Research On Long-term Deflection Of Long-span Continuous Rigid Frame Bridge Caused By Shrinkage And Creep Of Concrete

With the development of transportation in China, long-span continuous rigid frame bridge is used widely in recent years, because of it's unique predominances of easy construction, economic cost, reasonable mechanism and comfortable for driving. As more and more long-span continues rigid frame bridges are constructed, shrinkage and creep of concrete and long-term deflection of bridge have become serious problems, and they influence the further widespread of this bridge style in highway bridge construction.To solve this problem, the research projects of shrinkage and creep and long-term deflection of bridge are proposed. Relying on National High-Tech Research and Development Program (863 Program):"Long-term deformation and cracking-control technology of the long-span concrete bridges", shrinkage and creep of concrete and the main factors influencing deformation of bridge are researched in this paper, and relative improving measurements are proposed.Firstly, the principle of concrete shrinkage and creep and internal and external influencing factors are summarized, and some current prediction models in domestic and foreign research domains are list in this paper. Experimental datas of four important regions in China are collected, and the curves of concrete creep obtained by different experiments are analyzed. According to the common-used concrete creep prediction models, VB procedures are used to take numerical calculation. By comparing the calculated results and experimental datas, the differences between them could be found. In addition, the theory of long time deformation of concrete induced by short-time experiment, which is proposed by Professor Bazant is used. According to experimental datas, the creep curves are simulated by regression method. By comparison, it can be found that theory proposed by Bazant is suitable for the real condition of concrete component.Secondly, the mechanics and causes of deflection of long-span bridges are analyzed in this paper. Secondary Channel Bridge of Humen Bridge which is a continuous concrete rigid frame bridge with the span of 270m is taken as calculation example. According to the calculation results, the deformation in later operation period is analyzed. Then, the influence of concrete shrinkage and creep, prestressing tendon loss, automobile load and rigidness loss to the deflection of bridge are researched, and the change reluation of deformation with time history is obtained.Finally, the measurements including predicting shrinkage and creep of concrete, enhancing permanent bearing capacity of box beam, improving design of prestressed steel bar, controlling construction quality and strengthing management of bridge to reduce deflection of long-span continuous rigid frame bridges are proposed.