Vibration Characteristics Study And Dynamic Modification Of Steel Tube Truss Girder Bridge Under Environmental Excitation

As a key project of the existing national infrastructure,bridge has a decisive impact on people’s daily life and economic development.As the hub of the transportation system,the daily maintenance and operation of bridges after completion is becoming increasingly important.The finite element analysis of bridges and the subsequent related vibration test studies to fully understand the dynamic properties of the structure under operating conditions are the most important and effective way to ensure that bridges have a certain level of safety and stability during use.Therefore,this paper takes a certain type of steel tubular truss girder bridge as the research object,and studies its dynamic characteristics,and completes the FEA of the bridge,the EMA of the bridge deck and the longitudinal beam,and the OMA under environmental excitation.Research results for structure optimization design of the same kind of bridge has a certain guiding significance.In summary,this paper mainly completes the following research contents:(1)By using the Workbench module of finite element analysis software ANSYS,the calculated modal analysis of the deck and longitudinal beam is carried out respectively.Based on the Component Mode Synthesis(CMS)to get the whole bridge modal results.The modal frequency range and corresponding modal shapes of the three parts are obtained,which can provide reference for the experimental modal test and environmental excitation modal test of the deck and longitudinal beam of the steel tube truss girder bridge.(2)EMA test scheme of steel tube truss girder bridge deck and longitudinal beam was designed.The vibration response signal data was collected and sorted out by using hammer as the excitation method.The modal parameters identification method of LSCF was used to obtain the modal results of the bridge deck and longitudinal beam,and the EMA results of the whole bridge were obtained based on the CMS.(3)The environmental excitation mode test scheme of the bridge deck and longitudinal beam of the steel tube truss girder bridge is designed.The model car is used to apply excitation to the bridge deck and longitudinal beam,and the vibration response signals of the bridge deck and longitudinal beam are collected.The SSI modal parameter identification method was used to obtain the modal frequency,damping ratio and modal shape of the bridge deck and longitudinal beam,and OMA results were obtained based on the CMS.(4)By comparing the FEA,EMA and OMA results of the steel tube truss girder bridge,the correctness of the finite element model of the substructure is verified,and the weak positions of the bridge are determined.In view of the weak points,the structural dynamic modification of the deck and longitudinal beam is carried out,and the FEA of the modified steel tube truss girder bridge is carried out.The modal analysis results of the steel tube truss girder bridge before and after the modification are compared,and the validity of the structural dynamic modification is verified.