Investigating the Progressive Collapse of Steel Frames Considering Vehicle Impact Dynamics

The present study aims to investigate the progressive collapse caused by a vehicle impact to the columns of a steel structure. Two lateral load-resisting systems were examined including a medium moment frame system and a dual system consisted of the medium steel moment frame and the special eccentric braced frame. 4-, 8-, and 12-story buildings were considered. It was assumed that the structures were located in Tehran and were designed according to ASCE 7, AISC 360, and IBCS 2800. Three different approaches were evaluated and compared in terms of the progressive collapse. In the first approach, i.e., nonlinear time history analysis, the critical impact forces needed for column failure were determined by trial and error. Then, the corresponding critical velocities for vehicles with three different weights, i.e., 4, 8, and 12 ton, were obtained from the basic impact equations. The second approach was the progressive collapse analysis via a sudden column removal using nonlinear dynamic analysis. The third approach was similar to the second one, except that the column was removed after the impact. In this case, the impacted column and the neighbor members underwent considerable plastic deformation and damage. The results indicated that the third approach, which provides the most realistic simulation, suggests the most critical situation for the impacted structure in terms of the number of plastic hinges and the maximum deformations.