Study On The Long-term Performance Index System And Related Experiment Methods Of Concrete Girder Bridges In Mountain Areas

Along with the development of China's traffic and the deepening implementation of the western development strategy, the construction of highway bridges has entered a new glorious period of fast development. However, due to the long service time, the complicated environmental conditions and rapidly increasing of traffic load, the degradation problems related to the long-term performances of existing bridges gradually manifested themselves. Meanwhile, the number of unsafe bridges become larger and larger, and bridge maintenance tasks turn to be tougher and tougher. Moveover, the severe and harsh environmental conditions in the southwestern mountain area of China greatly endanger the safety, durability of highway bridges. Relies on the Construction Technology Project of Ministry of Transport and the National Natural Science Foundation of China Project, this paper conducted a series of theoretical and experimental researches focusing on the long-term performances of concrete girder bridges in a mountain area, and the main reseaches conducted are as follows:?The research status on the long-term performances of concrete girder bridges was investigated, which includes the following aspects: the concrete material, the durability of components and the long-term performances of concrete girder bridge. Then, combining with the research status on the long-term performances of concrete girder bridges abroad, the defiencies in the prevailing researches of the long-term performances were put forward.?The influencing factor to the durability, the diseases and their causes of concrete girder bridges were analyzed, and the influence of durability damages on the performances of bridge structures were elaborated. And then a long-term performance index system was set up, which contains two marjor parts: an index system to evaluate the durability of concrete materials and another to evaluate the long-term performances of concrete girder bridge. Among the later system, the following indexes are included: structural deformation, structural cracks, structure modes and structural displacement.?The research measures included in America's Long-term Behavior Plan on bridge(LTBP) and many more related domestic researches were summarized, and a research method on the long-term performances of bridges was explored based on a long-term field observation. Combing with the service environment and load characteristics of concrete bridges in mountain areas, a long-term observation was conducted on Wan'an Bridge whose approach bridge was deviated. By the summary of the diseases and analysis of causes concerning Wan'an Bridge, the particularity of a curved bridge's stress under loading was revealed together with lateral and longitudinal displaces of the bridge influenced by the shrinkage, creep and temperature effect of concrete, structural dead load, increasing vehicle load and temperature. Among all the influencing factor, temperature load is the most essential factor leading to the deviation of bridges.?according to the combination between the long-term performance index system as being demonstrated in chapter two and the domestic and overseas specifications on experimental methods, some new experimental methods related to the research on the long-term performance of concrete girder bridges were proposed based on indoor accelerating test, which includes the experimental method on the durability of concrete materials and the method on bridge structures under the coupling of environment and loads. Moreover, based on the multi-functional environment/loading coupling experimental system, the accelerating test method under the coupling effect of light aging environment and loads was proposed, and so was the accelerating test method on the longterm performance of corroded reinforced concrete beam under the coupling effect of freezing and thawing cycles and load.By exploring the indoor accelerating test on the long-term performances of concrete girder bridge, the paper provides experimental references for the research on the changing rules and experimental system of the long-term performances of concrete girder bridge in the southwest mountain area of China.