Analysis Of Boundary Variation Effects On The Dynamic Response Of Beam Bridge

Currently,the most effective and direct way on the assessment of the bridge carrying capacity can be regard as loading test.Traditional load test mainly focuses on static load test,but there are many disadvantages in static load test,such as long closed traffic,static load test,complex instrument installation and long test time.So now for the exploration of the carrying capacity of the most rapid assessment of bridge is based on the dynamic load test,and on the structural dynamic response evaluation system is not perfect,the structural damage evaluation focused on the component damage,without considering the boundary condition variation.The damage of the bridge structure includes the damage of the component itself and the variation of the boundary condition.The influence of the damage of the member itself on the dynamic response of the whole structure is far less than that of the boundary condition.In the case of damage identification,the dynamic response of structural damage may be submerged in the dynamic response of the boundary damage.In this paper,the dynamic deflection time history curve obtained from the dynamic response test of the vehicle is analyzed,and the rate of change of the frequency is analyzed,and some conclusions are also drawn.The main contents and results are summarized as follows:(1)Some classical theories of forced vibration is simply discussed,and by using the ANSYS APDL language compiled calculation command,some classic examples is used to verify the accuracy of the calculation results,and some problems and methods of the calculation of ANSYS about vehicle-bridge coupling action are discussed.(2)Some typical vertical boundary variation is simply discussed,including bearing separation,deflection,bearing pressure bearing etc.The influence on bridge structure dynamic effect is unequalizing support,The numerical simulation is used to analyze the sensitivity of typical dynamic parameters to the vertical boundary variation.(3)Some typical portrait boundary variation is simply discussed,including the debris jams in the end of bridge,the fence is not indivisible,etc.Numerical method is used to analyze the sensitivity of typical dynamic parameters to longitudinal boundary variation.(4)Based on the typical bridge boundary variation phenomenon was simulated,and compared with the measured results,we found that the longitudinal boundary variation on the bridge dynamic response effect is much larger than the vertical boundary variation;the frequency change rate on the vertical position of the lateral distribution of boundary variation is very sensitive;the frequency change rate of the longitudinal distribution of vertical boundary variation is not sensitive;when the expansion joint blockage rate of 0-20% range,the expansion joint blockage rate of growth on the frequency change rate is very fast,and in the range of 20%-100%,the frequency change rate tends to be stable.