Explosion and Fire Analysis of Steel Frames Using Mixed Element Approach

Abstract

This paper presents a mixed element approach for analyzing steel frame structures subjected to a localized explosion and followed by fire. Critical members that are subjected to direct action of explosion and fire are modeled using shell elements. Noncritical members that are away from the affected area are modeled using beam elements. The proposed approach is computationally efficient for modeling large-scale structures and accurate enough to capture detailed behavior of member inelasticity and instability associated with the effects of blast and fires. Section classification may change from static load to blast load because of the enhanced yield strength due to high strain rate. The beam element approach is found to overpredict the overall resistance of steel frame structures if local deformation of cross section occurred after the blast loads. Detailed finite element modeling of critical frame members is necessary to improve the accuracy of predicting the ultimate resistance of structures. The proposed approach is applied to study the ultimate behaviors of a steel column and a three-story steel frame under explosion and fire.