Aesthetics and Torsional Rigidity Improvements of a Triple-Cable Suspension Bridge by Uniform Distribution of Dead Loads to Three Cables in the Transverse Direction

Abstract

Suspension bridges with three cable planes provide an excellent solution to the suspension bridges’ downwarp problem with ultrawide decks, which implies their enormous demand and popularization prospect in the engineering scenarios. In this paper, a method for uniform allocation of dead load in the transverse direction to three cables of the suspension bridge with three cable planes (SB-3CP), which transforms the spatial stress mode into a plane model to simplify the calculation, is proposed. By altering the cross-sectional area of each hanger, the axial forces of the three hangers in the same cross section of the SB-3CP are equal. Therefore, the cross-sectional area and shape of the three cables are equal, improving the suspension bridge outlook in both the cross-sectional and facade views of the suspension bridge. Meanwhile, under the uniform allocation of the dead load, the side main cable bears a higher share of the dead load, which is conducive to improving the entire bridge’s torsional rigidity. In this study, conditions for compatibility of deformation and energy conservation are utilized to derive the relationship between the axial rigidity of the three hangers in the same cross sections. The effects of axial rigidity of hangers, flexural rigidity of the deck in the transverse direction, and length between the hanging points on the difference in the axial rigidities of the three hangers are analyzed and discussed in detail. Finally, an SB-3CP with a main span of 2,320 m and a width of 75 m was taken as an example. The cross-sectional areas of each hanger of the bridge were calculated using the proposed method. Then, its accuracy was validated through the finite-element analysis. This method’s design effect was verified by comparing the differences in the main cable diameter and torsional rigidity between the SB-3CP with uniform and nonuniform dead load distributions.