Modelling of Structures in Fire: An Example of the Boundary Condition

Abstract

The collapse of the World Trade Center Towers 1, 2 and 7 on September 11th 2001 has highlighted the need for proper understanding of the behaviour of structures in the event of a fire. A detailed analysis of the fires and the behaviour of the structures followed the events revealing numerous gaps of knowledge and uncertainties within the methodologies that are generally used by engineers and that are meant to deliver building designs that can be deemed as safe. Detailed modelling of the fire can only be achieved via Computational Fluid Dynamics (CFD) and of the structure using Finite Element Models. The integration of both models implies an adequate understanding of the boundary condition. This paper will analyse the boundary condition between the gas phase environment generated by the fire and the solid phase representing the structural members and protective elements. As an application example the performance of high-rise steel framed structures in the event of a large uncontrolled fire will be evaluated using the Fire Dynamics Simulator (FDS) CFD code and ABAQUS Finite Element Model.