Study On Long-term Deflection And Crack Of Long Span PC Continuous Beam Bridge

PC continuous girder bridge,namely prestressed concrete continuous girder bridge,is one of the most widely used bridge types in China,and its spanning capacity has been continuously improved with the development of engineering technology.In actual operation,engineers found that long-span PC continuous beam bridges are prone to cross-to-middle deflection and cracking problems.Previous studies have focused on the analysis of a PC continuous beam bridge or a certain factor,combined with the research conclusions of the predecessors,using numerical simulation methods to study five bridges of different spans,and working to solve the bridge life cycle.Deflection and crack control issues.main tasks as follows:The beam element model is built with midas Civil and the solid element model is built with FEA.According to the theoretical analysis of the causes of the downward deflection,five ideal conditions are defined.Comparing and analyzing the linear and mid-span mid-lower deflection values of the five bridges under five working conditions,the different modes of action of prestress loss and shrinkage and creep on the mid-to-lower deflection are proposed.Statistical analysis of the loss of steel bundles in the operation of five background bridges for ten years,comparing the longitudinal beam prestress loss components,proportions and losses of the top,bottom and web.The sensitivity of the prestress loss of the longitudinal steel bundle at different locations to the cross-to-middle deflection is further studied.According to the ten-year deflection variation value of the five bridges,it can be seen that the lower deflection values of the continuous beam bridges of highways and railways show significant differences,which are mainly related to the bridge structure size and the proportion of longitudinal steel bundles.According to the characteristics of PC continuous beam bridge cantilever construction,the full life model of the bridge is established,and the effects of loading age,relative humidity of the environment and frictional deviation of the tunnel on shrinkage and creep are observed.Using the nonlinear analysis function of FEA software,the bridge solid element model is established,and the cracking of five large-span PC continuous beam bridges is analyzed.The ability of vertical prestress to resist cracks is studied.Finally,the fatigue analysis of the five bridges during the operational phase was carried out to study the characteristics of fatigue failure of PC continuous beam bridges.