Study On Long-Term Deformation Of Long-Span Continuous Rigid Frame Bridge Of China-Laos Railway

As an important part of bilateral cooperation between the governments of Laos and China,the China-Laos Railway is designed and constructed using Chinese technical standards.Due to the influence of complex engineering environment and natural environment,the preparation of high-performance concrete for bridge and the long-term deformation control of bridge in high temperature and high humidity climate are the difficulties in engineering construction.Taking The Bannahan Mekong Bridge of China-Laos Railway as the engineering background,the long-term deformation of the long-span continuous rigid frame bridge and its influencing factors were deeply studied through a lot of tests and theoretical analysis.The main work and results are as follows:(1)The mechanical properties tests of concrete of the long-span bridge of China-Laos railway were tested based on the orthogonal test method,and then microscopic test of the cement paste and the shrinkage and creep tests of the concrete with different fly ash contents were carried out.The results show that the appropriate content of fly ash is 15%.According to this,the concrete construction proportion satisfying the actual demand of bridge was determined.(2)The influence factors of concrete creep prediction models with different codes were compared and analyzed.Compared with the experimental results,the calculated creep coefficient of JTG3362-2018 is in good agreement with the experimental results.On this basis,considering the natural environment of high temperature and high humidity,the creep coefficient correction formula was obtained.The bridge stress and deformation calculated by this formula is in good agreement with the measured results.(3)According to the principle of section stress equivalence,through a lot of analysis and calculation,considering the stress ratio of roof to floor,prestressed loading age and pile loading age,four test beams were designed and manufactured,and the long-term deformation test was completed.The experimental results show that the long-term deformation of the beam is much smaller when the stress ratio is 1.0 than when the stress ratio is 3.0.For the 4 experimental beams in this thesis,the ages of delayed prestressing and stacking increase the long-term deformation of the beams.The calculated deformation of the beam is in good agreement with the measured deformation by using the modified formula of creep coefficient at high temperature and high humidity.Part of the research results of this thesis have been applied to Banahan Mekong Bridge of China-Laos Railway.