Structural System Of Ultra-long Span Cable-stayed Bridges

At the beginning of the 21^st century, there are two cable-stayed bridges with ultra-long span born into the world, which makes the original span record of 890m up to the present 1088m. The increasing range of the span is so large that the original structural system for the cable-stayed bridge with 800m span or so is under suspicion. Therefore, it is very necessary to carry out a special research on the cable-stayed bridge with ultra-long span, for the current of increasing span even larger than 1000m. The dissertation probes into the concept of the structural system of the cable-stayed bridge as it is a premise for the further research and the structure of the paper is thereby based on the concept. The right structural system for the cable-stayed bridge with ultra-long span is suggested after analyzing the structural performance of the cable-stayed bridge of which main span exceeds 1000m.The paper looks back on the development history of the cable-stayed bridge at first, and introduces the status in quo of the structural system of the cable-stayed bridges with span about 800m in the world. Then, an analysis is lay out from the aspect of girder-tower system, cable system which comes from the concept of the structural system. It is based on the design of the Sutong Bridge, including static analysis and dynamic analysis. When the girder-tower system is under discussion, a new bearing system in which a vertical spring-damper is set on the location where girder and tower intersect is brought forward to deal with the minus bending moment of the location under the wind load and a value of the stiffness is suggested. Further more, the limit span is discussed on the premise of present technique conditions, the relation between the elements of girder-tower system including the comparative height of the tower, the ratio of side span and main span, and the design data of girder, tower and cable and the structural responses is put up, and some optimized values are proposed. At last, the structural performance of the cable-stayed bridge with ultra-long span is progressed when CFCC is adopted and various novel structural systems applicable for ultra-long span are summarized.The research in the dissertation solves the possibility of span exceeding 1000m of the cable-stayed bridge, and it is instructive for the design of the cable-stayed bridge with ultra-long span.