Technical Conference on tBuilding and Fire Safety Inof the World Trade Center 

Session VI -

Structural Fire Respo

Collapse Analysis

Standard Fire Test Find

September 15, 2005

John L. Gross

Building and Fire Research Labora

National Institute of Standards and Techno

U.S. Department of Commerce
Motivation for Conducting StandarResistance Tests of Floor Assemb

Fireproofing of the floors in the WTC towerissue from the original design of the floor sythroughout the service life.

 Decision to spray trusses directly was innova Need for test was expressed by Architect of 

Engineer of Record

 Uncertainty in how SFRM thickness was spe LERA report reviewed fire resistance of floor 

1975 fire 

 PANYNJ’s

decision to upgrade fireproofing a
Results From Standard Fire Tests a

Results From Standard Fire Tests a

Times t

o Reach End-Point Criteria (

min) 

Temp

eratur

e on

U

nexpose

d Surface Steel Temperatures 

Averag

e

(Am

bient

+250oF)

Maximum

(Am

bient

+325oF)

Averag

e

(1100oF)

Maximum

(1300oF)

1 35 ft, restrain

e

d,

3⁄4 in fireproofing

--- 111 66 62 (3) 116(

2

35 ft,u

nrestrained,

3⁄4 in fireproofing

--- ---

7

6

6

2 (3) 146(

3 17 ft, restrain

e

d,

3⁄4 in fireproofing 180 157 86 76 (3) 210(

4 17 ft, restrain

e

d,

1⁄2 in fireproofing

--- 58 66 58 (3) 120(

Failure 

to

Support 

Load

Tes

Term

ated

(min

T

e

st Descriptio

n

___________________________________________________(1) Imminent collapse(2) V

ertical displacement 

exceeded capa

bility to measure accurately

(3) Did not occur
NYC Building Code Requirement NYC Building Code Requirement

The test assembly with 1⁄2 in. fireproofing (SFRMwould not have met the 2 hour requirement of thBuilding Code

Sta

n

d

ard

F

A

S

T

M

E 119-61 

R

atin

g

R

e

1 3

5 ft, re

strain

e

d,

3/4 in fire

pro

ofin

g 116 1 1⁄2 

2

3

5 ft, u

nre

strain

e

d,

3/4 in fire

pro

ofin

g 14

6

2 

3 17 ft, re

strain

e

d,

3/4 in fire

pro

ofin

g

210

2

4 17 ft, re

strain

e

d,

1/2 in fire

pro

ofin

g 12

0

3⁄4

T

e

st D

e

s

criptio

n

T

e

st

T

erminate

d
Restrained vs. Unrestrained Test C

Restrained vs. Unrestrained Test C

Restrained(Test 1)

Unrestrained (Test 2)
Restrained vs. Unrestrained Test Con

Restrained vs. Unrestrained Test Con

For the 35 ft span tests with 3⁄4 in fireproofing, the fire resistance rating of 2 hours determined from unrestrained test was greater than the rating of 1 determined from the restrained test.

Sta

n

d

ard

F

A

S

T

M

E 119-61 

R

atin

g

R

e

1 3

5 ft, re

strain

e

d,

3/4 in fire

pro

ofin

g 116 1 1⁄2 

2

3

5 ft, u

nre

strain

e

d,

3/4 in fire

pro

ofin

g 14

6

2 

3 17 ft, re

strain

e

d,

3/4 in fire

pro

ofin

g

210

2

4 17 ft, re

strain

e

d,

1/2 in fire

pro

ofin

g 12

0

3⁄4

T

e

st D

e

s

criptio

n

T

e

st

T

erminate

d
Unrestrained Fire Resistance Ratings Unrestrained Fire Resistance Ratings

The 35 ft span restrained test assembly with 3⁄4 ifireproofing developed an unrestrained fire resisof 1 hour while the unrestrained test assembly wfireproofing developed an unrestrained fire resisof 2 hours.

Sta

n

d

ard

F

A

S

T

M

E 119-61 

R

atin

g

R

e

1 3

5 ft, re

strain

e

d,

3/4 in fire

pro

ofin

g 116 1 1⁄2 

2

3

5 ft, u

nre

strain

e

d,

3/4 in fire

pro

ofin

g 14

6

2 

3 17 ft, re

strain

e

d,

3/4 in fire

pro

ofin

g

210

2

4 17 ft, re

strain

e

d,

1/2 in fire

pro

ofin

g 12

0

3⁄4

T

e

st D

e

s

criptio

n

T

e

st

T

erminate

d
Scale of Test Scale of Test

For the restrained floor assemblies with 3⁄4 in. fire(SFRM) thickness, the 17 ft span assembly had rating of 2 h hours, while the 35 ft span assemblrating of 1 1⁄2 hours

Standard F

ASTM

E 119-61 

Rating Re

1 35 ft, restrained, 3/4 in fireproofing 116 1 1⁄2 2 35 ft, unrestrained, 3/4 in fireproofing 146 2 3 17 ft, restrained, 3/4 in fireproofing 210 2 4 17 ft, restrained, 1/2 in fireproofing 120 3⁄4 

Test Description

Test

Terminated
Support of Load Support of Load

Normalized Deflection of Center of Test As

Unexposed Surface Deflection/Span

-Center of Assembly0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045

0 50 100 150 

Time (minutes)

Deflection/Span

Re

Un

Re

Re

2 hours
Support of Load Support of Load

Based on four Standard Fire Resistance Tests cvarious length scales, insulation thickness, and econditions, the floor assemblies were shown to b

sagging without collapsing and supported their funder standard fire conditions for 2 hours.