Study And Application For Reliability Of Existing Structure Members

It is the key task in the domain of engineering structures that reliability appraisal and maintaining and reinforcement on existing structures. How to assess and inspection/repair existing structures scientifically and reasonably also become a subject that is followed with great interest at home and abroad. Therefore, a research on reliability assessment and inspection/repair theory for existing structures not only has important theoretical significance, but also has wide application prospects and great economic benefit and social benefit. The dissertation is summarized as follows:1. Considering with efficient algorithm of engineering structural reliability and monte-carlo method, fast calculation to reliability index is achieved by means of Matlab. Mathematical model to solve reliability index was set up, Combined with theory of nonlinear programming and method of optimization calculation for structural reliability. Fast calculation to reliability index was realized by Lingo, which is nonlinear programming software. With the example, the results prove the method was accurate and fast.2. Considered of damage of concrete and steel, and under the condition of materials being deterioration with time, it is posed that time-dependent strength calculating model about existing bending member of reinforced concrete with rectangular section, the double reinforced concrete with rectangular section and T-shape section. And it is given that the simple calculating formula of time-dependent resistance and time-dependent reliability indexes. By analyzing disadvantages of appraisal reliability and combining with characteristics of time-dependent reliability, the time-dependent determining condition is given, which judges that the structure is I kind of T-shape or II kind of T-shape. And it is posed that time-dependent strength calculating model and method about existing member of reinforced concrete column, under concentric or large eccentricity or small compression. And it is studied time-dependent reliability index of existing reinforced concrete column. Combined with calculated example, results prove this method is correct and scientific, and the calculated result is good fit with current appraisal reliability standard.3. Based on the tests on bond-slip constitutive relationship between bars and mortar for block masonry, two bond shearing stress-slip constitutive models between bars and mortar are proposed. Based on the tests on bond-slip constitutive relationship between bars and grout concrete, the bond shearing stress-slip constitutive model between bars and grout concrete is proposed. And considered with masonry and grout for concrete and steel being deterioration with time, it is posed that time-dependent strength calculating model on existing reinforced masonry structures under axial loading. And it is given that the simple calculating formula of time-dependent resistance and time-dependent reliability indexes. It is discussed that time-dependent reliability index of existing reinforced masonry in following different years, and it is posed that existing reliability analysis method for reinforced masonry based on time-dependent reliability.4. Study on masonry strengthening with FRP. Based on the test results, two new bond stress-slip constitutive models between FRP and masonry were proposed and they turned out to be good matches to the experimental results. Experiments of anchorage strength of FRP attached to masonry are done, and it is founded that a new anchorage strength models for FRP attached to masonry using the experiment data. The anchorage strength model for FRP attached to masonry is to provide the calculating basis for vast engineers. Experiments of compressive strength of FRP attached to masonry are done, and it is founded that a new compressive strength models for FRP attached to masonry using interval coefficient k_g. Theresults indicate that the calculated results of the new model are identical with the experiment data very good. Experiments of shearing strength of FRP attached to masonry are done, and it is founded that a shearing strength models for FRP attached to masonry and its design formula is suggested. And it is analyzed that the ratio of loading effect for reliability index, under the condition of dead load and office building live loading or dead load and floor live loading . Reliability research of masonry pre-and-post strengthened with FRP.5. It provides decision-making method based on reliability theory and Utility theory. Decision tree model is also used. On the basis of Utility theory and reliability theory, the residual service life of existing structure can be given taking into account the safe reliability and economic optimization; with the residual service life the optimum re-pairing strategy can be developed, and the optimum time for repairing is deter-mined with the economic benefit being maximual. Finally, a framework considering risk optimization and safety constraint is proposed for Maintain management of existing structures.