The characteristics of near-fault ground motions are significantly different from far-field ground motions. There are also great differences in the damage of concrete structures caused by these two kinds of ground motions. Earthquake damage indicates that the damage of concrete frame structures subjected to near-fault ground motions is more serious and collapse mechanism is more complicated. In this paper, the traditional alternative path method (APM) in the analysis of collapse was improved. Collapse mechanism of reinforced concrete frame was studied by numerical simulation method. A typical ten-story reinforced concrete frame model was established. Three harmonic waves and three practical near-fault ground motions were selected as acceleration time history input. The results show that different damaged parts of structure caused by strong earthquake have little effect on the final collapse mode when the structure is under free vibration. The failure mode of columns subjected to different ground motions is almost the same. Simple harmonic excitation whose period is close to the predominant period of ground motion can approximately simulate the failure mode of structure caused by earthquake.
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