Research On Finite Element Method Updating Of Bridge Based On Ambient Excitation

As an important part of highways or urban roads,bridges are the throat that guarantees the smooth flow of traffic arteries.With the increase of service life,various damages are unavoidable in bridge structures.Therefore,periodic damage diagnosis of bridges is a necessary means to ensure the safety of the bridge and normal service.At present,the finite element numerical simulation method is widely used in structural damage analysis,and the establishment of an accurate finite element model is the premise to ensure the correct analysis results.Engineering practice shows that correcting the theoretical finite element model based on the actual damage state of the in-service structure has good applicability and effectiveness.Among them,the modal parameter identification of bridge structures based on environmental excitation has more advantages than traditional methods,such as no need to interrupt traffic,cost savings,convenient data collection,and good security.Therefore,it is of great theoretical significance and engineering application value to carry out revision research on the finite element model of bridge structures based on environmental incentives.Relying on the National Natural Science Foundation of China and taking the Nanhu Bridge in Wuhan as the engineering background,this paper carried out the static and dynamic load test of the Nanhu Bridge,and made a preliminary judgment on the current service status of the Nanhu Bridge.According to the data,the first six orders of modal parameters of the bridge structure are identified using a random subspace algorithm.Based on the identification results,the first-order optimization algorithm and response surface method are used to modify the theoretical finite element model of the bridge.The effect of the method puts forward suggestions and provides a useful reference for the revision of the finite element model of this type of bridge.The main work and conclusions of this article are as follows:(1)Carry out on-site dynamic and static load testing of bridges,and use vehicle on-site loading to obtain the deflection,strain of the main measuring points under static loading conditions,and the natural vibration frequency,damping ratio and impact coefficient under dynamic loading test conditions.The damage situation,actual stress status and service status of the structure,etc.,to preliminarily judge whether the overall stress status and bearing capacity of the bridge structure meet the requirements.The static and dynamic load test results show that the main bridge has low rigidity after years of service.(2)Select key measurement points to deploy sensors,carry out on-site environmental vibration testing of the Nanhu Bridge,continuously collect acceleration time history data of the bridge structure under environmental excitation,and identify the Nanhu Bridge based on the covariance-driven random subspace algorithm and stability graph method.The first 6th order natural vibration frequency is used as the reference value of the finite element model correction.(3)The theoretical finite element model of the Nanhu Bridge was established according to the design document,and the calculated value of the initial finite element model was compared with the measured value.The key correction parameters were selected through parameter sensitivity analysis.The first-order optimization algorithm and response surface method were used to modify the initial finite element model of the Nanhu Bridge.The correction effects of the two methods were further compared and analyzed.For continuous concrete box girder bridges with stress concrete,the first-order optimization algorithm is more appropriate.The revision process of this paper can provide a reference for other actual projects,and the revised finite element model can reflect the actual service status of the bridge,and can be used as the basis for the subsequent maintenance and maintenance of the bridge and early warning of heavy traffic.