Influence of setbacks on the performance of high-rise buildings under blast loadings

Abstract

With the increase in terrorism worldwide, blast loading has received considerable attention. In January 1996, a 400kg bomb exploded at the entrance of the Central Bank Building in Colombo causing extensive damage. Blasts due to bomb explosions have become a new threat to buildings designed for normal static loads in Sri Lanka. Under blast loading, buildings are subjected to loads that are quite different from those governing their primary design in both magnitude and direction. Thus a better understanding of the behaviour of high-rise buildings under blast loads is of prime importance. Computer simulation has become an efficient tool in the analysis of structures under disaster loads, which are difficult and economically not viable to analyze with experimental methods. Dynamic inelastic analysis of three-dimensional models of buildings enables more realistic assessment of their performance under unpredictable time varying explosive loads. This paper explores three-dimensional nonlinear dynamic analysis of a typical highrise building in Sri Lanka under blast loading, with and without setbacks. A setback is a common geometric irregularity consisting of abrupt reduction of floor size in multistory buildings above certain elevations. Setbacks usually arise from urban design demands for illumination and aesthetic requirements.