John L. Gross, Ph.D., P.E.

Building and Fire Research Labora

National Institute of Standards and Techno

U.S. Department of Commerce

John.Gross@nist.gov

Federal Building and Fire Safety Inves

of the World Trade Center Disast

National Construction Safety T

Advisory Committee Meetin

Project 6 – Standard Fire Te

WTC Tower Typical Floor Cons

June 22, 2004
May 2003 Progress Report: Fire Protectio

In October 1969, ... , the Port Authority statletter to the fireproofing contractor, that

 “All Tower beams, spandrels, and bar joists r

on fireproofing are to have a 1⁄2

′′ covering of C

 “The above requirements must be adhered to 

maintain the Class 1-A Fire Rating of the New Building Code.”[1]

[1] Letter dated October 30, 1969 from Robert J. Linn (Manager

The World Trade Center) to Mr. Louis DiBono (Mario & DiBo

* Interim Report on Procedures and Practices Used for Pass

of the Floor System of the World Trade Center Tower Struc
WTC Tower Floor Truss Fireproofing WTC Tower Floor Truss Fireproofing

Reproduced with permission of U.S. Mineral Products Company dbaIsolatek International and Morse Zehnter Associates 

Reproduced with permission of U.SIsolatek International and Morse Ze
ASTM E119 ASTM E119 - Standard Test Methods for 

Standard Test Methods for 

Building Construction and Materials Building Construction and Materials

ASTM E119 prescribes a standard exposing fire 

controlled extent and severity

Performance is defined as the period of resista

standard exposure before the first critical pobehavior (conditions of acceptance or end pconditions) is observed.

Conditions of acceptance include (for floor syst

 Sustained applied load during classification p Maximum temperature on unexposed side of 

and

 Maximum and average temperatures of the s
Standard Fire Tests* of WTC Tower 

Construction

Test plan includes:

 “As-specified” fireproofing conditions; “As-installed” fireproofing conditions; U.S. practice for establishing a fire endu

of a building construction;

 Full-scale testing; and Comparison of thermal restraint conditio

* ASTM E119 - Standard Test Methods for Fire 

Building Construction and Materials
Original (or “as built”) Conditions... Original (or “as built”) Conditions...

Duplication of original conditions

 Geometry (including camber) Steel ASTM A242 Welding Metal deck Primer paint Lightweight concrete Welded wire fabric SFRM material – Cafco DC/F
SFRM Thickness SFRM Thickness

Thicknesses of SFRM as originally installed:

 “As Specified” = 0.5 in

• Letter dated October 30, 1969 from Robert J. L

Project Planning, The World Trade Center) to M(Mario & DiBono)

 “As applied” = 0.75 in

• Determined from thickness measurements of th

fireproofing on floors 23 and 24 of WTC 1 - perfAuthority in 1994

Thickness of SFRM as “upgraded” (since 1995)

 “As specified” = 1.5 in

• PANYNJ white paper titled “Fireproofing Requir

Trade Center Tenant Floor Joist Construction thInstallation Due to Asbestos Removal or Local Facilitate Construction,” August, 1995.

 “As applied” = 2.5 in

• Determined from thickness measurements – PA

Construction Audit Reports for floors affected b
Geometry of 35 ft Steel Truss Geometry of 35 ft Steel Truss
Standard Fire Tests of WTC Tower 

Construction

 Represents current U.S. practice for est

fire endurance rating of a building const

 Typical of the floor assembly test furnac

the U.S. testing laboratories that routinethe ASTM E119 test.

2 17 ft. Restrained 

1 17 ft. Restrained 

Thermal 

Restraint

Test Span
Standard Fire Tests of WTC Tower 

Construction

 Allows direct comparison of the effect of therm

fire endurance rating.

 Will bound behavior of a floor system that is in

restrained

 Twice the scale of the first test. Represents a f

assembly of a 35 ft floor panel. 

 Allows direct comparison to Test 1 of the effec

on fire endurance rating

4 35 ft. Unrestrained 3 35 ft. Restrained 

Thermal 

Restraint

Test Span
Additional Steel Members Additional Steel Members

0.5 in 0.75 in 1.5 in 2.5 

Main trusse

Steel bars St

Note: Bridging trusses not shown for clarity

SFRM on Steel Bars:
On-site Monitoring and Inspection site Monitoring and Inspection

NIST has overseen

 Design and fabrication of test specimen Casting of concrete slab and test cylind Curing and drying of concrete Instrumentation Application of SFRM

NIST will continue to monitor closely

 Instrumentation Specimen loading Conduct of tests
Instrumentation Instrumentation

Temperature Measurements (exceed ASTM 

requirements)

 Measurement of the temperature of the steel a

length of the members

 Measurement of the temperature of the unexp

(top) of the concrete slab

 Measurement of the temperature of the bottom 

concrete slab (steel deck)

Deflection (not required by ASTM E119)

 Deflection measurements will be made at 9 lo

the unexposed side of the specimen as well aon the bottom chord of both main trusses
Gas Temperatures (not required by ASTM 

 Gas temperatures will be continuously rec

three locations using plate thermometer aaspiration thermocouples

Heat Flux (not required by ASTM E119)

 Radiative heat flux will be measured at low

of metal deck and to the bottom flange of trusses using wide-angle radiometers

Instrumentation Instrumentation
Fabrication of Steel Joists Fabrication of Steel Joists
Steel Joists Ready for Welding Steel Joists Ready for Welding
Assembly in UL’s Toronto Test Facility Assembly in UL’s Toronto Test Facility
Casting Concrete in UL’s Toronto Test Fa

Casting Concrete in UL’s Toronto Test F
Instrumentation of Test Assembly Instrumentation of Test Assembly
Spray-Application of Fireproofing Materia

Application of Fireproofing Materia
Schedule for Testing Schedule for Testing

 Design of tests completed Fabrication of steel trusses completed Assembly of all four test specimens completed Curing of concrete to 28-day strength completed Drying of specimens to specified moisture equilibr Shop primer paint applied on all specimens Instrumentation installed on all specimens Fireproofing applied to two specimens – all work t

First week of July

 Testing to begin in late July – early August Results – will be available shortly after test comple