Model Test Study For The United Twin-Pylons Structure Of Cable Stayed Bridge With Separate Twin-Decks

With the increase of traffic volume, bridges are designed with more and more wide decks, a novel twin-deck bridge emerges as the times require. With spacious visual effect and good driving conditions, the twin-deck bridge gradually wins many people's good graces. The number of twin-deck bridges built at home and abroad gradually increases day by day. While most twin-deck bridges are parallel structures, which are in independent force state. Yongjiang super-large bridge being built in Ningbo is a twin-deck cable-stayed one, but twin pylons of separate twin-decks are transversely joined into a monolithic one. The forcing states in twin bridges are mutually transferred through the joint part of the pylon. Twin bridges are in coupling force state. The working state and the safe reserve of the united twin-pylons have attracted engineers'attention. On the basis of collecting and studying correlavite information at home and aboard, taking Yongjiang super-large bridge as an example, model test study on the united twin-pylons is made. The main research work is as follows:1. Taking model test study on the united twin-pylons of Yongjiang super-large bridge as the research object, specific implementation processes and procedures of the model test are described, such as structural design and production, materials testing, loading and testing design and so on.2. The internal forces of control sections of prototype and model tower structure are calculated and analyzed in detail. Equivalence principle of cable forces are introduced. In order to optimally detemine the assigning positions of stayed-cables, the number of stayed-cables and cable forces in the test, optimization theory is applied. Based on the optimization module (OPT) of finite element software ANSYS, two parameterized models are established and the above constrained optimization problem is solved and compared. Based on Matlab platform and ANSYS APDL language, the corresponding numerical calculation is programmed and by transforming the above constrained optimization problem into unconstrained optimization problem, all the calculation processes of optimization solution are achieved by ANSYS calling Matlab. Thus, at the same time of achieving the desired goal, the rate of utilization of stayed-cables is increased and the resource cost is reduced.3. Structural behaviors of united twin-pylons are studied in the model test. Displacements, stresses in control sections and cable forces are measured. The measured and the calculated results agree well. The rationality and feasibility of solution of equivalence cable forces basing on the optimization module (OPT) of ANSYS or numerical programm of Matlab is verified by the test results. The mutual influence among stayed-cables, especially among those between different pylons in the united twin-pylons are made clear. Finally, the ultimate bearing capacity is tested and it shows a high coefficient of safety for the united twin-pylons. The model test results show that the cable-stayed bridge with twin-united pylons and twin separate girders is feasible.