Seismic Response Analysis Of Large-span Steel Truss Arch Bridge By Multi-support Excitation

The simulation of ground motion is very important in the structural seismic design. Because of the influence of the traveling wave effect the local site conditions and the arbitrary coherency effect, the ground motion at the Long-span Bridge supporting points are different during a real earthquake. So it is necessary to take an analysis of the Long-span Bridge under the multi-support excitation. With the rapid development of the steel trussed arch bridges the seismic problems are increasingly concerned in recent years. In this dissertation, certain problems relating to seismic response behavior of large-span steel truss arch have been studied as following:1. The seismic input model:The simulation of the multi-support excitation based on the random earthquake ground motion is introduced firstly, then the models and related parameters of auto-power spectrum density, coherence function are suggested, and synthesized the Earthquake acceleration schedule based on the Code Response Spectrum.2. The methods of structure analysis:Large mass method is described in detail and is applied to simulate the ground motion at the bearing points of the long-span steel trussed arch bridge, and the implementation method of general finite element program is described.3. The seismic response analysis of the long-span steel trussed arch bridge:Based on the Xinshiji Bridge in Jiangxi province, the vibration characteristics and the influence to the dynamic response by the ground motion input in different directions are studied through the dynamic characteristic analysis of the bridge. The multi-point earthquake ground motion generated by the Seismic Design Code Response Spectrum is used to the dynamic time history analysis on the Xinshiji Bridge, and compared the seismic response between the multi-support excitation and the uniform excitation to investigate the influence to the seismic response of the long-span steel trussed arch bridge with different earthquake motion input.The results show that there is an significant influence of the spatial effect to the structure internal force response on the long-span steel trussed arch bridge, and because of the ignorance of the spatial effect by the regulation response spectrum theory and the uniform excitation method it always underestimates the internal force response under the earthquake action, meanwhile the influence of the vertical earthquake action also should be considered.