Collapse performance of composite steel frames under fire

Abstract

Collapse of steel structures under extreme hazards has been placed at the forefront of research in recent decades. While significant number of studies has been conducted in the past on steel members and subassemblies under fire, the response of steel buildings exposed to fire loadings has not received a similar level of attention. In addition, only handful of previous studies, mainly 2D with only one study pertaining to 3D frames, encompassed the full response of the system up to and including collapse. In this study, a 3D numerical finite element model is developed for a six-story steel-frame building with moment frames, gravity frames, and center concentrically braced frame to evaluate the collapse behavior of the structure under fire loading. A standard and a parametric fire curve are selected to simulate the fire loadings and are applied independently to the building model under two different contained fire scenarios. The two scenarios include first floor corner compartment fire and whole first floor fire. This allowed for the assessment of different global system response where collapse is triggered by twist of the entire structure accompanied by lateral deformation in the case of a corner compartment fire and progressive vertical displacement of the entire system in the case of the whole first floor fire. The simulation results show that structural response of steel buildings including collapse mechanism and behavior of structural members and connections during fire events can be predicted with reasonable accuracy using advanced numerical finite element analysis.