Research On Damage Identification Of Main Beam Structure Of Truss Bridge Erecting Machine Based On Vibration Mode Change And BP Neural Networ

Truss type highway bridge erecting machine is a kind of lifting and transportation mechanical equipment in modern civil engineering construction,which plays an indispensable role in the transportation industry.It can not only reduce the labor intensity of construction personnel,but also improve the efficiency of bridge erection.At the same time,the safety issues of truss type highway bridge erecting machine have also aroused widespread concern in the social community.Due to the frequent conditions such as transfer operations,complex construction environments,and untimely manual maintenance and testing,the main components of the bridge erecting machine are corroded,steel plates are cracked,bolts are loosened,and other damage phenomena are not detected.Once constructed,it is highly likely to bring huge losses to the lives and properties of the people.Although many scholars have made many breakthroughs in the field of structural damage identification research,the research on damage identification of the main beam structure of truss type highway bridge erecting machines is still in the stage of overcoming difficulties.In view of this,this article focuses on the research on damage identification of the main beam structure of truss type highway bridge erecting machines,with the main contents as follows:(1)Analyze the role of bridge erecting machines in the future civil engineering field,summarize the construction accidents of bridge erecting machines,and summarize the applicability of mainstream damage identification methods to the main beam structure.Based on this,it is found that the current research on damage identification of the main beam structure of truss type bridge erecting machines is still in the stage of overcoming difficulties,combining the operational characteristics of truss type bridge erecting machines,The damage identification method based on vibration mode change and BP neural network is selected to study the main beam structure of the truss bridge erecting machine.(2)Based on the finite element theory,using the method of element stiffness reduction,the parametric models of the main beam structure under different damage conditions are established using ANSYS software.Simulate the main beam structure of a bridge erecting machine in an unoperated state,conduct modal analysis on its truss type main beam structure under different working conditions,obtain its frequency and vibration mode,and study the impact of damage to the main beam structure on the frequency and vibration mode.Simulate the main beam structure of the bridge erecting machine under different working conditions,conduct transient analysis on its models under different working conditions,extract the structural response parameters(displacement and velocity)of the right node of the 29 elements of the main beam structure,compare the structural response parameters under different damage conditions,and study the impact of the main beam structure damage on the displacement response and velocity response.(3)In view of the problem of damage identification of the main beam structure of the triangle truss bridge erecting machine in the non operating state,relying on the long-span working condition of the JQG160t-40 m truss bridge erecting machine,the modal parameters of each unit of the main beam structure of the bridge erecting machine under 12 working conditions are extracted,and the change rate of the first modal strain energy of each unit is calculated using Matlab,which verifies the effectiveness and correctness of the method,Test the damage location effect and damage degree estimation effect of the main beam structure of the truss type highway bridge erecting machine using the element modal strain energy change rate method.(4)Aiming at the problem of structural damage identification for the main beam of a triangular truss type bridge erecting machine in an unoperated state,based on 12 simulated damage conditions on the main beam of the truss type bridge erecting machine structure,the modal difference curvature of the vibration modes under 12 different working conditions is extracted and calculated,and the damage is identified using the first order modal difference curvature damage index,and the approximate damage degree is calculated through multiple curve fitting,To test the damage location effect and damage degree estimation effect of the vibration mode difference curvature method applied to the main beam structure of the truss bridge crane.(5)In response to the problem of identifying damage to the main beam structure of the triangular truss type bridge erecting machine under operating conditions,a large-span suspension beam working condition was selected for numerical simulation.The single,two,and three damage positions and different degrees of damage on the upper chord of the main beam structure were simulated.A single hidden layer network was used to input the change rate of the maximum displacement of the node into the BP neural network.Through statistical analysis of test results,it can be concluded that the trained network can accurately predict damage to the main beam structure in operation,and can simultaneously identify the location and degree of damage.(6)Aiming at the damage detection of the main beam structure of a triangular truss type highway bridge erecting machine in two operating states,an implementation strategy based on vibration mode change and BP neural network damage identification method is proposed.The implementation strategy is divided into the main beam structure of a truss type bridge erecting machine in the non operating state and the main beam structure of a truss type bridge erecting machine in the operating state.The specific implementation strategies for the two operating states are given in detail,including the bridge erecting machine in the operating state,The feasibility of using the maximum displacement of element nodes-BP neural network damage identification method to identify the dynamic damage of truss type highway bridge erecting machines is verified by comparing on-site monitoring data and finite element simulation calculations.