A Damage Detection Method Based On Quasi-static Component Of Dynamic Response Induced By Vehicles Moving On A Simple-supoort Bridge

During the service life of bridges for decades or even hundreds of years,especially under the coupling effects of various unfavorable factors such as overload,fatigue accumulation,earthquake,typhoon,environmental corrosion and material aging,bridge damage will appear in advance and develop rapidly.Damage identification method based on measured dynamic response of bridges under moving loads directly,is more hopeful to develop a new method for rapid assessment of bridge safety.However,In addition to local damage may cause changes in bridge dynamic response,bridge natural vibration,moving speed,environmental impact and other factors will also cause changes in bridge dynamic response.In order to make the damage information contained in the bridge response not be concealed,the damage sensitive response components should be extracted from the bridge dynamic response and applied to damage identification.The purpose of this paper is to extract the signal component which are sensitive to damage in the dynamic response of bridges and apply this signal component in identifying the damage.It mainly includes the following three aspects:(1)Study on the sensitivity of signal components to damage in bridge response under moving loads is studied,(2)Study on the method of extracting quasi-static components from bridge responses induced by moving loads,(3)Study on quasi-static component based damage location and qmuantitative MethodFirstly,the dynamic response of bridges under moving loads is taken as an object of study,and the analytical solutions of the dynamic response of healthy and damaged bridge under moving loads are derived.Based on the analytical solution of bridge response,the signal components in response are analyzed in detail.It is found that the quasi-static component in response can better reflect the inherent characteristics of bridge.Numerical examples are carried out to compare and analyze the change of quasi-static component and other signal components in response after the birdge is damaged.It is found that The quasi-static component of bridge dynamic response is expected to develop more ideal bridge damage index..Then,based on the relationship between quasi-static component and bridge dynamic response,a method of extracting quasi-static component change from the dynamic response of healthy and damaged bridge is proposed.The method combines analytical mode decomposition(AMD)and moving average filter(MAF)to filter the signal components caused by bridge self-vibration,moving speed and other factors in dynamic response,and extract the quasi-static component changes caused by damage.Numerical example is carried out to analyze the influence of different damage degree,damage location,load moving speed and noise level on the extraction of quasi-static components.The results show that this method can accurately extract the quasi-static components of the moving load response under a certain load speed and noise level.Finally,in order to identify damage by using of the extracted quasi-static component change,a damage location and quantitative method is proposed.Damage location method is implemented by integrating quasi-static component changes in bridge elements to define damage location index.,and the damage quantitative method is implemented by integrating quasi-static component changes in whole bridge to establish the damage quantitative equation.Numerical example with vehicle-bridge coupling model is utilized to validate the efficacy of quasi-static components extracted by the method can accurately locate and quantify the damage.The results show that the proposed quasi-static component-based method can accurately locate and quantify damage.