SSI effects on seismic response of rc flat-bottom circular silos

Abstract

The main purpose of this study is to evaluate how different soil/foundation conditions affect the design forces and seismic behavior of circular silos, depending on their aspect ratios. A finite element (FE) analysis using solid elements was employed, utilizing the commercial ANSYS program. The numerical model considers the effects of bulk material-silo wall interaction, as well as the effects produced between the silo foundation and the underlying soil. FE analyses were performed for six different aspect ratios under a fixed base condition and four different soil/foundation conditions. The obtained findings are comparatively discussed in terms of the overpressures and the horizontal displacements of the silo wall. The findings show that squat silos were not significantly affected by the soil-structure interaction (SSI) in terms of overpressures. However, the seismic behavior of squat silos is similar to that of slender silos for soft soils. SSI becomes effective on the overpressure response of slender silos, leading to significant increases in horizontal displacements due to the reduced foundation/soil system stiffness in all squat and slender silos. Due to SSI, permissible displacement limits can easily be exceeded, and second-order effects can be revealed when evaluating the designs of silos.