Research On Bridge Damage Identification Based On Dynamic Load Test

In recent years,bridge accidents occur frequently,causing great losses to people's lives and property.Therefore,it is very important to accurately assess the health status of the bridge,which can prevent the occurrence of bridge accidents.Small and medium sized reinforced concrete beam bridge account for the majority of the total number of bridges,so it is necessary to evaluate the health status of the small and medium span girder bridges.For most small and medium bridges,bridge load test is generally only assess their overall carrying capacity,there is no bridge health monitoring system to establish comprehensive monitoring them.However,the bridge load test has not been able to diagnose the local damage,and can not judge the damage degree of the bridge.Based on this,this paper presents a suitable method for damage diagnosis of small and medium beam bridge.And the feasibility of the damage diagnosis is realized by wavelet analysis based on the vibration information obtained from the dynamic load test of the bridge.The dynamic load test of bridge load test is indispensable.The dynamic load test of bridge will measure the dynamic response parameters such as natural frequency,vibration mode,impact coefficient,resistance ratio and so on,and analysis of the mid-span deflection curve of the bridge when measuring the impact coefficient of the bridge.With reference to the reciprocal theorem of displacement in the static mechanics,when the sports car acts on the beam bridge,the mid-span displacement is related to the displacement caused by the cross-section of the bridge.Therefore,the singular information generated by the motion of the car at the damage location is contained in the bridge over mid-range deflection curve signal.After the dynamic deflection curve is normalized,the continuous wavelet transform is used to identify the location of damage,and the damage position is identified by combining the Wavelet coefficient grayscale graphics and the wavelet coefficients graphics.The Lipschitz exponent ? is obtained by the logarithm relation between the modulus maxima of wavelet coefficients and the wavelet analysis scale,and the Lipschitz exponent? is inversely correlated with the singularity of the damage signal,so as to diagnose the damage degree of the bridge.Therefore,the purpose of damagediagnosis of beam bridge is realized.In order to verify the feasibility of the above diagnostic methods,based on the single ANSYS APDL modeling environment,this paper constructs the threedimensional vehicle-bridge coupled model,Compiled by MATLAB bridge deck roughness numerical simulation program,and adds it into the vehicle-bridge coupled model.The dynamic load test of 7 span continuous beam bridge is carried out,The finite element model is corrected by measuring the dynamic response parameters of the bridge,the modified finite element model is calculated and analyzed,in order to simulate the effect of the test car on the bridge.Through the analysis of this paper,it is concluded that the one-dimensional continuous wavelet transform analysis can be used to identify the damage position of the bridge and determine the damage degree.Due to the singularity of signal generated by the wheel passing through the damaged position,the damage identification of the beam is better,and the recognition effect is not good for the other contact beams which are not in contact with the vehicle;Due to the wheel through the damage position will produce strange signals,it is reflecting that the mid-span deflection curve contains multiple singular information,When the time travel curve is normalized and then analyzed by wavelet transform,it will produce multiple extreme points,and the distance between this extremes is an axle length,and the corresponding position of the first extreme point is the place of damage.The feasibility of the bridge damage diagnosis method based on the test of the excitation beam bridge is verified.