Study For Design Theories Of Superlong Span Cable-stayed Bridges

The superlong span cable-stayed bridges are more and more favored in practices when the main span beyond 1000 meters compared with suspension bridges. Beside the Hong Kong Stonecutters Bridge and Su-Tong Bridge, planning and feasibility studies of some other large projects are also imagined in China. Focusing on some superlong span cable-stayed bridges such as Su-Tong Bridge, this dissertation deeply discussed many problems as following mainlined by design theories and special mechanical behaviors.1. Studies on the conceptual design and approximate calculation formulas.Based on the existing research results and practices, this paper systemically expatiates principles of some global design parameters and the structural detailing during the conceptual design. Approximate formulas about internal forces of pylon, girder and cables under dead load and traffic load are deduced on the assumption of beam on elastic foundation. Combined with theoretical deduction and statistical data, two formulas for basic frequency of cable-stayed bridges, such as the first-order bending and torsion vibration are presented. Compared with those formulas in the current specifications, the presented formulas have advantages of simpler form, higher accuracy and clearer physical meaning.2. Comparative studies on some optimization methods of cable forces for the reasonable final state and construction stages, and all kinds of nonlinearity effect of cable-stayed bridges.In the paper, many optimization methods of cable force are systemically studied and summarized. Associated with the practice of Su-Tong Bridge, ideal final and construction stages can be achieved by stressing all stay cables just one time. By using single cable model, the effects of three nonlinearity computing methods of superlong cable are compared. It is proved that cable simulating methods by 8 nodes or 8 sub-elements, in the range of spans from 1000m to 2000m, both have high precision. As to the final state and construction stages of Su-Tong Bridge, many kinds of geometric nonlinearity effects are systemically analyzed. Studies show that...