Failure Modes Analysis Of Structure In Progressive Collapse Under Severe Ground Motions

It may provide a new idea for this method to study structural progressive collapse mechanism and the overall damage evolution under different seismic excitation. In view of the variance of structural responses caused by the randomness in ground motions and the effect of the proposed randomness on the failure of structures in different sectional damage models, it is necessary to perform the statistical analysis on the failure modes of structures under the action of different ground motions, and thus, some conclusions with statistical significance can be attained. The greatest harm of mainshock-aftershock sequence earthquake to the structure is that the mainshock has caused a greater damage to the structure, and then cumulative damage effect of the aftershock may increase structural damage, change the structural failure modes, and cause structural collapse. Therefore, how to quantitative assess the additional damage on the structure under the action of aftershock and analysis the influence of mainshock-aftershock on the structural failure modes has become an important problem for earthquake engineering.Incremental dynamic analysis (IDA) based the platform OpenSees for a reinforced concrete plane frame structure. First, the structural failure modes under the action of different ground motions were investigated with three sectional damage models. A new failure mode was obtained with the statistical method based on weighted rank sum ratio. The differences between the new failure mode and the weakest failure mode were described through defining the similarity. And then the effect of the main-aftershock sequence of different aftershock probability of exceedance on structural failure modes, and the importance factor considering the cross-section of the floor position was introduced, then redefined the damage raion of the structure under the ground motion. Finally, the damage of the structure under aftershock was assessed probability based on probabilistic seismic demand model.The results show that the failure modes obtained with different sectional damage models are generally similar. Based on the standard design response spectrum, the position of the first failed section is the same when the discreteness between the different input ground motions is smaller. The proposed failure mode shows significant differences from the weakest failure mode. Moreover, the proposed failure mode exhibits statistical significance. With the increase of exceeding probability of aftershocks, the cumulative damage of aftershock on the structure is more significant, and it should not be ignored in the design of structure. Compared with structural under mainshock, it may not necessarily increase a lot of failed section numbers under aftershock. When the damage ratio under mainshock is larger, structural collapse has nothing to do with the grade of intensity the aftershocks.