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Damage Evaluation And Reliability Assessment Of Existing Concrete Beam Bridge

Posted on:2010-03-14Degree:DoctorType:Dissertation
Country:ChinaCandidate:X F YaoFull Text:PDF
GTID:1102360275488296Subject:Bridge and tunnel project
Abstract/Summary:PDF Full Text Request
On the basis of analysis of bearing capacity and safety state grade evaluation of existing concrete beam bridges at home and abroad, this dissertation draws lessons from the reliability appraiser standards of related fields, and studies the damage evaluation and reliability assessment of existing concrete beam bridges which accounts for the overwhelming majority of highway bridges in China. In detail, the following aspects are investigated:1. Considering diseases about the fourth and fifth degree bridges defined by Code for Maintenance of Highway Bridges and Culvers (JTG H11-2004), damage definition and classification was undertaken on the basis of wide range survey and data analysis. According to the frequency and importance of bridge damages, the author presented the assessment principles for typical concrete beam bridges by the three levels of system injury, component and material damage.2. Based on the studies about damage assessment on the level of materials and components, the author made a comparative analysis on the damage mechanism and applicable conditions, and put forward the amended formulas for calculating the flexural and shears capacity, which were defined in the Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts (JTG D62-2004). The assessment formula for shear capacity was established as well, and in which various impact factors of shear strength was considered comprehensively.3. Directed against the main forms of transverse connection in concrete beam bridges, model test and finite element analysis were carried out to find the impact laws of damage on concrete T-beam bridges, in which the three ways of hinged joint, flange rigid connection and cross slab rigid connection were considered. Transverse distribution and degenerate state of transverse connection were studied under various damage conditions. Based on the analysis of test and simulation results, the rule of live load adjustment coefficient (state) of T-beam bridge was put forward, as well as the calculation formula.4. In view of the influence of the damaged transverse connections to load effect, the load effect model was amended by live load adjustment coefficient. Based on the probability assessment model of existed and time-dependent, the resistance was amended with the help of the statistical parameters of resistance get by error propagation formula, in which amendment formulas on the materials and component-level about typical damage was used and the influence of material and component damages on resistance was considered. Then, safety analysis method was constituted considered the typical damage of concrete beam bridge. 5. By amending the reduction rate of loading capacity used in Code for Maintenance of Highway Bridges and Culvers (JTG H11-2004), a new reliable index is presented in the same safety standard to reflect the relation between load and resistance. According to the basic principal of calibration method, the recommended gradation index was computed under various factors such as different load combinations, vehicle operating status and different failure modes. With these calculated numerical values, the calculated reliability indexes standard for the estimation of safety degree of in-service concrete girder bridge members was ultimately obtained.6. Based on the related standards and results on crack and displacement that cannot continue to loading at home and abroad, the evaluation grade of the concrete beam bridge is proposed by analogy. In the foundation of experiment results, the evaluation ranks of the hinge, the flange rigid connection and diaphragm rigid connection was presented.7. According to the structural characteristics and research results of concrete beam bridges, safe assessment grades was established based on reliability and transverse connection damage. And assessment model and method was founded by means of Analytic Hierarchy Process. And the assess system find its way to apply in a real bridge.8. Considering the summarization of applicability assessment standard of other codes, applicability assessment grade of concrete beam bridges was founded in the view of max-crack and flexibility. And assessment model and method was put forward by means of Analytic Hierarchy Process; and reliability synthetical assessment flow and grades was established too.
Keywords/Search Tags:existing concrete beam bridge, damage evaluation, live load adjustment coefficient, calibration method, analytic hierarchy process, safety assessment, applicability assessment, reliability assessment
PDF Full Text Request
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