Effects of soil-structure interaction on seismic performance of a low-rise R/C moment frame considering material uncertainties

Abstract

This study investigated the effects of soil-structure interaction (SSI) on the performance of low-rise reinforced concrete (R/C) structures subjected to earthquakes. The uncertainty of material properties, such as steel yield and concrete compressive strengths, was addressed using the Monte Carlo simulation with Latin hypercube sampling. A planar R/C moment frame of three bays and three stories was subjected to 20 selected ground motions for this purpose. In the flexible-base models, the soil was modeled with springs and dashpots, and the mass and moment of inertia of the footing were lumped at the bottom of the column. In contrast, for the fixed-base model, the bottoms of the columns were fixed in all translational and rotational directions. A parametric study was conducted for the shear wave velocity of soil, varying from 1000 to 50 m/s. The responses of the flexible-base and fixed-base models were compared in terms of the ductility, maximum interstory drift, and maximum total drift (ratio of top displacement to building height) for three performance levels in ASCE 41-17: intermediate occupancy (IO), life safety (LS), and collapse prevention (CP). The pushover analysis results indicate that a higher shear wave velocity leads to a high er ductility capacity. The uncertainty of the material properties produces an extensive range of ductility factors. The seismic drift responses of the flexible-base models are larger than those of the fixed-base model, particularly in the range of shear wave velocities less than 180 m/s (i.e., soft soil). From the failure probability analyses, the threshold shear wave velocity below which the effects of SSI should be considered is approximately 180 m/s for IO and 100 m/s for both LS and CP.