| In recent years,the rapid development of highway bridge construction has played a catalytic role in improving the efficiency of the transportation system and ensuring the stable development of the national economy.According to authoritative statistics from the Ministry of Transport,by the end of 2019,the total number of highway bridges in China has exceeded870,000,of which the proportion of the small and medium span bridges is about 87%.The prefabricated reinforced concrete(RC)beam bridges are the most widely used in small and medium span bridges.Studies have shown that corrosion of steel bars is one of the main reasons for insufficient safety and durability of RC bridges.For the superstructure of the bridge,the corrosion of the steel bars will cause the resistance of the components to degrade,which in turn leads to changes in the lateral load distribution of the bridge.It has a serious impact on the performance of bridge components and systems.Reliability theory has been widely used in the evaluation of bridge performance,which can quantitatively evaluate the ability of the bridge structure to complete the predetermined function.Therefore,it is of great significance to carry out research on the time-dependent reliability evaluation of bridges considering the variation of the lateral distribution caused by the corrosion of steel bars.It is also of great significance to carry out research on the reliability evaluation of the bridge system considering the lateral connection damage.They provide the reasonable basis for the life prediction of bridge structures.In the process of existing bridge detection,some fuzzy detection information will be obtained.If the fuzzy detection information of the bridge can be applied to the reliability evaluation of the bridge structure,then the current operating condition of the bridge can be updated.The prefabricated RC beam bridge is a multi-beam structure,and the force characteristics and failure laws of the superstructure system have certain commonalities.However,due to the diversity of system reliability evaluation methods and the ambiguity in the selection of failure criteria,even for the same bridge,different researchers will give different assessment results.Therefore,it is of great significance to carry out the research on the general system reliability evaluation method of the prefabricated RC bridges.This article relies on the science and technology project of Jilin Provincial Department of Transportation.This project is "Research on the Safety Evaluation and Maintenance and Reinforcement Strategy of Expressway Bridges in Seasonal Frozen Area Based on Dynamic Reliability".The specific research work carried out is as follows:1.Research is carried out on the time-varying reliability assessment method of simply supported T-beam bridges in which the corrosion of steel bars affects the lateral load distribution.Based on Fick's second law of diffusion,a steel corrosion model considering concrete strength detection information is proposed.Taking into account the influence of factors such as the loss of the steel bar section surface and the degradation of the bonding performance on the stiffness of the bridge after the corrosion of the steel bar,the stiffness correction coefficient is proposed,and the modified load lateral distribution theory considering the corrosion of the steel bar is established.The Bayesian theory is used to update the probability model of bridge performance parameters by using bridge detection information,which improves the estimation accuracy of the probability distribution of structural performance parameters.According to the most unfavorable distribution principle,the lateral loading position of the vehicle is determined and combined with the vehicle load distribution model to calculate the load effect,and the reliability calculation method is established considering the load lateral distribution change caused by the corrosion of steel bars.By comparing with the calculation results without the above analysis method,it is verified that the method proposed in this paper can effectively improve the accuracy of the bridge time-dependent reliability.2.For hinged slab bridges widely used in small and medium-span bridges,hinge joint damage is a very common damage in this type of bridge,and hinge joint damage will adversely affect the system performance of the bridge.Based on the modified analytic hierarchy process(MAHP)and the modified hinged plate method(MHPM),the component reliability and system reliability evaluation methods of hinged slab bridges considering hingejoint damage are proposed.The MHPM is used to analyze the influence of hinge damage on the lateral load distribution of each slab,and the first-order second moment method is used to calculate the reliability index of each slab considering the hinge joint damage.On this basis,the system reliability of the hinged slab bridge is evaluated based on the MAHP.3.For multi-beam bridges that are widely used in small and medium-span bridges,such as hollow slab girder bridges,T-beam bridges and small box girder bridges,the system reliability evaluaton method of such bridges is deeply studied.Existing studies only use a single failure criterion to evaluate the system reliability,and there is no specific standard for the selection of the failure criterion.In order to reduce the error of system reliability evaluation caused by the selection of failure criteria,a general system reliability evaluation framework for multi-beam simply supported bridges is proposed.This method combines Copula function and analytic hierarchy process entropy weight method(AHP-EW)to consider multiple failure criterion.Based on the Copula function,the calculation formulas for the bridge system failure probability corresponding to three different failure criterion are established.The "Expert Questionnaire on the Suitability of Failure Criteria" is established,and the weights of different failure criterion are determined by the AHP-EW decision-making method,and the system failure probability considering multiple failure criterion is obtained.4.In the detection process,the existing detection technology often has ambiguities in the detection results of lateral connection damage.For hinged slab bridges,a component reliability evaluation method considering the fuzzy detection information of hinge joint damage is proposed.Based on the membership function in fuzzy mathematics,the uncertainty of the detection information of the hinge joint damage degree is characterized,and the membership function equivalent is randomized,so as to successfully transform the fuzzy information into random variables.Combining the Latin hypercube sampling method,the modified hinged plate method and the response surface method,a calculation method of the lateral load distribution factor considering the hinge joint damage is established,and the component reliability evaluation method considering the fuzzy detection information of the hinge joint is obtained.A component failure credibility index is proposed to characterize thedifferent contributions of component failure to system failure.Based on the Copula function,a system failure probability calculation method considering component failure credibility is established. |
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