Progressive Collapse Analysis for Steel-Braced Frames Considering Vierendeel Action

Abstract

After middle or corner column removal, multistory frames exhibit different anticollapse mechanisms, and one of the most important anticollapse mechanisms is Vierendeel action. Based on instantaneous column removal tests, a dynamic nonlinear analysis considering damage, damping, and strain rate was used to simulate Vierendeel action under column loss. Considering the combined contributions of bending, catenary, and Vierendeel action, two calculation models of progressive collapse resistance are proposed for middle and corner column removal and the models are verified by a two-dimensional (2D), four-span steel moment frame. To fully utilize the contribution of Vierendeel action, a new braced system is proposed on the basis of the vertically braced system; the braced system was set up on the prototype structure of the Ohio Union building. The results show that Vierendeel action reflects the redistribution of internal force by the columns; the new braced system can fully utilize Vierendeel action to improve the performance of progressive collapse resistance. Using the new braced system, the load transfer paths after columns removal are as follows: the loads in the failed span are transferred to horizontal braces and then to the foundation by vertical braces.