sample Area Data Sheet" used to record condition of sprayed

thermal insulation (212 ITK).

NISTNCSTAR 1-6A, WTC Investigation 185
Appendix A

ORIGINAL

Job Number 115 • Z45

COMMENTS

Vo Xa ,a 0 -H\cf

(^vjo-^fonA ' F^fP^ Spr«..y en . £a£f proof, r>^ Th< "£>ea.vnS.

£o<x4-cj! ui.VV 7-\ of narWf-o. I . ^a^pl* . a-f C e- «. S c«o.4<r<? w •

On* 5<1-»TLf'* fVojvv o- V<r4ic^l S upper" 4r 'B^o.

fro

Figure A-33 (Contd.). Example of "Sample Area Data Sheet" used to record condition of

sprayed thermal insulation (212 ITK).

186 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

THE PORT AUTHORITY OF NEW YORK & NEW JERSEY

MEMORANDUM

TO: Peter Sweeney, Engineering Program Manager

FROM: Joseph M. Englot

DATE: August 18, 1995

SUBJECT: STEEL JOIST SPRAY-ON REQUIREMENTS FOR NEW CONSTRUCTION

IN WORLD TRADE CENTER TOWERS

COPY TO: R. Davidson, J. Lin, F. Lombardi, E. Ramabhushanam, O. Suros

Attached is a white paper summarizing a study to detennine the spray-on thickness

required to achieve the required two hour rating for steel joist trusses in the towers of the World

Trade Center. This is intended for any new construction for which the Engineering Department is engineer-of-record. It concludes that 1-1/2 inches ofspray-on mineral fiber is sufficient when applied

directly to chords and web members.

/

J6seph M. Englot, P.E. 1/ Chief Structural Engineer

JME:ng

Attachment

Figure A-34. Results of 1995 study of thermal insulation for floor trusses during new

construction when tenants vacated spaces (3-P).

NIST NCSTAR 1-6A, WTC Investigation 187
Appendix A

FIREPROOFING REQUIREMENTS FOR WORLD TRADE CENTER TENANT

FLOOR JOIST CONSTRUCTION THAT REQUIRES INSTALLATION DUE TO

ASBESTOS REMOVAL OR LOCAL REMOVAL TO FACILITATE CONSTRUCTION

This serves as a basis for determining the minimum requirements for installing sprayed

mineral fiber fireproofing on the steel floor joist trusses supporting typical tenant floor areas within

the towers ofthe World Trade Center. Its purpose is to establish requirements for new construction

that meet local codes and ordinances.

The technical basis for the fireproofing requirement is Design No. G805 in the Fire Resistance Directory (BXRH) Published by Underwriters Laboratories. This UL design is based

upon fire tests conducted as per ASTM E-l 19 which is a basic Reference Standard (No. RS5-2) in the New York City Building Code for structural members and assemblies. Reference standard RS5-

1F, "Methods of Analytical Determination of Fire Resistance of Load Bearing Steel Truss

Assemblies", is not applied since it is intended for large trusses (Le. s deep trusses), too large to fit in the fire test compartments Since there is a wealth of fire tests on steel joists which approximate the ones used in the World Trade Center, joist test results are interpreted to arrive at an appropriate

spray-on protection thickness.

There are various parameters in the G805 design which have to be interpreted or approximated in the case of World Trade Center construction Each parameter will be discussed

individually.

Joist Spacing

G805: 48 inch and 66 inch spacing.

Actual: Double joist system - average joist spacing is 40 inches (spacing alternates between 8 inches

and 72 inches). Conservatively, use values for 66 inches since actual spacing is not uniform.

Metal Deck Protection

G805: Values tabulated with or without spray-on applied to bottom of metal deck.

Actual: Use values without spray-on applied to deck. Spray-on is only used in the World Trade

Center below trench headers. Follow design values without protected deck. Concrete Topping

G805: Values tabulated for lightweight concrete, 1 17 pcf unit weight, 3500 psi compressive strength

and a thickness oftopping over the metal deck of 3-7/8 inches to achieve a 2 hour rating.

Actual Lightweight concrete, 1 10 pcfunit weight, 3000 psi compressive strength and a thickness of

topping over the metal deck of 4 inches. The actual is judged equivalent to the G805 design for 2

hour rating

Wire Mesh Location j G80S: Provides a thickness of concrete from the top plane of the metal deck to the wire fabric of 1-j

1/4 inches for a 2 hour rating with 1-5/16 inch deep steel form unit. Actual. Has two layers of wire mesh. Thickness from top plane of 1-1/2 inch metal deck to center of wire mesh layers is 1.22 inches. Where rcbar is used instead of wire mesh, 1-1/4 inch thickness

Figure A-34 (Contd.). Results of 1995 study of thermal insulation for floor trusses during

new construction when tenants vacated spaces (3-P).

188 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

is provided. This is judged to be equivalent to the G805 design for 2 hour rating.

Steel Joist Parameters G805: Composite steel joist with a minimum area of steel (double angles) for top and bottom chords

(each) of0.708 sq. inches and minimum steel area ofweb members of 0.442 sq. inches in conjunction

with the "thinner" layer of spray-on (1-1/2 inches) applied directly to the joist without lath. Actual: Minimum area ofchords is 0.813 sq. inches and the minimum area ofweb steel is 0.665 sq. inches with composite behavior. 1-1/2 inches applied directly to the joist steel yields a two hour

assembly rating whether restrained or unrestrained. Ceiling

G805: A ceiling is not relied upon for fire protection in the design.

Actual: AD occupied areas in the World Trade Center have ceilings and they will add to the fire rating

ofthe floor system, however, a stringent study ofwhat rating values could be achieved for existing

types of ceilings is beyond the scope of this study.

Conclusion

It is concluded that a two hour fire rating for the steel floor joist trusses can be achieved by applying

a 1-1/2 inch thickness of spray-on mineral fiber fire protection material directly to the steel truss chords and webs. The value of the ceiling as a fire protection element is not relied upon to achieve

this fire rating. Attachments:

1. Excerpted pages from N.Y.C. Building Code.

2. G805 Design from TJ.L. Directory

Figure A-34 (Contd.). Results of 1995 study of thermal insulation for floor trusses during

new construction when tenants vacated spaces (3-P).

NIST NCSTAR 1-6A, WTC Investigation

189
Appendix A

288 FIRE RESISTANCE RATINGS - ANSl/UL 263 (BXUV)

Design No. G805

Restrained Assembly Ratings — 1, 1-1/2, 2 or 3 Hr

(See Items 1, 4 and 5) Unrestrained Assembly Ratings — 1, 1-1/2 or 2 Hr

(See Items 1, 4 and 5) Unrestrained Beam Ratings — 1, 1-1/2 or 2 Hr (See Item 5) ffZf

SeCTION A-A

1. Normal-Weight Or Lightweight Aggregate Concrete — Normal

weight concrete carbonate or siliceous aggregate, 150 pcf unit weight, 3500 psi Compressive strength, vibrated. Lightweight concrete, expanded shale, clay or slate aggregate by rotary-kiln method, 117 pcf

unit weight 3500 psi compressive strength, vibrated, 2 oz air enrrain- ment per bag of cement. The thickness of concrete topping over the top

plane of the steel deck varies according to the spacing of the structural

steel members, the hourly ratings and whether or not the steel deck is protected. When no Spray-Applied Fire Resistive Materials protection is used on the steel deck, the thickness of concrete topping over the top plane of the steel deck shall be as specified in the following table:

Restrained or Normal Weight Lightweight MinThk of Unrestrained Concrete Concrete Concrete Assembly Toppi ng Thk In Topping Thk In From Top

Rating Hi Joist Joist Joist Joist Plane of Spacing Spacing Spacing Spacing Steel Deck

48 In. 66 In. 48 In. 66 In. to Bottom of OC Max OC Max OCMax OCMax Reinforcement In. lh 3-1/8 3-7/8 2-3/8 3-7/8 1 l-!/2h 3-7/8 3-7/8 2-7/8 3-7/8 1-1/8 2h 4-5/8 4-5/8 3-3/8 3-7/8 1-1/4

When the steel deck is protected with the Spray-Applied Fire Resistive

Materials, the min thickness of normal weight or lightweight concrete topping above the top plane of the steel deck, and the min thickness of concrete from

the top plane of steel deck to the wire fabric, shall be as follows:

Restrained or Min Concrete Topping Mm Thk of Unrestrained Thk In Concrete From Top Assembly Joist Spacing Joist Spacing Plane of Steel Rating Hr 48 In. OC 66 In. OC Deck to Bottom Max Max of Reinforcement In. 2 h or less 2-3/8 2-3/8 1-1/8 3h 2-3/8 3-7/8 1-1/4

2 Welded Wire Fabric/Reinforcing Bars — As required, to develop the

structural capacity of the floor in accordance with the applicable ACI

specifications. 3 Structural Steel Members* — Composite joists with vertical leg of top chord angles embedded in concrete slab. Mm area of steel angles for the top and bottom chord members shall be 0.708 sq in. each, and the min area of web members shall be 0.442 sq in. when the sprayed material is applied directly to the joists. Mm area of steel angles for the top and bottom chord members may be reduced to 0.560 sq in. each, and

the min area of web members to 0.299 sq in. when the joists are protected with greater thickness of Spray-Applied Fire Resistive Materials with or without the metal lath or the nonmetallic fabric, as covered m

the Table under Item 5. Max joist spacing is 48 or 66 in. O. C. depending on the thickness and type of concrete topping, the hourly ratings, and the thickness of Spray-Applied Fire Resistive Materials applied to the steel deck (see Items 1 and 5). VESCOM STRUCTURAL SYSTEMS INC -Type V. 3A. Steel Joists — (Not Shown) — As alternate to Item 3, Min size 16K6

or heavier K-Series joist with min 3/4 in. diam or larger cross sectional area web members.

3B. Horizontal Bridging — (Not Shown) — Mm 1-1/4 by 1-1/4 by 1/8 in. thick steel angles for use with steel joists (Item 3A). Size and spacing per Steel Joist Institute specifications. Welded to top and bottom chords

of each joist. Min thickness of Spray-Applied Fire Resistive Materials on bridging angles is 1-1/2 in.

4. Steel Floor and Form Units —- For max 2 h ratings, nom 1-5/16 in. deep uncoated or galv corrugated steel form units. For 3 h ratings, composite or noncomposite, min 1-1/2 in deep, 22 gauge uncoated or galv fluted steel floor units. The steel floor and form units are not considered in calculating the load carrying capacity of the floor

5. Spray-Applied Fire Resistive Materials* — All surfaces to which

material is applied must be free of dirt, loose scale and oil before

spraying. Applied by mixing with water and spraying in more than one coat to the required thickness on the joists and the steel form units as tabulated below:

Thk of Spray Applied

Fire Resistive Mtt

In. on Steel Deck Min Area Min Area Normal Lightweight on Hi Rating

of Joist of Joist Wright Concrete loisl Restrained Unrestrained Chord Web Concrete Topping Assembly Assembly Sq In. Sq In. Topping Rating Hr Rating Hr

0.708 0 4-12 3/8 1-1/2 1 1 0.708 0.442 3/4' 3/8 1-1/2 2

2" 0.708 0.442 1-1/4 1 1-1/2 3 2 0.560 0299 3/8 2-1/2" 1 1 0.560 0.299 3/4 3/8 2-1/2" 2

Min avg and min ind density of 13/11 pcf, respectively for Types II or DC/F. Min avg and min ind densities of 22 and 19 pcf, respectively, for Type HP. For method of density determination, see Design Information Section, Sprayed

Materials. 'The 3/4 in. thickness may be reduced to 1/2 in. when (a) the joist spacing does not exceed 48 in. O. C. or (b) the Unrestrained Assembly and Beam

ratings are reduced from 2 to 1-1/2 h. "The 2-1 12 in. thickness of Spray-Applied Fire Resistive Materials shown may

be reduced to 2 in. when the metal lath or the nonmetallic fabric mesh is used. ISOLATEK INTERNATIONAL —Type D-C/F, HP or Type II, Type EBS or Type X adhesive/ sealer optional.

6. Metal Lath — (Optional, not shown) — Metal lath may be used to

facilitate the spray application of Spray-Applied Fire Resistive Materials

to steel bar joists. The diamond mesh, 3/8 in. expanded steel lath, 1.7

to 3.4 lbs per sq yd should be secured to one side of each steel joist with 18 SWG galv steel wire at joist web and bottom chord members,

spaced 15 in. O. C. max. When used, the metal lath is to be fully cov- ered with Spray-Applied Fire Resistive Materials with no min thickness requirements.

7 Non-Metallic Fabric Mesh — (Optional, not shown) — As an alternate

to metal lath, glass fiber fabric mesh — weighing approximately 2.5 oz

per sq yd, polypropylene fabric mesh — weighing approximately 1.25 oz per sq yd, or equivalent, may be used to facilitate the spray application The mesh should be secured to each joist web member and /or the chords to hold the mesh and the Spray-Applied Fire Resistive Materials

material in place during application. One method for attaching the mesh is by embedding it in 1/4 in. long beads of hot melted glue spaced a max of 12 in. O. C along the top chord of the bar joist. Another method is by using 1-1/4 in. long by 1/2 in. wide hairpin

clips formed from 18 SWG or heavier steel wire. "Bearing the UL Classification Mark

Figure A-35. Underwriters Laboratories Design No. G805 used as the basis for Port

Authority determination of retrofit thermal insulation thickness for floor trusses (213-1).

190 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

THE PORT AUTHORITY OF NEW YORK AND NEW JERSEY

CHIEF CHGIJir. .-<?"-. ;.fr,CL Ki>

P i. or n :'. : •! > REC'-P BUCKSLIP W9 m 25 PM 3:

TO:

FROM:

DATE:

SUBJECT:

COPY TO:

John Castaldo, Kent Piatt r^hn/Zio

Alan L. Reiss ^ March 24, 1999 tyKrT

World Trade Center Fireprooflng Guidelines For Tenant Spaces (/

E. McGinley, T. Kobel, E. Lorabardi J. Richardson, J. Napolitano, R. Rafferty, L. Menno, E. Moscovitz, C. Nanninga, N. Seliga, T. Stam

In order to establish clear and consistent guidelines regarding fireproofing repairs, replacement, and upgrades at the World Trade Center Towers, the following guidelines have been established with the concurrence of the Chief Engineer.

1) Full floors being demolished for new construction or renovation shall have

the fireproofing on trusses checked and upgraded if it has not already been done to the attached 1 995 Engineering Department Engineered Solutions

Standard. Adequate time must be allowed in any schedule to accommodate

this work, typically two weeks. This work may be performed by either the tenant or us but is a landlord obligation and reimbursable to the tenant

(typically $5/sq. ft.) if the work is performed by the tenant. Rcfireproofing

requires removal of existing material to insure adequate bonding and is subject to a controlled inspection.

2) Tenant spaces that are less than a full floor, undergoing either new

construction or renovation, need only meet the original construction standard. Fireproofing shall be inspected and patched as required to the greater of V*" or to match existing (it may already have been upgraded to the Engineered

Solutions Standard.)

3) On a new lease, trusses requiring patching at the time of lender of the space

are a landlord obligation, however, we normally will reimburse fair and

reasonable costs if performed by the tenant after authorization. For existing

tenant space being renovated, careful judgement should be used to determine

if the need for the work arose as a result of a tenant action, i.e. previous

construction work, or our obligation^ecause of our work over the years in the ceiling. Any recommendation should be discussed with project and

property management prior to being discussed with the tenant.

AT

,3

FILE POST

BF CJL RP

MAR 26 1999 3£

:]0HN LIN MANAGER

Q A D.

MA

RS

IR

Alan L Reiss

Director World Trade Department

Figure A-36. Port Authority 1999 guidelines for thermal insulation on floor trusses (3-P).

NISTNCSTAR 1-6A, WTC Investigation 191
Appendix A

FEDRA

Partial 1loor being vacated.

Required thickness

to match existing

Bum Happold

Whole floor being vacated.

Required thickness

is t '/i Inches

Patch

fireproofing to

1Va Inches

Figure 1: Fireproofing assessment process

Damage of existing fireproofing

Significant amounts of damage to the existing fireproofing occur during demolition after tenants move out. The

product used in the past can be easily dislodged as ductwork, partitions, hangers, etc. are removed. Additional damage that happened during tenant fit-out or later modifications that may not have been repaired at the time. As we understand it, in the majority of cases, the existing fireproofing requires so much patching that it is more

cost-effective to replace it.

Repairs

If the damaged fireproofing is to be patched rather than replaced, the cementrtious Monokote product is generally used regardless of what the in situ fireproofing material Is. This can result in joists that are fireproofed

by a combination of materials. This patching is generally done by hand rather than spray application. Repairs

are made such that a constant thickness of fireproofing is provided to all joist members.

Removal

The Cafco Blaze-Shield fireproofing is readily, removed using a high-powered water jet. The water from the jet is soaked up by the fireproofing which falls to the floor in a damp state. Usually all the water is absorbed by the

fire proofing, however, on occasion water does leak onto the floor below. The floor Is covered with protective sheets. The fireproofing is collected from these sheets and transported in waste buckets to a waste disposal

area. Any portions of fireproofing that are not removed by the jet are scraped away by hand. This often happens if there are sections of Monokote fireproofing and in the troughs that are formed at the bottom flange of the joist by the back-to-back angles. If the Monokote cannot be removed by hand, it is assumed to be fixed in place and

Is covered by the new fireproofing applications.

Application

When the fireproofing needs replacing, new fireproofing is applied to a thickness of Vh inches. While equivalent

products are permitted, Cafco Blaze-Shield mineral fiber spray is generally used as the replacement

fireproofing.

It is estimated that 60-70% of the material is lost to overspray.

It can take 2-3 passes to apply Vh inches. If it Is done in fewer passes, the fireproofing tends to fail the adhesion tests that are conducted after application. Sometimes ten feet fall of\ at once when tested. «

World Trade Center " Rev A.

Fire Engineering of Steelwork Phase 7 Report February 2000

g.ASST 77 wtc fire studyVeportsV000210 phaseTa.doc Page A

Figure A-37. Excerpt from draft report on the assessment of thermal protection of steel

in WTC (73-LERA).

192 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

SECTION 072SO - RREPROOBNQ

Wwt Mud«/ butii notmcMnrily untied to,** foHowing:

Pitching fireproofing damaged by iransattjon oTmw coratnjction.

Patching or replacing of existing or new ^reproofing where required to matt code.

Single Source RasporaibiUty: Obtain fireproofing materials from a angle manurecturer for each

different product

Rre Resistance Ratings: At trtdlcsaad by reference to design designation in UL Tin Resistance Director/ for fire-rated auemblie* in which fireproofing serves as dtet-appfled protection, tested per ASTM E 119.

Minimum firs resistance rating shall be 2 hours on decking floor assemblies, 3 hours on bearing columns, unlets indicated on the drawings otherwise.

Provide appropriate MEA6SA numbers for approved use in New York City.

Itaderwritsrf Laboratories, inc. - Fire Resistance Index. JOB CONOmONS

Provide venrMon In area to receive sprayed fiiaprocfog.lrrlrodijcing fresh air and exhausting

air continuously during and 24 hours attar apokaoon to maintain non-toxic, unpolluted, safe working area.

Provide temporary enclosures to prevent spray from contaminating air. WARRANTY

On completion, fumfch a certHcsJt confirming that work complies with these Specification*. rWROORNG MATERIALS

CeiMntitiout self-adhesive compound containing no asbestos, no free cryitaRn* silica and no

mica, for spray application, minimum density 0-T5 pounds per cubic foot: 'Monokota 6" by WA Grace, cormxrnsng to the foflowtig:

Dry density as required for prescribed rating and thickness: ASTM E606.

Minimum acceptable bond strength 100 psh ASTM E736. No cracking or deterdnation under deflection of 1120 of span or under impact of BCfc-'ASTM E759,E760.

10% maximum acceptable deformation: ASTM E761

Maximum acceptable weight loss .02 grnesq.ft.: ASTM ESS).

Bonding adhesive and easier for fireproofing: Cafco Bond SeaLdButed 3 parts to 1 part clean potable water.

MIXES: in accordance with rram/recturar's instructions,

APPLICATION

Apply bonding adhesive or primer to substrate as recommended by manufacturer.

Apply fi reproofing ovsr substrate, building up to required thickness with as many passes or

stags* necessary to cover substrate with monolithic blanket of uniform density and texture. Tamp fireproofing after application to provide a dense, medium smooth surface.

Apply sealer or curing compound to surface of fireproofing If recommended by manufacturer, in a space serving as a plenum.

Provide protection to spec* and occupants when working adjacent to or over tenant areas. Work shalbe dons off hours i defected by me Landlord

AssrUaj*

Patch damage to thJt work caused by other trades before firepreofing is covered up.

Uncover work covered before final approval for inspection before acceptance is granted.

Patch existing sprayed fireproofing which has been removed for attachment of new

construction, and restore to required fire resistant rating.

Figure A-38. Excerpt from 1998 specification related to SFRM for upgrade of public

corridors and bathrooms on 15,h

, 18th

, and 22nd floors of WTC 2 (3-P).

NISTNCSTAR 1-6A, WTC Investigation 193
Appendix A

SECTION 07250 - FlREPROOFING

SUMMARY

1. Patch fireproofing disturbed by remodeling operations.

PRODUCTS

1. Fire Performance: ASTM E 119, and local regulations. Cementitious Type for Conceded Use: 15 pounds per cubic foot dry density,

2. ASTM E 605.

3. Mineral Fiber Type for Concealed Use: 15 pounds per cubic foot dry density. ASTM E 605.

4. Exposed Sprayed—On Fireproofing: Match existing.

INSTALLATION

1 . Inspect existing and new structural members for proper fireproofing prior to close—in of

ceilings and walls.

2. Provide material thicknesses necessary to provide fire—resistance ratings indicated or required

by authorities having jurisdiction.

SECTION 07270 - FlRESTOPPING SUMMARY

1. Provide Firestopping at the Following Locotions: Penetrations through fire-resiistonce-rated

floor and roof construction; Penetrations through fire-resistonce-roted walls and partitions;

Penetrations through smoke barriers and construction enclosing comportmentolizfcd areas; Sealant

joints in fire—resistance—rated construction. PRODUCTS

1. Fire Performance: ASTM E 119, ASTM E 814. ond local regulations.

2. Through-Penetration Firestop Systems: Ceramic—Fiber and Mastic Coating; Endothermic, Latex Compounds; Intumescent Latex Sealant; Intumescent Putty.

3. Fire—Resistive Elostomeric Joint Seolonts: Single—component, neutral-curing, silicone seolont; Multicomponent, nonsog, urethane sealant; Single—component, nonsag, urethone sealant.

INSTALLATION

1 . Inspect existing ond new work for proper firestopping prior to close—in of ceilings ond wolls. 2. Provide materiol thicknesses necessary to provide fire—resistance ratings indicated or required

by authorities having jurisdiction.

Figure A-39. Excerpt from 2001 specification related to SFRM for upgrade on 48 floor

of WTC 2 (3-P).

194 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

Executive Summary

The development of fire safety engineering and in particular the performance of structure during fire has been developing rapidly over the last 5 years. Buro Happold has identified the value and

benefits of this work to many of our global clients. This has required major investment in research, and development, involvement with the development of new codes, working with government and

the employment of staff as part of a technology transfer from the universities carrying out this research. The ultimate aim is to ensure that the research and development is used in practical way

for real buildings in a short but realistic time scale. The extent to which fire safety engineering can be used in this respect has to be based on the local code development, the attitude of the client and

the authorities having jurisdiction The USA has been party to this development and now has its own performance based design codes. Historically fire safety engineering in the USA has only been done on special or difficult projects. However as the benefits are understood and are more widely accepted the quantity of performance based design is likely to increase significantly. This work on the World Trade Centre is significant and well contained example of what is possible now as a relatively low risk early development.

The components of this global development that have been most important from the point of view of the World Trade Centre are.

1 . Better understanding and the analysis of natural fires. 2. Analysis of structures at high temperatures during fire. 3. Improving relationship and understanding between the supplier and the designer

4. More data relating to the performance of materials.

5. The development of the fire safety engineering discipline and the risk assessment

process. On the basis of the current calculations and the risk assessment whilst taking a reasonably

conservative view the following conclusions can be drawn for the open web joists on the tenant

floors of World Trade Center Towers 1 and 2.

• The structural design has sufficient inherent fire performance to ensure that the fire condition is never the critical condition with respect to loading allowances.

• A single coat application is possible.

• Significant savings are possible.

• The target reduction of fiber content and increased long term durability can be achieved.

• Alternative materials should be considered.

World Trade Center Rev A

Fire Engineering ol Slee/worit - Final Report July 2000

\\barry\proiect\9917? wtc fim studyVeportsW00727 linal.doc Pagew

Figure A-40. Excerpts from 2000 report on thermal protection of floor trusses (3-P).

NIST NCSTAR 1-6A, WTC Investigation

195
Appendix A

7 Recommendations

The calculations, the reliability of information, the concsrvative assumptions, and the risk assessment have been carefully judged to determine a reasonable compromise between the

following: -

• Compliance with the defined performance criteria and a reasonable level of safety.

• Value engineering to reduce costs or improve performance. Performance can be based on long term durability and robustness, reduction in fibre content, insulation of steelwork during liie arid ease ol appiio-lio.i.

• The need for margins of safety to ensure lhat the decision making and the approvals process are more straightforward. This in combination with the sensitivity tests covers

the fact that the calculations and predictions for the phenomena of fire can never be

exact.

If the most optimistic assumptions are made the thickness of the fire protection can be as low as 30% of the current thickness. However taking into account the variables, the following recommendations can be made.

7.1 Thickness

For the existing material, there is some uncertainty about the performance of this material due to lack of available data. If the material performs to the insulation standard defined at ambient temperature in the manufacturers data a thickness of 0.5 inches can be used whilst still maintaining

a reasonable margin of safety. If however the material does degrade to some extent as suggested

by the UL listings then a greater thickness of up to 1.3 inches is recommended. Further tests or lest data would be required to achieve the lower thicknesses. The issues of reduced filjre coiiieiM and

long term durability have not been addressed with this selection. II is likely that only a single coat will be required for the 0.5 inch case.

7.2 Choice of System

The true cost of a system can only be accurately determined following a market test. The long term costs are a complex and are a function of the following:

Material cost Required thickness Maximum thickness per application

Time before the next layer can be applied

Volume of dry material required

Volume of water required in spraying procedure

Overspray and other wastage

Durability

Etc.

An assessment of a variety of materials has been carried out in this report and judging from the

results alternative materials should be considered for use in the World Trade Center. For example,

the Carboline Pyrocrete 239 could be applied to a thickness of 0.75 inches, subject to receipt of confirmatory test data. This product is significantly more durable than the current product and

therefore could reduce the overall life-cycle costs of the fireproofing system.

World Trade Center Rev A

Fire Engineering of Steelwork - Final Report ° July 2000

\\barry\project\991 77 wtc fire study\reports\K)00727 final doc Page 26

Figure A-40 (Contd.). Excerpts from 2000 report on thermal protection of floor trusses

(3-P).

[96 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

MJH

Executive Summary Wcekl Trade Center New York, New York

Structural The building structures to be in adequate overall condition. Major structural repairs following the 1993 bomb

blast were successfully completed and signed-off by a Permit

to Occupy or Use issued by the Port Authority Office of the Chief Engineer on October 10, 1997. The repairs appear to have been properly engineered and executed. Following the bombing incident, stringent security measures were

implemented at the vehicular entrances to the Plaza and

subgrade facilities.

In the buildings we observed only minor cracking in some

slabs, partitions or in stairwells of the buildings. Some

minor slab cracks have been noted which should be

monitored by the PA's structural consultant The slabs at the truck dock and delivery area on level B-l have deteriorated due to ice-melting salts that enter the building on vehicles during the winter. A slab replacement program is ongoing

and should be continued until all of the damaged slabs are

replaced. The monitoring of the visco-elastic movement

dampers in the two Towers is an essential program mat has

been strongly recommended for continuation by the PA's

outside structural consultant Building movement is monitored by analysis of measurements taken and recorded by devices located in the 108th floor of 1 WTC. Analysis of

these records is done by the Port Authority's independent

engineer (LERA) and should continue in the future. In

addition, physical sampling and analysis of the condition of

the visco-elastic dampers is reportedly continuing on a 5-year

cycle, with the next sampling to be done in 2001. The slurry

wall that surrounds and contains the subgrade levels of the complex has some seepage that is contained by curbing and

leaders, and is discharged by sump pumps in the lowest

levels.

The slurry wall and the adjacent floor slabs mat brace the wall are inspected on an ongoing basis to ensure that unsafe

conditions do not develop. Structural Integrity Inspection

(SH) Report 1-38, dated April 3, 1998, provided in the Data Room, found the conditions to be acceptable. These periodic

inspections should continue.

The rating of the structural fireproofing in the Towers and

subgrade has been judged to be an adequate 1-hour rating

considering the fact that an Tower floors are now

sprinldered. An ongoing program of re-fiieproofing the

structural steel to the Ml thickness for 2-hour raring is in

place. This work is done on a lease rollover basis whenever

there is a full floor of space being biah out for new

occupancy. To date approximately 30 floors have been

completed in the two towers. The PA wffl require this program to continue. The presence of asbestos containing

December 6, 2000 20-25 IE - Sections I-IV - Page 15

Figure A-41 . Excerpt from 2000 report on condition assessment of the World Trade

Center (7-P).

NISTNCSTAR 1-6A, WTC Investigation 197
Appendix A

CiX A. C. h&i&h

J. R. PAUL

ugust 10, 1^67

Fir. H. .'.alter

Zonolite Division

W. R. Crace a Company

135 South LdSailc- Street

Cnicagc, Ilii.-.oii jOoOj

Dear iiarty:

It was nice to get together with ycu and your good associates

this week at Madison to see tne spraying of your fireproofing

cn steel joists.

1 . I think the people from .the Fort Authority were impressed with

the good jot ycu did cn cur joists, ar.a I hope that ycu are successful in your effort with the Authority and the plastering

contractors in New York.

Mr. Hay Monti, the general superintendent of the World Trace

Center towers, callec yesterday tc as* if we cculd furnisr. some trusses similar to those ycu had used in the spray

application, so I presume there will be considerable activity regarding the spray-on material in the next few week.-.

If there is anything further we can be doing for you, cc net

hesitate to call upon us. T know Jim Paul is expecting a call from you concerning what effort might be mace tc run some fire tests on the coated trusses and joists. Clve us a call the next time ycu are in town.

Eest personal regards.

Yours very truly,

LACLEDE STEEL COMPANY

A. Carl V/eber

Vice President

ACW : p j z

Figure A-42. Example of correspondence referring to fire endurance testing of coated

floor trusses (70-1).

1 98 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

FIRE TESTING

While not advocating the omission of fire testing, it is clear

that numerous examples of non-tested assemblies are incorporated

into major buildings --under the watchful eye of responsible

building officials and with the full knowledge of designers,

builders and constructors. Obvious examples include:

(1) The floor assembly of the Sears Tower; and

(2) Typical composite beams supporting composite

deck construction, with unsprayed steel deck.

The latter is an example of industry "standard" construction,

accepted on a nationwide basis, but not supported by fire

testing.

Reasons for this lack of testing of special construction (such

as Sears and World Trade Center floors) is not to be found on account of a lack of desire on the part of designers or builders. The problem is quite straightforward:

V -I J

J- L. J.O JIU L ^VO L. UJLJ. j-> A UViLi^ L- > U11U CJ.JLJL combinations of products prior to contract award.

For example, Leclede trusses were accepted on

October 4, 1967 and Cafco fireproofing on March

26, 1969.

(2) Proper testing of the one-way World Trade Center

floors would have required a floor furnace

capable of testing an assembly 60'xl5'.

(3) Proper testing of the two-way World Trade Center

floors would have required a floor furnace

capable of testing an assembly 60'x80'.

(4) With the limited availability of such furnaces,

it is nearly impossible to schedule a test program

in time to meet construction requirements.

These special floor assemblies would best be fire tested- -since

actual testing is the only known, reliable method known to assure compliance with fire resisting requirements. At the same time the writer knows of no example wherein testing has

been accomplished- -the problems of time and scheduling appear

to preclude such testing.

-10-

SKILLINC, HELLE, CHRISTIANSEN, ROBERTSON

Figure A-43. Excerpts from 1975 post fire report indicating need for fire endurance

testing to establish a fire rating for the floor system (3-P).

NISTNCSTAR 1-6A, WTC Investigation 199
Appendix A

Early drafts of the revised Code required the 3-hour rating.

Later drafts and the final version of the Code allow a 2-hour

rating.

It is unlikely that a fire- test of the 4-inch World Trade Center

slab, making use of materials actually incorporated into the work,

will pass a 3-hour test. It will almost surely pass a 2-hour

test and would not be challenged on this account.

The World Trade Center construction of 4 -inch reinforced concrete

slab atop 11/2 inch steel deck formwork is more fire -resistive

then the most commonly used construction of today (1975) --a

3 1/4 inch slab atop 1 1/2 inch composite steel deck without

benefit of spray fireproofing.

Available Fire Rating

The fire resistive requirements for the project were subjected to

continuous modification as a result of the development of the new Building Code.

The decision to provide for 1/2 inch of Cafco was made in full

realization that:

(1) the floor slab provided only a 2 -hour rating; and

(2) the new Code provided for a 2-hour rating.

We presume, but do not know, that the Cafco decision was based

on the need for a 2-hour rating. Even without benefit of full

scale testing we do know that a 3-hour rating cannot be achieved

by the floor slab. We know also that the basic World Trade Center

floor slab is superior to construction provided commonly throughout

the country and does exceed a 2 -hour requirement. Without benefit

of a full-scale fire test we cannot establish a rating for the

floor assembly.

Fire Performance

The construction performed as expected during the fire of February,

1975. While some reports indicated that the fire was very hot, no evidence of temperatures reached is available to the writer.

In any event, at the very least, it can be said that the February

fire provided no evidence that the construction was not satisfactory

for its intended purpose.

We hope that this report will provide some insight into the fireSKILLING. HELLE. CHRISTIANSEN. ROBERTSON

Figure A-43 (Contd.). Excerpts from 1975 post fire report indicating need for fire

endurance testing to establish a fire rating for the floor system (3-P).

200 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

Fire Testing

While it is difficult to document through the media of project

correspondence, the question of full scale fire testing occupied

the minds of the planners and designers of The World Trade Center.

In March of 1964 Mr. C. H. Yuill, Manager Fire Research Section,

Southwest Research Institute wrote to SHCR in response to its

inquiry. The tone of the letter reflects a little the many

problems associated with such tests; size of furnace, non-standard

test procedures, long waiting time and the like (see page 8.1 and

8.2).

In June 2, 1965, SHCR transmitted truss loads for use in a fire

test by U.S. Mineral Products Co. Designs of that era assumed

conventional trusses- -not the Laclede variety actually incorporated

into the work. While not privy to the results of the test we understand (from discussions with Mr. Soffer of Port Authority)

that another test program was carried out in small scale using

Mono-Kote spray-on materials.

The Underwriters v Laboratories, Inc., test of July 26, 1969

(Fire TLst R4374, 68NX2435) makes use of Mono-Kote materials

and Laclede trusses and provides a 3-hour rating. A copy of

that report is attached (appendex) . The test is not completely

representative of World Trade Center trusses in that the members

are lighter, the span is shorter (16' -10") and the trusses are shallower, (see page 8.3). It should be noted also that the test was conducted subsequent to the contracting for World Trade

Center fireproofing. There is no evidence of when the report

came to the attention of Port Authority; it was given to SHCR on March 24, 1975.

SKII.LING. WELLE. CHRISTIANSEN. ROBERTSON

Figure A-44. Excerpt from April, 1 1975 post-fire report referring to fire endurance test of

floor truss system with sprayed thermal insulation (3-P).

NISTNCSTAR 1-6A. WTC Investigation 201
Appendix A

fGHACEj

ZONOLITE

INSTRUCTION PRODUCTS DIVISION

GENERAL

The subject of this report is a 3-hour fire endurance rated

assembly composed of Laclede Composite Joists supporting

a concrete slab over corrugated steel centering, protected

with Mono-Kote cementitious fireproofing spray-applied

directly to the surfaces of the joists and to the underside

of the steel centering.

The object of the investigation was to establish a 3-hour

fire resistance classification for the assembly, constructed

with the materials and in the manner as herein described,

by means of the Fire Test of Building Construction and

Materials, ASTM E-119 (UL 263).

DESCRIPTION

MATERIALS : The following materials were used in the test assembly.

Laclede Composite Joists - Type 10H5C, spaced 3 ft. 6 in. on center with a 16 ft. 10 in. clear span.

Corrugated Centering - No. 28 gauge steel attached to

joists with welding washers

Concrete - Average 28 day strength of 4290 psi, readymixed concrete, poured to a thickness of 2-3/4" as measured

over the crests of the corrugated centering.

Temperature Reinforcement - No. 8 SWG, 6 in. by 6 in.

wire mesh.

Mono-Kote Cementitious Spray-Applied Fireproofing - Applied directly to the surfaces of the joists to a thickness

of 1-1/2" and to the underside of the centering to a thickness

of 1/2", following the contours of the joists and the

corrugated centering. Bags of Mono-Kote contained the UL

label for "Cementitious Mixture,"

Figure A-45. Reports of 1970 fire endurance test of floor truss system with sprayed

thermal insulation (3-P).

202 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

GRACE

ZONOLITE

>NSTRUCTION PRODUCTS DIVISION

ERECTION OF TEST ASSEMBLY : The assembly was constructed at the Northbrook, Illinois,

testing facility of Underwriters' Laboratories, Inc. in

accordance with the attached construction drawing Nos.

UL 100-1 and -2, dated 2/27/70, under the observation of

members of the staff of Underwriters' Laboratories, Inc.

FIRE ENDURANCE TEST : The test was conducted in accordance with the Fire

Test of Building Construction and Materials, ASTM E-119

(UL 263 test method)

The assembly was loaded to provide a uniformly distributed

live load of 126 psf or a combined live and dead load of

169 psf, producing a maximum stress of 30,000 psi in the joists.

RESULTS

Observations of the Exposed Surface - All of the MonoKote cementitious fireproofing remained in place throughout

the 3 hour 13 minute test duration.

Temperatures of the Assembly - The initial average

temperatures of the unexposed surface was 69F. Based,

therefore, on a maximum average temperature rise of 250F

and a maximum individual temperature rise of 325F, the

average limiting temperature was 319F and the individual

maximum limiting temperature was 394F. At 180 minutes

(3-hours) , the average limiting temperature of 319F was

reached. At this time the maximum individual temperature

was 352F.

Figure A-45 (Contd.). Reports of 1970 fire endurance test of floor truss system with

sprayed thermal insulation (3-P).

NIST NCSTAR 1-6A, WTC Investigation 203
Appendix A

ZONOLITE

NSTRUCTION PBODUCTS DIVISION

Deflection of

Time

60 min

90 min

120 min

150 min

180 min

the Assembly

Deflection

22- 1/2

33- 3/8

4- 3/4

Temperatures of the Joists -

Top Diagonal Bottom

Time Chord Web Chord Average

60 min 235F 485F 485F 301F

90 min 395F 915F 1,150F 814F

120 min 486F 972F 1,243F 900F

150 min 550F 1.200F 1,543F 1 ,095F

180 min 622F 1.280F 1.580F 1,160F

CONCLUSIONS

The assembly achieved a 3-hour fire endurance rating in

accordance with ASTM E-119 and as verified by the attached

letter dated March 26, 1970, from A. F. Abbasi of Underwriters'

Laboratories, Inc.

Submitted by:

lIurMiio R Fxit

Thomas P. Feit - Manager

Technical Services

TPF/jac

Figure A-45 (Contd.). Reports of 1970 fire endurance test of floor truss system with

sprayed thermal insulation (3-P).

204 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

UNDERWRITERS' LABORATORIES, INC.

033 PF1NCSTEN HOAI) NOIITHHROOK, ILLINOIS 60062 an independent, not-for-profit organization testingfor public safety

AIR MAIL ; - - '-' ; March 26, 1970

in reply, please refe/ lo . ^

. ; - -* R4374

68NK2453

Zonolite Construction Products Div.

W. R. Grace & Co.

62 Whittemore Ave.

Cambridge, Massachusetts 02140

Subject: Fire Endurance Test of Composite Bar

Joist and Concrete Deck

Attention: Mr. T. P. Feit

Gentlemen:

This letter summarizes the results of the fire

endurance test of floor assembly of the subject matter.

The floor assembly was constructed according to

.Drawing No. LS101UL dated July 26, 1969 of Laclede Steel

Company. It consisted of 3 bar joists type 10H5C with

3 ft 6 in. spacing on centers and 16 ft 10 in. clear span,

supporting concrete deck over corrugated centering. The

thickness of concrete was 2 3/4 in. over the crests and

3 1/4 in. over the valleys, and was reinforced with 6 by

6 in. No. 8/8 wire mesh. The bar joists and the corrugated

centering were sprayed with Mono-Kote MK of the following

thicknesses

1. Bar Joists - An average of 1 1/2 in. thick

directly applied over all the exposed surfaces of bottom

and top chords and webs.

2. Corrugated Centering - An average of 1/2 in.

thick following the contours of the exposed surface of the

corrugations.

The average strength of concrete at 28 days was

4290 psi. The equivalent uniform live load of 126 p. s. f, was applied on the assembly. The total live and dead load

was 169 p. s. f. which produced a maximum stress of 30,000

psi in the bottom chord of the bar joist.

Figure A-45 (Contd.). Reports of 1970 fire endurance test of floor truss system with

sprayed thermal insulation (3-P).

NISTNCSTAR 1-6A, WTC Investigation 205
Appendix A

UNDERWRITERS* LABORATORIES, INC.

- 2 - March 26, 1970

The floor assembly was tested on February 27, 1970,

and the test was continued for 3 hours 13 minutes and 10

seconds. The structural performance of the floor assembly

during the test was considered satisfactory. The average

temperature of the unexposed surface before the fire test was 69F. At 3 hours of test time the average temperature

of the unexposed surface reached 319 F and the maximum individual

temperature was 352 F. The maximum deflection of the unexposed surface at 3 hours was 4.76 in.

The assembly was further loaded with an additional

live load of 126 p. s. f. on March 2, 1970 which increased

the maximum deflection by 0.35 in. without any apparent

structural damage.

We shall be preparing a formal report which will

contain details of the test.

Very truly yours,

A. F. ABBASI

Fire Protection Department

AFA:ck

Figure A-45 (Contd.). Reports of 1970 fire endurance test of floor truss system with

sprayed thermal insulation (3-P).

206 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

ORG. NO. ULIOO-2

DATE: 2- 27-70

LACLEDE STEEL CO. FIRE TEST 2-27-70

v- CORR. CENTERING

SP3AY-ON MONO-KOTE--* ^-lOHCS

3" FLOOR SLA B WITH TRUSSES COATED

WITH I *'2" v'IN. SPRAY - QN MONO- KOTE

B DETAIL A"

1 2"

ft - « T

scale : i '/z" = i'-o" j*" SLAB REINF. 6x6 " 8 /*8 WWF. .041 SO. IN. / FT.

J- SLAB - 7

- MONO -KOTE

2" MIN

I ''2 MIN.

\ «

2 MIN. l' 2" MIN.

SECTION A-A

scale : 1 lJ z" - i'-o'

2" COVER

SPRAY-ON

MONO-KOTE

r

1 _

. a 3" .

' S '32" Lb

, CORR. CENTERING

.75' i'DIA. |lz"M!N. COVER

DETAIL A

scale: 4' l'-0*

STEEL PROPERTIES

TOP AND SOTTOM CHORD ANGLES

AREA; .708 IN. 2

, f / : 50.000 PS.I. WEB

AREA : .442 IN. 2

, fy -" 3 6 ,000 PS.I.

SLAB REINE

DECK

3" AVG. SLAB

SPRAY-ON MONO-KOTl

SECTION 8- B scale: 3" - i'-o'

FIRE ENDURANCE TEST UNDERWRITER'S LABORATORIES INC. R 4374 68 NK 2435 333 PFiNGSTEN ROAD

NORTHBROOK. ILL.

Figure A-45 (Contd.). Reports of 1970 fire endurance test of floor truss system with

sprayed thermal insulation (3-P).

NISTNCSTAR 1-6A, WTC Investigation 207
Appendix A

THEORETICAL CONSIDERATIONS

Port Authority specified in a letter dated October 30, 1969, to Mario $ DiBono Plastering Co., Inc., 0.50 inch thickness of

Cafco Blaze-Shield Type D for the steel beams, spandrels and

bar joists. In the ULI report of July 26, 1969, for 3-Hour

Fire Endurance Assembly with Mono-Kote Spray-applied Cementitious

Fireproofing and Laclede Composite Joists, the test assembly

achieved a 3 -hour fire endurance rating in accordance with

ASTM E-119.

In the test assembly the Mono-Kote fireproofing was 0.50" on the steel deck formwork and 1.50" on the surfaces of the

joists with 0.75" diam. webs and 1.50" x 1.25" x 0.135" chord

angles.

Cafco Blaze -Shield for the WTC floor trusses the same 3 -hour

fire rating may be extrapolated in a very approximate way

on the basis of the thermal conductivity of the two materials.

The thermal conductivity in units of BTU/HR-FT2 -1°F/IN, is 0.27

for Cafco Blaze-Shield and 0.61 for Mono-Kote. The required

thickness of Cafco Blaze-Shield is computed to be 0.50" for

the Laclede trusses with 1"0 webs and chord angles thicker than

3/16"; 5/8 "thickness would be needed for 3/40 web members.

It must be emphasized, however, that theoretical extrapolation

of fire endurance tests must be viewed with caution.

-12-

SKILLING, HELLE, CHRISTIANSEN. ROBERTSON

Figure A-46. Excerpt from 1975 post-fire report indicating interpretation of 1970 fire

endurance test of truss floor system with sprayed thermal insulation (3-P).

208 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

REV. | PR A LESLIE E- ROBERTSON ASSOCIATES

CONSULTING STRUCTURAL ENGINEERS P iWbll4- DRAWING NO.

ORAFT

DESIGN l*fM

CHECK /z/f /fz.

Ccx^uMMS, /a/ 77/6- WofZcJ> 7~tl**rC><2 C&ajJ&I

Various ~phckajgss€s cp- F-itept^ofrHc, A££ ;

'1 1

Figure A-47. Excerpts from 1992 report on thermal insulation thickness for repair of

missing insulation (240-LERA).

NISTNCSTAR 1-6A, WTC Investigation 209
Appendix A

REV.

1 PDA LESLIE E. ROBERTSON ASSOCIATES l"tlirA CONSULTING STRUCTURAL ENGINEERS p /ooynj- DRAWING NO. 2/37

DRAFT

/pjpi-oDjcr) o*j

DESIGN \Np*\

CHECK

(8), CO) (F) AMD (C,) tt>e*ijl&&p HtfHCfif B&wy *jo

//J 70 7)M&. Tin?. &Ai!>U/?S

j>&i&fiA4*to&? fry LQMpirit, 7Pb0fit£x» MjI Columns

Ja'fJH\ JXrAfSr [7¥/<&*/&sds IfafywAf ^2 f tip&uf \ j

L ;. ...

' Joa<^.,^<S4vv^ APpMcADAL. \ SfJFf^iNG \

\

\

|„_ 1 pi^Af&s. *«v> ' &0t)/iji{/&,\ B/L/k&$rs to£LD%P\ 7& j .4 p&zj?t>j m&tit $p4*J\ "Tins /Ua^^c-\

MLS mrojr

XM<,Lu0£& \ jaI pU£ (2f^juuA^oJ\ As***. 1

Tfrfl-ifiJA* 7>GAi£ JT>_ SAyO- M>P if" Sffcbcti \

; £e>7l^i*i3? AoAJisf TV&i^Ac ^a^^A- \

Figure A-47 (Contd.). Excerpts from 1992 report on thermal insulation thickness for

repair of missing insulation (240-LERA).

210 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

REV. CD A LESLIE E. ROBERTSON ASSOCIATES

I— UnM CONSULTING STRUCTURAL ENGINEERS DRAWING NO.

DRAFT

DESIGN V^PM

CHECK

frx&fSZ&c^wti <e&s?u/&&v f&Z. B&Aa^/S typeset? /V

B£AH A

0 t

Fe/Z

V

uo

z

Figure A-47 (Contd.). Excerpts from 1992 report on thermal insulation thickness for

repair of missing insulation (240-LERA).

NISTNCSTAR 1-6A, WTC Investigation 211
Appendix A

REV.

1 CDA LESLIE E. ROBERTSON ASSOCIATES LtllAA CONSULTING STRUCTURAL ENGINEERS DRAWING NO.

ORAFT

OESIGN VtpM

CHECK /I /} /f i.

/IfAy &6 A&jOiflSR Of c*Z T&co*/.

Ratios.

* Wn *72 usa® at

Uj-. Bc

rm

4*5

Figure A-47 (Contd.). Excerpts from 1992 report on thermal insulation thickness for

repair of missing insulation (240-LERA).

212 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

REV.

1 CDA LESLIE E. ROBERTSON ASSOCIATES

I— t. CONSULTING STRUCTURAL ENGINEERS p /oayiLf DRAWING NO.

DRAFT

3c£/i ^t s

DESIGN W^M

CHECK

MQuotum ~7yp^ Z-/°6? £

UL 7%s/«,aj {g&F&L&ic& a)) AJTZo

4o<~ Be^M£ i*JiTH ^/t> a,/t£Af&z. /m*s So jma\/ us£ Vfe N720

Acj&#M*ny£(~y, this Vhcxjjzx fiMy s& /£&>ucev &y oswc* 7»e

h - fViacM6^ op. . . ... p-ie&p/zoof^/jj^.

Juesc^/pr I - Svesnrvn?

Aferel 3ue^jprZ=Vt Ssffc^L

"T^g. lAJ/Pt A PATH) C&S fH*At G64*1 VALUES

1.1- £uv 3io' Y./8

"

2. IB '4-

2 /2g v ::::::

3-6, /.!£>

Figure A-47 (Contd.). Excerpts from 1992 report on thermal insulation thickness for

repair of missing insulation (240-LERA).

NIST NCSTAR 1-6A, WTC Investigation 213
Appendix A

REV.

1 ERA LESLIE E. ROBERTSON ASSOCIATES

I— CONSULTING STRUCTURAL ENGINEERS DRAWING NO.

DRAFT &£A^ 3

DESIGN lA^?M

CHECK

^£JJI3€.T^ TtHOcjuGSSG S Z'l^e AVer Bt£Mi Sc/BSppspo+J &puAr?py,

V/p fuoon.

,/Z

Z./g

Z / 2g:

5-6, /.7S AO/

iLz />£ 75

g ! ff'-tL,"' G&pj 74

f

J. IB 77

7g /M

7^ /•Of 7?

Figure A-47 (Contd.). Excerpts from 1992 report on thermal insulation thickness for

repair of missing insulation (240-LERA).

214 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

REV.

1 EDA LESLIE E. ROBERTSON ASSOCIATES ^LillA^ CONSULTING STRUCTURAL ENGINEERS p /oo}//i/ DRAWING NO. »/v

DRAFT 3&w B

DESIGN

CHECK & Acer IX^a^p/lav

UL Tksto*j A/7//

^SiMttA^ 70 rue twof*z&/tcus cas&s, £u-* pcoctfs £xc6pr 8^

K'&v/s&P //Haccess£i (C&£ 36**1 Sc3SVM?s*J &<><Mno*))

7~fHCJ£-AJ<~S.S %

.e>5

A/3 Ac/ 7v" ;

/*7&Z\ 2./B ^7 Alb

Z . UB:

A76 75 lis

A/8 . 86

X a ; 77 A 18

9 A/3 7e> /.<*5 5/%»

A2c>

V

/.03 7V'

Figure A-47 (Contd.). Excerpts from 1992 report on thermal insulation thickness for

repair of missing insulation (240-LERA).

NISTNCSTAR 1-6A, WTC Investigation 215
Appendix A

REV.

1 CDA LESLIE E. ROBERTSON ASSOCIATES UtrlM CONSULTING STRUCTURAL ENGINEERS p /ooyi/tf DRAWING NO.

DRAFT

OES1GN (i^f

CHECK

CALCULATIONS ivtcc 7>£f&lM>*j£-

A)

fiZAflO. .

j£)(/?0Z&? *f P/ff&USrnf GtJSvJWi^** WITH!*! V^r *>U4fT

,

Figure A-47 (Contd.)- Excerpts from 1992 report on thermal insulation thickness for

repair of missing insulation (240-LERA).

216 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

REV. EDA LESLIE E. ROBERTSON ASSOCIATES

L» 11 /A CONSULTING STRUCTURAL ENGINEERS p /tX>}jJlf DRAWING NO.

DR^FT

DESIGN l^?M

CHECK

^4 £4>vAT)orJ TO P&f&t-<* !*>£ Type Z-IOC fz//L&fK£>OfiAjG

A*. z

AJcfE. JTMf 7~)S6i US6r Op THIS £:<^uA^lo^ IS, At Of A44*JDA TT*Z.y

/r MUST vs&P tempos SAMccZ'L TfM&

36

/kujt is .8/25* ?wc^

ITZb

26>e> ">/,

Figure A-47 (Contd.). Excerpts from 1992 report on thermal insulation thickness for

repair of missing insulation (240-LERA).

NISTNCSTAR 1-6A, WTC Investigation 217
Appendix A

REV. 1 PDA LESLIE E. ROBERTSON ASSOCIATES L.tll#n CONSULTING STRUCTURAL ENGINEERS P iooy/>-f DRAWING NO.

"'An

ORAFT

DESIGN tV^M

CHECK

(&) CArfdO 5b0 j MAAJUfACjVfieD BY /SoLATBK ^/StA/4?tou*c

F&z. gepuctAj** -p^r twcjc^6ss speaker? /*j 2>£s/&w

Tv^r ly&JV&fZ. Also Stxj&p that it<JjU~- TWcj£*i£ss

dt&K "So

7/Xs- coujMfj is A ^)Cft\ jute

^/o - nj2_ , /. 0% jV4lsis cess t»6*/d &>e

l'4") ' CoUvVS 5011 502^01 §Lcri so

Figure A-47 (Contd.). Excerpts from 1992 report on thermal insulation thickness for

repair of missing insulation (240-LERA).

218 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

REV. 1 PR A LESLIE E. ROBERTSON ASSOCIATES L-tllAA CONSULTING STRUCTURAL ENGINEERS p /ooy/^ DRAWING NO.

DRAFT

DESIGN ifM

CHECK i^hln

TaHS 5H^f& A H&U>NT A>JD f4^AAJ(fi6r WiDTff /O*.

~W?p - = /« 2£ A? ^6SS 72AfV 7*^

/0<^) COU>""!> 50/, 50Z, bat fjbOZ,so

Figure A-47 (Contd.). Excerpts from 1992 report on thermal insulation thickness for

repair of missing insulation (240-LERA).

NISTNCSTAR 1-6A, WTC Investigation 219
Appendix A

REV. 1 PDA LESLIE E. ROBERTSON ASSOCIATES

1— ^— tlr\ CONSULTING STRUCTURAL ENGINEERS p/003/<f3 DRAWING NO.

DRAFT WPM

2.1-1

oeswN WpM

CHECK

fc? pp£^p«-oofep. "Se-e. *=^H€>puu£ ^=>si F^E- 2.2-1.

- ^cx^mms 1 003 A^D IOC4- A^e- Mot; A^so&SSl&cC, ffcoM

Figure A-48. Excerpt from 1994 design document related to reapplication of SFRM to

accessible members in elevators shafts of WTC 1 (659-P).

220 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

TO: FROM:

SUBJECT:

REFERENCE:

COPIES:

M. Geraroan ft DATE: April 12, 1973

E. J.- Boland 4 THE WORLD TRADE CENTER - CONTRACT WTC 320.00 - ELEVATORS AND CONTRACT

.00 - SPRAY- ON FIREPROOFING- - TOWERS A & B

TJFTTtman to Otis - dated 3/22/72

R. Belsky, R. Linn, C. A. Smith, F. H. Werneke; G. Hughes, B. Weinstein (TRCC);

File

VWTC 113.

*ErrTeT~HT

As reported to this office, the slack condition in compensating

cables, especially on shuttle cars, is causing a chafing condition against

finished spray-on fireproofing on structural steel within hoistweys.

The chafing has caused extensive damage to the spray-on vhich

has been patched at considerable expense in the past. However, the damage re-occurs

As evidenced in the referenced letter, TRCC has previously pur- sued this slack condition problem vith Otis but it has not been corrected

to date.

Patching costs due to cable chafing should be backcharged to the Otis account. For hoistvsys where patching workhas not been completed,

the chafing area will not be done until this problem is resolved by Otis.

Any comeback costs. for later repair work on spray-on fireproofing

should also be for Otis' account.

Boland

Supervising Engineer

The World Trade Center

EJB/lp

Figure A-49. Correspondence indicating that slack cables within elevator shafts

damaged the thermal insulation (246-1).

NISTNCSTAR 1-6A, WTC Investigation 221
Appendix A

B. £. Schlecner

r. K. Stanpf jBly 29* I960

CAFCO Bond Strength

In our recent vibration tests we have noted scse poor bond characteriarties erf our CAFCO BLAZE and FEAT-STIEU). This was contrary to work which mm bad dene in the past on laboratory sixes. Since this difference was noted several tiaes in the past, se decided to see if there was any difference in

bond strength between plant and lab nixac forsnlas. As trill be seen in the

attached data sheet, there is quite a difference and nost of it is in favor

of the lab cixed fornolas. This is particularly true in the critical lew

d»*>sity ranges cf FEAT and EU£S-3FlilZ> for both wet and dry conditions.

This low bond strength can be a very serious defect to our products

since at 11 lbs. per square foot bond, reasonable vibration should shake the aaaa loose. At a wet strength of 3£ lbs. per square foot, installed CAFCO

which beeoir.ee wet and is subject to coderate vibration should delsalnete.

All specinens were sprayed under ideal laboratory conditiens rhich ceans they

were given the proper ancunt cf -seter, proper spraying angle, and proper

taaping. In the field, cost of these conditions are not net "shich would

further indicate peer perfcrnance of the product . It just happens that CAFCO

is usually applied in areas liere" there is not excessive vibration end its

weight is belo- the 3 lbs. per square fect range.

Before we start d etcreining the difference in nixing procedures,

changing ferrules, etc., this appears to be a good tiro to set a cininun

bond strength standard of perhaps 2C lbs. per square foot and that this

check be a part of the quality control procedure. Kext, we can study the

taxing which appears to be non-unifena as evidenced by previous difficulties

with S0U1C-SFI7TT vurift-iens arc with the research isood fiber fcnaula which

never resulted in the uniforc blend. Se think it is also aendstory tc regulate the nodule size of wool entering the cixer rather than depending upon

the aixer to do this. In the lab nixer, irith its tunbling action," the wool

asbestos and binders gently treble wfcicb results in unifcrc ccating. In

the plant cixer the constant breshing up of the wool nodule is never perKited to be cot.ted «ith the asbestos fibers and binders. This cay be s key

to our prcblec.

Under Section E cf the attached data sheet is dcta of bend tests run previcusly, naoely an audit in July 1959 and the original audit in February 1956. ~e can not answer thy the bend strengths fcr the 1956 audit were as good as they -aere except that in these days we aero using cteca

blxrun wool.

Figure A-50. Correspondence indicating poor bond performance of sprayed thermal

insulation during vibration testing (51-ITK).

222 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

0011814

"-"v.; - « - M.ir.ti, Cor.i.LrvCti.o.1 1*E".."..: „

..." fs*". F. K. Vcrncxc'- • -

" sate: -vcrch 6 V 1S6S

SUSJ2CT: IKE V.'ORID TRADE CENTER - FIELD TEST -??EE EEVICX C.7C0 TYPE "E" FEi;E.rECOFIEG

REFERENCE:

copy TO: ""Messrs. Levy w/att., Endler (TRCC) w/att.

The attached are letters dcted March 1, i&6£, from both Edited

States Mineral Products Company ted Mario & LUBono Plastering Company,

plus a memorandum from Tony Calebrese, dated March A, 1966, relative to an "on-the-job" application of Cafco spray-ron insulating material. The

co^xent6 of all are factual with no exaggeration. I was truly amazed at the ability of this material to adhere to the steel and to itself under

adverse weather conditions. I examined the material again on this date

and found it to be in tact.

In my opinion this material can be applied successfully :o tr.« exterior steel ur-dar adverse v.'ciz:.i- c zr.LLz'Lzr.t ;...Z. L2 _>i real it z.^z^z.iczy I car. reruest a repeat test at a cenparat_re of 2G~2> Of course, zEs insulating value of this materiel will have to be determined at tEe mccE-up

test in St. Louis.

F. E. Herneke

Assistant Construction Manager

The World Trade Center

FFi.7em

Figure A-51. Correspondence indicating acceptable performance of BLAZE-SHIELD

Type D when applied under adverse weather conditions (250-P).

NISTNCSTAR 1-6A, WTC Investigation 223
Appendix A

Jaaaary 14, 1110

Mr* Jooopk Forro

Dopoty CooBlatlooor

Tho City of In York

Dopartaoot of BalUUia

2 Lafayotto itml

Bar York, Bov York 10007

III TBI V0KU> TJLASB CHXH * TXIXFEOGfHQ

Xy tear fn—lnf nmn

TrtAatettte barevith la a rotoro* of a tprayo4 flreproofini

use eoateetoa' by tha fort iathorlty* The notorial w applite oa

Jaaaary 21, 1963 aster item woothnr Modlttom ate «no tei^

qooatly lntporte oa July 22 9 lMt ate ftete to bo in good, ooaJltloa.

Tboro Is aUo attaohte * report fro* tho U« I. Mistral frotetta

Coapaay oa tho notorial ote toohntejoi vote la tho appllootioo. Tho

anuria! vote wi o oonoatoalooa taboatao liter nboot crate mm it

Cafao Typo 9* Z ob oloo oaalotias o oopy of tho 9. 1* X« catalog*

Too will alto* moto fro* tho roport that pltttroa voro taboo of tho

installation* Z no abtaiBiof aofloa ami will forwote thoo to yen

lo tho soar faenro*

I hopo thio isferoatioo will ho ooofol to yon. Aay additional

Information no hoot la, of aonrto* at too* diapoool*

iUtirtly»

Malaola r. Uff

fool,

MPL:fg:Jtm

bec: Messrs. J. Kyle, R. Monti

Figure A-52. Correspondence sent to New York City Department of Buildings in 1970

providing information on the performance of BLAZE-SHIELD Type D (92-ITK).

224 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

-J*P* Vcrhulcn

a ll*rry Cropp DaUt Doc. 11,

«fc Last: shipment of special Typo D to World Trado Contor

Tho last 800 beg shlpcent (20 tons) shipped to tho World Trade Center was

aprayod on Friday, Dec. 5th, Saturday, Doe. eth end half of Sunday, Dec, 7th.

Of the 20 tons of material sprayed to. tho 10th floor exterior colussia on thla

projoct, approximately 600-700 bags of the tutorial vashed off at clean as a vhlstle froo the exterior columns on this Job*

On reporting thl* experience to frank Stumpf, ho couldn't bollevc that this

could happen, On Dec. 9th, 196T, Frank StunpJ and Slggy Suoskl visited tho

Vorld Trade Centor In the cocpany of Allen Bmouor to view this *•* —*

-r^e,,

Aa Allen reports to me, he sot tho, ytual dribble of suggestion* as to hew to

cure the probloa* Such ac, ve are spraying tovot, we should change the

dlsperaor tip from a 60 to a 75 tip and there wao too much hose en the floor*

At Allan knows, as I knov, as you knov, at Frank Stumpf knova, and as lob Rath

knout, none of those suggestion* era going to cure vhat Is the real probloa

of this Biterlal on tho Vorld Trade Canter* Since vo all knov tho problecj, but

unfortunately don't have the guts to tall each other In our ovn corpany. we. know

that the real problem la the busy,* poor, aub-etanderd product that vo exc, trying

to £«t our customers to accopt and apply, and don't give ne that the veathcr may

have beon cold, or tho distance of the Spray noitle tw> •« incorrect, or 4hu amount

-}f tho blower pressure cay be off, or tho.dlsporeer tip cay b« tho wrong one, bocause

all of theao things have been actually field tried on this Job and ve arc hoadod

for potential disaster - to put it vary bluntly.

If this cocpany doetn'c realise now, that the product ve are shipping to our

customers is poor quality. Inferior quality for vhlch ve are asking list prices

or prices above whet is aakod for by our competitors, end for vhlch ve are asking

our applicators to apply 20 to 30 per cent more material for, and for which ve have no right or. reason to ask a greator price for, no cutter how you look «t It,- then

ve had better veke up very, very soon to this fact,

I can no longer accept that ve are trying very hard to ©vcrcooe our problems.

Our customers really don't give a daB hot/ hard a foreman or superintendent

work? In our plant. It dootn't mean two good dams to hla that a superintendent

is loading a truck. All he wants, and ho hat a porfect right to expect, alnce

he la paying a prenlua and applying extra material over what Our cocpetltora do,

la a product that does what wo say It will do,

Vhether wo have the dally IBM inventory raport, or whethur we aoasure something on a slide rule really Isn't pertinent to our real corporate problems. The sooner

ve begin to leam vhat our real problems are, then and only then will «c bo able

to achieve profitable sale*.

Figure A-53. Intra-office correspondence dealing with adhesion problems during

spraying of exterior columns in WTC 1 (248-ITK).

NISTNCSTAR 1-6A, WTC Investigation
Appendix A

- 1 •

Tor ov«r one year, tha S»loi Deportment h*» lived vUh aub-atandard, tub -par*

oalov quality MttrUl produces* My wa, «nd ayeolf, have ovcrcowo complaint

upon cooplalnt with very few contractor* Asking for compencatlon for export aneoa

due to rocks, vlre, nutf, bolts, lath, paper btff in the product*. I foal ve

hav« con* to the end of the lino* Our contractor* fool va havo cone to tho ond

of the lint. PXocte, no furthor ostblsuous excutea* You vent 4 company • then

let** sckt the product*

Harry Crepp

eel I« JUth

r. stunpf

A* BoastMr

H fit D PHi

VIC file

tie

Figure A-53 (Contd.). Intra-office correspondence dealing with adhesion problems

during spraying of exterior columns in WTC 1 (248-ITK).

226 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

T-»- X-HtMt

1>A"T> .

• nUjri-T.

MEMORANDUM

Hrr-n

E. BolanJ r

1 1 l.T'Cuauagtio ' Harch 15. 1971 TIE WORLJ TRADE CENTER - Cft; TRACT VTC-113.00 - TOWEH A - ELEVATOR BANK C SHAFTS 39, AO & 41

C.~.'.*.'. "Smith, File

Spray-on fireproof ing work was performed by Mario & DiBoao in

Shcfts 32. 40 & 11 from 2/4/71 to 7/17/71. This work was done during

extremely cold temperatures in an attempt to meet existing construction

schedules

During a recent inspection of these shafts, it was: ootei that

the Cafeo fireprcofing treated with Hark II overspray hns not cured or hardened according ro specif i cations. The writer believes that this

improper hardening was caused by the low temperatures during vhich the

Hark II sealer was applied.

This inspector recommends that shafts 39, 40 & 41 be re-sprayed

with 'lark II sealer.

L. Guadagno

Construction Inspector IV

l£/iuk The World Trade Center

Figure A-54. Correspondence related to inadequate hardening of thermal insulation

applied to core columns (660-P).

NIST NCSTAR 1-6A, WTC Investigation 227
Appendix A

VIM

FROM: E. J. Boland

SUBJECT: XHE WORLD TRADE CENTER - CONTRACT WTC 113.00 - TOWER "B" ELEVATOR SHAFTS

#10 t. #11 - LOOSE AND FALLING SPRAY-ON FIREPROOFING

REFERENCE: photos attached, B-l, B-2, B-3, B-4

COPIES: R. Linn, c. A. Smith; B. Weinstein (TRCC) ; File

Our inspection of the above mentioned shafts indicates that

the spray-on fireproofing has been improperly applied in several areas.

The fireproofing has come loose and fallen at floors 35, 40

and A3 in shaft #10 and at floor 31 in shaft #11. Also several small

sections have come loose from perimeter box beams in both shafts.

We request that you direct the contractor Mario & DiBono

,

to re-spray the above mentioned areas as required under their Contract.

Please refer to Chapter II, Page 123, Section 13.03 - Product Qualifi - cations , "...the material shall resist the normal abuse resulting from

the construction work of subsequent trades, shall not crack, craze,

dust or disintegrate and shall adhere to the base surfaces with sufficient strength to insure against any loosing and falling off of

applied material." And Page 126, Section 13.07 - Workmanship "4. The

sprayed-on fireproofing and sprayed-on insulation, when completed,

shall be free from seams, staging breaks, holes, spalls, cracks, flaking

and dusting action, and other defects of any kind."

RV/lp

(2-

Eg/J. Boland

Supervising Engineer

The World Trade Center

SEP 2 4 W/J ^

r

- t—

iXiU.

Figure A-55. Correspondence related to dislodged thermal insulation within elevator

shafts of WTC 2 (658-P).

228 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

WORLD TRADE CENTER

Structural Integrity Inspection

Accessible Columns 8 1/2,4 and 5 WTC

P1103904 & 3927

29 January 1993

Page 1 of 9

EXECUTIVE SUMMARY

This report details the findings of the inspection of

accessible columns in the elevator shafts of 1, 2 and 5 World

Trade Center.

No structural deficiencies such as cracking or bowing were found in any of the columns inspected.

The most common irregularities observed were missing

fireproofing and light surface rusting of exposed steel.

We recommend that fireproofing be repaired on all columns in

the elevator shaft

Figure A-56. Excerpts from 1993 structural integrity inspection report related to

condition of thermal protection on accessible columns (16-FEMA).

NISTNCSTAR 1-6A. WTC Investigation

229
Appendix A

LERA

WORLD TRADE CENTER

Structural Integrity Inspection

Accessible Columns 8 1,2,4 and 5 WTC

P1103904 & 3927

29 January 1993

Page 5 of 9

PROCEDURE 6 LIST OF INSPECTED COLUMNS

The visual assessment of the accessible columns in the elevator

shafts was carried out from top of the elevator cars. The

elevator was operated by a field inspector from National

Elevators

The operator ran the elevator at a very slow speed from top to

bottom and if any irregularity was noticed the car was stopped

and the defect was duly noted and, at times, recorded using a 35mm camera.

A total of 10 elevator shafts were selected. This selection

included 8 local elevators and 2 express elevators. Table A

gives a listing of all the elevators and columns inspected

during this survey.

Figure A-56 (Contd.). Excerpts from 1993 structural integrity inspection report related to

condition of thermal protection on accessible columns (16-FEMA).

230 NIST NCSTAR 1-6A, WTC Investigation
Referenced Documents

LERA

WORLD TRADE CENTER P1103904 & 3927

Structural Integrity Inspection 29 January 1993

Accessible Columns 6 1,2,4 and 5 WTC Page 6 of 9

TABLE A

Tower Elevator

Shaft Number

Floors

Inspected

Adjacent

Column Number

Face of Column

Inspected

A

(1 WTC) 21 4-78 606 East

4-78 607 West

36 1-32 701 East, South

1-32 801 East, North

63 45-67 701 East, South

45-67 801 East, North

73 43-74 703 North, West

43-74 803 North, West

83 78-93 701 East, South

78-93 801 East, North

B

(2 WTC) 15 4-78 602 North

4-78 603 South, West

29 1-16 707 South, East

1-16 806 South, West

56 45-54 707 South, East

45-54 806 South, West

78 78-86 707 South, East

78-86 806 South, West

Northeast

Plaza

(5 WTC) 28

1-9 E=l

28

W

See Appendix A for the plan locations of the above columns.

Figure A-56 (Contd.). Excerpts from 1993 structural integrity inspection report related to

condition of thermal protection on accessible columns (16-FEMA).

NISTNCSTAR 1-6A, WTC Investigation 231
Appendix A

LERA

WORLD TRADE CENTER P1103904 6 3927

Structural Integrity Inspection 29 January 1993

Accessible Columns e 1,2,4 and 5 WTC Page 7 of 9

OBSERVATION

Appendix B-2 shows the typical cross sections of columns used

in elevator shafts. These columns are encased with sprayed on fireproof ing . (Photo 1)

The most common irregularity in the express elevator shafts was spalling & missing fireproof ing . The probable cause of this

spalling may be attribute to:

• rubbing of the hoist cables against the face of column.

• air pressuresinduced due to high speed of the elevators

moving up and down the shafts

Photograph 2 shows a patch of missing fireproofing at support

brackets for conduits and elevator hardware. It appears that

the fireproofing was removed when this bracket was installed.

Photograph 3,4 & 5 show typical patches of spalled fireproofing

caused probably by rubbing of hoist cables against the girder

and column faces.

Large areas of fireproofing were missing from the faces of

column 606 and 607 in one World Trade Center.

The columns in local elevator shafts were generally well

protected by fireproofing.

Isolated areas of spalling fireproofing were noticed on some of

the columns in the local elevator shafts. (Photo 7,8,9)

Photograph 10 shows large areas of damaged and spalling

fireproofing on column E-7/28 in the North East plaza building.

Light surface rusting was typically noticed in areas of exposed

steel

Figure A-56 (Contd.). Excerpts from 1993 structural integrity inspection report related to

condition of thermal protection on accessible columns (16-FEMA).

232 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

LERA

One and Two World Trade Center

Strucural Integrity Inspection

Accessible Columns

14 April 1995

File: P1113903

Page 1 of 10

Executive Summary

Leslie E. Robertson, r.l.l.p., (LERA) carried out a survey of

the accessible columns in the elevator shafts of One and Two

World Trade Center as part of the ongoing structural

integrity inspections. This survey was undertaken for the

purpose of ascertaining the condition of the accessible

columns in the elevator shafts in terms of the overall

structural integrity of the accessible columns, for signs of

rust or cracking, bowing, or deviation from plump, to

identify specific locations of structural distress or damage,

to identify locations of damage to the fireproofing

envelopes, for lateral displacement or rotation of the column

about a vertical axis where the column is braced directly on only one axis by connecting beams or abutting concrete slabs

due to large beam offset dimensions, for signs of rust, or deformation of the slabs on ground surrounding each column at

sub-level, and to provide recommendations for remedial work

for both structural and fireproofing damage.

Most of the information presented in this report originates

from on-site observations of selected columns within elevator

shafts made by LERA during March 1995. The visual assessment

of the accessible columns in the elevator shaft was carried

out from the top of the elevator cars, by a field inspector.

A total of 24 (Twenty- four ) elevator shafts and 56 (Fifty-six)

elevator pits were selected, this selection included 10 local

elevators and 14 express elevators.

The accessible columns in the selected elevator shafts of One

and Two World Trade Center are generally in good condition,

no structural deficiencies such as cracking or bowing were

found, the most common irregularities observed were missing

fireproofing and light surface rusting of the exposed steel.

Based on our observation and our evaluations of the

inspection, we believe that the structural integrity of the

accessible columns within the selected elevator shafts are satisfactory. Areas of concern, in terms of remedial work to

be taken, are the fireproofing envelopes and the corrosion of

the exposed steel. We recommend that the fireproofing be

repaired on all columns within the selected elevator shafts.

We also recommend that the exposed areas of steel be cleaned

orior to re-fireproof ing

Figure A-57. Excerpts from 1995 structural integrity inspection report dealing with

accessible columns (17-FEMA).

NISTNCSTAR 1-6A, WTC Investigation 233
Appendix A

One and Two World Trade Center

Strucural Integrity Inspection

Accessible Columns

14 April 1995

File: P1113903

Page 5 of 10

INSPECTION METHODOLOGY

Since the concurrent visual inspection of all the accessible

columns or even a major portion of them is not a practical

goal, a statistical approach is followed. This approach

involves the sampling of those components and systems which

are more important to structural integrity, and at locations

with a relatively higher potential for occurrence of defects

or problems. A visual inspection of the accessible columns

located in the rectangular core (the elevator area) was made

from the top of the elevator cars and from a walk- through of

the elevator pits. The elevator car was operated by a field

inspector from A.C.E. Elevator Co. The operator ran the

elevator car at a very slow speed from the top of the car. Within the bounds of the suggested sampling procedure, the

inspection frequency and the building layout, it was anticipated that the inspection work could be organized to

proceed in a more or less linear sequence to minimize both

wasted motion and duplication of effort, and to help assure

that no important item was missed. The inspection team

carried a set of reduced drawings, individual field notebook,

a camera and a flashlight, methods and procedures were conformed strictly to the Port Authority safety regulations.

Visual inspection was supplemented by the use of simple hand

tool such as a screw driver as needed. Where structural

steel columns or the connecting beams were covered by spray- on f ireproofing, removal of loose, cracked or rust-stained

cover material was provided to examine the steel. A number

of on-site visits were made to obtain the current condition

of the accessible columns. No lifts were used for the

inspection. The inspection findings were recorded on copies

of architectural drawings. The accessible columns were not

directly visible due to their fireproof ing; therefore, the

focus of the visual observations depended largely on the

condition of the fireproof ing . However, in several

instances, the structural columns and the connecting beams

were visible for inspection purposes or due to spalling of

fireproof ing

Figure A-57 (Contd.). Excerpts from 1995 structural integrity inspection report dealing

with accessible columns (17-FEMA).

234 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

LERA

One and Two World Trade Center

Strucural Integrity Inspection

Accessible Columns

14 April 1995

File: P1113903

Page 7 of 10

DETAILED INSPECTION FINDINGS

This report details the findings of the inspection of the

selected accessible columns within elevator shafts. Our

inspection findings and our opinions concerning the findings

and our recommendations for remedial action are summarized

below. Detailed inspection findings can be found in

Appendix E and F.

The inspection was undertaken to ascertain the condition of

the columns in the elevator shafts in terms of the overall

structural integrity. Columns were observed for signs of

rust or cracking, bowing, or deviation from plump, to

identify specific locations of structural distress or damage,

to identify locations of damage to the fireproofing

envelopes, for lateral displacement or rotation of the column

about a vertical axis where the column is braced directly on only one axis by connecting beams or abutting concrete slabs

due to large beam offset dimensions, for signs of rust, or deformation of the slab on ground surrounding each column at

sub- level, and to provide recommendations for remedial work

for both structural and fireproofing damage.

Most of the information originated from on-site observations

of selected columns within elevator shafts made by LEPA

during March 1995. The visual assessment of the accessible

columns in the elevator shafts was carried out from the top

of the elevators cars, by a field inspector. A total of

24 (Twenty- four ) elevator shafts and 56 (Fifty-six) elevator

pits were selected, this selection included 10 (Ten) local

elevators and 14 (Fourteen) express elevators.

The accessible columns in the selected elevator shafts of One

and Two World Trade Center are generally in good condition,

no structural deficiencies such as cracking or bowing were

found, the most common irregularity in both the express and

the local elevator shaft were spalling & missing of

fireproofing, the probable cause of this spalling may be

attribute to rubbing of the hoist cables against the face of

column, or air pressure induced due to high speed of the

elevator cars moving up and down the shaft, or due to testing

purposes. The exposed steel revealed only light to moderate

surface rust.

Figure A-57 (Contd.). Excerpts from 1995 structural integrity inspection report dealing

with accessible columns (17-FEMA).

NISTNCSTAR 1-6A, WTC Investigation 235
Appendix A

LERA

One and Two World Trade Center

Strucural Integrity Inspection

Accessible Columns

14 April 1995

File: P1113903

Page 9 of 10

CONCLUSIONS AND RECOMMENDATIONS

Our opinions concerning the findings and our recommendations

for remedial action are summarized below. Detailed suggested

remedial action can be found in Appendix B, E and F. Based on the survey data we collected and our evaluations of

this data, we believe that the structural integrity of the

accessible column in the selected elevator shafts is

satisfactory. We recommend that remedial action to be taken

where spray fireproofing is damaged, deteriorated or missing

and where there is corrosion of the column base due to water

leaks in the elevator pits.

The following are our specific recommendations for the

structural and fireproofing damage we observed.

Spalling, Missing and Damaged Fireproofing

We recommend that the exposed areas of steel be properly

cleaned and then protected with fireproofing. The existing

spray fireproofing may contain asbestos, therefore, adequate measures need be undertaken to ascertain the presence of

asbestos and to ensure both the protection of personnel and

the proper handling of the material.

Water Leaks, Corrosion and Accumulation of

Debris in Elevator Pits

At express and local elevator pits of both 1 WTC and 2 WTC,

where evidence of past or present water leaks has occurred, we recommend that the following action be taken: areas of current water leaks be drained;

• where steel has been corroded, chip away the floor

concrete surrounding corroded steel to a depth where

corrosion no longer exists;

clean and inspect all the steel, welds and bolts at these

locations to determine the extent of corrosion;

• repair steel, welds and bolts as required; and

prior to re-fireproof ing steel, paint with a zinc-rich

paint

We also recommend that the accumulation of debris in elevator

pits be removed and a maintenance program involving cleaning

be provided.

Figure A-57 (Contd.). Excerpts from 1995 structural integrity inspection report dealing

with accessible columns (17-FEMA).

236 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

THE PORT AUTHORITY OF NY AND NJ MEMORANDUM

TO?

FROM:

DATE:

SUBJECT:

£. Ramabhushanam

S.M Solomon

March 17. 1994

WTC Existing Fireproofing

REFERENCE:

COPY TO: V. Berndt, C. Bognacki, Eng. Files

As requested, the Chemical Division performed numerous thickness measurements

on existing fireproofing located on the 23rd and 24th floors of the WTC North.

Damaged and/or absent fireproofed areas on the 23rd Floor were repaired with

patch material; These areas were not measured. Truss members located adjacent to the

outside walls (within 3 feet) are devoid of fireproofing material Visual inspection ofthe

truss members on the 24th floor was not possible, as this area still has a lowered ceiling in

place. Tests were taken through areas where ceiling tiles were removed. Thickness

readings were taken on 16 random truss members on each floor. Measurements were

taken from both flanges and webs of the truss member.

At each of these locations, a total of six individual measurements were made and

averaged. These mini averages are listed on the attached table along with a total average,

standard deviation, high value and low value for each floor.

Figure A-58. Correspondence and data related to 1994 measurements of thermal

insulation thickness on floor trusses for 23rd and 24th floors in WTC 1 (3-P).

S.M Solomon

Chief of Chemical/

Environmental Testing

RG

NISTNCSTAR 1-6A, WTC Investigation 237
Appendix A

MAR-17-1995 16:31 FROM PA MATERIALS DIU. TO

NUMBER TWO WTC

EXISTING TTREPROOFING THICKNESS

108555 P.003/003

41

Readings, inches: 0.60

0.53

0.70 0.76

0.88

0.76

0.60

0.90

0.72

0.64

0.69 0.80

0.83

1.17 0.88

0.71 0.82

0.68

0.65 0.67

0.77

0.96

0.52

0.69

0.66

0.65

0.62

0.64 0.52

1.11 0.95 0.56

Average 0.73 076

Standard Deviation 0.14 0.15

High 1.17 1.11 LOW 0.52 0.56

Fiaure A-58 (Contd ). Correspondence and data related to 1994 measurements of SMM^id^on floor trusses for 23- and 24th floors in WTC 1 (3-P).

238

NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

Lombardi, Frank

From:

Sent: To:

Subject:

Lombardi, Frank Tuesday, February 12, 2002 3:03 PM

'edepaola@severud .com' WTC - 1 1/2" SPRAY-ON FIREPROOFING UPGRADE

Fireproofing Upgrade

The 1 Vz" spray-on fireproofing was established in 1995, to address any new construction for which the PA's

Engineering Department was the Engineer-of-Record and to acknowledge that IVi" of spray-on mineral fiber was sufficient when applied directly to chord and web members of the floor

trusses to provide the 2-hour fire rating for the floor.

It was required on all full floors being demolished for new construction or renovation either by the tenant or the PA. Because it was a landlord obligation, reimbursement was made to the tenant if the work was performed by

the tenant.

Tenant spaces that were less than a full floor, undergoing either new construction or renovation, needed only to meet the original construction standard. Fireproofing had to be inspected and patched as required to the greater

of V" or to match existing (it may already have been upgraded to the 1 V2").

The PA was also responsible to test the application of the sprayed-on fireproofing for conformance with ASTM

E-605, "Thickness and Density" and ASTM E-736, "Adhesion/Cohesion". The tests were also in conformance

with the NYC Building Code.

Here's the information about the VA" upgrade in the upper third zone of both Towers (77th floor and above).

Based on our records, a total of 1 8 floors in Tower 1 and 1 3 in Tower 2 were upgraded with 1 W spray-on

fireproofing.

The entire impact zone for Tower 1 (92-99) was upgraded with the 1 V2" spray-on fireproofing. Only the 78th

floor was upgraded with the 1 W spray-on fireproofing within the impact zone in Tower 2 (78-84).

We're still working on the population and should have it to you shortly.

Figure A-59. Port Authority correspondence indicating number of floors where thermal

insulation on floor trusses was upgraded to 1

1/2 in. (73-LERA).

NISTNCSTAR 1-6A, WTC Investigation 239
Appendix A

THE PORT AUTHORITY OF NY AND NJ MEMORANDUM

TO:

FROM:

DATE:

SUBJECT:

COPY TO:

Eli Moscovitz

Dorian Bailey

September 28, 1999

World Trade Center: Test of Fire Resistive Material

Contract WTC - 697.00 W.O. #4682 Charge #W02-857090

C. Bognacki, J. Bullard, P. Ortiz, J. Shanahan, M.Young, E.F.

As requested, the Materials Engineering Division has tested the application of the

sprayed-on fireproofing, CAFCO Blaze-Shield II for conformance to Port Authority

specifications. The material was applied at the 102nd floor of WTC #1

The tests were performed in accordance with ASTM E-605, "Thickness and

Density" and ASTM E-736 "Adhesion/Cohesion" of Sprayed Fire Resistive Materials

Applied to Structural Steel Members".

The results are as follows:

Minimum Requirements

TEST AREA #1

1WTC 102od Floor

Truss 131 North

Bottom oftruss TEST AREA #2

1 WTC 102"d Floor

Truss 231 East

Bottom oftruss

Density

lbJcu. ft.

15.00

16.47

16.87

Adhesion/

Cohesion

\bJsq. ft.

ISO

333

Thickness

Inches

1.50

3.25

333 3.25

TEST AREA #3

1WTC 102"" Floor

Truss 313 South

Bottom oftruss

15.93 315 2.11

Figure A-60. Example of test report on upgraded thermal insulation for floor trusses

(3-P).

240 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

The test results indicate that the applied fireproof material, CAFCO Blaze-Shield II meets

Port Authority specifications. Therefore the Materials Engineering Division recommends

the acceptance of the fireproofing material.

Dorian Bailey

Staff Services Engineer

Figure A-60 (Contd.). Example of test report on upgraded thermal insulation for floor

trusses (3-P).

NISTNCSTAR 1-6A. WTC Investigation 241
Appendix A

THE P0HTAUnM0RIIY®[FR[R7©KM]

March 23, 2004

John L. Gross, Ph.D., P.E. Leader, Structures Group

United States Department of Commerce

National Institute of Standards and Technology

Gaithersburg, MD 20899-0001

Dear Dr. Gross:

Following are responses to your questions, which are repeated here in bold italics. The PDF file attached has information previously submitted to NIST as a reference to some of your questions.

In 1994, the Port Authority's Chemical Division carried out measurements ofexisting

fireproofing on the 23rd and 24th floors of WTC 1. Averages of6 individual measurements at 16

random locations on each floor (for a total of32 locations) were reported in a memorandum of

17 March, 1994. While the information reported is useful, additional information is necessary

to determine the true statistics ofthe fireproofing thickness. NIST would like to request the

following:

1. Please provide individual measurements, rather than the averages, for all the tested locations.

The current supervisor and staff of our Chemical/Environmental Testing Laboratory cannot find the supporting information for Mr. Solomon's memo of March 17, 1994. They do, however, state that the procedures similar to those described below in response to question 2 were followed at the time to establish the average thickness data listed in the table.

Construction audit reports ofupgradedfireproofing thickness (floors 92-100 of WTC 1 and

floors 77-78, 88-89, 92, 96-97 of WTC 2) indicate that thickness measurements were performed

in accordance with ASTM E-605. There is, however, a discrepancy between the required

procedure established by ASTM and the Port Authority 's audit report data, which states that values were recorded only at the "Bottom of Truss " (seefor example, memorandum of

November 24, 1999, regarding material applied on 79th floor of WTC 1). Regarding this discrepancy, NIST would like to request thefollowing:

Figure A-61. Correspondence from Port Authority addressing questions related to

thickness of thermal insulation on floor trusses (681 -P)

FRANCIS J. LOMBARD!, P.E. CHIEF ENGINEER 225 PARK AVENUE SOUTH, I8TH aOOR

new yORK, ny I0003

(212) 435-7449

(212) 435-6689 fax

flomfcw rd@panynj.gov

242 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

THE P0m-JUITH0RflY(l)(?KJi7©[iM

John L. Gross, Ph.D., P.E. National Institute of Standards and Technology

March 23, 2004

Page 2

2. Please clarify specifically what procedures were used to measure thefireproofing thickness. A depth gage is used to determine thickness as follows: A thickness probe made of a needle that extends out along a measured scale is inserted into the fireproof material and stopped at the surface of the steel. The reading of how deep the needle extended into the fireproofing material is shown on the probe and recorded by an inspector. Thickness measurements are taken around the entire member. For the report in question of 1 1/24/99, 8 discrete measurements were taken to support the result of an average thickness measurement of 2.36 inches.

3. Please clarify why only datafrom the "Bottom of Truss" were reported.

The labeling of "Bottom of Truss" pertains to the location of collection of the physical sample, not

field-testing of thickness. A test sample was obtained from the bottom of the truss for density

testing, and also represents the location of the pull test. Fireproofing thickness measurements were taken from the truss diagonals as well as the upper and lower truss members, not only at the "Bottom of Truss".

4. Please provide individual measurements rather than averages.

The original thickness measurements taken from this report are: 2'/«, 2Va, 2

lA, 2

3/t, 1lA, \Va, Wa, 2%

inches.

Finally, in 1995 the Port Authority stated in a memorandum and white paper (memorandum

dated August 18, 1995 by Joseph M. Englot) that 1.5 inch thickness ofspray-on mineralfiber was required to achieve a 2-hour rating for steeljoist trusses in WTC 1 and 2. Based on the

1995 information, guidelines forfireproofing repairs were established in 1999 (buckslip dated

March 24, 1999 by Alan L. Reiss).

5. Please clarify what is meant by the requirement that 1.5 inches ofspray on fireproofing was

to be required only on "new construction. "

The term "new construction*' means any construction performed in the World Trade Center through a contract or work order that required the application of fireproofing. For example, re- fireproofing floors that have had asbestos mitigation, or otherwise re-fireproofing truss joists

where the removal of old ceilings, ducts, light fixtures, and installation of new finishes required

significant repair or replacement of the old fireproofing material.

6. Please clarify the technical basis for permitting tenant spaces where less than a fullfloor was being renovated to be patched to % " ofspray-on fireproofing rather than the 1.5"

required to achieve a 2-hour rating.

Figure A-61 (Contd.). Correspondence from Port Authority addressing questions related

to thickness of thermal insulation on floor trusses (681-P).

NIST NCSTAR 1-6A, WTC Investigation 243
Appendix A

THE PORTAUTHORITY < RM

John L. Gross, Ph.D., P.E. National Institute of Standards and Technology

March 23, 2004

Page 3

For questions 5 & 6, the NIST investigative team needs to understand that the guidelines that were

developed for upgrading the fireproofing were developed as part of an overall fire safety program

that looked at active and passive fire protection along with operating procedures, developed in consultation with outside fire protection experts by the Port Authority's Engineering, Risk

Management, and World Trade Departments.

To understand the rationale developed for the fireproofing, one needs to go back to the early 90s. The Port Authority had been relocating tenants in the first zone of One WTC, performing asbestos

abatements of the fireproofing on the trusses, re-fireproofing and installing sprinkler loops. The

Meridian Plaza fire in Philadelphia caused the Port Authority to accelerate this program and to minimize the number of contiguous floors that were not sprinklered since the benefits of sprinklers were well known and their effectiveness was dramatically shown during the One Meridian Plaza

fire.

Subsequent to the 1993 terrorist attack on the World Trade Center, the PA performed a critical self evaluation of the World Trade Center and decided on a number of upgrades including new

decentralized fire alarm systems for the complex, fire command consoles in the lobby of each tower staffed around the clock by FDNY certified fire safety directors, continued acceleration of

the sprinkler installation within the towers, including the sky lobbies, and increasing the fireproofing requirements for the trusses.

The new fireproofing thickness requirements were incorporated immediately into contracts being

written for the abatement and re-fireproofing of floors in the first zone of One WTC and whenever

space was demolished and made ready for potential re-leasing. Subsequent to J. Englofs 1995

memo, questions, though, continued to arise regarding whether or not the fireproofing upgrade was required during minor alterations done by tenants. Tenants were required to file Tenant

Alteration Applications (TAAs) before any work was performed in their space to make sure the PA could inspect the work. While there were some major alterations, there were many more

minor alterations such as the installation of computer and communication network cabling,

sprinkler head relocation, adding an air conditioner for a conference room, lighting upgrades, etc. To properly apply the new thickness, at least two sprayed on applications with a sufficient drying

time between applications was required. This was not practical in occupied office space where the work consisted of minor alterations such as just installing additional data and voice lines. The

implementation of the new 1 .5" standard during these minor alterations resulted in situations where ten feet of a single truss, where the ceiling tiles were removed, was upgraded while the balance remained untouched. There was ongoing consideration given to the question of how to properly upgrade the fireproofing if tenant partitions were still standing up to the underside of the

slab. As a result, overall benefit of the partial upgrade was brought into question.

Figure A-61 (Contd.). Correspondence from Port Authority addressing questions related

to thickness of thermal insulation on floor trusses (681 -P).

244 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

THE POHrJlimiOHnYaX?Ii!K7©D8y)^^

John L. Gross, Ph.D.. P.E. National Institute of Standards and Technology

March 23, 2004

Page 4

Therefore, in consultation with the Office of the Chief Engineer, the 1999 policy was developed to address this issue. It was based on an overall fire-engineering approach, namely:

1. The sprinklerization of tenant spaces.

2. The new redundant decentralized fire alarm systems with consoles located in each tower.

3. Monitoring of the tower fire alarm systems around the clock by FDXY.

4. Certified fire safety directors (whose only responsibility was watching the fire alarm

system). Port Authority Police who were stationed at the WTC were trained in structural

fire fighting and were immediately notified of any alarm.

5. PA Police had a direct hot line with the Manhattan Fire Dispatchers so they knew what

they were responding to, i.e. water flow alarm on a floor or multiple smoke detectors, etc.

6. The removal from the lobbies for tenanted space such as the airline counters and package

counters.

7. Periodic testing of the sprinkler system and its components.

There were many occasions where small sections of the original fireproofing had been dislodged

by work in the ceiling and it was feasible to patch these areas using a troweled-on patch to the original 3/<" thickness, but not to 1 .5 inches. Hence, the 1999 policy was developed with the above

factors in mind, along with operational test procedures. This provided a process for the phased

upgrade of the entire fireproofing system in the World Trade Center in accordance with the Chief

Engineer's new requirements, while ensuring the overall safety program was maintained.

These requirements were written into the net lease documents for the World Trade Center to make

sure the process continued after the transition from Port Authority operation and management of

the WTC. The following is from section 6.2.1:

1. One World Trade Center and Two World Trade Center Fireproofing - Hie existing policy of

the Port Authority to upgrade steelfireproofing to " thick (based on UL Guideline G508)

on the earlier to occur of(i) a fullfloor becoming vacant, (ii) a fullfloor being completely

renovated or (Hi) for any remaining non-compliance office space, within twenty-five (25) years

from the Commencement Date, unless the tenant never does a major alteration, shall be

applicable to the Lessee, provided the following standards remain in force:

a) allfloors in One World Trade Center and Two World Trade Center, including Mechanical

Equipment Rooms (once the work described in paragraph 7 ofSchedule 6.2.3 has been

completed) and Sk\ Lobbies, are sprinkled in conformance with the Port Authority Manual

andNFPA 13;

b) the Fire Command Centers in the lobby shall be (i) staffed with a New York City Certified "Fire Safety Director" at all times, and (ii) a total video surveillance system is installed and operating and is being monitored at all times, then the sprinkler plan may exclude the

Figure A-61 (Contd.). Correspondence from Port Authority addressing questions related

to thickness of thermal insulation on floor trusses (681 -P).

NISTNCSTAR 1-6A. WTC Investigation 245
Appendix A

the roin-jumioiiiTYseK^iBJ)

John L. Gross, Ph.D., P.E. National Institute of Standards and Technology

March 23, 2004

Page 5

310 level ofboth One World Trade Center and Two World Trade Center. There will be no

other permanent or temporary uses within the lobby, other than (i) the Command

Center(s), visitors ' desk(s), and mail boxes, provided each such area contains steel frames

with marblefronts and composite/laminate tops, and (ii) temporary holiday displays

composed ofnon-flammable materials;

c) the Lessee continues the current programs and implements additional programs as necessary to ensure the inspection, testing, and maintenance procedures ofandfor the sprinkler systems and the components thereof which include, but are not limited to, the water supply, fire pumps, gravity tanks, piping and valving.

These programs shall be designed to comply with the intent ofNFPA 25 and the other

requirements contained in the Port Authority Manual; and

d) when the Lessee is performing the testing ofthe sprinkler system 's waterflow and alarm

transmission, the specific system pressure indicated at the gage downstream ofthe pressure-reducing valve shall be recorded at the time ofsuch testing, to ensure conformance with the minimums/maximums indicated on the valves.

If the practices described in clauses (a) through (d) above are not adhered to, the Lessee shall immediately begin such fireproofing, even ifsuch work causes the Lessee to relocate the affected Space Tenants.

I hope this answers your questions. Please call or reply otherwise if you need further information.

Very truly yours,

Francis J. Lombardi, PE

Chief Engineer

Attachment

PA memoranda.pdf

Figure A-61 (Contd.). Correspondence from Port Authority addressing questions related

to thickness of thermal insulation on floor trusses (681 -P).

246 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

THE PORTAUTHORITY©J U&S FRANCIS J. LOMBARD!, P.E. CHEF ENGINEER

225 PARK AVENUE SOUTH, 18TH FLOOR NEW YORK, NY 10003

(212) 435-7449

April 14, 2004

John L. Gross, Ph.D., P.E. Leader, Structures Group

United States Department of Commerce

National Institute of Standards and Technology

Gaithersburg, MD 20899-0001

Dear Dr. Gross:

Following are responses to your questions in your letter to Joe Englot dated April 5, 2004, which

are repeated here in bold italics.

By this letter, I am requesting information from The Port Authority on fireproofing ofthe

interior and exterior columns of the World Trade Center towers. Specifically, please provide

the following:

1 ) Fireproofing material and thicknesses for the exterior columns as follows:

• Plates 1 and 2 (these plates face the outside of the building and were covered by the aluminum column panels)

• Plate 3 (interior plate within the occupied space)

• Plate 4 (spandrel), both interior and exterior surfaces

2) Fireproofing material and thicknesses for the core area box columns.

3) Confirmation that the wide flange column sections were specified to be fireproofed as follows using Cafco Type DC/F:

• Columns smaller than J4WF228 - 2-3/16 in

• Columns greater than or equal to 14WF228 - 1-3/16 in.

In response to your first three questions, Mr. Englot inquired throughout the Port Authority and was not able to find any information related to these questions other than that information

already turned over to NIST.

4) Any information the Port Authority has regarding measurements of the in-place

fireproofing material thickness. We have no records in our Materials Division of ever repairing or replacing fireproofing on

exterior columns due to their inaccessibility and, therefore, have no recent thickness measurements of any re-applied fireproofing.

Figure A-62. Correspondence from Port Authority dealing with thermal insulation on

WTC columns (672-P).

NISTNCSTAR 1-6A, WTC Investigation 247
Appendix A

THE PORTAUTHORITY<Mf RTC 9s KM

John L. Gross, Ph.D., P.E. National Institute of Standards and Technology

April 14, 2004

Page two

We have no records in our Materials Division of ever repairing or replacing fireproofing on core columns due to their inaccessibility (other than columns which are accessible within the elevator

shafts) and, therefore, have no recent thickness measurements of any re-applied fireproofing for core columns.

The only records of thickness measurements we could find were for the columns that are accessible within the elevator shafts. The Port Authority Materials Engineering Division took them and they correspond to World Trade Center Tower 1 elevator shafts. Discrete readings were taken at shaft 10/1 1 from the basement to the 45th Floor in Tower 1 in a report dated

4/7/1999. Mean thickness values were found for shaft 14/15 from the basement to the 80th Floor

in Tower 1 in a report dated 8/4/1997. These measurements cover the full extent of these two

elevator shafts. One was an express from the concourse lobby to 44 with a machine room on 47

and the other was express from the concourse to 78 with an EMR on 8 1 . The readings for both

of these shafts are attached (Excel file).

Discussions with Engineering Department staff and former World Trade Department staff indicate that these two shafts had asbestos abatement and were re-fireproofed. The measurements

also show a "Minimum Thickness Required" of fireproofing. Staff members recall that there was a schedule of replacement fireproofing thickness that was prepared by the firm Leslie E. Robertson Associates (LERA). One staff member located a copy of one schedule, which will be

forwarded under separate cover as a sample. We have contacted William Faschan of LERA and

it appears that the "Minimum Thickness Required" is the thickness called for in a schedule that appeared in documents for the work that was prepared by LERA. The sample schedule indicates

that the fireproofing applied was "Type Z-106". We will try to locate the specification book for

this material. This information may be among the documents that LERA assembled for NIST at the Port Authority's 225 Park Avenue South office. We will continue to search for more

complete sets of this information.

In the meantime, I hope this answers your questions. Please call or reply otherwise if you need

further information.

Very truly yours.

Francis J. Lombardi, PE

Chief Engineer

Att.

Figure A-62 (Contd.). Correspondence from Port Authority dealing with thermal

insulation on WTC columns (657-P).

248 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

Physical Performance"

^nrtarp O Ul IQLC Ritrni U U 1 I i 1 no1 1 EL ASTM Method 1 BLAZE-SHIELD DC/F BLAZE-SHIELD II BLAZE-SHIELD HP

Flame: 0 Flame: 0 Flame 0 E84 Smoke: 0 Smoke. 0 Smoke 0 Combustibility CAN4-S114

E136

Nuncombustible Noncornbustibie Noncornbustibie

Density E605 13 pel 15 0 pel 26.2 pcf (208 kg/m } !?5G kg/ni i {419.2 kg/m ) Cohesion/Adhesion E736 295 psi 360 psf 1.421 psf ;14.? kPa) (17.2 kPa) (68 kPa)

Deflection E759 No Cucks oi Deiaimnatioas No Cracks or Del3it)inations No Ciacks or Oelaminatiotis Bond Impact rirn t/60 No Cracks or Deiaminations No Cracks or Delammalions Nu Cracks o« Delaminations Compressive Strength E761 828 psf 2.380 psi 7.980 psf (39.6 kPa) 1 113.9 kPa) (382 KPa)

Air Erosion Resistance E859 0.000 g/U 0.000 g/ft

:

' o ooo r./ff (0.000 fi/m") (0.000 g/m ) (0 000 g/m)

Corrosion Resistance E937 Does Not Promote Docs Not Promote Does Nol Promote

in Mil Sid 810 Corrosion of Steel Corrosion of Steel Corrosion ol Sleel Sound Absorption C423 0.85 NRC 0 75 NRC 0 85 NRC

1/2" (12.7 mm) 1/2" (12.7 mm) 1/2" (12.7 mm)

onto deck & beam onto deck & beam onto deck & beam

Thermal Conductivity C518 3.45 R Value 3.33 R Value 2 43 R Value

Air, 1; •• liiftil ..l li i: 3tMA R«er so rdi'jTSijjl prcduu !;: tliiirw !<.-: :-:anC5'd «v«u i iiiiiita!e .is l-t jfif IKllislKilli* li! 1* .::.• ! • :1

Figure A-63. Excerpt from manufacturer's product catalog showing properties of

BLAZE-SHIELD DC/F obtained from independent testing under controlled conditions

(Source: www.buildcore.com/cOcafco.htm).

NISTNCSTAR 1-6A, WTC Investigation 249
Appendix A

Pacific Car and Foundry Company

Hnrch 5, I960 f'CF CD6&6-0y

TtiE PORT OF IrZ'A If OF;?. AUTHORITY

Office of tnc ConaL ruction finnacnr

30 Church Street - Roou 1119

Now York, New York 10007

Attention: Mr. S..M. Monti

Construction Manager

Refarencc; World Trade Center

Contract V.*TC-214 . 00

Project D679

Gent letscn

Please find enclosed 2 copies of PCF pointing specif icotions for

Contract WTC-214.00.

A copy of thin letter and specif icotionfl ban been foTvnrded directly

to Mr. Jo White (Sl!CR).

Ploaoe note particularly Clause 5.3 which we believe entloMen tS<* erector'o requirements for these panels.

*'c arc about to paint our first production panels and request your

early approval of thin Bpc c 1 f i ca 1 1 on

Figure A-64. Letter from Pacific Car and Foundry regarding painting specification and

excerpt from that specification (656-P).

Youth very truly,

PACIFIC CAP. U POUHLRY COMPANY

R.C. Synea, Project Engineer

Structural Steel Divioion

RC5/dv

Encl.

cc: J. White (SUCK)

J. Endler/A. Guttontag (TRCC)

250 NISTNCSTAR 1-6A, WTC Investigation
Referenced Documents

5 • 0 P AINT, INHIBI TOR S AND PRE SERVA'fTVj^S

5.1 Tnemec 99 Rod Metal Primer is the only paint approved for

use on this project.

5.2 Hilled surfaces and bevels for field welds shall be treated

vith one cuat Tc\'3CO ?L3 rust proofing compound.

5.3 All panels shall be stencilled, showing full engineering

panel number and weight of panel in tons, thus:

103-22-19 (12 T

) Weight shall be taken to nearest ton above actual weight.

Stencilled marks shall be placed on Plate 3, center column

of panel, directly above the bottom hand- hole. Tnemec

99-G Green Metal Primer shall be used for all stencilled

marks and letters and numbers shall be 3" high.

Figure A-63 (Contd.). Letter from Pacific Car and Foundry regarding painting

specification and excerpt from that specification.

NISTNCSTAR 1-6A, WTC Investigation

251
Appendix A

This page intentionally left blank.

252 NISTNCSTAR 1-6A, WTC Investigation
Appendix B

Thermophysical Properties Test Data

Table B-1. Specific heat capacity results of the three SFRMs from Laboratory B DSC.

Specific heat capacity (J/kg K)

Temperature (°C) BLAZE-SHIELD DC/F BLAZE-SHIELD II Monokote MK-5

35 1204

40 939 1009 1243

45 972 1047 1276

50 1004 1087 1302

55 1034 1134 1325

60 1064 1186 1355

65 1094 1237 1391

70 1130 1295 1423

75 1175 1355 1415

80 1227 1417 1348

85 1284 1479 1279

90 1369 1546 1253

95 1491 1623 1236

100 1663 1755 1183

105 1892 1945 1 122

110 2187 2199 1100

115 2495 2528 1290

120 2740 2908 1851

125 2756 3298 3094

130 2074 3672 5117

135 1658 3293 7488

140 1785 2235 8589

145 2050 1937 6528

150 2062 2038 4713

155 1763 1934 5146

160 1536 1796 4459

165 1437 1700 1629

170 1375 1637 1244

175 1328 1587 1162

180 12X4 1546 1152

185 1254 1506 1161

190 1220 1466 1174

NISTNCSTAR 1-6A, WTC Investigation 253
Appendix B

Specific heat capacity (J/kg K)

Temperature ("C) BLAZE-SHIELD DC/F BLAZE-SHIELD 11 Monokote MK-5

195 1190 1414 1196

200 1167 1368 1226

205 1145 1320 1251 210 1125 1284 1266

215 1110 1248 1 283

220 1094 1217 1309

225 1077 1183 1332

230 1063 1149 1364

235 1050 1112 1393

240 1035 1082 1428

245 1022 1053 1460

250 1006 1025 1492

255 991 996 1521

260 977 961 1544

265 965 926 1567

270 958 891 1590

275 956 857 1622

280 945 807 1636

285 936 765 1656

290 924 729 1669

295 911 701 1673

300 899 675 1665

305 888 649 1651

310 878 627 1625

315 S76 613 1578

320 S77 610 1512

325 880 620 1400

330 893 642 1245

335 911 682 1042

340 932 734 892

345 455 789 940

350 475 857 1042

254 NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Data

Table B-2. Specific heat capacity of 5/8 in. gypsum panel A.

Temperature

(°C) Cp (J/kg K)

Temperature

(°C) Cp (J/kg K)

50 1248 192 3569

100 1416 196 5020

125 1608 200 8087

135 2155 202 9200

140 3118 204 9356

142 3890 206 8816

144 5210 208 7948

146 7428 210 6497

148 1 1 148 212 4496

150 15341 214 2771

152 18490 216 2010

154 19671 218 1695

156 19648 220 1550

158 18822 225 1389

160 17476 250 1156

162 15728 300 1094

164 13734 350 1089

166 11 553 400 1046

168 9436 415 890

170 7034 430 453

172 5107 445 506

174 3501 460 808

176 2768 475 966

178 2417 500 1104

180 2297 550 1192

184 2544 600 1245

188 2923

NISTNCSTAR 1-6A, WTC Investigation 255
Appendix B

25000

20000

15000

Cl

o 10000

5000

5/8" Panel A

A'Ml -| -]h20 + [- |I i O

| ^jH2 0->y-CaS04 +f^jH 2 0

1 P ° ° to y-CaS04 ^p-CaSO,

Jvi /

_l I I I I I l_ J I I I I I I I i I I

' 100 200 300 400 500 600 700

Temperature (°C)

Figure B-1. Specific heat capacity of 5/8 in. gypsum panel A.

256 NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Data

Table B-3. Specific heat capacity of 1/2 in. gypsum panel.

Temperature

(°C) Cp (J/kg K)

Temperature

(°Q Cp (J/kg K)

50 1325 192 3693

100 1544 196 4957

125 1764 200 7730

135 2457 202 8774

140 3801 204 9088

142 4769 206 8644

144 6418 208 7693

146 8787 210 6364

148 12015 212 4487

150 15429 214 2888

152 17532 216 2090

154 18399 218 1828

156 18349 220 1672

158 17769 225 1495

160 16776 250 1278

162 15564 300 1185

164 13895 350 1188

166 12124 400 1159

168 10357 415 1015

170 8263 430 667

172 6180 445 642

174 4459 460 930

176 3383 475 1091

178 2768 500 1235

180 2545 550 1350

184 2632 600 1416

188 3006

NISTNCSTAR 1-6A. WTC Investigation 257
Appendix B

25000

20000

15000

XL

Cl

O 10000

5000

1/2" Panel

CaS04 -2H,0-»CaS04

- rn

H2 0 +

,2j v2j

H,0

CaSCX

/ 1 N H2 0->y-CaS04 + H,0

f tf« y-CaS04 -->f3-CaSOz

_i i i i I i i i i I i i i i I i i i i I i i i i I i i i i I i i

' 100 200 300 400 500

(O,

600 700

Temperature ( C)

Figure B-2. Specific heat capacity of 1/2 in. gypsum panel.

258 NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Data

Table B-^ . Specific heat capacity of 5/8 in. gypsum panel B.

Temperature

( M Cp (J/kg K)

Temperature

(°C) Cp (J/kg K)

50 1250 1^2 3624

100 1507 196 4886

125 1711 200 7769

135 2486 202 8848

140 3966 204 9102

142 5001 206 8727

144 6728 208 7705

146 9142 210 6210

148 12341 212 4342

150 15681 214 2775

152 17740 216 2052

154 18550 218 1770

156 18374 220 1621

158 17667 225 1451

160 16401 250 1233

162 14914 300 1148

164 13190 350 1168

166 11251 400 1130

168 9096 415 984

170 7108 430 568

172 5091 445 646

174 3658 460 930

176 2814 475 1084

178 2516 500 1232

180 2364 550 1347

184 2567 600 1432

188 2936

NIST NCSTAR 1-6A, WTC Investigation 259
Appendix B

25000

20000

15000

Q.

o 10000

5000

5/8" Panel B

CaS04 -2H 2 O^CaS04

- H2 0 + (1)"-° v2y

CaS04 |-- H 2 0-+Y-CaS04 + H,0

A y-CaS04 ->(3-CaS0,

-I I I I I I I I I I

' I 1 1 I I I I I I I I L 0 100 200 300 400 500 600 700

Temperature (°C)

Figure B-3. Specific heat capacity of 5/8 in. gypsum panel B.

260 NISTNCSTAR 1-6A, WTC Investigation
Thermophysical Data

Table B-5. Specific heat capacil y of 1 in. gypsum liner panel.

1 a mnpr-i turn

(°C) Cp (J/kg K)

Temperature

(°C) Cp (J/kg K)

50 1192 192 3583

100 1495 196 4876

125 2293 200 7346

135 3766 202 8360

140 5548 204 8872

142 6987 206 8787

144 8876 208 8164

146 11092 210 6847

148 13303 212 5256

150 15076 214 3305

152 15999 216 2260

154 16160 218 1787

156 15787 220 1597

158 14949 225 1408

160 13925 250 1192

162 12577 300 1137

164 10840 350 1146

166 8755 400 1060

168 6481 415 822

170 4676 430 609

172 3296 445 794

174 2685 460 971

176 2369 475 1079

178 2252 500 1200

180 2288 550 1306

184 2577 600 1378

188 2959

NISTNCSTAR 1-6A, WTC Investigation 261
Appendix B

25000

20000 -

15000

CL

O 10000

5000

1" Liner Panel

CaSO, -2H,0->CaSO,

' 3

l H,0

t

CaS04

- - H20-*y-CaS04 +

\2J [2

H,0

y-CaS04 ->(3-CaS04

•

' 1 1 '

1 ' '1 1

' ' ' 100 200 300 400 500 600 700

Temperature ( C)

Figure B-4. Specific heat capacity of gypsum 1 in. liner panel.

262 NISTNCSTAR 1-6A, WTC Investigation
Appendix C

Debris Impact Tests of BLAZE-SHIELD DC/F

Sprayed Fire-Resistive Material

INTRODUCTION

This appendix presents experimental observations obtained from a series of debris impact tests on steel plates and bars with the sprayed fire-resistive material (SFRM) BLAZE-SHIELD DC/F. The tests were

performed to provide evidence regarding the assumption that, within the debris field created by the

aircraft impact into WTC 1 and WTC 2, the SFRM used for thermal insulation of structural members was damaged and dislodged.

Engineering judgment, based on the aircraft impact damage analysis (NIST NCSTAR 1-2), was used to develop test parameters that were also within the limitations of the experimental facility. Two sets of

controlled experiments were designed: a high-speed low-mass test, which used uniform size lead pellets

(buckshot) for debris and high-speed impact, and a low-speed high-mass test, which used a lower speed

and several types of projectiles to simulate a random debris size distribution.

The SFRM on the steel plates and bars was subjected to a field of impacting projectiles fired from a universal receiver (a modified gun) at various orientations. For the high-speed low-mass impact, a debris

field was simulated by buckshot fired from a modified shotgun. Since firing of conventional shotgun

shells would result in average buckshot speed in excess of 682 mph (304 m/s), controlled firing with

custom-made shot shells was needed to reduce the impact speed within the range found for the debris

field in the aircraft impact analyses of the WTC towers (NIST NCSTAR 1-2).

The speed of the aircraft at impact was estimated to be 443 mph ( 198 m/s) for WTC 1 and 542 mph

(242 m/s) for WTC 2. Therefore, the speed of the debris field in each tower ranged between the maximum aircraft speed at impact and zero, when the debris came to a rest. As no single speed or debris

size could represent the debris field in the towers, a range of debris speeds and sizes were selected that were within the limitations of the test facility, as noted above. An average speed of 341 mph (152 m/s) was chosen for the debris impact velocity for the high-speed low-mass impact tests. For low-speed high- mass impact tests, an average speed of the projectiles ranging between 112 mph (50 m/s) and 201 mph

(90 m/s) was selected.

The desired impact speed was achieved but the universal receiver could only accommodate small

projectiles, which did not represent actual debris shapes and sizes. Therefore, the impact kinetic energies

from the projectiles were significantly lower than those from actual impacting debris in the WTC towers

due to differences in size (mass). However, when the impact kinetic energies were normalized by the

impact area, the impact conditions used in the tests approximated those in the towers, based on the

following order-of-magnitude analysis.

The kinetic energies of the two aircraft before they impacted the WTC towers differed somewhat, but were of the same order of magnitude. Based on the aircraft masses and initial speeds reported in NIST

NCSTAR 1-2, the kinetic energy of the impacting aircraft were approximately 3.4 x 10

9

ft lb (2.5 x 10

9 J)

NIST NCSTAR 1-6A, WTC Investigation 263
Appendix C

and 5 x 10

9

ft lb (3.7 x 1

9 J) for WTC 1 and WTC 2, respectively. Based on the aircraft impact analysis

(N1ST NCSTAR 1-2), the speed of the aircraft fragments as they approached the core were about 0.4 to 0.7 of the initial impact speed for WTC 1 and WTC 2, respectively (energy is proportional to the square

of the speed). In addition, portions of the aircraft masses were stopped prior to reaching the core. As a

result, it might be expected that the energy associated with the aircraft debris at the core were on the order

of 10* ft lb to 10

9

ft lb (10

8 J to 109 J).

For the purpose of this study, it was assumed that the energy of the debris impacting the SFRM was

distributed throughout a debris area that was about five floors high (60 ft or 18 m) and 150 ft (45 m) wide,

or an area of about 9 x 10

3 ft

2 (8 x 102 m2

). Thus, the energy per unit area would be on the order of

O(104 to 10

5 ft lb/ft2 ) (O(105 to 106 J/m2 )). The total kinetic energy of the buckshot impact per unit area

in the experiments was estimated, based on an average pellet size of 0.33 in. (8.4 mm), a mass of 0.1 oz

(3.5 g), and a speed of 341 mph (152 m/s), to be of the same order of magnitude, O(104 to 10

5 ft lb/ft2

) (0(1O5 to 10

6 J/m2 )). Therefore, the impact parameters (impact speed and kinetic energy per unit area)

used in the experiments are considered representative of these parameters in the aircraft impact analysis

of the WTC towers. However, the debris impact test condition simulated an instantaneous impact by a

burst ofdebris whereas the actual scenario involved a three dimensional field ofdebris, with a depth,

width, and height, continuously impacting the target(s) for a finite duration over a large area. In

addition, since the samples used in the tests were not restrained in the same way as actual structural elements would be, the response of the steel component and SFRM to debris impact in terms of

dislodgement of SFRM may differ somewhat from that of an actual structural member.

EXPERIMENTAL APPARATUS AND TEST PROCEDURE

The experimental set-up and procedure used to perform the debris impact tests are described here. All

ballistic tests on the SFRM were performed at the ballistic research test facility at NIST.

Ballistic research test, facility

The facility consists of two pieces of ballistic firing equipment (small and large universal receivers), an

optical device (two optical interrupters) to measure average projectile speed, an adjustable platform to mount the target, and a projectile trap. Figure C-l shows a schematic of the facility.

The small universal receiver was configured to a 12-gauge shotgun using a custom-made barrel. This

universal receiver was remotely triggered in the adjacent control room. The shells used No. 00 lead

buckshot with a diameter of 0.33 in. (8.4 mm). The shot shells were specifically tailored to achieve

nominal average projectile speeds between 307 mph (137 m/s) and 375 mph (168 m/s) by adjusting the

amount of gunpowder and the number of buckshot used in the shells. For all tests using the small

universal receiver, 0.3 oz (10 g) of gunpowder (Hodgdon Titegroup) and 2 oz (63 g) of buckshot were

used.

The large universal receiver was configured to have a custom-made barrel with an inside diameter of

3. 1 5 in. (80 mm). The receiver was air operated and could be triggered only at the gun station. The shot

shells consisted of two halves of Styrofoam wads that held 2.2 lb (1,000 g) of projectiles. The projectiles were comprised of a random combination of steel bolts and hexagon nuts that were larger and heavier

than the buckshot (the largest nut size was 2 in. (50 mm) wide by 1.2 in. (30 mm) thick hexagon nuts for a

1 % in. (32 mm) bolt). Air pressure was adjusted to achieve nominal average projectile speeds between

264 NIST NCSTAR 1-6A, WTC Investigation
Debris Impact Tests

1 12 mph (50 m/s) and 201 mph (90 m/s). Thus, the large receiver simulated impact by fields of

projectiles with larger mass density than those of the small receiver, but at slower speeds. Photos of the

typical shot shells for ballistic impact tests using the large universal receiver are shown in Fig. C-2.

9 m ——

|

Figure C-1 . Schematic of the ballistic research test facility.

Figure C-2. Typical shot shells used in the large universal receiver. A penny is also

shown for comparison.

The target was mounted 29.5 ft (9 m) from the universal receiver for testing of the steel plate specimens

and 15.7 ft (4.8 m) for testing of the steel bar specimens. A plywood enclosure was built around the

target area to contain ricocheted buckshot. A laser sight was used to position the target area with respect

to the barrel. The impact angle was varied from a 0 degree (target perpendicular to the barrel) to 60

degree angle (measured from the 0 degree position).

NISTNCSTAR 1-6A, WTC Investigation 265
Appendix C

Sample (impact target) preparation

The steel plates were V* in. x 12 in. x 12 in. (6 mm x 300 mm x 300 mm) and unprimed. Four nuts,

arranged in a square pattern, 8 in. x 8 in. (200 mm. x 200 mm), were welded on one side of the plate to mount the sample for testing. The 1 in. (25.4 mm) diameter bars were 20 in. (508 mm) long for the small

universal receiver tests and 36 in. (914 mm) long for the large universal receiver tests. The steel plates

and the 36 in. long bars were shipped to Isolatek, Inc. in Stanhope, New Jersey, for application of

BLAZE-SHIELD DC/F to a thickness of 1.5 in. (38 mm). The 20 in. (0.5 m) long bars had been

previously prepared and sprayed by Isolatek at NIST with a nominal thickness of 1.5 in. (38 mm). Figure

C-3 shows a steel plate with SFRM mounted in the ballistic research test facility ready for a test.

Figure C-3. Photograph of a steel plate with SFRM mounted in the ballistic research test

facility.

Test matrix

Table C-l summarizes the tests conducted in the debris impact tests.

Table C-1. Test matrix.

Debris speed/mass

Universal

Test Specimen

Impact Angle

receiver 0° 20° 30° 45° 60°

Small Steel plate (unprimed) xxxx XX XX XX

High speed/low mass Small Steel bar (unprimed) X

Small Steel bar (primed) XX

Low speed/high mass Large Steel bar (unprimed) XX

'x' = 1 run

266 NIST NCSTAR 1-6A, WTC Investigation
Debris Impact Tests

Test procedure

Each sample was photographed before and after each test. The steel plate or bar test sample was first mounted on two parallel L-brackets at the target location. The L-brackets were attached to a base plate,

which could be rotated to adjust the impact orientation. A laser sight was then loaded into the chamber to center the target with respect to the barrel. The sample impact angle (0 degree, 20 degree, 30 degree, 45

degree, or 60 degree) was set using a protractor. Impact angle was measured with respect to the leading

edge of the adjustable platform, which was set to be perpendicular to the laser beam. A 0 degree impact

angle was defined as the target oriented perpendicular to the direction of the projectiles. Other impact

angles were measured with respect to 0 degree.

After the impact angle was set, the laser sight was removed from the chamber of the barrel. The shot

shells were prepared in the ammunition laboratory. The receiver was fired and the average projectile

speed was recorded. The impact tests were viewed through a bulletproof observation window in the

control room. After the test, the sample was examined and photographed to assess damage to the SFRM

by the projectiles.

The nominal impact area by the buckshot fired from the small universal receiver at a distance of 29.5 ft (9 m) had a diameter of approximately 6 in. to 8 in. (0.15 m to 0.2 m). For the large universal receiver,

the nominal impact area by the projectiles (bolts, nuts, and buckshot) had a diameter of approximately

24 in. (0.6 m). For the steel bars, the impact area was reduced to about a 4 in. (0.1 m) diameter, which was approximately the diameter of the SFRM layer on the bar, by moving the bar closer to the receiver to increase the likelihood of projectiles hitting the target.

TEST RESULTS AND DISCUSSION

In this section, damage to the SFRM due to debris impact is assessed and photographic evidence is provided.

Steel plate and SFRM specimens

All tests on steel plates were performed using the small universal receiver (high-speed low-mass). In these tests, the impact area was much smaller than the sample surface area. Table C-2 summarizes the

test parameters for the steel plates with an SFRM layer. The kinetic energy per unit impact area was

estimated based on the projectile speed, an average pellet mass of 0.1 oz (3.5 g), and an impact area equivalent to the cross section area of the pellet 0.09 in

2 (5.52 mm2

). Tests at a 0 degree impact

orientation had damage to the SFRM at the points of projectile impact, which was marked by distinct,

approximately circular indentations on the layer. The vibration of the plate caused by the impact was

severe enough to break the adhesive bond and completely separate the SFRM from the unprimed steel plate (see Figure C-4). Similar observations were made for tests at a 20 degree and 40 degree impact

angle, as shown in Figure C-5 and Figure C-6, respectively. However, at a 60 degree impact orientation, the SFRM remained attached to the steel plate. Several projectile exit points were noted, which were due

to projectiles ricocheting off the steel surface. Figure C-7 shows the entry points of the projectiles and the

damage to the SFRM, and illustrates the size of the debris impact field relative to the specimen size. Two

0 degree impact tests were also conducted with the four edges of the SFRM layer taped to the steel plate

(see Figure C-8) to simulate better adhesion to the plate and to prevent the separation of the SFRM from

NISTNCSTAR 1-6A, WTC Investigation 267
Appendix C

the plate upon impact of the projectiles. However, when the tape was carefully removed after the test, no

adhesion of the SFRM to the steel plate was found; this also occurred for the 0 degree impact test without

duct tape.

Table C-2. Summary of test parameters for using unprimed steel plates with SFRM.

Test#

Impact orientation

(degree)

Average projectile speed

(ft/s (m/s))

Kinetic energy per impact area

(ft lb/ft

2 (J/m2 ))

Small

universal

receiver

(low

mass,

high

impact

velocity)

rLOl 0 511 (155.8) 5.3 x 10

4 (7.7 x 10

5

) PL02 55 346 (105.5) 2.4 x 10

4 (3.5 x 10

5

) PL03 60 574(175) 6.7 x 10

4 (9.7 x 10

5

) PL04 0 541(165) 5.9 x 10

4 (8.6 x 10

5 ) PL05 20 469(143) 4.5 x 10

4 (6.5 x 10

5

) PL06 20 563 (171.6) 6.4 x 10

4 (9.3 x 10

5 ) PL07 40 561(171) 6.4 x 10

4 (9.3 x 10

5

) PL08 40 568(173)* 6.5 x 10

4

( 9.5 x 10

5

) PL09

** 0 558(170) 6.3 x 10

4 (9.2 x 105 ) PLIO" 0 225 (69) 1.0 x 10

4

( 1 .5 x 10

5

) * Receiver misfired initially at 102 ft/s (31 m/s); a few shots hit but there was no visible damage to SFRM; sample reused for 2

n'

shot.

** The edges of the SFRM layer were taped to the steel plate using duct tape.

Figure C-4. Photograph showing damage to the SFRM after a ballistic impact at 0 degree.

The SFRM layer completely separated from the steel plate.

268 NISTNCSTAR 1-6A, WTC Investigation
Debris Impact Tests

Figure C-5, Photograph showing damage to the SFRM after a ballistic impact at 20 degree. The SFRM layer completely separated from the steel plate and landed on the

floor.

Figure C-6. Photograph showing damage to the SFRM after a ballistic impact at 40 degree. The SFRM layer completely separated from the steel plate.

NISTNCSTAR 1-6A, WTC Investigation 269
Appendix C

Figure C-7. Photograph showing damage to the SFRM after a ballistic impact at 60 degree. The SFRM layer did not separate from the steel plate.

Figure C-8. Photograph showing the edges of the SFRM duct taped to the steel plate

before the ballistic tests at 0 degree.

270 NISTNCSTAR 1-6A, WTC Investigation
Debris Impact Tests

Steel bar and SFRM specimens

The ballistic impact tests for the steel bars were performed using both the small and large universal

receivers. A summary of the test parameters used for the steel bars with SFRM is given in Table C-3.

For these tests, the adjustable mounting table was moved closer to the receiver to reduce the number of

projectiles that might have missed the target bar. The distance from the chamber of the universal

receivers to the target was 15.7 ft (4.8 m).

In tests using the small universal receiver (high-speed low-mass), the projectiles dislodged the SFRM

completely at the impact area of both the primed and unprimed bars, exposed the steel bar, and resulted in loss of adhesion (not cohesion) of the remaining SFRM on the bar. After the ballistic impact, the

remaining SFRM rotated freely with respect to the bar. Figure C-9 and Figure C-10 show the damage to the SFRM on the unprimed and primed bars, respectively, which were tested with the small universal

receiver. In Figure C-9, the projectiles impacted the upper portion of the bar specimen and missed the center and lower portions.

Similar results were observed for tests with the large universal receiver (low-speed high-mass). The

projectiles dislodged the SFRM completely at the impact area of the bars, resulting in exposed steel bar

and loss of adhesion of the remaining undamaged SFRM on both sides of the impact area. Figure C-l 1 and Figure C-l 2 show the damage to the SFRM on unprimed steel bars tested with the large universal

receiver. In Figure C-l 2, the projectiles also missed the lower portion of the specimen.

Table C-3. Summary of test parameters used for the steel bars with SFRM.

Test# Configuration Impact

orientation

(degree)

Total mass of

projectiles

(oz (g))

Average

projectile

speed

(ft/s (m/s))

Kinetic energy / impact area

(ft lb/ft

2 (J/m2))

Small

Universal Receiver

BAR01 unprimed 0 2 (63)* 443 (135) 4.0 x 10

4 (5.8 x 10

5

)

BAR02 primed 0 2 (63)* 556 (170) 6.2 x 10

4 (9.1 x 10

5

)

BAR03 primed 0 2(63)* 543 (166) 5.9 x 10

4 (8.7 x 105

)

Large

Universal Receiver BAR04 unprimed 0 32 (1,000)** 282 (86)

3.2 x 10

4 - 5.3 x 104

(4.6 x 10

5 -7.8 x 10

5

) BAR05 unprimed 0 32 (1,000)** 344(105)

4.6 x 10

4 - 8.0 x 105

(6.8 x 10

5 -1.2 x 10

6

) Projectiles consisted of only No. 00 lead buckshot.

Projectiles consisted of a combination of hexagon steel nuts of different sizes. The minimum and maximum kinetic energy per

unit impact area were estimated based on the smallest and the largest nuts and the minimum and maximum nut cross sections

as impact areas.

NISTNCSTAR 1-6A, WTC Investigation 271
Appendix C

Figure C-9. Photograph showing damage to the SFRM on an unprimed steel bar (BAR01)

after a ballistic impact at 0 degree using the small universal receiver.

Figure C-10. Photograph showing damage to the SFRM on a primed steel bar (BAR02)

after a ballistic impact at 0 degree using the small universal receiver.

272 NISTNCSTAR 1-6A, WTC Investigation
Debris Impact Tests

Figure C-1 1 . Photograph showing damage to the SFRM on unprimed steel bar (BAR04)

after a debris impact at 0 degree using the large universal receiver.

Figure C-12. Photograph showing damage to the SFRM on unprimed steel bar (BAR05)

after a debris impact at 0 degree using the large universal receiver.

SUMMARY OF FINDINGS

Based on the observ ations made in the ballistic impact tests, the SFRM was dislodged by direct impact

with solid objects that had a kinetic energy per unit impact area approaching 10

4 to 105 ft lb/ft2 (105 to 10 J/m2

). In addition, SFRM that was not dislodged after the debris impact lost its adhesion to the steel surface in all but one test. The SFRM on the steel plate was dislodged upon impact of the projectiles,

except for the ballistic impact at a 60 degree angle to the plate. When the SFRM was taped to the steel plate and the tape carefully removed after debris impact at 0 degree, no adhesion of the SFRM to the steel plate was found, the same result found for the 0 degree impact test without duct tape. For SFRM on steel bars, the remaining SFRM after impact rotated freely with respect to the bar.

NISTNCSTAR 1-6A, WTC Investigation 273
Appendix C

When the debris field dimensions were similar to the specimen dimensions, the SFRM was dislodged

completely from the steel component. For instance, the SFRM was dislodged over the width of the steel bar specimen when the debris field was centered over the specimen width. However, the steel plate

dimensions were much larger than the debris field dimensions and the SFRM was damaged only where

the impact occurred; the surrounding SFRM remained cohesively intact but lost its adhesive bond to the

steel plate.

The test results demonstrated that there was dislodgment of SFRM at locations subject to direct debris

impact. For direct debris impact up to a 60 degree orientation, the SFRM adhesive bond to the steel component was lost, but there was no loss of the SFRM cohesive bond.

In the WTC towers, where the debris fields were larger than the dimensions of steel components (i.e., such as trusses, beams, and columns), these tests show that SFRM would have been dislodged for a wide

range of debris sizes and speeds. The test results support the assumption that, within the debris field created by the aircraft impact into WTC 1 and WTC 2, the SFRM used for thermal insulation of structural members was damaged and dislodged.

274 NISTNCSTAR 1-6A, WTC Investigation