Damage Sensitive-Stories of RC and Steel Frames under Critical Mainshock-Aftershock Ground Motions

Cumulated damages caused by the past earthquakes lead to structural damage. Ensuring the safety of individuals – especially in highly populated buildings – and the continuity of immediate occupancy in consecutive earthquakes with short periods is an important matter to consider in seismic design codes. The use of strategies, such as identifying damage sensitive stories, can help ensure the safety of such buildings. This paper identifies damage sensitive stories for reinforced concrete (RC) and steel frames based on damage distribution caused by critical mainshock-aftershocks. In this regard, short, medium and relatively tall steel and RC frames with 3 and 5, 7, 10, 12 and 15 stories are analyzed under single and successive scenarios in the OpenSees software. Damage distribution of frames show that the upper stories in frames with low and medium height and middle stories toward higher stories in relatively tall frames are damage sensitive stories. Also, when tested against successive shocks, the initially-damaged steel frames experienced more destruction than RC frames. In severe conditions, the increased damages of steel frames were about 57%, 94%, 42%, 33% and 84% more than those of the RC frames. Moreover, steel frames with 15 stories were better able to sustain additional damages than RC frames (by about 1.84 times).