Kuldeep Prasad and Howard Baum

Building and Fire Research Labo

National Institute of Standards and Tec

U.S. Department of Commerce

kprasad@nist.gov

Federal Building and Fire Safety Inves

of the World Trade Center Disast

Simulating the Coupled Fire, Therm

Response of World Trade Cente

October 19, 2004
Objectives Objectives

 Development of Fire Structure Interface (FSI) to 

Dynamics Simulator (FDS) with the thermal respstructural elements.

 Reconstruct the time-evolving and spatially evo

fields in the steel and concrete for World Trade 1, 2, and 7.

 Construct thermal loading data files (temperatur

the structural models. 

 Evaluate the role of variability in fireproofing thic

damage caused by aircraft on steel temperature

 Estimate the sensitivity of model parameters.
Temperature 

histories

Fire Simulations

CFD

Fire – Thermal Thermal – Structural 

Structural 

Structural Analysis

FEM

Write Node 

(Element) file.

Resume structural model. 

Read Body Load File.

C

Thermal Analysis

FEM

F

link

Plane Layer Analysis.

Boundary Conditions.

, , , ( , , )

2

T T L f x y t

FDS ANSYS File Transfer

u amb κ =

Fireproofing 

Damage
Pre / Post Impact Damage to Firep

Pre / Post Impact Damage to Firep

• Insulation was not applied evenly over 

• Renovations ?• Effect of vibrations over an extended period.

Bar Radius + 

Fireproofing 

Thickness

Center 

Line

Referen

ce 

Length

•Aircraft 

3⁄4 Deb3⁄4 Acc3⁄4Defo
WTC1 Floor 96 Truss Damage WTC1 Floor 96 Truss Damage for Realistic Anal

 for Realistic Ana

Damage to Slab 96/Truss 95 Damage to Slab 96/Truss 95 83 

in

2320 in

(58 columns at 40-in 

spacing)

Structural Damage to concrete slab, core beams and trussesFP damage to trusses and core beams based upon debris path of Floor 95

560 x 723 in

800 x 220 in

160 x 160 in

1040 x 1603 in

480 x 240 in
North Tower North Tower

 Aircraft Impact Damage and Fire Scenarios

 Severe  Realistic

 North Tower Model

 Floors 92-99 Model includes structural and fireproofing 
North Tower : Severe Case

Floor 99Floor 98Floor 97Floor 96Floor 95Floor 94Floor 93Floor 92

North F

Temperature C
North Tower : Severe Case

North F

Temperature C
North Tower : Severe Case

No

Temperature C
North Tower : Severe Case

North 

Temperature C
North Tower : Severe Cas

94th Floor 97th 
North Tower

Severe Case Realist
North Tower : Severe Case
North Tower : Severe Case
North Tower : Realistic Ca

North Tower : Severe Cas
South Tower South Tower

 Aircraft Impact Damage and Fire Scenarios

 Severe case  Realistic case

 South Tower Model

 Floors 78-83 Model includes structural and fireproofing 
South Tower : Realistic Case

South Tower : Severe Cas
South Tower : Realistic Case

South Tower : Severe Cas
South Tower

Severe Case Realist
Status: Status:

 Fire Structure Interface (FSI) – completed. Sensitivity to model parameters – completed. Component analysis – completed. Standard cases for evaluating collapse hypotheses 

 Realistic Scenario for North and South Tower – c Severe Scenario for North and South Tower – co Other Fire and Aircraft Impact Damage Scenarios 

 Thermal loading files provided to SGH for structural a
Kuldeep Prasad and Howard Baum

Building and Fire Research Labo

National Institute of Standards and Tec

U.S. Department of Commerce

kprasad@nist.gov

Thank you

Federal Building and Fire Safety Inves

of the World Trade Center Disast

Simulating the Coupled Fire, Therm

Response of World Trade Cente