Damage Identification Of Steel Truss Bridge Based On Natural Frequency And Curvature Mode

The safety of civil engineering structure is not only related to the safety of people's lives and property,but also a necessary condition for the stable and sustainable development of a country's national economy.However,civil engineering structures have been affected by environmental erosion,material aging,artificial or natural mutation effects in the course of decades,even over a hundred years,resulting in a decline in the ability of the structure to resist natural disasters and environmental effects,resulting in catastrophic accidents.It can not only reduce the cost of maintenance,but also guarantee the good performance of the structure and prolong the service life of the structure.Therefore,it is of great social and economic value to study effective damage identification methods,damage assessment index and damage repair technology.In this paper,a simple supported steel truss bridge is taken as the research object.Based on the analysis and introduction of various structural damage identification methods at home and abroad,the damage identification method based on the natural frequency and the damage identification method based on the curvature mode are combined to carry out the structural damage identification.It is divided into two steps to identify the structural damage.First,the natural frequency is used to form a fast and accurate method of damage identification combined with curvature from modal to part.The main research contents are as follows:(1)analysis and introduction of various structural damage identification methods at home and abroad,and summarize the advantages and limitations of various methods.The damage identification methods based on natural frequencies and damage identification methods based on curvature mode are mainly analyzed.The advantages of the combination of the two methods are analyzed.To explore a fast and efficient method for damage identification.(2)the relationship between the parameters of the dynamic characteristic identification(natural frequency,frequency change ratio,frequency change square ratio,regularization frequency change rate,curvature mode,curvature mode ratio,curvature mode ratio)with damage position and damage degree before and after the truss bridge damage is theoretically analyzed.The sensitivity of various damage indicators to structural damage is studied.(3)the finite element software(MIDAS)is used to simulate the 3.2m truss bridge model,and the change of the natural frequency damage index and the damage index of the curvature mode before and after the damage of the truss bridge are studied.Theeffectiveness of the two step method,namely the first frequency and the curvature method,is analyzed.(4)the static load test of the steel truss bridge is carried out in the laboratory,and the variation of the strain and the mid span deflection under various working conditions is analyzed,and the feasibility of the damage identification combined with the strain and deflection is analyzed.To explore the idea of damage identification and detection with static and dynamic combination.(5)the vibration experiments of the steel truss bridge model are carried out in the laboratory to analyze the frequency variation of the truss bridge model under different working conditions,compare the experimental results with the finite element simulation results.The results show that the structure can be identified by the natural frequency,and the relative reliability of the finite element numerical simulation is verified.