Seismic Response Analysis Of Double-deck Continuous Girder Bridge

With higher requirements of space utilization for urban transportation, the double-deck bridges become increasingly popular. The Xinghai Gulf Bridge is a typical double-deck bridge project, consisting of a double-deck steel truss earth-anchored suspension bridge with a span of460m as the main bridge and tens of kilometers long approach bridges mainly in the form of double-deck prestressed concrete continuous girder bridge. Under strong earthquake, the losses caused by the damage of approach bridges are no less severe than the direct destruction of main bridge. At present, researches on seismic response of normal bridge with one floor are quite mature, but applicability of those theories to double-deck bridges requires further check. As researches on double-deck bridges are limited, it is necessary to study on the elastic and plastic state regularities of double-deck continuous girder bridge in a strong earthquake.In this paper, significant seismic disasters in the past few years are reviewed as the background, with special attention paid to the damage of double-deck bridges. Traditional aseismic bridge design methods are listed and seismic ductility design and capacity design methods are introduced as the theoretical basis.With the help of Midas-civil software, a3-D finite element model of double-deck continuous bridge is established. Modal analysis, response spectrum analysis and linear time history analysis are performed to understand the seismic response regularities of double-deck continuous girder bridge.Moment-curvature analyses of column sections of the double-deck continuous bridge in this paper are performed by the commercial section analysis software XTRACT. Influence factors of abnormal sections’curvature ductility are discussed here. And the axial-force moment interactions are also studied.Considering the influence of axial-force variation and coupling effect of bi-directional moment, an elasto-plastic fiber beam-column element is used in the nonlinear dynamic time history analysis. Seismic response regularities of double-deck continuous girder bridge under rare earthquake are discussed, and some valuable conclusions are drawn.