Research On Calculation Of Impact Coefficient Of Highway Long-span Continuous Girder Bridge

During the operation of the bridge,when vehicles drive across the bridge at a certain speed,due to the impact of sensitive factors such as the characteristics of the bridge and the unevenness of the bridge,the bridge will bear the dynamic load of the vehicle,that is the bridge vibration problem caused by the vibration of the bridge.With the repeated impact between the vehicle and the bridge,especially when the resonance between the vehicle and the bridge is too severe,it will inevitably lead to fatigue of the bridge structure and reduce the safety and durability of the bridge.At present,the current design codes fail to comprehensively consider the impact factors of long-span continuous girder bridges,and only use the fundamental frequency or span to determine the impact coefficient.Whether it is reasonable or not requires further research and determination.Therefore,carrying out the analysis and research on the vehicle-bridge coupled vibration response and impact coefficient of long-span continuous beam bridges has important practical significance for the evaluation of the safe operation of such bridges.The topic is selected as an important part of the key research and development project of Shanxi Province "Research on the Dynamic Characteristics of Long-span Curved Continuous Beam Bridges Based on the Effect of Sensitive Elements"(No.201803D31076).Based on a large-span continuous beam bridge,five projects are derived based on the Largange equation.The axle trailer vehicle model uses the mode superposition method to establish the bridge motion equation,and selects the triangle series method to establish different levels of spatial bridge surface unevenness models.The real bridge simulation model is established by finite element analysis software,and the modal synthesis method is applied to the vehicle-bridge coupling model.Based on the principle of displacement coordination and force balance,the vehicle-bridge coupled vibration equations are established,and the Newmark-βnumerical integration method is used for iterative solution.This paper uses numerical software to compile the vehicle-bridge coupling vibration program of a five-axle trailer,analyzes the vehicle-bridge coupling vibration response and the change law of impact coefficient under the influence of different sensitive parameters,and compares it with the impact coefficient of multiple countries.The impact coefficient is subjected to a stepwise regression analysis.The main research results are as follows:(1)When the unevenness of the bridge deck changes,it has the greatest impact on the impact coefficient of the bridge,showing a positive correlation,and its calculated value is quite different from the value specified in the code;When the driving speed of the vehicle changes,the impact coefficient of the bridge fluctuates up and down,and no obvious law is found;Changes in vehicle load and bridge damping ratio are negatively correlated with changes in bridge impact coefficient;While vehicle suspension stiffness is positively correlated;When the vehicle suspension damping changes,as the vehicle suspension damping gradually increases,the impact coefficient fluctuates,showing a law of change that first decreases and then increases.(2)The quasi-horizontal orthogonal test method was used to determine 25 different working conditions,and the SPSS numerical analysis software was used to perform stepwise regression.The sensitivity of each parameter to the impact coefficient was obtained,and the calculation formula for the impact coefficient of the long-span continuous beam bridge was given.Relevant research results can provide references for the design,inspection,safety assessment and post-maintenance of such bridges.