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Experiments and Modeling of Structural Steel Elements Exposed to Fire. Federal Building and Fire Safety Investigation of the World Trade Center Disaster.


pdf icon Experiments and Modeling of Structural Steel Elements Exposed to Fire. Federal Building and Fire Safety Investigation of the World Trade Center Disaster. (19804 K)
Hamins, A.; Maranghides, A.; McGrattan, K. B.; Johnsson, E. L.; Ohlemiller, T. J.; Donnelly, M. K.; Yang, J. C.; Mulholland, G. W.; Prasad, K. R.; Kukuck, S. R.; Anleitner, R. L.; McAllister, T. P.

NIST NCSTAR 1-5B; 352 p. September 2005.

Keywords:

World Trade Center; high rise buildings; building collapse; disasters; fire safety; fire investigations; terrorists; terrorism; experiments; steel structures; fire models; thermal environment; fuel flow; heat release rate; gas temperature; heat flux; smoke; carbon monoxide; carbon dioxide; oxygen; velocity; tempeature measurements; compartment fires; thermal response; thermocouples

Abstract:

Reconstructing the fires and their impact on structural components in the World Trade Center (WTC) buildings on September 11, 2001, requires extensive use of computational models. For the use of such models to be a viable investigative tool, it is essential to know the accuracy with which they capture the physical phenomena of the fires and the concurrent heat transfer to the building structure. This report documents a series of large-scale experiments that was conducted in the National Institute of Standards and Technology (NIST) Large Fire Laboratory from March 10 to March 26, 2003. The experiments represent one phase of an effort to ascertain the validity of the models for the NIST WTC Investigation. The objective of the experiments was to assess the accuracy with which (1) the NIST Fire Dynamics Simulator (FDS) fire model predicts the thermal environment in a burning compartment and (2) the NIST Fire Structure Interface (FSI) model in combination with the ANSYS finite-element model predicts the temperature rise of structural steel components in a burning compartment. The experiments also had the potential to improve input parameters in the modeling, if appropriate, and, in general, help to increase understanding of the sequence of events that occurred in the WTC tower fires. Within a steel-frame compartment (3 m by 7 m by 4 m) lined with calcium silicate board were placed four steel components: two trusses, one thin-walled column, and a rod. The components either were uninsulated or had fibrous sprayed fire-resistive material (SFRM) applied; two thicknesses were tested. The 2 MW and 3 MW fires were generated using liquid hydrocarbon fuels introduced by a two-nozzle spray burner onto a by 2 m pan. The fuels were a commercial blend of heptane isomers and a mixture of the heptane blend with toluene. Six experiments were conducted.