A pseudo-static method for seismic responses of underground frame structures subjected to increasing excitations

Abstract

The determinant factor for the seismic response of underground structures is the deformation of surrounding soil, which is different from above-ground structures. Considering that the existing deformation-based seismic design methods for underground structures are based on elastic hypotheses, this study proposes an improved Finite Element method called New Pseudo-Static Analysis (NewPSA) to predict the nonlinear behavior of underground frame structures subjected to increasing horizontal seismic excitations. A new method for one-dimensional(1-D) seismic analysis of soil layers is proposed to calculate the distributions of displacements and shear stresses along the depth in the free-field with increasing bedrock motions. Pseudo-static Finite Element analysis is then carried out by imposing the distributions of body forces derived from the 1-D analysis. A series of comparisons were made to validate the applicability of the proposed method. Its prediction capacity was also compared with that of a well-known method. The proposed method is able to predict the nonlinear performances of underground structures under horizontal earthquake loadings. Particularly, similar to the push-over analysis of above-ground structures, the method has the potential to predict the seismic capacity of underground frame structures subjected to design seismic loadings.