Progressive collapse of Murrah Federal Building: Revisited

Abstract

As a typical incident of progressive collapse of RC structures caused by the terroristic vehicular bomb attack, the large-scale collapse of Murrah Federal Building (MFB) in 1995 has been attracting extensive attentions. The alternate path method and the direct simulation method are commonly adopted to evaluate the progressive collapse resistance of buildings. However, the simultaneous damage of the structural members adjacent to the removed column and the instantaneous interactions between the blast wave and the structures are neglected. This paper aims to revisit the progressive collapse of MFB through the high-fidelity numerical simulations. Firstly, the hybrid finite element model of MFB was established including both the near-range refined model and far-range simplified model. Secondly, based on the explicit dynamic finite element program LS-DYNA, the Arbitrary Lagrangian-Eulerian (ALE) method and Fluid-Structure Interaction (FSI) algorithms were adopted to simulate the ignition of explosive, propagation of air blast wave and its interactions with the building structures, which was validated based on an external explosion test on RC frame structure. Furthermore, the collapse of MFB was predicted and compared with the on-site photographs in terms of the collapse scopes of entire building and the damage of local structural members. Finally, three seismic resistant design schemes of MFB were proposed, and the corresponding progressive collapse resistance of which was further evaluated. It derives that, (i) the numerical simulation combining the hybrid modelling and ALE approaches can well reproduce the collapse process of MFB; (ii) the progressive collapse of MFB is mainly caused by the insufficiency of flexural bearing capacity of the transfer girder due to the failure of three supporting ground columns, rather than the rotation of the transfer girder; (iii) the three improved schemes can partially prevent the shear failure of the ground columns and mitigate the collapse scopes of MFB by 25%–50%, while the progressive collapse still occurs due to the shear failure of transfer girder; (iv) transfer girder is not recommended for blast-resistant buildings due to its low redundancy.