ABSTRACT
With the vigorous development of bridge construction in the western region, there are more and more bridges with special structures such as high and low piers and large spans. Especially for areas with complex terrain, high pier structures of unequal height are often used. For continuous rigid frame bridges with high piers, in order to reduce the secondary internal forces caused by temperature and concrete shrinkage and creep, two-limbed thin-walled piers with lower longitudinal rigidity are usually used. When the pier height is high, in order to ensure the longitudinal stability of the structure, longitudinal transverse beams are usually added between the two-limbed piers to improve the overall longitudinal rigidity of the bridge. The arrangement of longitudinal transverse beams not only improves the static stress state of the bridge structure, but also affects the dynamic characteristics of the entire bridge. Especially under the action of seismic loads, the seismic response of the structure will change significantly. In order to study the influence of main pier and transverse beam parameters on the seismic performance of high and low pier continuous rigid frame bridge, the finite element Midas civil model for dynamic analysis of the whole bridge is established based on the Xialong Wushui super large bridge of Zhang-Ji-Huai high speed railway (prestressed concrete double thin-walled high and low pier continuous rigid frame bridge with a span of (94+168+94) m). Artificial seismic wave, which is acquired on the base of the design seismic response spectrum, has been performed time-procedure analysis, and the variation law of bridge natural vibration characteristics and seismic response influenced by parameters such as main pier wall thickness, pier height ratio and the number of transverse beams have been obtained. Moreover, the fitting response surface function and objective optimization function has been deduced according to the different distribution positions of the three transverse beams along the pier height, so as to optimize the seismic performance of the bridge. The results show that with the increase of the main pier wall thickness and pier height ratio, the natural vibration period of the first few orders of the bridge gradually decreases, while the high-order mode natural vibration period basically tends to be the same. When the wall thickness of the main pier is 2.75m and the pier height ratio is 0.67, the seismic response of the key section is significantly reduced compared with the original structure. The installation of tie beams has a greater impact on the first mode of the structure, while the other modes of the bridge are less affected by the tie beams. Increasing the number of tie beams can significantly reduce the seismic response of the bridge. With the location combination of three tie beams (down/middle/up = 0.2181H/0.5H/0.85H, respectively), the seismic performance of the bridge is optimal.
