Experimental Study On Three Towers Cable-stayed-Self-anchored Suspension Continuous Cooperative System Bridge

With the advantage of cable-stayed bridge and suspension bridge, the three tower cable-stayed-self-anchored suspension continuous cooperative system bridge is a complicated continuous collaboration system, consisting of the two cable-stayed-self-anchored suspension bridges and a single-tower cabled-stayed bridge, and it is known for its beautiful appearance. This kind of bridge is troubled by several design and construction problems because of many differences in structural behaviour, construction technique between self-anchored suspension system and cabled-stayed system, which make the behaviour complicated such as the highly nonlinear behaviour of the total structure, the coupling effect of the tower, girder and cable, the complicated system conversion during construction phase. The actual behaviour of this bridge can not be reflected just by numerical simulating, and the problem existing in construction phase is not easy to find as well. So it has important theoretical significance and practical value to carry out experimental study on this new kind of bridge.Relying on the Xi Erhuan bridge project in Han Zhong city, the validity of the theoretical calculating method and the feasibility of construction technique is conformed by fabricating a reduced-scale model with the proportion of 1:20. Taking the nonlinear characteristics of composed systems firstly, simulation analysis of all construction steps has been done with the help of finite element method, and the effect and displacement of the main cable, stayed-cable, suspender, main girder and main tower under different construction phase were gained and compared with the measured value. The effect of different suspender tensioning methods on the behaviour of the total structure, the variation regularity of special line shape of the cables and the overall performance were analyzed through model testing, and the key technique during the construction phase is studied as well.The analytical results and measured results show that, when tensioning the cable, the nonlinear characteristic of the bridge system was significant The controlling factor should be focused on the none-stress length at tensioning stage, and taking the force of cable into consideration as well, when the system converts, the controlling factor should be reversed. The measured value is in accordance with theoretical results, which conforms that the theoretical model can simulate the stiffness, mass distribution and boundary condition of actual structure; the finite element model basing this theory and method could reflect actual performance of bridge, which provided the designing work with technique support.