Study On Theory Of Probabilistic Reliability Assessment For Existing Reinforced Concrete Bridges And Its Engineering Application

Currently, the existing bridges traditional assessment methods commonly used empirical method, check count coefficient method, system integration method, reliability analysis of four. Reliability assessment method is the use of statistical inference theory, many uncertainties affect the structural reliability assessment using reliability theory level of reliability, the reliability of the method in which the probability of having a clear concept of targeted features. Reliability Theory of Probability in bridge design specification is the practical stage, but for scaling methods to assess the current use of existing bridges, almost experience, this method is simple to operate, but theories are inadequate to assess, evaluate system is not perfect, assessment methods should be improved.At present, there are four common methods of bridge assessment, namely traditional experience method, check coefficient method, system synthesis method, and reliability analysis method. Based on the theory of statistical inference, reliability analysis method is used to analyze many uncertain factors influencing structural reliability and used to evaluate the reliability level by using the reliability theory which includes the probabilistic reliability method with the features of clear concept and clear target. Probabilistic reliability theory is practical in the bridge design specification stage in our country but is almost a kind of pure experience about the scale method applied at present to evaluate the bridge. As we all known that the method above is simple and feasible with unadvanced evaluation theory, imperfect evaluation system and evaluation method to be perfected.The statistical parameters of the structural resistance and load effect of the bridge are calculated through measurement and analysis which are used to evaluate the existing probability of bridge reliability. Because the reliable index is more intuitive than the failure probability and according to the current research results show that most the target reliability index or the minimum reliability index of the structure is required. We can determine whether the existing bridge reliability meets the requirements by calculating reliability index, and comparing with the minimum reliability index using the statistical parameters of the resistance and effect. The main research content of this paper is as follows:We discusses the structural reliability theory in detail which leads to the reliable indicator and the differences and relationship between the reliability of the existing structure and the proposed structure.With regard to concrete carbonation and steel corrosion resulting in the degradation and decay of the existing performance of reinforced concrete bridge, we analyze in detail and summarize the mechanism and the rule of the time-varying which lays a solid foundation for the probability of reinforced concrete bridge reliability assessment.Starting from the principle, we show the advantages and disadvantages of the method of calculating the iteration steps through drawing lessons from the relating formula of bridge design code, using Monte Carlo method analyzing the structure resistance of the bridge, considering the load changes with time, using reasonable load probability model and calculating reliability index by the center point method, JC method, mapping transformation method and practical analysis method.Taking the existing reinforced concrete bridge as an example, we analyze the reliability of the flexural bearing capacity of the cross-section about the bridge including load effect and structure resistance by text analysis, and finally we compare the minimum reliability index with the reliable index calculated by the statistical parameters of the effect and resistance which comes to a conclusion whether the reliability of the flexural bearing capacity of the cross-section about the bridge meets the requirements. At the same time, it proved that probability reliability method is a more objective and reasonable method with better engineering adaptability。...