Durability Evaluation Of Bridge Based On Bayesian Dynamic Linear Model

The evaluation of the durability of the bridge helps the manager to master the health of the bridge.It provides a scientific basis for rational decision making of bridge maintenance.The carbonization of concrete is one of the main reasons for the corrosion of reinforcement,and is also an important part of concrete durability.However,the current research focuses on the study of the carbonization performance of concrete materials.There are few studies on the carbonization of concrete structures in actual operation under different stresses,cracks and even acid rain conditions.In this paper,concrete carbonization test is carried out for above factors.The influence coefficient of each factor on carbonization is given,based on the experiment and the finite element simulation.At the same time,based on Bayesian dynamic linear model and reliability theory,the durability dynamic evaluation method is given on the level of bridge component and system.The main research and conclusions are as follows:(1)Concrete carbonation test is carried out.Through experimental results analysis,it is found that compressive stress has inhibitory effect on concrete carbonation rate,while tensile stress is just the opposite.The larger the tensile stress is,the faster the carbonation rate is.Based on the experiment,the influence coefficient of tensile and compressive stress carbonization is fitted,and the former non load-bearing concrete carbonization model has been corrected.(2)Through the test results and finite element simulation,the carbonization depth of concrete cracks is analyzed under the diffirent crack width and crack depth.It is found that the crack width has greater influence on the carbonization depth than the crack depth.The increase coefficient of carbonization depth at the crack is put forward and the expression is given.(3)Based on the Bayesian dynamic linear model,a dynamic updating model of concrete carbonization depth is established.In view of the defect that the prediction model has a gradual expansion of the deviation with time,the idea of using the detection information to improve the priori model and the prediction model step by step is proposed.The example test shows that the prediction accuracy of the improved model is improved.(4)Based on the carbonation depth,the reliability evaluation model of the durability of the component is given.The effects of tensile stress,compressive stress and crack on the time-varying characteristics of reliability are analyzed.It is found that the influence of the three on durable life is not allowed to be neglected.The influence of cracks on durability is the most prominent.The thickness of protective layer should be increased for tensile members.(5)Based on Bayesian dynamic linear model and differential equivalent recursive algorithm,considering the correlation among components,a dynamic reliability evaluation method for bridge system is established,and the operation process is given.Through the durability reliability sensitivity analysis of arch bridge system,it is found that the members with the lowest reliability have the greatest impact on the reliability of the system and should be considered first in the maintenance.