Influence of foundation flexibility on seismic fragility of reinforced concrete high-rise buildings

This study investigated the effect of foundation type and layout on the seismic vulnerability of tall reinforced concrete buildings using fragility curves. To this end, the seismic fragility of 12-, 18-, and 24-story buildings sitting on shallow and pile foundations (i.e., with rigid and flexible pile caps) were evaluated. The uncertainty in the structural and soil properties was assessed by using the Latin Hypercube Sampling method and the seismic uncertainty was incorporated using several nearand far-field earthquakes. The results showed that the use of flexible pile caps reduced the seismic fragility and base shear of superstructures compared to the piled structures with rigid pile caps. Furthermore, the flexible pile caps improved the seismic performance of pile foundations by reducing the earthquake-induced pile head forces and deflection. The findings of this study can help the engineers to select the appropriate foundation layout to optimize the seismic performance of buildings.