Study On The Multi-scale Damage Prognosis Methods Of Cable-stayed Bridge Based On Structural Health Monitoring

During the past 20 years,certain achievements have been obtained in the area of structural health monitoring,but it is difficult to identify the early damage of structures.The development still remains in the monitoring data accumulation and abnormal event assessment.Prognosis technology may be one of effective methods to overcome the technological bottleneck of the structural health monitoring.Damage prognosis(DP)attempt to detect the current damage and assess safety conditions of the structures using the on-line monitoring information,estimate the future loading environments,and predict the remaining useful life and safety performance of the structure through simulation and past experience.This paper proposed a multi-scale DP method based on the structural health monitoring of Guanhe Bridge,which is located in Yanhai Highway,Jiangsu Province.The main tasks in this paper were listed as follows:1.Research on vehicle load model of cable-stayed bridge.Based on WIM of Guanhe Bridge,study on the statistical characteristic of traffic,gross vehicle weight,speed,wheelbase and vehicle gap.Moreover,the actual vehicle load model can be obtained.2.Multiscale finite element model validation of composite cable-stayed bridge.Firstly,multiscale finite element modeling method is proposed based on Arlequin theory and dynamic equilibrium equation;then a two-step response surface method is employed to multiscale model updating;Finally,study on the multiscale finite element model validation based on Probability Box(P-Box)theory.3.Fatigue DP of composite cable-stayed bridge based on vehicle load model and Multiscale finite element model.Firstly,the basic theory and algorithm of wavelet neural networks are introduced,and they are used to predict vehicle load model of cable-stayed bridge in the future;futhermore,fatigue reliability,fatigue life and failure probability of key position can be predicted based on fatigue reliability method.4.Considering complex environment condition,study on the DP of composite cable-stayed bridge based on P-Box theory.The proposed method gives sufficient consideration in environmental impact statements,and predicts the safe reliability in the future.5.The working mechanism and DP of metamaterial cable-stayed bridge.Firstly,Negative mass and negative stiffness are introduced,the relationship between the frequencies's stopbands and local absorber's parameters;then the efficiency of the metamaterial I-girder is verified via numerical testing;finally,the DP of metamaterial cable-stayed bridge is studied.The main conclusions were listed as follows:1.The vehicle load model can be obtained based on generalized extreme value theory,the actual vehicle load is 0.49 times of the highway-I level standard load,the means of vehicle load are different during different seasons,and the actual operation vehicle load gradually growth.2.Based on two-step response surface method and multiscale finite element model,the results shows a satisfactory accuracy for multiscale FE model updating,with the maximum error being no larger than 8%and the values of MAC being over 90%.Moreover,the model validation of Guanhe Bridge indicates an overall satisfactory result of the P-Box approach,the overlap ratio index of each modal frequency is over 89%without the average absolute value of relative errors.3.Based on wavelet neural network and multiscale finite element model,the fatigue DP results of cable-stayed bridge show that the fatigue reliability of steel girder is 5.19 at the expiration of service,the fatigue life of Guanhe Bridge is 152 years based on fatigue reliability method.4.Considering complex environment condition,based on P-Box theory,the DP results of composite cable-stayed bridge shows that the main tower and main girder have more safety reserve,and the stay cable has less safety reserve,but they are within the scope of safety.5.Metamateral is efficient in energy dissipation and vibration attenuation.the fatigue DP results show that the fatigue reliability of steel girder is 6.28 at the expiration of service,the fatigue life of Guanhe Bridge is 209 years based on fatigue reliability method;the seismic DP results show structural response will decrease,and local dampers are efficient in energy dissipation and seismic mitigation when the stopbands of metamaterials are designed reasonable.