Study On Damage Identification And State Evaluation Of Bridge Life Cycle

With the increasingly urgent demand for transportation across regions,a growing number of bridges are erected on rivers,lakes,canyons and even the oceans.In order to further consummate the bridge management,improve its service life,and guarantee safety during their normal life period,it appears particularly vital to monitor the bridge real-time status.However,due to the imperfection of the current monitoring theory and methods and the immaturity of the technology,the development of the bridge monitoring research are greatly limited.In view of the aformentioned issue,the theoretical analysis and method study were made in terms of the damage identification and state evaluation in the course of the bridge life cycle monitoring from the construction stage to the operation stage.Taking the Juhe Bridge as the engineering example,the construction and implementation of the integrated monitoring system for the bridge life cycle were discussed and analyzed as follows:(1)First,based on the commonly-used optimal layout of measuring points and evaluation criteria,the influence of different parameters on the optimal layout of the measuring points was analyzed.Then,taking a tyical bridge as an example,the tradtional optimal metnods like effective independent method,kinetic energy method and QR decomposition method were adopted to investigate the measuring points layout,and a precise measuring points layout was proposed by stepwise adding and subtracting sensors.The caculational results show that the propsed method could meet the requirements of sensor optimization in the practical bridge engineering.(2)Built on the sensitivity method,the current modification methods of the typical calculation model were analyzed and a stepwise bridge modification method was proposed.Through the two-stage modification of the structural component parameters and local component parameters and the function fitting operation with the characteristic parameters as the target could greatly improve the modification efficency.The results show that this optimization method could reduce the true response of the bridge structure to a large extent,and select the accurate "benchmark model" for the life cycle monitoring of the bridge.(3)In order to further improve the damage identification precision and accuracy in bridge monitoring at the operation stage,the relevant parameters in the existing curvature mode recognition methods were further studied,and several improved methods were proposed.The practical bridge example verified that the improved method proposed in this paper was more effective in damage identification than the traditional methods.In addition,the further studies showed that the different characteristics of different parameters had a certain impact on damage identification.(4)In order to remedy the defect that the existing damage identification methods was unable to define the damage degree,the curvature curve parameters were deeply studied and the relationship between the damage degree and the curvature curve was analyzed.And then the polynomial fitting and neural network fitting were used to define the accurate damage degree.The results show that the proposed methods could satisfactorily identify the damage location and degree.Last,the curvature mode shape difference and its distortion area were deduced,which had some reference value for real bridge damage monitoring researches.(5)Under the framework of Bayesian theory,a bridge state evaluation on the basis of B-TBU model was put forward.The probability algorithm was applied to the bridge state evaluation to reduce the impact of human subjective factors to certain extent.Besides,the neural network algorithm was introduced into the model.The results show that the proposed method could obtian better evaluation results and that the results of the neural network algorithm were also consistent with that of the proposed method.(6)The monitoring signficance,monitoring content,system characteristics and functions,equipment and other aspects of the life cycle monitoring system composed of bridge construction and operation periods were fully discussed and analyzed.Taking a brideg as the engineering example,a life cycle integrated monitoring system was constructed to monitor Ju bridge from the construction period and to the operation period,which would guarantee the safe construction and operation of Ju bridge and provide valuable reference for the layout of the monitoring system of the same kind of bridges.