Research On State Evaluation Of Arch Bridge Based On Suspender Degradation And Time-varying Reliability

With the continuous improvement of material life,the arch bridge is well integrated with local culture by virtue of its unique style and artistic shape,which greatly meets people’s spiritual and cultural needs.Therefore,as an indispensable part of modern urban landscape,the importance of structural safety of arch bridge is self-evident.The safety state evaluation of urban arch bridge is conducive to provide theoretical basis and reference opinions for the maintenance and repair of arch bridge.Therefore,relying on urban suspender arch bridge,this paper studies the structural stress analysis,reliability evaluation and state evaluation of arch bridge after suspender performance degradation.The main research contents and results are as follows:(1)Based on the measured dynamic characteristics of arch bridge,a model correction method for twice modifying the design parameters of arch bridge finite element model by establishing agent model through neural network is proposed,The modified design parameters are substituted into the finite element model to obtain the theoretical dynamic characteristics of the final modified finite element model.Compared with the measured results,the errors of the two meet the accuracy requirements,which shows that the method of modifying the design parameters for many times has a good effect.(2)The modified finite element model is used to simulate various degradation conditions of the suspender,and the redistribution law of the suspender internal force,the change law of the arch rib stress,the change law of the main beam displacement and the change law of the suspender stress under the degradation of the suspender performance are revealed.(3)This paper explores the service life of suspenders in different stages under the influence of natural environment,obtains the theoretical model of suspender time-varying degradation,and determines the relationship between suspender resistance reduction coefficient and time in combination with the provisions in the specification.(4)Through the allowable stress of the suspender,the suspender function is established to calculate the suspender reliability.Combined with the statistical parameters of the probability density distribution function of each random variable in the existing data statistical function,considering the change of structural resistance with time,the time-varying reliability index of the suspender of important components of the arch bridge is calculated,and the reliability of the suspender during the service time is analyzed,so as to provide a theoretical basis for the subsequent state evaluation of the arch bridge.(5)This paper introduces the advantages and disadvantages of the current commonly used state evaluation methods,and focuses on the hierarchy division and weight calculation process of analytic hierarchy process.Aiming at the limitation of too strong subjectivity of expert opinions in the weight calculation of analytic hierarchy process,an improved analytic hierarchy process based on structural reliability index to construct judgment matrix to calculate the weight is proposed.Establish the arch bridge evaluation system,calculate the weight according to the improved analytic hierarchy process,determine the scoring standard of the bottom index of the suspender,and finally evaluate the state of the arch bridge suspender.The evaluation results show that the improved analytic hierarchy process can make up for the lack of too subjective judgment matrix constructed by expert opinions,make the evaluation process more objective,and the evaluation results are consistent with the actual state.