Collapse Analysis of Steel Frames Considering Fracture of Braces and End of Beams

Abstract

The 2011 Tohoku Earthquake ruptured multiple faults simultaneously, generating strong ground motions over a long duration at long periods. Such severe events have recently begun to be considered in structural design, requiring explicit calculation of the low cycle fatigue capacity and fracture point. This paper presents a numerical study of dual moment and braced frames, with either conventional or buckling-restrained braces. Both brace and beam end fracture is considered, and incremental dynamic analysis (IDA) used to determine the ultimate failure mechanism under extremely large ground motions. Fragility curves are generated, demonstrating the significant role that member fracture has on the seismic performance of braced frames.