Cause Analysis And Engineering Measures Research Of Serving Long-Span Prestressed Concrete Continuous Rigid Frame Bridge’s Mid-Span Down-warping In Yunnan Province

Yunnan province is located in the plateau mountainous area, long-span continuous rigid-frame bridges are very common in various-class roads, and many of them have experienced many serious diseases, especially mid-span down-warping, so it is a very practical topic for long-span continuous rigid-frame bridges to analyze and research the causes and measures of mid-span down-warping. The dissertation investigated the operation status of six continuous rigid-frame bridges including K209+499.6Honghe bridge and K288+642Amojiang bridge on the Yuanmo Expressway, and researched the causes of down-warping by studying the world’s largest span unequal span continuous rigid-frame bridge’s finite element model (58m+182m+265m+194m+70m), meanwhile, raised detailed engineering measures and evaluated reinforcement effect by studying representative K288+642Amojiang bridge(70m+2×130m+70m). This dissertation performed the following work based on the research before:First, the dissertation investigated the operation status of six PC continuous rigid-frame bridges’diseases detailly. and sunmmarized some universal laws of continuous rigid-frame bridge’s diseases, especially mid-span down-warping, meanwhile, it had done an nitial analysis of mid-span down-warping and box girder cracking.Secondly, it outlined the long-span continuous rigid-frame bridges’structure mechanical features after long-term deflection、the calculation method for prestress lose and the deformation produced by prestress、concrete shrinkage and creep theory and the calculation for deformation of the statically indeterminate structure、the evaluation and calculation for box girders after cracking.Thirdly, it analyzed the continuous rigid-frame bridgess mid-span down-warping effects of construction management control parameters. it focus on the research and realization of K288+642Amojiang bridge and established3-D finite element model, and analyzed emphatically the impacts of the loss of prestress、shrinkage and creep effecfs of concrete and box girder cracking on long-span continuous rigid-frame bridges’mid-span down-warping, meanwhile, it also compared and analyzed the difference between the theoretical value and monitoring data.Finally, the dissertation raised Engineering measures on restraining continuous rigid-frame bridges’s mid-span down-warping in stages of design、construction、operation and Activation, and taking K288+642Amojiang bridge for example, meanwhile, it raised engineering measures detailly, primarily is add external prestressed tendons. It compared and analyzed the difference of the whole structure by establishing3-D finite element model. In order to verify its reliability, it also analyzed local stress of added deviators and lamina denticulate by establishing entity models by use of Midas FEA and principle of equivalent load of prestressing, and provide practical experience sharing for other engineering applications.