Effect of soft sediments modeling on the seismic response of a 3D mid-rise RC building: high-resolution physics-based ground-motion simulations and empirical factors

Abstract

Ground-motion simulations have progressively become a key resource in earthquake engineering. Nevertheless, the challenge of accurately simulating ground motions in regions with low shear-wave velocities, such as basins and shallow sediments, persists and is often constrained by the associated computational demands. Motivated by the potential unavailability of suites of simulations resolving low velocities for a specific region or site of interest, this work assesses the implications of using different approaches for modeling low shear-wave velocities on structural response. Two methods are investigated: one relies on simulation models capable of resolving low shear-wave velocities, while the other combines simulations that resolve high shear-wave velocities with empirical site amplification factors. An M7 Hayward Fault strike-slip earthquake in the San Francisco Bay Area and a three-dimensional ten-story reinforced concrete building are used as case study. Findings from this work demonstrate significant differences in the prediction of ground-motion intensities and building responses (from moderate to extensive damage) when different modeling methods are employed. Such differences manifest at sites with low shear-wave velocities as well as at stiff sites in their vicinity. This is caused by the concurrent effect of the specificity of the seismic velocity structure for the considered region and wave propagation, which is adequately captured only by the simulation model incorporating the (target) low shear-wave velocity. Evidence from this study indicates that empirical factors should be used and processed (i.e., transfer functions tapering) with consideration for the specific geological characteristics of the domain of interest, especially in regions lacking representation in the databases of historical records, such as the San Francisco Bay Area. From a structural engineering perspective, these insights contribute to a better understanding of the complexities involved in soft sediment modeling and its implications in structural engineering applications.