Study On Damage Diagnosis Method Of Urban Rail Transit Bridge Based On Vehicle-Induced Vibration Responses

Because of its convenience,safety and efficiency,urban rail transit is becoming the main way to relieve traffic congestion in large and medium-sized cities in China.As the extension of the existing bridge of urban rail transit,under the action of vehicle load and the external environment,the structures and their components will inevitably produce different degree of damage,but most of the existing railway bridge damage detection method is geared to the needs of railway bridges in orbit.The damage detection methods directly facing the urban rail transit bridge structure are rarely carried out.For the urban rail transit bridge,the train load has obvious repeatability and regularity,and the vibration amplitude of the bridge under the train action is much larger than that during the period of not being open to traffic,which is more conducive to the appearance of structural damage.Based on this,this paper attempts to use vehicle-induced vibration response to diagnosedamagesfor urban rail transit bridges.The main contents are as follows:(1)Based on the engineering background of a typical urban rail transit bridge,a finite element model was established.Its strength and stiffness were checked by static analysis,and the dynamic characteristics of the structure were obtained by modal analysis.The results show that the strength and stiffness of the finite element model meet the requirements,and the dynamic characteristics are reasonable.(2)The vehicle-rail-bridge coupling finite element model was established,and the vibration response of the urban rail transit bridge under the train load was obtained through dynamic time-history analysis,and the sensitivity of vehicle-induced vibration response to bridge damage was proved by differential method.The results show that the difference of acceleration response between the measured points of bridge and the measured points of wheel set and bogie before and after damage can be used for damage location.(3)Taking the difference value of the vibration response of the bridge and the vehicle before and after the damage as the research object,the wavelet analysis was used to decompose and reconstruct it,and the wavelet coefficient amplitude change was used to realize the damage localization and quantification of the bridge.The results show that when the train runs at medium speed,the damage location and quantification of the bridge can be achieved by using the wavelet coefficient modulus of acceleration response difference of the bridge and the vehicle,but the identification accuracy decreases with the increase of the test noise.