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Simulating the Fires in the World Trade Center.

pdf icon Simulating the Fires in the World Trade Center. (1327 K)
McGrattan, K. B.; Bouldin, C.

Volume 2;

Interflam 2004. (Interflam '04). International Interflam Conference, 10th Proceedings. Volume 2. July 5-7, 2004. Organised by Interscience Communications Ltd. in association with National Institute of Standards and Technology, Building Research Establishment; National Fire Protection Association; Society of Fire Protection Engineers; and Swedish National Testing and Research Institute, Edinburgh, Scotland, Interscience Communications Ltd., London, England, 999-1008 pp, 2004.


fire science; fire safety; World Trade Center; validation; experiments; simulation; temperature; fire investigations; building collapse; fire spread


In the months following the attacks on the World Trade Center and the Pentagon, there was an active debate in the fire protection engineering community about the fires that erupted following the impact of the aircraft on the buildings. Because fires of this magnitude in these types of buildings are rare, there is a wide spectrum of opinion about the fire temperatures and their effect on the structural steel. Much of the fire literature consists of empirical correlations derived from experiments ranging from bench scale to room scale. Extrapolating these well-known correlations to the WTC requires a re-examination of the underlying assumptions. Many of these correlations are appropriate for a narrow range of fire sizes and building geometries, and can not be directly applied to the WTC fire scenarios. As a result, computer fire models that have been developed over the past decade are being applied to the analysis. The National Institute of Standards and Technology (NIST), an agency of the United States Department of Commerce, is conducting an investigation of the collapse of WTC 1, 2 and 7. WTC 1 and 2 were the 110 floor towers, and WTC 7 was the 47 floor office building north of WTC 1 that collapsed at 5:20 in the afternoon of September 11, 2001. As part of the investigation, NIST has conducted simulations of the fires in each building using a computational fluid dynamics (CFD) model known as the Fire Dynamics Simulator (FDS). This paper will describe the experiments conducted at NIST to calibrate and validate the FDS model for use in the WTC project, and it will describe the techniques developed to simulate the very extensive fires that spread over 6 to 12 floors in the different buildings. This paper does not present any of the subsequent work to analyze the thermal response of the steel structure, nor does it present any collapse hypotheses. These efforts will be described elsewhere.