Study On Safety Evaluation And Time-varying Reliability Of Reinforced Concrete Aqueducts In Service

Aqueduct structure is an important part of hydraulic structures,and its safety and stability are very important.Reinforced concrete aqueduct structure is widely used in water conveyance projects because of its diverse and beautiful shape,convenient material acquisition and good mechanical performance.At present,about half of the existing aqueduct structures in China have approached or even exceeded their design and service life.A large number of reinforced concrete aqueducts are facing the problems of structural aging,concrete carbonization,steel corrosion and other safety and stability decline.Aiming at the common disease phenomenon of concrete aqueduct in large irrigation area,combining with in-service reinforced concrete aqueduct in Yinqin irrigation area,this paper carries out on-site quality detection and three-dimensional numerical simulation analysis,carries out scientific evaluation and disease analysis on the safety and stability of in-service reinforced concrete aqueduct,In addition,considering the randomness,fuzziness and grey of the influencing factors,the time-varying reliability of the existing reinforced concrete aqueduct is studied.(1)Combined with the Dongfanghong aqueduct project,the quality of the aqueduct is tested and analyzed on site.The static and dynamic state of the aqueduct under various working conditions is simulated by finite element software.The safety and stability of the local and overall reinforced concrete aqueduct are evaluated and analyzed scientifically from various angles,a set of detection and analysis methods suitable for in-service reinforced concrete aqueducts is explored,and the corresponding reinforcement scheme is put forward.(2)Based on the existing reinforced concrete aqueduct structure,considering the time factor and the randomness and fuzziness of the durability deterioration factors caused by concrete carbonization,and taking the concrete carbonization depth of aqueduct structure as the basic control parameter,the time-varying fuzzy reliability model of concrete carbonization depth varying with time is established,The corresponding program is compiled by using MATLAB,and the calculation and analysis of engineering examples are carried out.The calculation results show that the time factor can reflect the dynamic reliability index of aqueduct structure which changes with time better,so that the repair time of aqueduct can be grasped more accurately.On the basis of time factor,the solution obtained by considering the randomness and fuzziness of variables is smaller than the classical reliability solution,which is in accordance with the actual project and more close to the real situation of the project.(3)Grey system theory is introduced into reliability analysis and life prediction of reinforced concrete aqueduct in service.GM(1,1)model of carbonation depth of reinforced concrete aqueduct changing with time is established,and the prediction formula of carbonation depth changing with time is deduced.On this basis,time-varying grey reliability of aqueduct structure is calculated.The results show that the relative error between the predicted value and the measured value is less than 8%,and the predicted value has good fitting accuracy and predicted reliability.On the basis of time factor,the grey solution considering variables is smaller than the classical reliability solution.This is in line with the actual project,closer to the real situation of the project.