State of the art large scale simulation of buildings in fire : the case of WTC7

Abstract

This research aims to develop an integrated simulation environment for performing state of the art large scale simulation of buildings in fire and uses World Trade Center building 7 (WTC7) as a case study for testing the developed framework. A thorough review of the investigation reports of the WTC7 collapse is first performed followed by a literature review of the experimental and theoretical literature on the behaviour of composite floors in fire. The performance of OpenSees for Fire framework for modelling composite slabs is then tested including the shell elements, cross-section discretisation, and concrete damage plasticity model. After ascertaining the accuracy of OpenSees in modelling composite floor systems, the development of the integrated simulation environment began. The developments that followed allow for: (1) importing the geometric information of structures from building information models, (2) creating OpenSees for Fire models using a graphical user interface, (3) linking the OpenSees model with computational fluid dynamics models, (4) performing heat transfer analyses automatically, (5) running the thermomechanical analysis in OpenSees, and finally (6) post-processing the results. This framework was then used to build several models used for assessing the response of WTC7 to a potential fire in the mechanical room. It was found that if the diagonal members of Truss 2 in the mechanical room were under-protected then they were likely to buckle. This would cause total failure of the transfer structure and may initiate the progressive collapse of WTC7. Further study is still necessary to assess the effect of this failure on WTC7 by considering load redistribution and comparing the simulated and observed mechanisms. Using WTC7 as a case study allowed for further development of the integrated simulation environment and paved a path for future research and development regarding the large-scale modelling of structures in fire. Moreover, this work shed light upon the hypothesis that a mechanical room fire may have contributed to the collapse of WTC7.