Reliability Investigation Of RC Bridge In-service Based On Non-probabilistic Theoretical Model

For limitation of traditional probabilistic reliability analysis, a kind of structural reliability analysis with small requirement for information, low calculating costs and conservative results has become an urgent need in the engineering field. Since the 90s of last century, with the concept of non-probabilistic reliability proposed by Ben-Haim and Elishakoff, after 10 years of development, scholars have done a lot of research work in this field and turned it into a hot research direction. Especially for the non-probabilistic reliability theory based on interval model, which has been perfected theoretically and applied in geotechnical, mechanical and aerospace fields. However, for lack of algorithm, wild application of this theory in the engineering filed was limited. On basis of this, the dissertation makes researches on algorithm of interval model non-probabilistic reliability. In addition, by combining finite element analysis, it lays foundation for application of non-probabilistic reliability theory.Reliability evaluation of existing bridge has long been a concern of scholars and management departments; based on inadequacies of existing assessment methods, this dissertation introduces non-probabilistic reliability evaluation system into existing bridge and makes non-probabilistic reliability evaluation based on limit state of carrying capacity and normal condition. On this basis, prediction for life and stage life of existing bridge is completed. Lastly, the dissertation discusses anti-optimization problem of existing bridges and provides technical supports for maintenance and strengthening of them; in addition, it also makes in-depth discussion for existing bridge by applying probabilistic and non-probabilistic analysis.In short, the dissertation first solves algorithmic problems of non-probabilistic reliability index. On this basis, it introduces non-probabilistic analysis into existing bridge. Specific researches are as follows:(1) Due to inadequacies of conventional algorithm and one-dimensional optimization algorithm of non-probabilistic reliability index, it proposes to improve one-dimensional optimization algorithm; through verification of samples, it proves effectiveness and feasibility on improvement of one-dimensional optimization algorithm. Improvement of one-dimensional optimization algorithm mainly aims at solving non-probabilistic reliability index with explicit limit state equation; however, if analytical expression is not available, then, it is unable to have solution. Therefore, this dissertation explores non-probabilistic response surface analysis (RSA) based on finite element; the method can effectively solve non-probabilistic reliability index with undefined structure in limit state equation. The dissertation also proposes Failure Point Optimization Method based on finite element, which is of no needs for large numbers of FEM (Finite Element Method) and iterations. The method can wildly be applied in structural evaluation of non-probabilistic reliability.(2) Bridge is a complex structure with relatively large variables. If we want to find solution of non-probabilistic reliability index with consideration of each variable as interval variable, the workload will be very large and sometimes it even could not be calculated. Simultaneously, large human and financial resources would be consumed if each variable of bridge were to be measured. Therefore, it provides evidence for variables of non-probabilistic reliability evaluation and guidance to on-site measurement. At one time, by judging monotonicity of each parameter and providing supports for algorithm of non-probabilistic reliability index based on finite element, the dissertation makes sensitivity analysis for parameters.(3) Introducing non-probabilistic reliability theory into existing bridge, establishing non-probabilistic reliability evaluations for limit state of carrying capacity and normal condition of existing bridge, and apply them in real bridges.(4) By considering time varying of concrete carbonation, concrete strength, steel corrosion, corroded steel strength and loads of cars and crowds synthetically, the dissertation establishes dynamic non-probabilistic reliability model based on carrying capacity limit state and predicts its life. Simultaneously, based on controls to crack width and deflection of normal limit state, it proposes the concept of stage life prediction. Finally, the dissertation makes prediction to overall and stage life of real bridge respectively.(5) By making researches to anti-optimization design of existing bridge, it establishes two types of anti-optimization models respectively:load limitation and reinforcement; and verifies effectiveness of the proposed methods via samples. Hybrid model combined by probability and non-probability will be the focus of future researches; based on summarization of existing hybrid model, the dissertation puts forward a kind of new probability and non-probability hybrid model and makes solution for reliability index of hybrid model. Results of coMParative analysis show that methods proposed in this dissertation have a certain amount of practicability.