Force condition analysis of a long span single main cable suspension bridge in process of system transformation

The Shuangyong Bridge in Liuzhou, Guangxi is a ground anchored suspension bridge with double towers, a single main cable and with a main span of 430 m. The construction technology for the bridge is that the main cable is erected and the main girder is incrementally launched in the same step and the suspenders are then tensioned in batches. The bridge is characteristic of the particularity of the transverse force effect of the single main cable system and the system transformation of the bridge is technically difficult. To understand the structural mechanical responses of the bridge in the different state in the construction, the unstressed state method and the software ANSYS were used to set up the finite element model for the whole bridge and the changing laws of the parameters including the internal forces of the suspenders and the main cable, the alignment of the main cable, the offsetting of the towers and the support reaction forces of the main girder in the process of the system transformation were analyzed. The results of the analysis show that the safety coefficients of the suspenders and main cable can satisfy the requirements, the changing amplitude of the sagging of the main cable at the midspan is up to 8.852 m, the offsetting of the tower tops is within ± 150 mm and the deformation and force conditions of the towers are rational. After the construction of the second phase dead load is completed, the alignment and the internal force state of the completed bridge are well accordant with the anticipated design goal and the various measured parameters can satisfy the relevant requirements in the design and codes.