Progressive collapse analysis of steel frame structures considering influence of steel connection

Most progressive collapse analyses of steel frame structures exclude the failure of connections and axial force-moment interactions of connections. A computational efficient steel frame model was proposed to study the progressive collapse behavior of steel frame structures. The model proposed was verified by experimental results. Based on the models above, energy-based Pushdown analysis method was utilized to study the ultimate progressive resistance capacity, failure mode and progressive collapse resisting mechanisms of two typical ten-story steel frames buildings. Research results show that connection models neglecting axial force-moment interaction effect may overestimate the ultimate progressive resistance of steel frame buildings. Typical collapse modes of steel frame structures are horizontal collapse mode induced by buckling of steel columns and vertical collapse mode induced by fracture of simple connections under cantenry actions. The steel frames suffer from horizontal collapse mode with minor vertical displacement when removal column is connected by rigid joints. The major progressive collapse resisting mechanisms is axial forces and moment at beam end and vierendeel action resulting from uneven distributed axial forces at different stories. The steel frames suffer from vertical collapse mode with large vertical displacement when removal column is connected by simple joints. Catenary action of steel beam and membrane action of steel-composite floor contribute significantly to the resisting mechanisms before and after the fracture of simple connections. © 2015, Science Press. All right reserved.