The Research On The Structural Reliability For Self-anchored Suspension Bridges

At present, self-anchored suspension bridges are greatly appreciated for their aestheticappearances, low costs and high adaptabilities. Many self-anchored suspension bridges havebeen constructed or are in construction now. This kind of bridge has its own features, which isgreatly different from the conventional suspension bridge both in construction and inmechanical performances. No matter in the theoretical research on static and dynamicmechanical performances or in the supervision of design and construction, the research on theconventional suspension bridges has been greatly developed with a large number of relatedpapers. With the rapid development and wide adoption of the self-anchored suspension bridge,the research on its design theory, static and dynamic mechanical performances, limit span,ultimate carrying capability and construction control has been carried out deeply. Based onthe structural reliability theory and combining engineering practice, this doctoral paper isfocused on the evaluation of reliability for self-anchored suspension bridges under servicelimit states and ultimate limit states, analyzing the dynamic reliability under seismicexcitations. Moreover, the durability design for concrete self-anchored suspension bridges isalso discussed in the paper. The main research involves the following:(1) As for the problem of reliability evaluation that the limit state function of the large,complex bridge structures can not be expressed explicitly, an improved response surfacemethod (IRSM) is proposed based on the existing response surface method (RSM). It issuggested that the IRSM is highly efficient. And it can simulate the real limit state curvedsurface so that it will be helpful to improve the convergence of the existing RSM. At last,based on the large commercial software MATLAB and combining the general structuralanalysis software ANSYS with it, the program is established for any complex structuralreliability analysis under service limit states.(2) The stochastic static analysis method for the self-anchored suspension bridges isestablished through applying the RSM, in which the variation of material, geometricdimension and external loads are taken into account. The response law is studied for theself-anchored suspension bridges with variation of the diversified stochastic factors. Then it iseasily seen how the diversified stochastic factors affect the self-anchored suspension bridges.The reliability for self-anchored suspension bridge is evaluated under service limit state bythe IRSM.(3) The system reliability method is established for the self-anchored suspension bridgesunder ultimate limit states. The globalβ-unzipping method and the different equivalentrecursion algorithm are adopted to recognize the significant failure models and equivalent limit state functions. The results show that the globalβ-unzipping method is highly efficientand accurate in recognizing the main failure models of structural system. The bond of failureprobability of the self-anchored suspension bridge system is calculated by the Ditlevsen'stheory.(4) The pseudo excitation method is introduced in the structural dynamic reliabilityanalysis, which overcomes the shortcoming of time consuming of the random vibrationapproach and makes it possible to apply the random vibration approach for large and complexbridge structures. In the paper, the reliability of important structural component, piers andtowers used as resist the seismic action, is analyzied in detail. It is special considered that thespace effect, non-stationary and damping ratio can impact on the dynamic reliability.(5) The girder of the suspension bridge is made of concrete material, which makes itinevitable to face the common durability problem as the reinforced concrete structures do. Inthis paper, a new equivalent resistance durability design method is introduced based on theexisting durability researches. In the method, calculating the time dependant reliability indexis used as the item to check the reinforcement calculation, concrete grade and cover thicknessare meet the requirement or not.