Analysis Of Seismic Responses Of A Suspension Bridge At P1 Level

As the great development of national economy, the long-span bridge is built more and more. The suspension bridge, which has super long span for its characteristics of cable bearing, is favored in design for the technologic and economic superiority than the others. As a bridge of lifeline engineering, seismic design is an indispensable part in bridge design because of seismic influences on the safety and reliability of the structure. Plentiful studies are reported on the dynamic behaviors and the seismic design methods, and more focuses are on the seismic responses of suspension bridges. Because of different structural models, excitations and methods in those studies, there are different results. In order to analyze the seismic responses of a long-span suspension bridge, the time-history dynamic analysis is used, which can directly input the real records of earthquake waves and reflect the factual dynamic behaviors of structures subject to earthquake wave so that one can observe the dynamic responses of structures in the whole period of earthquake. The three dimension model of the long-span suspension bridge is firstly developed using ANSYS. Based on the 3D model, the influences of the prestress of the main cable on the preliminary equilibrium configuration are analyzed, and that of stress stiffening and large deflection on its mode shapes and frequencies are also done. Then programs for the artificial seismic wave are developed in MATLAB language. These programs are utilized to simulate artificial waves including wave passage effect and spatial coherence effect respectively. Finally based on the 3D FE model, the nonlinear seismic responses are calculated by means of time-history dynamic method, including consideration of spatial variation. Upon these results, a comparison is drawn among dynamic responses of bridge to the uniform excitation, traveling effect input and multi-support input; and an attempt is made to analyze the influences of large deflection on the seismic response of the bridge in comparison with that of small deflection.