Probabilistic Damage Identification Of Bridge Structure Based On Finite Element Model Validation

Bridge structural health monitoring and safety evaluation has always been one of the research hotspots and focus of attention at home and abroad.The load and environment of bridge structures have uncertainties and randomness;the information of monitoring and inspection is incomplete;and the computing and simulation methods are simplified;etc.,so that the accuracy and precision of damage identification can been affected.The early damage detection of the bridge structures has become one of the bottlenecks restricting the development of bridge structural health monitoring.Based on the finite element model updating and model validation technology,and considering the influence of parameter uncertainty,the probabilistic damage identification theory and method of bridge structure are established.And an effective way to early damage diagnosis of bridge structure is explored.The main works are as follows:(1)The damage index based on the change rate of element modal strain energy is explored,and its effectiveness in the application of deterministic and probabilistic damage identification for bridge structures is discussed;(2)Taking Guanhe Bridge as the engineering background,the uncertainty quantification and transmission are studied;(3)A finite element model updating and validation method based on PSO optimized BP neural network is proposed,and is used in Guanhe Bridge model updating and validation;(4)The probabilistic damage identification of Guanhe Bridge based on model validation is carried out by considering the uncertainty of parameters;(5)The damage identification of cable-stayed bridge based on probabilistic box theory is explored.The main conclusions are as follows:(1)By considering the parameter uncertainties,the damage index based on the change rate of element modal strain energy can identify the damage location and damage degree of simply supported beam model with single or multiple damages,and has potential for being applied to the damage identification of real bridge structures.(2)The uncertainty quantification models of the environment temperature,vehicle load and structural response of Guanhe Bridge are established,and can be used in the uncertainty transmission,finite element model validation and probabilistic damage identification of Guanhe Bridge.(3)A finite element model updating and validation method of long-span cable-stayed bridge based on PSO optimized BP neural network is proposed.The contact ratios of each order frequency of Guanhe Bridge finite element model after updating are above 80%.The maximum relative error between the calculated frequency and measured frequency is less than 5.09%.And the model credibility is more than 95%.The finite element model after validation can be further applied to the probabilistic damage identification of Guanhe Bridge.(4)Based on the Guanhe Bridge model after validation and considering the uncertainties,damage identification results of Guanhe Bridge indicate that: The vertical first-order damage index can recognize the girder damage location.The index are basically obeying normal distribution,and the mean can better identify the degree of the girder damage;When processing random damage identification of the cables,the accuracy and efficiency of BP neural network are better than the response surface method.(5)The filter method is a good way to separate the uncertainties of the environment temperature and vehicle load which can influence the structural response uncertainties.The probability box models of the structural response uncertainties are established,which can be used to provide the basis of damage identification of Guanhe Bridge based on probability box theory.(6)A damage identification method of Guanhe Bridge based on probabilistic box theory is proposed and verified.The analysis of simulative damage identification shows that: The vertical first-order damage index can express fully the damage identification effectiveness of Guanhe Bridge when considering the uncertainties;The damage identification method based on the probabilistic box theory is suitable for the uncertain damage identification study of bridge structures,and it has a good potential application prospect in the field of damage identification and damage prognosis of real bridge structures.