The Seismic Response Analysis Of CFST Truss Beam Bridge

Based on the engineering background of Ganhaizi bridge, free-vibration characteristic analysis, seismic response spectrum analysis and time history analysis are applied to the first unit of the bridge with 11 spans. The main research contents include the follows:1,By established three-dimensional space finite element model with finite element software to calculate the free-vibration characteristic of the bridge.2,Using response spectrum analysis methods in seismic response analysis, draw some conclusions. The effects of horizontal and three directional seismic load were considered.3,Using time history analysis method in seismic response analysis, draw some conclusions. Horizontal seismic wave used El-centro_h earthquake wave, three directional seismic wave used El-centro_v earthquake wave, and according to the actual site conditions and other factors to adjust the peak of the seismic waves.The main conclusions drawn from above include:Firstly, the first vibration mode of Ganhaizi bridge is consistent longitudinal vibration. It shows that smaller main girder longitudinal restraint is conducive to earthquake resistance and shock absorption. The first 10 vibration modes of the main girder do not show torsion mode. Secondly, under the earthquake loads in three directions, the axial force of bottom pipe, brace and the moment of bridge deck increase more significantly than those under the horizontal earthquake. Thirdly, the vibration mode of main girder is superposition of the first vibration mode(longitudinal floating vibration mode) and the second vibration mode(lateral bending vibration mode). Finally, compared with response spectrum results of shear at the bottom of the pier, the calculated results of using dynamic time history method were smaller.