Soil-structure interaction in the seismic vulnerability analysis of RC buildings. Application to a case study building located in southwestern Spain

Abstract

Most seismic vulnerability analyses do not consider the Soil-Structure Interaction (SSI). However, it has been proved that SSI does not equally affect all types of structures and all types of soils. The analysis of the state of the art reveals that SSI especially affects the performance of mid/high-rise buildings under soft/inelastic soil conditions. This leads to overestimating the capacity of buildings and to obtaining unreliable results. This paper aims to assess the soil influence in the seismic vulnerability analysis of a reinforced concrete (RC) building. Three models of a real case study building have been determined (low-rise (real), mid-rise and high-rise). A pre-code 1970s case study building, located in Huelva, has been selected. This building shares typical constructive and structural characteristics with most RC buildings constructed during that period. The 3D continuum model of the soil has been carried out to simulate its nonlinear behaviour. The most probable soil profile has been defined, observing a clayey soil. Therefore, the analyses have been performed under undrained conditions. Nonlinear static analyses have been carried out to determine the seismic capacity of the models through the finite element method (FEM). The damage has been assessed by means of the local procedure, defined in the European seismic code, and the global fragility procedure. The results have shown that the soil does not significantly influence the behaviour of low-rise buildings. However, in the case of mid- and high-rise buildings, the maximum capacity can be reduced by up to 10% and 30%, respectively.