Richard G. Gann, Ph.D.

Senior Research Scientist

Building and Fire Research Labo

National Institute of Standards and Tec

U.S. Department of Commerce

rggann@nist.gov

Federal Building and Fire Safety Inves

of the World Trade Center Disast

Reconstruction of the Thermal an

Environment

June 22, 2004
Project Objective Project Objective

Reconstruct, with assessed uncertainty limits, thtemperature, thermal radiation, and smoke fieldCenter buildings 1, 2, and 7 for use in evaluating and fate of occupants and responders and the sperformance of the buildings
Project Approach Project Approach

• Due to lack of physical evidence, we rely almos

• Fire insight• Computer simulations• Experiments• Photographic evidence• Eyewitness accounts

• Since this type of reconstruction has never been 

have re-defined the state-of-the-art in fire and thmodeling

• Integrated with other Projects, esp. 2 and 6
Tasks

1. Visual collection and time line development [Pitt2. Characterization of combustibles [Gann] 3. Characterization of partitions [Averill]4. Characterization of structural insulation [Yang]5. Fire model development [McGrattan]6. Experiments for model development [Mulholland7. Fire reconstruction [McGrattan]8. Reconstruction validation [Hamins]

Total: 32 people
Status

• Gathering of visual evidence - completed• Building information – generally complete; specif

floors would be useful:

• Verification of absence of high combustible lo

• Verification of location and nature of interior w

• Building combustibles - completed• Aircraft contents - completed• Insulation property data – completed
Status

• Reports in process:

• Shake table tests of ceiling systems: complet• Fire tests: heat transfer to steel members: co

• Fire tests: single workstations: complete draft• Fire tests: multiple workstations: draft mostly • Visuals collection and analysis: draft mostly w

and interpretation still ongoing)

• Current technical activity:

• Execution of Fire Dynamics Simulator (FDS) 

fires in all 3 buildings (cf. McGrattan presenta

• Execution of Fire-Structure Interface (FSI) run

coated assemblies in all 3 buildings (cf. Pras

presentations)

• Further analysis of visuals (cf. Pitts presentat
Interim Findings Interim Findings

• Loading of building combustibles was on the ligh• Mass of aircraft solid combustibles was significan

mass of the building combustibles in the impact z

• Ceiling tiles were likely to have been dislodged th

impact floors

• View of fires through many windows was hindere

walls, as well as by steep viewing angles and sm

• Some fire damage of exterior columns and floors 

after the aircraft impact

• FDS and FSI can be used with confidence to rec

effect of a given WTC fire event
Summary of Fire Experiments Summary of Fire Experiments

• Three sets of large-scale tests, generating data f

• Accuracy assessment of heat transfer to and 

structural components, testing of FSI

• Upgrading the combustion module within the • Verifying the accuracy of FDS fire growth pre
Heat Transport and Transfer Exper

Heat Transport and Transfer Expe

• Gas burner tests in a large enclosure• Various steel shapes; bare, two thicknesses of i• Measured temperatures, heat fluxes
Single Workstation Fire Experimen

Single Workstation Fire Experimen

• Conducted under a hood with a confined ceiling• Variables: presence of jet fuel, 30 % coverage by inert • Measured heat release rate (HRR), sample mass, [CO• Materials data from Cone Calorimeter

0

2000400060008000

1 104

0 5

Full Wo

Heat Release Rate (kW/m2)
Multiple Workstation Experiments Multiple Workstation Experiments

23 ft

4ft 4 ft

3 ft

1 ft 

5 ft

8.5 ft 20 "

equidistant Platform to 

 8.5 PLPL

PLATFORM 3
Multiple Workstation Experiments Multiple Workstation Experiments

• Variables:

• Presence of jet fuel• ca. 70 % coverage by inert 

material

• Ventilation• Condition of workstation

• Measured HRR, mass of each 

workstation, [CO], temperatures, heat flux; video

• FDS predictions completed 

before experiments
Richard G. Gann, Ph.D.

Senior Research Scientist

rggann@nist.gov

Federal Building and Fire Safety Inves

of the World Trade Center Disast

Reconstruction of the Thermal an

Environment

Thank you