Study On Vehicle-induced Vibration And Early-stage Warning Of Long-span Steel Box Girder Highway Suspension Bridge

The effect of vehicle loads on the service performance of long-span steel box girder suspension bridges is directly related to the operational safety of the overall bridge structure.How to calculate the dynamic response of the bridge structure under the actual vehicle load during service,to provide early warning of structural abnormality,is a major challenge in the research field of long-span steel box girder suspension bridges.Firstly,this paper takes the suspension bridge of Runyang Bridge as the research object,proposes the sampling and loading method of random traffic load,and establishes a vehicle-bridge coupling calculation system suitable for large and complex bridges.Secondly,the structural dynamic response of the longspan steel box girder suspension bridge and the dynamic reliability of the main girder structure under random traffic loads are studied.Thirdly,a filtering method suitable for structural health monitoring signals is proposed.Finally,based on the acceleration data of the real bridge structure health monitoring,the early warning of the abnormal state of the structure under the long-term operating vehicle load is carried out.The main research work and achievements of this paper are as follows:1)A vehicle-axle coupling calculation system based on the principle of structural modal simplification and the refined time history integration method is established.The system includes the preprocessing of ANSYS finite element software,the connection between ANSYS finite element software and MATLAB software,and the decoupling of the interaction relationship between vehicles and bridges in MATLAB software.Based on the vehicle subsystem model,the bridge subsystem model,the vehicle-bridge interaction subsystem model and the pavement roughness model of the bridge,the dynamic balance equation expressions of the vehicle model and the bridge model in the vehicle-bridge coupling action are deduced.The applicability and accuracy of the vehicle-bridge coupling system in the dynamic response problem of the vehicle and the bridge are shown through the coupled vibration test of the vehicle and the steel beam.2)The vibration law of the deck of a long-span steel box girder suspension bridge under the interaction of vehicles and bridges is revealed.Based on the vehicle-bridge coupling system,the influences of road roughness level,vehicle speed,and one-way and two-way driving on the dynamic response of the main girder of a long-span steel box girder suspension bridge are deeply studied.The changes of the main girder joint force,vehicle body displacement,acceleration response and its power spectrum caused by the changes of the three control variables are revealed.The influence of road roughness grade,vehicle speed and one-way and two-way driving on the impact coefficient of long-span suspension bridges is analyzed.Parameter analysis shows that: in the process of vehicle-bridge interaction,road surface roughness level has the most significant dynamic response to the long-span suspension bridge,while vehicle speed and vehicle direction are the secondary factors affecting the dynamic response of the long-span suspension bridge.3)The vehicle-induced vibration of a long-span steel box girder suspension bridge under the action of multi-lane random traffic flow is studied.According to the traffic flow data of the actual bridge,combined with the lateral distribution of vehicles on roads and the distribution of vehicle spacing in Jiangsu Province,a random sampling method for multi-lane random traffic flow is proposed.On this basis,the dynamic response difference of the long-span steel box girder suspension bridge under random traffic flow at different times is studied,and the structural vibration analysis of the main girder is carried out.At the same time,the dynamic reliability of long-span steel box girder suspension bridges is studied based on the bridge dynamic response results under random traffic flow and the first pass failure theory.The analysis of vehicle-induced vibration of the suspension bridge of Runyang Bridge shows that the 3/8 span position of the bridge is most sensitive to vehicle vibration.The research on the dynamic reliability of the bridge shows that under the load of the operating vehicles,the dynamic reliability index of the 1/4 span position of the bridge is the lowest.4)A bridge acceleration signal filtering method based on the principle of fractional conservation and empirical mode decomposition method is established.The filtering method has extremely high applicability in processing the acceleration signal of the bridge.Aiming at the filtered vibration data of structural health monitoring,based on the modal compliance method and the modal curvature method,the structural abnormal state evaluation of the Runyang Bridge suspension bridge under the action of long-term traffic load is carried out.The structural abnormal state assessment of the bridge shows that the vulnerable position of the suspension bridge of Runyang Bridge under the action of long-term traffic load is in the interval between 1/4 span and 3/8 span of the bridge.