Study On Damage Detection Method Of Suspension Bridge Based On Index Of Strain Impact Factor

Under the background of building a transportation power,the long-span bridge has become the key hub of transportation network.Under the influence of traffic load and environment,the damage and damage accumulation of each component degrade the structural performance of the bridge.In order to ensure the safety and durability of bridges in service,a feasible,efficient and accurate bridge damage detection technique should be developed.To solve this problem,this thesis takes a long-span suspension bridge as the background,and studies the damage detection method of suspension bridge based on index of strain impact factor.The main work of this thesis are as follows:(1)The stepwise finite element model correction method of bridge based on static and dynamic response surface was proposed.Firstly,the sensitivity analysis method was used to screen out the parameters to be modified,and the cubic polynomial was used to fit the static and dynamic response surface.Then,the deflection of stiffening girder and the natural vibration frequency of the bridge were used to construct the objective function,and the constrained optimization model was established.The sequential quadratic programming method was used to solve the optimization step by step according to the order of static-dynamic.Finally,the reference finite element model of the suspension bridge was established according to the optimization results,which laid the foundation for the subsequent simulation.(2)An improved damage identification method based on impact coefficient was presented.The motion equation and basic principle of the vehicle-bridge coupling vibration system were described in detail,and the existing methods were improved.First,the speed range sensitive to impact factor was searched by classification.Secondly,the quantitative relationship between damage index and damage degree was established by numerical simulation.Taking a 40 m simply supported bridge as an example,the application flow of this method was explained in detail.(3)Using the reference finite element model of the suspension bridge,the strainbased impact factor of the bridge was obtained through the vehicle-bridge coupling vibration analysis program.Based on the strain impact factor of intact bridge and damaged bridge,the damage index was constructed,and the peak value of the damage index and the overall trend of the damage index were analyzed,so as to realize the damage localization and quantitative evaluation of the damage degree of the suspension bridge.In addition,the influence of factors such as uneven degree of bridge deck,vehicle weight and noise on the damage detection effect of this method were analyzed.(4)Taking the scaled suspension bridge model in the laboratory as the research object,the suspension bridge damage detection test was carried out by using the truck for excitation.Different damage parts were used to simulate the real damage of suspension bridge stiffening girder and suspender.Considering the influence of vehicle weight,speed and other factors on the damage identification effect,the effectiveness of the proposed method in the localization and preliminary quantification of bridge damage were verified,which provided a reference for the application in practical engineering.