Dynamic Analysis And Seismic Response Control Research Of The Cable-stayed Bridge With CFRP Cables

Carbon Fiber Reinforced Polymer (CFRP) has caught the extensive attention of the civil engineering realm. These would be attributed to its good performances, such as light weight, high strength, corrosion resistance and fatigue resistance. CFRP material embodies some advantages when used in the super large-span cable-stayed bridges. On one side, the performance of high strength can be made full use. On the other side, the weight of super bridge will be lightened. At the same time, the spanning ability and the carrying efficiency will be heightened.At present, there's a few research and practical projects about CFRP cables used in cable-stayed bridge at home and aboard. And studies on dynamic test and seismic response control of the CFRP cable-stayed bridge are even more rarely. Consequently, under supports of the National Science Foundation of China (50678074), some researches on the modal test of the first CFRP cable-stayed test-bridge in China, on dynamic characteristics and seismic response analysis and its control of the large-span CFRP cable-stayed bridge have been done in this paper. Main research contents summarized as follows:1. Modal test and dynamic analysis of the CFRP cable-stayed test bridge. On the existing basis of static load tests, modal test was carried out on the bridge. Forms of the incentive, signal acquisition system and its method, and the main contents of the test and data processing are described in details. The calculated results of finite element model and the experimental measured results are analyzed comparatively. That the premise of reasonable arrangements for testing time, the acquisition of real-time test data are given duly by testing the bridge and its cables through pre-set measurement points on the bridge. With real-time test data, the impact of creep and shrinkage of concrete and CFRP on the mechanical properties of the test bridge will be analyzed. Under the axial stiffness equivalent principle, the bridge cables are replaced in the finite element model. Dynamic characteristics and seismic response of the cable-stayed bridge with different cables are analyzed.2. Analysis of nonlinear dynamic characteristics of the large-span CFRP cable-stayed bridge. This part summarizes the dynamic analysis of cable-stayed bridges and its research status, the main contents and common methods. On the basis of the existing research results of the group and tests, the finite element models of CFRP and steel cable-stayed bridge whose main span reaches 1000 meters-class are established and improved further. The main vibration frequencies and mode shapes of two kinds of cable-stayed bridge are analyzed comparatively with subspace iteration method.3. Seismic response analysis and seismic checking of the large-span CFRP cable-stayed bridge. This part describes the status about seismic response analysis of the CFRP large-span cable-stayed bridge, and elaborates on the general method for seismic design of long-span bridges and the seismic input. On the basis of dynamic analysis, the calculation model is amended further. Seismic response time-history and the response peak of key sections of two kinds of cable-stayed bridges are analyzed comparatively with time-history analysis method. Finally, seismic performances of two kinds of cable-stayed bridges are checked and evaluated.4. Research to seismic response control of the large-span CFRP cable-stayed bridge. In the exploratory study on seismic response control of the CFRP cable-stayed bridge, elastic connection and viscous damper are used. Several objective functions are selected, including: longitudinal displacement at the end of the main beam, vertical displacement at the middle of the main span, longitudinal displacement on the top of towers, bending moment and axial force at the bottom of towers, internal force and deformation of seismic reduction devices. By parameters sensitivity analysis, and considering objective functions' values comprehensively, flexible connection stiffness k, damping coefficient C and speed indexαare selected reasonably. Simultaneously effects of two measures for seismic response control applied in two kinds of cable-stayed bridges are analyzed comparatively.Through above study in this paper, the first-hand data for experimental analysis and the findings and conclusions from expansion study are obtained, which lays a solid foundation for later tests and performance evaluation of the CFRP cable-stayed test bridge. At the same time, some theoretical basis and practical reference are provided for analyzing dynamic characteristics and seismic performance of large-span CFRP cable-stayed bridge. The exploratory study for seismic response control of the large-span CFRP cable-stayed bridge is also done.