Research On Dynamic Characteristic And Seismic Response Of Prestressed Concrete Cable-stayed Bridge With Cooperative System

The prestressed concrete cable-stayed bridge with cooperative system is widely used,depending on its advantages of improving the overall stiffness of the cable-stayed bridge,meliorating the internal force of the girder, the economic application and construction convenience. In the past, most researches on this kind of structural system are mainly about the static performance, the research on the dynamic characteristics and the seismic responses of the structural system are few. As a key factor in the transportation network, Bridge is the important link of rescuing the people’s lives and properties and resuming production as soon as possible and reducing the secondary disasters in earthquake. Therefore,it is necessary to study the dynamic characteristic and seismic responses of the prestressed concrete cable-stayed bridge with cooperative system.The three dimensional spatial dynamic calculation model was established by Midas Civil and Ansys in this thesis. The mechanical properties and seismic responses of the structure on dynamic analysis are studied based on a prestressed concrete cable-stayed bridge with cooperative system in service.The main works involved in this research are as follows.(1) The finite element analysis software Midas Civil and Ansys were used to establish the dynamic model of the whole bridge. The first ten natural frequencies and modal of the structure are obtained.Based on the measured data and observation results acquired by the actual bridge static and dynamic load test, it modify the finite element model by using a first-order optimization algorithm in the Ansys optimization module. The calculated results of modified model are in good agreement with the measured data.(2) The influences of the tower beam connection stiffness, the setting of the auxiliary pier and collaborative span on the dynamic performance of the structure was studied based on the modified model. The results show that with the connection stiffness along longitudinal direction increases, the frequency of the longitudinal floating modal increases. When the connection stiffness is more than a certain value, longitudinal vibration modal does not appear obviously,but coupled with vibrations of other directions. The setting of the auxiliary pier has less influence on the first order longitudinal floating frequency,and has certain influence on the transverse vibration and the vertical vibration of the structure. The vertical vibration and lateral vibration frequency of the structure have different degree with the increase of the stiffness of the cooperative part. The change of the span is mainly influenced by the vertical stiffness of the structure.(3) Seismic response was researched by means of response spectrum analysis method based on the modified model. And then, the general rules of seismic response under waves in longitudinal,transverse,vertical direction and their combinations are acquired. The influences of the parameters such as tower beam connection stiffness and collaborative span on seismic response of the structure are analyzed based on the response spectrum method as well. The results show that increase of tower and girder longitudinal connection stiffness can significantly reduce longitudinal displacement of the girder under the action of the longitudinal seismic wave, but the internal force of the structure increases correspondingly; cooperative system cable stayed bridge can maintain good seismic performance through the adjustment of cooperation part stiffness and collaboration span.(4) Dynamic history analysis method was used to analyse the response of structure under synthetic seismic wave based on the modified model. The calculation results of reaction spectrum method and time history analysis method are compared. Calculated results in two methods are very close,which proves the correctness of the calculation results. The research results can provide a reference for the design of the prestressed concrete cable-stayed bridge with cooperative system.