Research On Direct Displacement-based Seismic Design Of Continuous RC Bridge

Compared with classic design method, performance-based design is theoretically and practically appropriate. Not only the strength of structural component but also the capacity of displacement and energy-dissipation of structure under seismic and wind hazard are important parameters of performance-based design. Displacement-based seismic design is paid much attention to with easy concept and wide study. The main points of this dissertation are to present the improved method of assessing the target displacement of RC continuous bridge with circular section, review the procedure of DDBSD design method incorporating the improved method to calculate target displacement, and establish the FEA model to implement the nonlinear static analysis and nonlinear time-history analysis. The layout of the paper is as follows:The chapter1is the introduction of the development of seismic design in earthquake engineering around the world and improvement of seismic code in China; The basic concept, the principle in use and the design procedure of the classic design method;The brief basic concept, the principle in use and the design procedure of the DDBSD method, and the difference between the classic and the new. In addition, this chapter illustrates the main research content of dissertation.In chapter2A new improved method of assessing the target displacement of the RC continuous bridge is established based on material strain and curvature of the cross section of the pier taking account of the structure system and the relation of components of the structure. The stress-strain relation, strain-curvature relation and plastic hinge model are introduced to construct the target displacement function. Function of longitudinal target displacement of the bridge under different conditions and suggestions of calculating transversal target displacement are given.In chapter3, applying the content of chapter2we consider a design example to illustrate the procedure of a given circular section RC bridge of DDBSD method. It involves the determination of the longitudinal target displacement of the RC bridge. According to the relation of ductility and damping, the elastic over-damping displacement spectrum is established to calculate the natural period of substitute structure; Calculate the equivalent stiffness and then the strength demand to decide the desisn of the section. In chapter4Construct the FEA model of designed bridge according to the calculation of chapter3to implement nonlinear static analysis and nonlinear time-history analysis. On monitoring the strain of the critical section of piers of the bridge, the displacement capacity of the bridge is evaluated using nonlinear static analysis. With the nonlinear time-history analysis, the displacement response of the bridge structure under different PGA is given. The result can meet the need of the requirement.