Damage Identification Of Beam-type Bridges Using Dynamic Response Of Moving Vehicle

Vibration-based damage identification technology is a hotspot in the field of bridge health monitoring.Damage causes variations in structural modal parameters such as natural frequencies,mode shape,damping ratio and so on.Thus the damage can be localized and quantified by the change in modal parameters.Damage identification methods based on the mode shape curvature change possess the advantages of simple principle,intuitive results,and high efficiency.However,their application is limited by the requirement for high spatial resolution,and the central difference induced low anti-noise ability and difficulty in quantification.A two-stage damage identification strategy,i.e.,localization and then quantification is proposed in this paper by utilizing the mode shape with high resolution extracted from the moving vehicle response.Firstly a damage localization index(DLI)is defined based on the change of the regional mode shape curvature and used to detect the number and the location of damage.Then finite element model(FEM)is employed to formulate a damage quantification equation for estimating the extent of the damage localized in the last stage.Finally an experiment is carried out to verify the proposed damage identification method.The main work and conclusions are as follows:(1)The spring-mass model for vehicle-bridge coupled system response calculation is established by using FEM.The bridge mode shape with high spatial resolution is extracted from dynamic response of moving vehicle using Hilbert transform and band-pass filter.Numerical examples are utilized to study the effects of vehicle speed and random traffic flow on the accuracy of the identified mode shape.Thus the theoretical foundation is established for the following moving vehicle response based damage identification.(2)Taking advantage of the high spatial resolution of the mode shape extracted from moving vehicle response,the regional mode shape curvature(RMSC)and the corresponding DLI is defined to localize the damage in beam-type bridges.Numerical examples indicate that the proposed DLI can detect single and multiple damages effectively.The effects of noise,uneven velocity of vehicle and road roughness are also studied via numerical simulation.(3)After localizing the damage,FEM is established to obtain the relationship between the damage extent and the change of RMSC.Then combining with the measure RMSC,a damage quantification equation is formulated to estimate damage extent.Numerical examples indicate that the damage quantification equation can quantify single and multiple damages with satisfactory accuracy.(4)Vehicle and bridge model are created in lab for experiment.A wireless sensor is installed on vehicle to capture its dynamic response when travelling along the beam.Then the mode shape of the beam is extracted for damage identification.The results of the experiment indicate that the proposed method is effective in damage localization and quantification.