Key Pylon Design Techniques for Irregular Cable-Stayed Bridge with an Inclined Pylon

The main bridge of Xiakou Xiangxi River Bridge is a hybrid girder cable-stayed bridge with an inclined concrete pylon that creates two spans of 90 m and 238 m. The superstructure in the main span consists of flat steel box girders, while the superstructure in the side span is composed of two-cell concrete box girders. The pylon is - shaped along bridge length, but diamond-shaped along bridge width, resembling a Pipa (a traditional Chinese musical instrument). The pylon rises 126 m, and inclines towards the river bank, forming a 10° angle with the vertical plane. The pylon is made of C50 concrete and consists of upper, intermediate and lower columns. After completion of the bridge, the stresses in the cross-section of the intermediate column and edges were not uniformly distributed, to address this issue, transverse external prestressing tendons were added to the ornamental steel tubes in the pylon base, and a 8 000 kN pre-tightening force was applied to improve the stress condition of the intermediate pylon column. To reduce the accumulated bending moment in the intermediate pylon column during construction, three struts were installed to support the inclined pylon, through which forces could be applied to push the pylon along the bridge length, and the effect of two groups of pushing forces were compared, in accordance with the results, smaller pushing forces were determined for the three struts, specifically 2 400, 3 000, 3 300 kN for the No. 1, No. 2 and No. 3 struts, respectively, which could not only ensure construction safety of the intermediate pylon column, but also serve as supports and load bearing components. During the construction of the upper pylon column, the struts were dismantled after the installation of the steel box girder No. 9 and the second-time tensioning of the stay cables, to alleviate the inclined pylon from excessive loading. After the demolition of struts, the steel box girders in the main span warped upward, the pylon displaced towards the river bank, and the displacement of the structure was great. To minimize the pylon-top displacement deviation and to ensure uniform structural displacement in each demolition step, the strut No. 3 was first dismantled, then followed the strut No. 2 and the strut No. 1. © 2023 Wuhan Bridge Research Institute. All rights reserved.