Strand element analysis method for interaction between cable and saddle in suspension bridges

Abstract A stable cable-saddle connection relying on the frictional resistance is essential for the safety of suspension bridges. However, the frictional resistance cannot be adequately quantified due to the unclear contact forces, giving rise to a thorny anti-slip problem that particularly troubles the design of multi-tower suspension bridges. In this paper, the cable-saddle interactions are therefore studied by means of theoretical modeling and experimental verification. First, the feasibility and strategy of analyzing the PPWS (prefabricated parallel-wire strand) cable from the perspective of strand are demonstrated. The geometric and mechanical models of 37-, 61-, 91- and 127-wire strands are created, and a strand element analysis (SEA) method with recursive algorithm is then developed. Large-scale model tests are further conducted to investigate the cable-saddle frictional mechanism and to verify the SEA method. Finally, a typical multi-tower suspension bridge is taken as an example for an extended case study. The results show that the proposed SEA method can offer reliable predictions for the contact behavior of multi-strand cables in the saddle. The strand tensions at the critical slip state are unevenly distributed, while slight changes are present on the average tensions of the strand on both sides of the saddle. The use of two vertical plates can improve the frictional resistance by about 30%, and adopting a fewer-wire strand specification and arranging the strands in a higher pattern is also beneficial to improve the cable-saddle frictional resistance.