Study On Key Techniques Of Cable Structure Construction

Cable is an important component to bear loads in cable structure. In most cases, the cable anchor point of the cable structure has a certain degree of flexibility. For the cable that use individual anchoring of parallel steel strands, both anchor points of the flexible support approach each other when stretching a latter strand, which makes the force in prophase tension strand reduce, eventually lead to inconsistent tensile stress in each strand of cable. Strands that the tensile stress is beyond the ultimate strength will sudden break under larger loads. Then the larger loads added to the remaining steel strands further causes steel strand sudden break one by one, and it will lead to cable structure failure ultimately. Under the larger dynamic or impact load, this kind of situation will become more prominent. Therefore, it will affect the reliability and security of structure seriously if the tensile stress in each strand of cable is inconsistent after construction.It commonly needs to calculate the installed tensile force in every strand before using individual anchoring method to construct the cable structure. However, this task must use the stiffness of the cable structure when calculating the installed tensile force in strands. In fact, it is unable to determine the stiffness of the cable accurately due to various nonlinear factors, such as size effect, material nonlinearity, geometric nonlinearity, etc. Most of the existing studies determine the stiffness of the cable structure before constructing the cable structure, but the inaccurate calculation of the stiffness value will result to the initial inconsistent stress of the strands. Therefore, the tensile stress in each strand of cable is inconsistent factually, and the structural reliability and security is a widespread hidden danger.In order to solve the problem, this thesis puts forward a construction process named "climbing" tension method which is not need to use the stiffness of the cable structure according to the principle of equivalent tension method. By analyzing the force relationship between strands during the "climbing" tension, then we propose a method of calculating the stiffness of the cable between anchor points. A construction scheme of a bridge was improved by the use of "climbing" tension theory, and we also compare the "climbing" construction technology and the existing methods, furthermore, we use the stiffness measurement theory of "climbing" method to analyze the force of strands in an active structure.The adoption of the "climbing" method can make the force in every strand consistent, and the cable force will be equivalent to the theoretical design value. The stiffness that was measured during the "climbing" tension can be used to guide the construction of the cable. If the stiffness presents a linear variation, the tension within two periods can be calculated, this will reduce the number of tension. Otherwise, we should use the "climbing" method until the state that the force in each strand is consistent and the cable force is equivalent to the theoretical design vale is achieved. In addition, the stiffness can also provide the necessary basis for cable force adjustment, replacement and mechanical analysis and so on at later stage.