Collapse of Damaged Steel Building Frames because of Earthquakes

Abstract

The present study investigated the vulnerability of damaged building frames to sway collapse under seismic excitation. Crucial to the investigation was the identification of the critical damage scenario that triggers complete or partial sway collapse. This was accomplished by a simulation procedure aided by genetic algorithm, plastic analysis, and pushover analysis of the frame. The procedure, genetic plastic pushover analysis (GPPA), enabled creation of various potential damage scenarios that lead to the collapse of the frame under response spectrum compatible earthquakes of different intensities, represented by the peak ground acceleration (PGA) values. The damage scenario, which required the least value of the PGA for collapse, was identified as the critical damage scenario. If a frame had a damage scenario the same as the critical damage scenario, then it was likely to collapse under a similar earthquake having a PGA equal to the least value of PGA as described previously. A 1-story steel building frame was used as an illustrative example to demonstrate the application of the method. The result of the study was validated by performing a nonlinear time history analysis for response spectrum compatible ground motion, and by comparing analytical prediction with existing test results available in the literature. The numerical results showed that there exist certain localized damages in a building frame that may trigger collapse, leading to complete failure under an earthquake. If the damage of the building can be evaluated beforehand, the building’s vulnerability to collapse under future earthquakes can be predicted using the methodology presented in this paper.