Seismic fragility assessment for existing RC frames considering structure-soil-structure interaction

Abstract

Neglecting structure-soil-structure interaction (SSSI) would introduce errors in the seismic assessments of structures within densely built areas. However, the study on probabilistic seismic fragility assessment considering SSSI remains scarce. Taking typical RC frames built on a common medium-stiff soil with multiple layers, this study conducts probabilistic seismic fragility assessments incorporating SSSI on these RC frames with and without the possibility of seismic pounding by employing nonlinear high-fidelity finite element models. Seismic fragility assessments are also conducted on the fixed-base RC frames and RC frames considering soil-single structure interaction (SSI) for comparison, with uncertainties in RC frames and seismic excitations quantified using Latin hypercube sampling. For RC frames without seismic pounding, compared to those adopting fixed-base assumption and those considering SSI, the exceedance probabilities of the immediate occupancy (IO), life safety (LS) and collapse prevention (CP) states for those considering SSSI are consistently lower across all seismic intensities. For RC frames with seismic pounding, the influence of SSSI on their median seismic capacities is slight, whereas SSSI increases the exceedance probabilities for their LS and CP states under low seismic intensities. Neglecting SSSI in the seismic design of typical equal-height RC frame clusters without the possibility of pounding on medium-stiff soil conditions can be considered a conservative practice.