Key Technical Study Improving The Durability Of Concrete Bridge In Alpine Region

Reinforced concrete bridge is very widely applied structure form;as a result of the reinforced concrete structural materials and environmental features, the durability problems of concrete structures exist.Domestic and foreign information shows the economic loss due to perdurable diseases of concrete structures is very great ,and as the environment changes and functional requirements of the increased, durability will be an increasing prominence。In Tibet, the bridges are in the condition of cold, oxygen, drying, freeze-year long period, long sunshine hours, annual evaporation, climate variability, seasonal unknown and large temperature;there is chloride ions, sulfate ions and other harmful ions in part of the rivers, so the durability of the bridges is more serious threat in such harsh environment . The research on the durability issues of concrete bridges in Tibet has a very urgent and practical significance。This paper studies the durability issues of concrete bridges, and the main work are as follows:①On the base of site investigation, full use of existing material , soliciting Tibet transportation construction, maintenance departments and well-known experts, I have scientific and objective evaluation on bridge durability research of alpine region inTibet.②Based on the operation condition of large amounts of reinforced concrete bridges that have been built in Tibet, through analytic hierarchy process with alpine region, cure of the multi-factor mechanism of concrete durability such as construction condition, maintenance condition. The circumstance such as freezing and thawing of concrete, concrete carbonation, stress on the damage of concrete, sulfate attack, concrete cracks, bridge construction, maintenance, operation and under the influence of multiple factors,which affect the durability of concrete bridge structures.③To improve freezing and thawing, salt and corrosion, anti-shrinkage properties of swelling and deformation proceed, after a series of accelerated tests, develop composite multifunctional additive and admixture that can be used in alpine region of Tibet.④Study structure and structural details of the impact on the durability of the bridge; for the first time systematic and structural details from the system, waterproof performance, transsexual, testing set for durability and other aspects of the design principles and methods, analyze the specific design measures,and give more detailed examples and design requirements.⑤Comparing with site maintenance test, summarize the conservation methods for concrete available inTibetan, and gives details of the conservation steps.Finally, use research results achieved the basis, relying on field precast beams and comparing with the tests , verify further the effect of the research results obtained. Results show that: the concrete durability of the main beam is greatly enhanced. Research results of this passage have positive and realistic significance to improve the durability of concrete bridges in Tibet , ensure the safety of existing bridges, save construction funds , accelerate the pace of road construction, and improve the quality of road construction.