Theoretical And Practical Study On Evaluation And Reinforcement Of Arch Bridges

Using analytic hierarchy process, fuzzy mathematics, reliability theory and risk theory, FEM as tools, a theoretical system has been established to evaluate the arch bridge before and after the reinforcement. And a number of arch bridges have been evaluated using this theoretical system. The evaluation results show that arch bridges possess high reinforcement feasibility, using the reinforcement methods provided in this study. Accordingly, the standardized methods are proposed to reinforce arch bridges. The main works are as follows:Firstly, a thorough research of the mechanics behaviors of the arch bridges has been done. And the factors for the arch bridges with high bearing capacity potential are studied. Three main factors that affect the bearing capacity of the arch bridges are studied. These include the combined effect, main arch ring and the shape of main arch ring. Then the effect of defects of the arch bridges on the bearing capacity has been studied.Secondly, the evaluation methods which use the bearing capacity potential of the arch bridges are put forward. Based on the mechanics behaviors, the analytic hierarchy process and fuzzy mathematics are used as tools. The idea of evaluating the arch bridges using arch bridges' bearing capacity potential is proposed and the detailed methods are given. A safety evaluation system for the full-web masonry arch bridges is established.Thirdly, the reliability theory is applied in practice in evaluation of the arch bridges is applied in practice. Based on some basic assumptions, the procedure to evaluate the reliability of the arch bridges before and after the reinforcement is proposed. Then the time-dependent reliability is considered so the service life prediction can be achieved to consider that the vehicle load and structural resistances vary obviously with time.Fourthly, the risk analysis based on the reliability theory and related decision theory is applied to evaluate the arch bridges. Some collapse cases of arch bridges are collected and the main factors leading to the arch bridge accidents are studied based on the statistical analysis of the collapse cases. Three models of the expected losses have been proposed. The first one is that before reinforcement of the bridge and the second one is that after the reinforcement of the bridge. The third one is that the bridge is dismantled and rebuilt. The risk eliminating criterion is defined and formulated. Then the decision making rules based on the risk eliminating criteria are given.Fifthly, the further study is carried out for the reinforcement methods. Specifically, a series of new methods are put forward to reinforce the open spandrel arch bridges and an optimization has beeb proposed using numerical analysis. For the full-web arch bridges several methods are obtained. Then a comparison has been made for the numerical results of different reinforcement methods. Based on the comparison, the optimal method to reinforce the full-web arch bridge is wrapping reinforced concrete strips on the arch soffit. When there is no data about the arch bridge which needs reinforcement, a method called equal stress method is proposed. The problem of how to determine the reinforcement parameters such as the thickness of reinforced concrete and the reinforcement ratio has been solved.Sixthly, the research results of the evaluation and reinforcement of the arch bridges are given. Using the proposed methods, some reinforcement cases carried out in our practice are analysed and the results show that all of the cases possess high reinforcement feasibility. So it can be said that most existing arch bridges can possess high reinforcement feasibility using the proposed reinforcement methods.Finally, a new idea for the arch bridges reinforcement by the standardized methods has been proposed. Based on the research results, the details of the standardized methods, including the subject, construction, measures, procedures and key steps are summerized.