Model Test Study For The Jointed Pylon Structure Of Cable-Stayed Bridge

The cable-stayed bridge is a kind of indeterminate flexible structure with many redundant degrees of freedom, which consists of three basic members: pylons, girders and cables. The original design of Yongjiang River super-large bridge is a jointed pylon cable-stayed bridge with four cable planes and twin separate prestressed concrete girders. The pylon is the Double-Pylon-Connected Structure that is a new complex structure system. The joint part is under the state of combination with torsion, flexure and shear. The forcing state in separate twin bridges is in coupling conditions.In view of this actual situation, and in order to assure the safety and credibility of the jointed pylon, the test for the whole pylon is done with a scale of 3: 40. At the same time, the related calculation analysis and the experimental study are enriched and perfected. Firstly, the similarity theories and the structural design and loading methods for the testing model are briefly introduced. Then, the test for the whole pylon has been carried out. In the model test, the most unfavorale forcing conditions of the structure were simulated through tensioning the cables on the pylons. To minimize the tensioning of the cables and in order to facilitate the control of the tensioning, the mathematical programming model for optimization of cable force of the least numbers of the cables is created, the relevant numerical program is coded and the corresponding equivalent cable force and the tensioning forces of the cables at different loading levels are determined. The results show that the cable force optimization method as provided in the thesis is feasible and the forcing conditions of the pylon structure are safe in the process of the tensioning. Through the finite element analysis and the model test, finally the results can be summarized as follows.1. The interaction between the cable forces is small. In particular, when the cables are in different pylons, the interaction is smaller. The results show that the stiffness of the tower and the jointed pylon structure is big enough.2. The structure is safe and reliable, both the load bearing capacity and the stiffness of the structure have enough margin.3. In the service stage, the structure does not crack under the most unfavorable forcing conditions. The overall forcing behavior of the structure is good. The tensile stress appers in the concrete of the jointed pylon structure, which shows that the crack resistance is relatively weak.