Endurance Time Analysis of the Bridges with Unbonded Prestressed Piers

The endurance time method (ETM) is a novel dynamic seismic analysis, which employs intensified artificial earthquakes as the input. This method can ensure both the structural dynamic effect and computation efficiency when conducting the seismic evaluation of complex structural systems. Based on these advantages, this study investigated the applicability of ETM in the self-centering bridges incorporating prestressed concrete-filled steel tube (CFST) piers. A 3D finite element model of a typical four span continuous-beam bridge which adopted prestressed CFST piers was established by OpenSees software. Compared with the incremental dynamic analysis (IDA) results, the feasibility of ETM to predict the seismic response of self-centering bridges was validated. Also, the effect of prestressing force in piers on the seismic performance of self-centering bridge systems was studied by ETM. Numerical results show that ETM can be used in the seismic evaluation of bridges with prestressed self-centering piers. The seismic response, such as PT force and residual displacement, can be well predicted by using this method. In addition, the influence of prestressing force on the seismic response of bridges is related to the type of bearings and the intensity of earthquakes. For the superstructure, the displacement of main deck can be reduced by increasing prestressing force, but the shear force of fixed bearings increases accordingly. For the substructure, the piers with sliding bearings are less influenced by prestressing force, while seismic internal force of fixed piers increases with the occurrence of prestressing force. Therefore, it is necessary to comprehensively consider the structural system arrangement and seismic basic intensity of site during the seismic design of such bridges.