Research Of Stress And Calculation Method On Cross Diaphragm Of Cablestayed Bridge With Two Edge Girders

The cable-stayed bridge with two edge girders is more and more widely used in the bridge engineering, the main beam section is composed of two girders on both side and bridge deck, the width of main beam is generally larger, so the lateral connection of edge girders is weak. The cross diaphragm is a very important structural member that contacts girders and deck to work together for bearing the load, it enhances the lateral rigidity of main beam and ensures the safety of the whole bridge. So the rationality of the cross diaphragm is a very important lin k in bridge design. In the design of cross diaphragm, the engineers usually use the simplified bars model to calculate the internal force, which ca uses a big error. Based on the engineering background of the Zhujiang River Bridge in Chaoyang city Liaoning province, The function of cross diaphragm is discussed. Moreover, the stress characteristics of the cross diaphragm under the load are analyzed in detail during the finished bridge state and the construction stage. A corrected simplified calculation model for the cross diaphragm is put forward and the different tension s scheme of prestressing tendon on cross diaphragm are compared.Firstly, in this article, the solid model of full-bridge is established by using the finite element software Midas/Fea. Through comparing the bridge include and not include cross diaphragm, the function of cross diaphragm is discussed from the full-bridge global stress, the deck stress and the torsional behavior of the main beam. The analysis results show that the cross diaphragm can increase lateral stiffness of main beam, reduce the relative displacement of girder and dec k, and greatly reducing the lateral stress of bridge deck. At the same time, the cross diaphragm can enhance the torsional behavior of the main beam under partial vehicles load.Secondly, Three current simplified calculation method for cross diaphragm are evaluated by co MParing the simplified model and accurate model. According to the order of accuracy from high to low, in turn, the Simplified calculation method is part entities model, simply supported beam model, consolidated beam mode. Based on the data of analysis, the section of calculation and the boundary conditions are amended in the simplified calculation method, then a corrected simplified bar model for the cross diaphragm is put forward, which can meet the engineering accuracy requirements.At last, the solid model of construction stage is establish ed by using the finite element software Midas/Fea. Through analyzing the variation trend of cross diaphragm stress in the process of cantilever construction, the conclusion suggest that the additional stress in previously pouring cross diaphragm decreases gradually under the load of deadweight, prestress and cable tension, with the increase of distance from currently pouring cross diaphragm. For the previously pouring cross diaphragms, the influence of deadweight at about 6 cross diaphragms, the influence of prestress at about 3 cross diaphragms, and the influence of cable tension can be ignored. In view of the Zhujiang River Bridge, three different tension schemes of prestressing tendon on cross diaphragm are designed, the result shows that the schemes of Integrated Formwork for the full-bridge makes the stress of the cross diaphragms most uniform, and there is no significant difference on stress uniformity between the other two schemes which the prestressing tendons are tensioned by one time or by batch.