Capacity-spectrum-based Displacement Seismic Design

Displacement based seismic design method, developed in recent years, starting from performance target of structure and target displacement, has arrested the attention of the civil engineers. But a great number of displacement based seismic design procedures proposed by present scholars are very complicated with iterative procedures, due to their use of equivalent elastic structure with efficient stiffness and viscous damping instead of the nonlinear structural response. Based on capacity spectrum method improved by Fajar, a simple displacement based seismic design method suitable for provision of our seismic codes is presented in this paper. The seismic demand spectrum is obtained by using acceleration spectrum specified in current seismic design code for highway engineering (JTJ004 89). A bilinear force displacement model with a post yield stiffness ratio of 5% is used to obtain the capacity spectrum of the seismic structure. Considering the given target displacement and ductility demand, the seismic design can be done easily without linear elastic substitute structure and iterative procedures. An illustrated example proves that the proposed method in this paper is a simple but efficient displacement based seismic design method.