Abstract
In Japanese seismic design for railway structures, the surface ground is classified into eight types by its natural period, which is computed based on the initial rigidity of each soil layer. If the level of the input earthquake motion is larger, however, the rigidity of the surface ground becomes smaller. The accuracy of type of soil is, therefore, affected by the nonlinear characteristic of each soil classification. In this paper, we propose the method to calculate the equivalent natural period of surface ground taking into account the soil classification and try to classify the ground based on the period. We verify the efficiency of our proposed method by comparing with the results obtained using the type of soil shown in the current design standard for railway structures.
