Modification of Park-Ang Damage Index to Accommodate Effect of Aftershocks on RC Structures

Seismic design codes do not consider the effects of aftershocks on structures.Moreover, most damage estimation methods disregard the effects of consecutiveearthquakes. Recent earthquakes have demonstrated that the aftershocks can causemajor damage to mainshock-damaged structures. After a strong seismic event, itshould be determined if a mainshock-damaged building is safe for reoccupation inthe event of aftershocks. This study examined the effects of both the main shock andaftershocks on the damage index of reinforced concrete (RC) structures. Recordsfrom ۱۹ mainshocks that occurred in the Japan seismic region with momentmagnitudes of greater than ۴ were examined. More than ۱۰۰ acceleration timeseries from these events (mainshock + aftershock events) were applied to evaluatethe damage index. Seismic damage analysis was performed on a series of RCcolumns and RC frames. The natural period of these structures varied from ۰.۱ to ۲.۵s. The damage index introduced by Park and Ang was employed to estimate thestructural damage. Acceleration time series were applied to the structures in twosteps. First, only mainshocks were applied to the structures and the damage indexwas obtained. Next, both the mainshock and aftershocks were applied to thestructures and structures damaged by a mainshock were analyzed under periodicaftershock events. The results showed that the increase in structural period and thePGA of the aftershocks amplified the damage index under the effects of theaftershocks. A modification to Park-Ang damage index is proposed using a dimensionlessterm to accommodate the effect of aftershocks.

کلیدواژه ها:

Aftershock ، Damage Index ، RC structures ، Natural Period