Performance of RC Frames with Mass and Stiffness Irregularity under Sequential Ground Motion

The seismic design codes consider only single earthquake events, ignoring the possibility of multiple earthquakes. In case a structure suffers damage during first event and prior to its repair more aftershocks occur the structure may collapse. An elaborative directive study on the inelastic seismic response of 11storey RC (2-D) moment-resisting frame having mass irregularity at sixth floor, and stiffness irregularity in sixth story has been done has been done. The frame has been examined under a sequence of a main shock followed by six aftershocks. Time history synthetically generated from the design response spectrum explained in IS-1893 Pt II: 2016 has been taken for non linear dynamic analysis with the help of SAP 2000 software. A comparison is done to understand the inelastic response of the frame taking into account the location of plastic hinges, maximum top displacement, residual top displacement, and storey drift. It is seen that the structure with the stiffness irregularity is the most vulnerable amongst all.