Rapid Damage Detection For Small And Medium Span Bridges Based On Vehicle Induced Response Of Bridges

Bridges are an important part of transportation infrastructure,and the bridges in China are characterized by large numbers,short life span,concentrated construction period and serious aging trend.Among them,the small and medium span bridges are difficult to popularize the health monitoring system and highly dependent on the traditional visual inspection based assessment.It is of great significance to identify the damage of small and medium span bridges by fast and effective methods,and then formulate the corresponding maintenance and reinforcement plan.In this paper,rapid damage detection methods based on vehicle-induced bridge response are carried out for small and medium span bridges.The main contents are as follows:(1)Based on the frequency decay induced by breathing cracks under vehicle loads,a rapid damage detection method without base-line data is proposed.The influence factors of bridge frequency are introduced,and the influence of vehicle on the nth frequency of the bridge in vehicle-bridge interaction system is deduced theoretically.The damage index based on the frequency decay and the flowchart of damage detection are proposed,and the method is validated by numerical simulation and experiments.The effects of measuring point location,damage degree,road roughness,vehicle weight and vehicle speed on the damage detection results are studied.(2)Based on the quantitative assessment of the non-linearity of vehicle-induced bridge response,a rapid damage detection method of bridges without base-line data is proposed from another point of view.The source of non-linearity in dynamic responses are introduced.The quantitative delay vector variance algorithm is applied to bridge damage detection,and the damage detection is realized by setting the empirical damage threshold.Numerical studies on a simply supported beam under moving vehicle loads are conducted to investigate the influence of different crack models in identifying damage.Experimental studies are carried out to verify the applicability and effectiveness of the proposed method.(3)A bridge damage location method based on the correlation of vehicle-induced response of the bridge is proposed.The effectiveness of Pearson correlation coefficient,Spearman rank correlation coefficient,Kendall correlation coefficient,maximum information coefficient and cross-correlation function amplitude on different degrees of damage is compared and analyzed,and the influence of road-surface roughness on damage location is discussed.The proposed damage location method is verified by numerical simulation and experiments.(4)Based on the moving-window correlation coefficient of signals under vehicle loads,a bridge damage location method with limited sensors is proposed.The damage location is determined by the scatter diagram of damage vector peak,which is verified by numerical simulation and experiments.The influence of different response types,road-surface roughness,number and distribution of sensors,length of moving-window and moving step and the deviation of vehicle parameters on the accuracy of damage location are discussed.(5)Based on the correlation between the vehicle-induced bridge response in the two-dimensional plane,a damage localization method for bridge transverse connections is proposed.Numerical simulations are used to verify and analyze the effect of vehicle loads on the damage localization effect at different transverse locations of the bridge.Experiments of steel-concrete composite beam under vehicle loads are conducted to verify the effectiveness of the method in locating transverse connection damage in bridges.