Study On State Evaluation And Bearing Capacity Decay Of Simply Supported Girder Bridge Of General Speed Railway

In this paper,the analytic hierarchy process and the finite element method are used based on a special railway transportation line in Shaanxi Province,aiming at the limitations of the current railway bridge inspection work,such as the scattered state evaluation system and the insufficient consideration of the disease i MPact in the bearing capacity inspection.The health status assessment and bearing capacity assessment methods of existing railway bridges are studied.The aim is to enrich railway bridge inspection and evaluation methods by considering material degradation and structural disease quantification,so that the improved method is easy to operate,systemic,and the results are intuitive and reliable.The main research contents of this paper are as follows:(1)The common diseases of railway simply supported beam bridges and their great influence on structural safety are counted and analyzed.The parts and important diseases that need to be paid attention to in daily inspection and regular inspection are given combined with the statistical results and mechanical principle.(2)Analytic Hierarchy Process(AHP)and binary co MParison method are used to complete the hierarchical research of railway bridges,and an evaluation method is proposed to evaluate the apparent diseases of each level and weigh and sum them,and finally use the scores to reflect the state of railway bridges.(3)The law of decay of bridge bearing capacity due to material strength dissipation is studied,and the quantitative calculation methods of the influence of concrete strength dissipation,steel bar corrosion and prestress decay on bearing capacity are summarized,as well as the concrete carbonation depth and the time prediction model of concrete carbonization depth and chloride ion corrosion rate.(4)Two commonly used evaluation methods of bridge bearing capacity are summarized.A bearing capacity evaluation method considering the damage degree of the bridge is proposed,and the introduction of sub-item inspection coefficient is used to modify the design expression to evaluate the bearing capacity of the bridge aiming at the problems of insufficient consideration of the disease situation in the railway verification code and the complicated operation of the load test evaluation method.The consideration factors and value method of correction coefficient are optimized to achieve the purpose of simple operation and comprehensive consideration.(5)The influence of four typical diseases on the bearing capacity of bridges under different damage degrees using the method of ANSYS software simulation,such as alkaliaggregate reaction,concrete strength reduction,steel bar corrosion,and structural appearance defect,is studied.The results show that among the four typical diseases,the appearance defect has the greatest influence on the decay of bearing capacity of the bridge structure.Finally,the weight of coefficient in the bearing capacity evaluation method considering damage degree is modified according to the calculation results of finite element software.(6)The whole set of testing and evaluation methods proposed in this paper are applied to engineering practice.The relationship between the bearing capacity evaluation method considering damage degree and the bearing capacity evaluation method based on load test is studied and based on the accurate evaluation results of bearing capacity based on load test,through theoretical analysis.The key coefficients in the two methods are linearly fitted and analyzed,and the bearing capacity evaluation method considering the damage degree is improved,so that the results are consistent with the bearing capacity evaluation results based on load experiments,to achieve the purpose of rapid and accurate evaluation.