Seismic Fragility Analysis of Steel Moment-Resisting Frames (MRF) Designed in Canada in the 1960s, 1980s, and 2010

A typical steel moment-resisting frame (MRF) of six stories was designed for three different provisions of the National Building Code of Canada (1960s, 1980s, and 2010) and for two different cities (Vancouver and Montreal). Numerical models were developed in OpenSees to understand the seismic performance of the structures. These models accounted for strength and stiffness degradation through the appropriate representation of the beam-column connection behaviour. The beam-column connection models were calibrated against experimental results available in the literature. The behaviour of the buildings was evaluated through pushover and nonlinear time history analyses. The 1960s and 2010 steel MRFs of both cities presented strong-column-weak-beam behaviour and the failure in the connections provoked the collapse of the structures. The 1980s steel MRFs of both cities showed column sway mechanism. Fragility curves were developed for the steel MRFs using nonlinear time history analyses.