Structural Performance and Reasonable Cross-Ratio of Cross-Cable Multi-Tower Cable-Stayed Bridges

The Queensferry Crossing in the UK is the first multi-tower cable-stayed bridge in the world to use mid-span cross-stayed cables to improve structural rigidity. To study the structural performance and economy of cross-cable multi-tower cable-stayed bridges, a total of 11 finite element models were established using two cross-cable setting methods. By changing the number of crossed cables in the mid-span, the variation laws of structural deformation and internal force are obtained. The cross-cable efficiency based on structural stiffness and the cross-cable economy based on the consumption of cables used in the entire bridge are quantitatively analyzed, and it is considered that there is a reasonable cross-ratio of cross-cables. Combined with the current design specification and the empirical data of the actual bridge, the limits of the double indicators were determined, and a scheme comparison chart was formed. The results show that under the action of unbalanced load, the cross cable can greatly reduce deformation and balance the internal force of the structure. The optimal solution is to form a mid-span cable crossing by adjusting the cable spacing, and the reasonable range of cross-ratio is 15%~35%. If the structural stiffness is improved by adding additional cross cables, the cross-ratio should be controlled within 16% to ensure structural economy. This provides a reference for the design and research of cross-cable multi-tower cable-stayed bridges in the future.