Research On Structural Damage Identification Method Of Main Beam Of Truss Beam Lifting Machine Based On Vibration Power Flow

The girder lifting machine is a special gantry crane designed for bridge construction.The truss girder lifting machine is mainly composed of assembled main girder,outrigger and crane.The components are connected by pins and high-strength bolts,which are widely used in beam yards and other places.As the main bearing structure,the main beam is composed of upper and lower chords,vertical rods and inclined rods.The main girder will bear random effects such as lifting load,vibration,environmental corrosion and impact during service.Long-term and frequent use will cause local damage to the structure,which will affect the safety and durability of the whole machine.How to effectively identify small structural damage has become a research hotspot and difficulty.Under the support of the Natural Science Foundation Research Program of Shaanxi Province(2022JQ-576),this paper takes the local structure of the main girder of a truss crane as the research object,and uses theoretical analysis,finite element simulation and experimental verification to carry out the research on the damage identification method of the main girder structure of the truss girder lifting machine based on vibration power flow.Firstly,the theory of vibration power flow is described in detail.The beam vibration theory and the calculation formula of power flow in the beam are introduced.The related theory based on the visualization of structural vibration power flow is introduced,which provides a theoretical basis for the visualization of the main beam.Secondly,taking the lossless beam structure as the research object,the power flow transmission characteristics of the beam structure are studied.Based on the characteristics of vibration power flow,the power flow observation diagram,power flow transfer vector diagram and cloud diagram under different influencing factors such as excitation frequency,constraint condition,excitation force position and wall thickness are obtained respectively.Through the study of the propagation path and vibration characteristics of the vibration power flow of the non-destructive beam,the propagation direction and distribution characteristics of the vibration power flow are clarified.Then,based on the power flow transfer law,the beam structure with damage is selected as the research object,and the vibration power flow characteristics of simply supported beam and cantilever beam with different excitation frequency,constraint conditions,excitation force position,wall thickness and different damage positions are obtained respectively.Compared with the calculation results of the non-destructive beam,the vibration power flow in the diagram will have a mutation at the damage site,and the damage position in the beam structure can be obtained.Finally,the cantilever beam power flow test is designed.The experimental results show that the method can effectively identify the damage and determine the location of the damage,which proves that the proposed method is feasible and effective.The above method is applied to the damage identification of the main beam of the truss girder lifting machine,which can accurately determine the damage location.The research in this paper can provide guidance for damage identification and health monitoring of other engineering structures,which has research significance and application value.