Study On Safty Evaluation Of Bridges In Service Based On Structural Reliability Theory

Because of the natural environment and artificial factors, the bridge performance in service can gradually deteriorate, damage and collapse, which will greatly affect the safety of the structures. Therefore it is necessary to assess the security of the bridges in service through reasonable and effective methods.The assessment method for the safety of bridges in service, based on the structural behavior of reinforcement concrete structures and their reliability theory, is presented in the paper, and the main contents are given as follows:(1) The usual methods, such as First-Order Reliability Method (AFOSM), JC method, Response Surface Method, and Monte Carlo Method, are summarized and compared as they are utilized in the assessment of bridges in service.(2) A mixing analysis method to the analysis of the reliability index for the structural system is presented, base on the basic theory of structural reliability, i.e., the fitted response surfaces of the bridge under the limit states can be obtained by combining the response of surface method with the finite element software ANSYS, thus the reliability index of the fitted response surface can be solved by using MATLAB programs base on the Mont-Calo important samples method and the improved First-Order Reliability Method, by loop calculations until the calculating results to minimum error, and the feasibility and effectiveness are verified by the examples given in the paper.(3) The structural reliability in term of deflection and cracking in the normal service limit state for a T-typed beam bridge, a continuous beam bridge and a two-way arch bridge are analyzed, with taking all random variables of probabilistic models for material and load into account, therefore the structural performance is assessed and the reliability index with time-varying characters are obtained under the normal service statement.