ITLApplied  Computational Mathematics Division
ACMD Seminar Series
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Coupled Fire Dynamics and Thermal Response of Complex Building Structures

Kuldeep Prasad
Building and Fire Research Laboratory, Fire Research Division

Tuesday, January 20, 2004 15:00-16:00,
NIST North (820), Room 145
Tuesday, January 20, 2004 13:00-14:00,
Room 4511

Abstract: Simulation of the effects of severe fires on the structural integrity of buildings requires a close coupling between the gas phase energy release and transport phenomena and the stress analysis in the load bearing materials. The connection between the two is established primarily through the interaction of the radiative heat transfer between the solid and gas phase with the conduction of heat through the structural elements. This process is made difficult in large, geometrically complex buildings by the wide disparity in length and time scales that must be accounted for in the simulations. A procedure for overcoming these difficulties used in the analysis of the collapse of the World Trade Center (WTC) towers is presented. Radiative heat flux to subgrid scale structural elements is computed using a formulation based on a simple "two layer" compartment fire model. The methodology is used to predict the thermal response of the critical structural elements of the WTC towers. A finite element model is constructed to compute the temperature distribution in concrete floor deck supported by steel trusses. The resulting time temperature curve at any location on the steel truss is highly variable and bears no relation to the ASTM E119 curve. Statistical methods are used to investigate the effect of varying levels of fire-proofing thickness. The role of aircraft impact damage on the thermal response of perimeter and core columns is studied. Spatial and temporal variations in temperature result in thermally induced stresses/strains and reduce the load bearing capacity that could lead to failure of the structure.

Speaker Bio: Dr. Prasad develops mathematical and numerical models for simulating complex multi-dimensional, multi-phase chemically reacting fluid flows. His research interests include modeling physical and chemical processes in combustion, fluid dynamics and large scale computing using DNS or LES models. Dr. Prasad received a Bachelor of Technology degree from Indian Institute of Technology (IIT) in 1986 and Doctor of Philosophy degree in Aerospace Engineering from Georgia Institute of Technology in 1991. He did postdoctoral research at Yale University with Prof. Mitch Smooke, where he designed a comprehensive multi-layered combustion model for studying the burning rates of solid rocket propellants. Prior to joining NIST, Dr. Prasad worked at the Naval Research Laboratory, where he developed mathematical models for simulating water mist suppression of liquid methanol pool fires. He has over ten publications in refereed journals and over fifty presentations as an invited or meeting speaker. His recent work at NIST has focused on development of multiblock grid embedding techniques and in constructing a thermal interface between fire dynamics modeling and structural analysis as part of the World Trade Center investigation.

Contact: P. M. Ketcham

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