Evaluation of performance of post-tensioned special steel moment resisting frames against progressive collapse

Due to Inappropriate performance of the moment welded connections in the Northridge earthquake in 1994, different details for moment connections was proposed to make more ductile response against earthquake loading. Using Post-tensioned (PT) connections in steel moment frame was approach to achieve to more ductile response that different methods for these connections have been proposed by the researchers. Experimental investigation demonstrated that post-tensioned connections to have strength, stiffness and proper self-centering ability and high energy dissipation capacity if used energy dissipating element. In this study, we used three types of structures with the number of 15, 10, 5, stories to study the progressive collapse. Nonlinear analysis of structures has been performed by OPENSEES software. The analytical results show that the failure of columns located in the corner of the plan has more intense effect on structures. Also, with increasing number of stories, the vertical displacement decreases in the connection above the removed column, which indicates that redistributing the unbalanced gravity loads due to column removal in structures with a greater number of stories is better. In the 5 and10 story special moment frame in the corner column removal scenario rotation of the beam adjacent the removed column is beyond the corresponding rotation of the life safety performance level, whereas the value of rotation in PT frame is significantly less than level of life safety performance