Evaluation of Seismic fragility of infilled frames subject to mainshock/aftershock sequences

The purpose of this paper is to assessment the seismic fragility and residual capacity of reinforced concrete frame (RC) with masonry infills subject to mainshock/aftershock sequence in the far and near field ground motions. In standard incremental dynamic analysis (IDA), only the effect of the main shock in the analysis is considered, so the double incremental dynamic analysis (D-IDA) method is used to consider the after shock effects. double incremental dynamic analysis approach is used, based on the combination of the mainshock (MS) at different intensities with a set of spectrum-compatible aftershocks (AS) scaled in amplitude with respect to peak ground. In this study, 20 near field records and 20 far field records were selected. In each analysis, a same record has been used for the main shock and after shock. Also using the results obtained from incremental dynamic analysis, the frame residual capacity diagrams is defined and the infilled frame response is compared with bare frame at different intensities of the main shock. According to the results obtained for infilled, the seismic fragility of the reinforced concrete frame is greatly reduced due to the mainshock and aftershock. It can be said that when only 100% collapse occurs in the bare frame, the probability of the frame collapsing with the infill wall at the same intensity as PGA (maximum ground acceleration) for near and far field earthquake records is significantly reduced.