Cable - Stayed Bridge Seismic Response Analysis And Mitigation And Isolation Studies

The extradosed cable-stayed bridge is one kind of newly developed bridge style in recent 20 years, it has the structural characteristies which is between the cable-stayed bridge and the continuous girder bridge.By now, the seismic response of this new style bridge style and the study of shock absorption design were seldom studied, especially for the extradosed cable-stayed bridge with single pylon and single-cable-plane. Therefore,studying on dynamic characteristics and shock absorption method for the new style bridge style, and making proposition and reference to the earthquake resistance design are a important and significative work. Establish the extradosed cable-stayed bridge model on the basis of the sifang Bridge located in Suijiang County, and conducted the following study by using the finite element analysis software SAP2000:(1) Establishing the beam element model and plate element model, and you can find the following conclusions through compare the natural characteristics of the two models:The first four modes of two models are basically the same, and all the bending vibration mode, the frequency of the maximum error is less than 1.6%; reverse mode appeared at the fifth-order modes in plate element, then the dynamic characteristics of the two models emergence of some differences. Considering the relationship between the purpose and efficiency, the paper plate element model used space as dynamic characteristics model, while in the response spectrum and nonlinear time history analysis of the overall selection of the backbone model for seismic analysis.(2) Make study of the dynamic characteristics of the extradosed cable-stayed bridge through a series of main control structure parameters,which include the boundary conditions,cable and the ratio between height of girder and length of main span. The results showed that:the consolidation of the connection form on pier and girder are the better seismic form for the sifang bridge; cable little effect on the dynamic characteristics; the ratio between height of girder and length of main span is mainly reflected in the girder mode of the vertical bending and torsionalvibration. (3) The E1 seismic response of the sifang bridge is computed with response spectrum analysis method. The effects caused by input ground motion,the higher vibration modes, joint effects of modal decoupling and effect of pile-soil are discussed. The results show that the response spectrum of each component in the sifang bridge under E1 earthquake are in flexible working stage.(4) The relative parameters in the analysis of time-history are introduced, and according to seismic standards of the sifang bridge checking the components of the bridge under the action of E2 earthquake.The results show that:in the E2 earthquake, all components are in the stage of flexible working,in addition to bearing can't meet seismic performane requirements.(5) Choosing a series of LRB and study its effects of the seismic isolation of the bridges. The results showed that:after joining the LRB, the vertical force of pier and pile cap and the vertical and horizontal force of the main tower are significantly improved,.but the performance of the vertical and horizontal isolation effect are different. When pier stiffness increases to a certain extent,the pier at the bottom basically stable internal forces. Draw the conclusions that from the perspective of increased stiffness of the sifang bridge's pier to improve the lateral seismic performance of the bridge is meaningless.Finally, getting better value for money by selected seismic bearing type according to the actual cross and vertical seismic capacity needs, and achieve the objection of reducing the size and amount of steel for the pier section by reducing the seismic force.