The Research On The Reasonable Structure Of Long-span Harp-shaped Cable-stayed Bridge With No Backstays

The cable-stayed bridge with no backstays is a new concept bridge construct. With the elimination of the backstays, the inclined pylon would rely on its own dead weight, serving as a counterbalance to support the dead loads and live loads on the deck. It would enriched the harmonious relationship between bridge construct and natural landscape, In addition, the particularly exquisite shape would be formed, and the conventional design concept would be broken free from the upright pylon in conventional cable-stayed bridges. Though its mechanical behavior is more complicated than the upright pylon in traditional cable-stayed bridge, the cable-stayed bridge with no backstays not only has been widely accepted but also has been getting more and more applications because of its particularly exquisite shape and outstanding effect of natural landscape. So it is very valuable to research the reasonable structural system and provide some reference for the design and construction of the congener bridge. In this paper, refers to the Alamillo bridge and other bridge of the same bridge type, some studies on the reasonable structural form of no back-stays cable-stayed bridge are carried out by using the plane and space FEM in which the paper changes some important parameters from the point of design based on the Hongshan Bridge, Changsha, Hunan Province, China. The contents are as the following: 1. The paper contrasts the difference of the mechanical behavior between the cable-stayed bridge with no backstays and the traditional upright pylon cable-stayed bridge. Referring to the information about the ten congener bridge built and building and classifying the structure system according to the different disposal form of the towers, the girders and the cables, it draws a conclusion that rigid structure with auxiliary span can minishes both the deflection at the middle of girder's span and the longitudinal and the vertical displacement of the inclined pylon leaning to the side of the main span. At the same time, it can also increase the vertical stiffness and the natural logarithm of the structure. 2. This paper researches the rational structural system of the large span cable-stayed bridge with no backstays by changing the design parameters of the Hongshan bridge's pylon and the main girder, such as the increase or decrease of the weight and the variety of the rigidity to girder and tower, the selection of reasonable obliquity to inclined pylon, the selection of structural system and sectional type, the location and form of the anchors within inclined pylon, the length of auxiliary span and no-cable area of girder, the reasonable join constitution of girder end and construction technique of girder. 3. The variability and the sensitivity of the cable force of the Hongshan bridge is analysed though the results of the cable force which was tested by the apparatus during the cable installation and calculated by the simplified formula of chord vibrant theory and frequency method. 4. At last, this paper draws the final conclusions and puts forward the problems to be solved.