Study On Cross Stays Structure Of Super-span Cable-stayed Bridge With Partial Ground-anchorage And Cross Stays

The traditional super-span cable-stayed bridge has some insurmountable diffi-culties，just like excessive axial force of main girder、excessive height of tower、excessive small stiffness of main girder in mid span and so on. In order to solve theseproblems, a new type of cable-stayed bridge with partial ground-anchorage and crossstays is proposed. It can expend the economic span of cable-stayed bridge to1400mor even greater. The cross stays structure is the key of this novel cable-stayed bridgesystem to break through the bottlenecks of traditional super-span cable-stayed bridge.In this paper, a detailed study on the cross stays structure of the new bridge structuresystem is carried. The main contents of the research are as follows：(1)The particular structural system makes differences between this novel ca-ble-stayed bridge system and traditional cable-stayed bridge system on internal forcedistribution、cable-girder anchorage structure and local stress distribution of maingirder. Therefore, it’s necessary to conduct a comprehensive analysis of main girderof this new cable-stayed bridge system. In order to analyze the stress distribution ofmain girder under the anchor effect on basis of the results of the global analysis, thesingle-girder beam element model and the local accurate model are built up in accor-dance with an1408m cross stays cable-stayed bridge project and an1408m traditionalcable-stayed bridge project. The results show: comparing to the conventional system,the maximum axial force of this new system under the dead load is greatly reduced by28.7%, the maximum axial force under the live load is greatly reduced by27.5%; themaximum Mises stress of anchorage zone in the cross stays segment is108MPa;without the accumulation of the horizontal pressure force of cross stays, the stress ofmain girder is in a low level. This new cable-stayed bridge system shows excellentmechanical performance of main girder, and the new cable-girder anchor in crossstays segment shows it’s rationality.(2)Because of the cross stays have longer length and smaller angle, a detailedstudy is carried on the static characters of the cable stays. In accordance with the1408m cross stays cable-stayed bridge project, the static characters of super longstays is calculated. After calculation, the vertical stiffness of cross stays in the girderend and the loading efficiency of the cross stays can be get. The loading efficiency ofeach pair of cross stays is about0.85. (3)The computing method of quantities and unit price of the novel cable-stayedbridge system is illustrated. Basis on that, total cost of the1408m cross stays ca-ble-stayed bridge project and the1408m conventional cable-stayed bridge project iscalculated. Comparing of these two calculation results, the total cost of new bridgeproject is reduced by10.8%. The influence of newly increased stays over the eco-nomical efficiency of the novel cable-stayed bridge system is analysed. The resultshows: The most economic ratio of cross stays segment length and main span length isabout0.25; The longer cable stays and shorter tower can be more economic when thecross stays are installed.