Numerical investigation of steel moment resisting frames with reduced Cross-Section under progressive collapse

Abstract

The progressive collapse is a random and complex event. The exact simulation of the progressive collapse scenario is complex because of its complicated nature and the economy involved. Considering these limitations, sub-assemblies are widely used as experimental setups to analyze progressive collapse. However, numerical models help to study progressive collapse behaviour cost-effectively. The present study carried out a numerical investigation using a finite element model developed in ANSYS® Workbench. The effect of asymmetric spans with reduced beam sections having span ratios varying from 1 to 1.5 was studied as per the FEMA 350 and United States Department of Defense guidelines. The beam-column sub-assemblies do not consider the effect of lateral confinement provided by the transverse beams. Hence, the effect and contribution to progressive collapse resistance offered by transverse beam joining at the removed column with span aspect ratio varying from 1 to 1.5 were evaluated. The present study showed that lateral confinement significantly enhanced the load-carrying capacity by 88%. The onset of catenary action was found to be earlier when the span ratio of asymmetric span increased from 1 to 1.5, reducing the contribution of flexural action. It was identified that catenary action was a reliable mechanism at later stages of loading when the span to depth ratio was varied from 15 to 20.