Experimental Research On Shrinkage And Creep Of Prestressed Steel Reinforced Concrete

At present, In China, Research and Application of PRC structure approaches the international advanced level, and the SRC structure research and the application also has a good beginning. The PSRC structure has differently performance with the SRC structure and the PRC structure. The main goal to establish Prestress on the PSRC structure is to improve the SRC structure the crack resistance ability. Therefore, understanding and grasping the effect of Prestress in the SRC structure, clarifying the PSRC structure crack development mechanism, establishing the reasonable crack control criterion, are the keys to apply and promote this kind of new structure. Although the PSRC structure is used in domestic and foreign, there is no integrated theory system and corresponding design standard or corresponding regulations of PSRC structure. At present the computation and the analysis of the PSRC structure are lied on the elementary theory of the SRC structure and the PRC structure. However, these theories do not have the universal significance feasibility to the PSRC structure. Therefore, first steps to study to the PSRC structure are①Computation the loss of Prestress which is caused by the concrete shrinkage and creep.②Section stress analysis and crack controlling theory.③Joint stress performance and structure measure.④PSRC structure mechanics and computation theory.The research of concrete shrinkage and creep has been made deeply and the nature of concrete shrinkage and creep has been understood deeply on the basis of a great many domestic and foreign information about it. Under steel ratio, the shrinkage and creep calculation formula which is simple, useful and accurate has been promoted by researching the shrinkage and creep experiments of PSRC, PRC and PC, analyzing the concrete shrinkage and creep under steel ratio, discussing the loss of Prestress and section forced distribution caused by shrinkage and creep and comparing some shrinkage and creep calculation formulas to understand the features and find the problems of all kinds of models.Through the theoretical analysis and the experimental study, following conclusions have been made.①The concrete structure's shrinkage and creep, by its reinforcement, is much smaller than the structure without reinforcement. So does PSRC.②The loss of Prestress caused by concrete shrinkage and creep can not be neglected. The higher the steel ratio is, the smaller the structure's loss of Prestress caused by shrinkage and creep is. That's because steel reduces the structure's shrinkage and creep.③Steel force distribution caused by concrete shrinkage and creep reduces the concrete stress. Therefore, Attention should be paid on reduction of anti-crack ability.④The loss of Prestress reduces by steel ratio by elevating steel ratio, but the elevating steel ratio causes the stronger reinforcement and the more reduction of concrete stress. Therefore, the steel ratio of PSRC structure should be controlled strictly.⑤The calculation formulas about concrete stress and the loss of Prestress of steel structure have been promoted in this essay. The calculation result of the loss of Prestress has much difference from its measurement result. The calculation result of concrete's the loss of stress is almost the same as its measurement result by comparison between the formula computation and figures achieved by experiments. These calculation formulas needs to be compared by more experimental results in order to establish its reliability.