Dynamic Characteristics Analysis And Redesign On Short Suspenders Of Bridge

In recent years,under vehicle loading for a long time,the suspenders in the half through and through arch bridge fracture owning to corrosion and fatigue,which seriously threats the life of the bridge structure.It dramatically amplifies the dynamic effects that the stiffness of the short suspender is larger than long suspender,furthermore,under dynamic loading the stress amplitude of the short suspender is also obviously larger than long suspender,which cause the fatigue damage degree of the short suspender is larger and the short suspender more easily occur fatigue failure during the same period.Based on vehicle-bridge coupling method,the reason why short suspender more easily fracture has been discussed,and calculating the fatigue life of the suspenders under dynamic loading,finally the suspender structure has been redesigned for the sake of enhancing the fatigue life of the suspenders.The primary contents are as follows:(1)A vechicle-bridge coupling vibration model is built.Three dimensional finite element model of the steel box girder arch bridge,two axial vehicle model and the road roughness model are built respectively.The vechicle-bridge coupling vibration model consisted of arch bridge model,vehicle model and load model.According to the coupling model analyze the stress response of the suspender,compared with the data that measured in loading test to confirm the accuracy of the vehicle-bridge coupling vibration model,which shows the model could commendably simulate the stress state of the suspenders.(2)Dynamic response of the suspenders has been analyzed based on the vechiclebridge coupling vibration model.Dynamic response of the suspenders are calculated in conditions of different vehicle speed,vehicle weight and road roughness,the answer indicates that suspender structure observably produce impact effect under vechicle loading,and no matter what conditions,the impact coefficient of the short suspender is the maximum,which explained why short suspender more easily occur fatigue failure.(3)Fatigue life of the suspenders have been analysed in detail.choosing appropriate vehicle loading spectrum to produce random vehicle loading,then calculating the dynamic response of the suspenders by combining random vehicle loading and bridge model,finally the fatigue damage degree and life of suspenders have been calculated based on the fatigue cumulative damage rule and the suspender's S-N curve.The results show that the fatigue damage degree of short suspender is larger than long suspender during the same period;the life of long and short suspender is able to reach expectations without thinking about corrosion,but when suspenders become corrosive,the life of the suspenders decrease suddenly,especially to short suspender.(4)Focus on the problem that short suspender more easily occur fatigue failure,the suspender structure has been redesigned,and evaluating the redesigned structure by calculating the dynamic response of the suspenders.The results indicate that the impact resistance and life of the suspender have been improved obviously when the suspender structure have been redesigned,compared to long suspenders,short suspenders improved more visibly.