Steel framed structures subjected to the combined effects of blast and fire - Part 2: Case study

Abstract

Design of public infrastructure against terrorist attack has become a rising concern to reduce the level of damage to properties and the loss of life. Some of the terrorist acts take the form of blast followed by fire causing catastrophic failure of the structure. This two-part paper aims to study the response of steel framed structures subjected to the combined effect of blast and fire. In Part 1 of the companion paper, an overview is made on the methods for determining the blast load and finite element techniques for dynamic and impulsive analysis. In this paper, a typical five-storey steel framed building with concrete slab system and external masonry cladding, subjecting to mid-scale bomb and then followed by fire, is analyzed using a dynamic analysis software, LS-DYNA. A sequential procedure for a dynamic blast-fire analysis is proposed. The effect of blast on active and passive fire protection systems is assessed. The local and lateral-torsional buckling failure modes associated with members subjected to the combined effect of blast and fire are identified in contrast with the failure modes predicted based on fire analysis alone. Collapse analysis showed that blast load could affect on the performance of passive and active fire protection system, and the blast damaged structure possesses very little resistance to fire.