Research On Design Methods Of The Large Prestressed Concrete Tank Without Joints

Large rectangular concrete tank is widely used to water supply or water treatment projects. It is also an indispensable structure in municipal construction of China. And its impermeability and durability is of great importance. However, fewer researches have been conducted on the "no joints" design methods for large rectangular concrete tank. And the number of large rectangular concrete tank without joints is relatively small at home and abroad. In this paper, mechanical behavior and "no joints" design methods of this type of tank are systematically discussed. This paper mainly including aspects as follows:(1) The calculation methods of the direct effects and indirect effects of the large rectangular concrete tank are elaborated in this paper, which focuses on the related researches and calculation methods about temperature actiont, humidity actiont, shrinkage actiont and creep actiont.(2) Based on the theory of long wall under continuity constraints, the mechanical behavior and stress calculation of the tank wall under the temperature action and prestress action are introduced. The results of calculation fomula match the results of finite element method. Using the finite clement analysis software ANSYS, a parameter study has been conducted to investigate the stress under the temperature actiont and prestress actiont, finding the change rule related to the stress distribution in the tank wall.(3) The optimized design of prestressing tendon distribution in the wall of large rectangular prestressed concrete tank without joints can be conducted, including the horizontal straight tendons, mixing horizontal curved tendons and straight tendons and vertical tendons. The optimized design of horizontal straight tendons is according to the wall stress distribution formula when the wall suffers temperature action and prestressing action. And "mixing horizontal curved tendons and straight tendons" means that the horizontal curve prestressing tendons and ordinary steel are determined according to the ultimate limit state, and the horizontal straight tendons are determined according to the serviceability limit state. The optimization of vertical tendons is similar to the horizontal tendons.(4) Equivalent load method and separate modeling can be both used to simulate the prestress effect in ANSYS, and their results are the same. The former method is simple, but the interaction between concrete and tendons can not be simulated; the latter are on the contrary.(5) To solve the conflicts of stress distributon rules in tank wall under temperature action and prestressing action, a prestress optimization method-"subsection tension, partial tendons full-length design", which is applied to avoid joints, is developed. According to this optimized method, segment lengths and the number of tendons in different zones are determined by the crack resistance requirements of the structure.(6) The finite element analysis software ANSYS is used to analyse the traditional tendon design method and "subsection tension, partial tendons full-length design" method in some underground sewage treatment pool of Nanjing. The results prove that the latter is more efficient.(7) According to the crack control principle "resistance with relax", the related measures of large rectangular prestressed concrete tank are introduced from the aspects of materials, the design and construction.