Pushover And Seismic Performance Research On Long-span Continuous Rigid Frame Bridge With High-rise Piers

As is known to all, bridges are important projects in an traffic system,so it is very necessary to ensure the working performance when the earthquake happens. With the emergence of large numbers of long-span continuos rigid frame bridges with high-rise piers in many regions, to study on the seismic performance of this kind of bridge become incresingly important. At the same time, simple and reliable methods are needed for evaluation of seismic performance to save engineers a lot of time and energy. Pushover is a simple and convenient method in the seismic performance evaluation of building structures and has been widely applied, but it’s remained to be seen whether this method is suitable to the long-span continuos rigid frame with high-rise piers or not, so some research on this method is done tentatively in this paper:(1) Induction and summary of the earthquake damage of bridge and seismic design method based on the performance-based seismic design theory have been carried on. In addition, the concept of the seismic design based on performance was introduced and the development of Pushover Method was summarized.(2) Introduction of the basic principle and steps of the pushover was made, and the procedure of capacity spectrum to evaluate the seismic performance of bridge was descriped. Considering the high weight of superstructure, the inverted triangle loading mode and uniform loading model are improved. Then the three loding modes(concentrated fore mode, improving-inverted triangle and uniform mode) were used to analyze a long-span continuous rigid frame bridge with a 80-m high pier. Comparing the results of Pushover with dynamic elastic-plastic time history by Chopra’s improving capacity spectrum in different earthquake magnitude(0.2g 0.4g 0.6g),we find that the results of inverted triangle model closer to the results of time-history analysis method in the longitudinal direction of bridge, and that concentrated force mode is more accurate than the other in the transverse direction of the bridge.(3) Considering the distribution shape of modal and more modal, the modal combination of lateral force is no more than the first-modal results. Furthermore, the displacement results of first-modal loading mode is relatively close to MPA, however, MPA is more reasonable than first-modal loading mode with Pushover Method in the aspect of base shear.(4) At last, Combining with the standard response spectrum, seismic performance of this bridge is evaluated with the first-modal loding mode, and discuss the damage of plastic hinge in the 9 degree earthquake.