Effect of Soil–Structure Interaction on the Damage Probability of Multistory RC Frame Buildings with Shallow Foundations

The purpose of this study is mainly to investigate, through fragility curves, the effect of soil–structure interaction (when it is neglected during design) on damage probability. It also examines how realistic it is to conduct a performance estimation with rapid assessment methods without considering soil–structure interaction. Three RC frame buildings, with varying numbers of stories, were designed according to the Turkish Seismic Design Code, 2007. Incremental dynamic analyses of the considered structures, both with and without soil–structure interaction (SSI), were performed using 21 ground motion records to determine the damage limits. The cone model with springs was used to take soil–structure interaction into account. The discrete damage probabilities of each considered performance level were calculated, using statistical methods, in terms of elastic spectral acceleration, and continuous fragility curves were obtained. The results show that the effect of SSI on fragility was remarkable and that damage probability generally increases when soil–structure interaction is taken into consideration. The effect of site class becomes significant for life safety and collapse prevention performance levels. The increase in the probability of exceeding the collapse prevention performance level can reach up to 72% due to the existence of SSI. Thus, the results of damage estimation made without considering SSI can sometimes be significantly misleading.

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