Seismic Response Analysis On Long-span Continous CFST Arch Bridge

Three methods of the seismic analysis, the response spectrum method, the time history method and the random vibration method, were introduced firstly. Based on the time history analysis theory, the direct acceleration method and the large-mass method were extended to make investigation to the multi-supported seismic analysis of long-span bridges.Two simplified models were extensively investigated to examine the spatial effects on the structural seismic responses. The effects of the primary factors such as excitation pattern, seismic waves, wave velocity, geonomic nonlinear and spreading direction of the earthquake wave and so on have been investigated. Based on the large-mass method, the seismic responses analysis of long-span bridges under multi-support excitation were realised on the platform of commercial finite element program Midas/Civil.The input mode of structure seismic analysis under traveling wave effect and multi-support excitations was discussed, and the application of the input of the large mass method was mainly researched.The calculated results reveal that the key points of side arch also may be the reference points of the long multi-span arch bridge under action of seismic excitation, which should be considered in engineering design. The seismic responses of the bridge varies greatly with different excitation patterns of earthquakes, especially traveling wave effect can improve fixed pier, so three-dimensional seismic wave, the travelling wave excitation and the multi-support excitation should be considered.It is necessary to make an indepth study and analysis to the seismic performance of these bridges, which is an important factor for safety.In this thesis, choosing a3-span continuous through concrete-filled steel tubular(CFST) tied-arch bridge as project background, carry out the seismic response with the finite element analysis software Midas/Civil.The study includs the following aspects:1.The finite element model of the structure was built through reasonable simplification, and vibration mode were studied by using the famous program of Midas/Civil.2.The corresponding dynamics equations were established to describe the bridge’s dynamic actions while appropriate method was chosen to solve these equations. 3. Three acceleration time-history curves whose amplitudes have been adjusted including Tianjin wave, Taft wave and El-Centro wave were chosen to analyze seismic time-history response under the uniform excitation, the travelling wave excitation considering geometric nolinear by using three-dimension finite element model.4.Inputing the modified acceleration time-history curve along longitudinal direction, longitudinal and transverse direction and3D direction, the internal force and displacement of the control sections are gained.5. Taking non-consistent excitation travelling wave effeet into account, the consistent excitation and non-consistent excitation earthquake time-history acceleration were inputted, and the seismic reactions of the bridge under the different wave velocity were compared to explore the impact of the spatial variability of earthquake ground motions in large-span bridges.6.The artificial waves involved in spatial and temporal variability were used to analyze seismic time-history response under the uniform excitation, the travelling wave excitation and multi-support excitation comparing results of different patterns of earthquake excitations by using three-dimension finite element model and the application of large mass method was mainly researched.