Impact Effect Analysis Of Rigid Hanger In Arch Bridge Subjected To Moving Vehicles

Hangers(or suspenders)are critical and vulnerable structural components for a half-through or through arch bridge.In serving cycle,the impact effect triggered by the moving vehicles makes the internal force and deformation of hangers larger than that produced by the static force.In addition,the vehicular impact effect on the deck slab will also increase the stress amplitude of hangers,which will lead to an increase in the count of fatigue cycles and greatly reduce the service life of the suspender system.Therefore,the Tianyuan bridge in Xiamen was employed as the engineering case in this study.The dynamic impact effect of the rigid hangers in arch bridge was investigated with the vehicle-bridge coupling vibration analysis method.The specific works are listed as follows:(1)Two spatial vehicular models,HS20-44 and 5axle-CHN,were derived based on the virtual work principle.And three different road roughness samples were simulated based on the inverse Fourier transform method.Then an iterative method for three-dimension vehicle-bridge coupled system was built in the finite element software.The simulation case of a simply supported beam was conducted to verify the calculation accuracy of the proposed method.(2)In the present study,five vehicle speeds ranging from 30km/h to 90km/h,with an interval of 15km/h,were used to examine the relationship between the vehicle speed and impact factor.Additionally,three different road surface conditions,nine vehicle loading positions distributed on variable lanes,four space of vehicles in the most disadvantageous lane and two different vehicular models were respectively arranged to analyze the influence of these various factors to the impact factor of hangers.The results show that vehicular model and road surface condition have great influence on the impact effect of hangers,while the vehicle loading position and vehicle spacing have relatively small influence.Finally,the relationship was fitting analyzed between the impact factor and natural frequency of hangers.(3)Based on the random traffic flow simulation theory,two traffic flow samples with dense operation state and general operation state were respectively created.The distribution law of impact factor of the hanger system was discussed with the combined action of vehicular type,weight,spacing and travelling speed.(4)Finally,a practical method was proposed to estimate the impact factor utilizing the dynamic strain monitoring data from hangers in actual service condition.Statistical analysis was carried out with vast real-time impact factor values.Comparing the equivalent value of impact factor obtained with vehicle-bridge coupling vibration system to that on the curve of statistical standard daily spectral,the quantile was suggested according to the calculation results.