| With the implementation of our country’s transportation power policy,the national economic level has entered a stage of rapid development,the level of bridge engineering construction has continued to improve,and the number of bridges has also increased.At the same time,various bridge safety issues have gradually emerged,especially the bridge projects located in the special climatic environment in Northeast China.Due to the extreme low temperature,frequent freezing and thawing,as well as the chloride ion erosion caused by artificial snow removal and sprinkling of deicing salt,there are many risk factors for bridges in this area and the safety of bridges is threatened.In order to ensure the safety of bridge projects in such special environments,safety assessments should be done first.This paper proposes a reliability assessment method for the overall safety performance of reinforced concrete bridges in cold regions and a reverse diagnosis technology for bridge risk factors based on the MCS method and Bayesian network theory.It has realized the intelligent grade assessment of the various safety performance of the bridge and the accurate identification of the main risk factors,which provides a substantial reference basis for the maintenance and reinforcement of the in-service bridge.The main research contents of this article are:Firstly,based on the structural reliability assessment theory,it is determined to conduct safety assessments of the bridge structure in the cold area from three aspects of safety,applicability and durability.According to the environmental characteristics of bridges in cold regions,representative bridge risk factors are selected,and combined with experiments,to construct an overall bridge safety performance assessment network model and a method to determine the statistical parameter information of the root node of the network.Secondly,based on the MCS method,evaluate the reliability of bridges in cold areas.Consider the environmental factors to select the appropriate material degradation model on the basis of the environmental conditions,combine with the relevant theories of structural reliability,define the limit state equations and failure domains for evaluating the safety performance of the bridge,and solve the corresponding reliability indicators,according to the reliability indicators.Carry out a grade assessment of the various safety performance of the bridge,and provide reasonable suggestions for whether the in-service bridge needs maintenance and repair.Finally,based on the basic theory of Bayesian networks,a technical method of reverse diagnosis of bridge risk is proposed.A Bayesian network model for the evaluation of reinforced concrete bridges in cold regions is constructed,and then a method for calculating the likelihood parameters of the Bayesian network is proposed based on the MCS method,and the network parameters are initialized.Later,the reverse diagnosis technology of the main risk factors of the bridge could be realized.Relying on the low-temperature bending beam test may verify the correctness and universality of the bridge reliability grade evaluation method and the bridge risk factor diagnosis technology proposed in this paper.This method realizes the rapid assessment and classification of the various safety performance of the bridge,provides suggestions for the maintenance of the bridge,and provides a guarantee for the structural safety of the bridge. |
