Effect of the soil-structure interaction on performance assessment of the energy-based cumulative damage index in concrete reinforced frames

In most of the conventional design methods, the soil beneath the structure is assumed to be rigid, but this assumption is not true in reality. Up to now, many studies have been performed concerning the interaction effect on the structure response but the effect of this phenomenon on the structure damage has not been considered seriously. In this research the effect of Kratzig non-cumulative damage index which is an energy-based damage index, is investigated for target ductility levels of 3, 4 and 5 in the 5, 7,10,12,15, 18 and 20-story concrete moment resisting frames and under 7 different accelerometers. The soil beneath the structure is also modeled using the cone models. The results show that in the low-rise frames, which have lower slenderness, ignoring the effect of soil-structure interaction is on the behalf of safety, but with increase in the height of frames (increase in slenderness) together with increased ductility, the effect of soil-structure interaction causes increased damage at some stories and this increase in some points reaches to 14%, especially at the upper stories and this issue indicates the importance of taking into the account the soil-structure interaction in slender structures. For medium soils, in most cases the responses are very close to that of the rigid case. But investigating the overall damage criterion in the frame, the effect of soil-structure interaction causes reduced damage index. With the energy-based cumulative damage index, the effect of soil-structure interaction on the damage index is greater in the beam element than the column element