This extensive work was carried out to demonstrate the variations in inelastic displacement ratios (IDR) of degrading concrete structures under repeated earthquakes. While the development of sophisticated methods for assessing the seismic demands under repeated earthquakes has been ongoing, these methods are still based on simple material models. None of these models consider the degradation effect. Similarly, the seismic provisions currently in use do not consider repeated earthquakes. They assume that the structure resists the main shock only. The stiffness and strength of the structure is reduced as a result of initial loading, and likewise, the retrofitting of the structure cannot be provided in a brief time; hence, the successive shocks cause more structural damage or failure. Material deterioration effects are evident in structures that experience repeated earthquakes. Even though they survive under the main shock, they collapse under smaller aftershocks. This study comprises the simulation of repeated earthquakes, running simulations with degradation taking into account, preparing IDR curves, and comparing the results that show repeated earthquakes have a profound impact on the IDR of concrete structures compared to single earthquakes, and degradation provides significantly lower IDR values for both single and repeated earthquakes.
Akdeniz et al. (Thu,) studied this question.