Determining Anchor Span Strand Tensions in the Completed State of a Suspension Bridge: An Analytical Algorithm

Abstract

Integral components of suspension bridges are anchor spans, consisting of separate strands splayed from the main cable between the splay saddle and the front anchor plane. The main cable is separated into several strands and anchored to the anchorage through the twisting and dispersion of the splay saddle. Tensions in the anchor span strands are related to the overall structural safety of the suspension bridge, the geometric form, and internal stresses in the main cables generated in the completed bridge state. Therefore, the calculation and analysis of anchor span tension are particularly significant. Meanwhile, analyzing tensions in the anchor span strands is quite problematic, insofar as each strand in the saddle groove of the splay saddle is horizontally and vertically bent and then into a spatial catenary, while individual strands form a complex spatial system. This study first determines the spatial orientation of the anchor span strands passing over the splay saddle and their positions relative to the splay saddles. Analytical solutions are found by assuming that the strand tensions are equal at the point of tangency in each strand in the completed bridge state. Therefore, it can be ensured that the tensions in the anchor span strands are equal, which further leads to a sufficiently high safety factor for the cable strands. Given that the strands are separated from each other, an analytical approach is adopted for geometric coordination and mechanical analysis. Tensions in all anchor span strands, tangent position, and angle of each strand in the splay saddle can be determined quickly and precisely. A regular distribution pattern about the calculation results is observed according to the relative position of strands. A comparative validation is performed for strand tensions calculated theoretically against the measured values in a calculation example, proving the feasibility and high accuracy of the proposed method.