Evaluation of blast-induced progressive collapse in steel structures with conventional braces, moment-resisting braces, and buckling-restrained braces using LS-DYNA software

Abstract

Today, considering the increased cases of terroristic operations, structural design engineers are starting to acknowledge blast-induced loads alongside other design parameters. Since a blast-induced load exhibits a much shorter period than the natural period of the structure, it is unlikely to induce general damages or stimulate the entire structure immediately after the loading, but rather local damages in individual structural elements are the common form of damage. These local damages, however, can set the scene for the gradual failure of the structure. The present study on structures with moment-resisting frames, buckling-restrained braces (BRBs), and conventional steel braces was conducted through an alternative load path (ALP, also known as column elimination) and exact modeling of the blast on the steel frames was undertaken using LS-DYNA software. In this work, the behavior of three five-story steel frames under a blast-induced load of 100 kg TNT equivalent at a distance of 10 m from the structural columns for a period of 100 ms was investigated. Results of analyzing the blast-induced effect on the frames showed that the frame equipped with buckling-restrained braces (BRB) exhibited improved overall peak displacement across the entire frame, peak induced velocity, and peak induced acceleration by 30%, 30%, and 46%, respectively, as compared to other steel frames exposed to blast loads.