The bi-cable system enhances the vertical stiffness of the middle pylon, enabling the use of a traditional pylon in multi-pylon suspension bridges. However, research on multi-pylon suspension bridges utilizing a bi-cable system remains in its early stages, with parameter analysis still being limited. The benefits of bi-cable systems in long-span three-tower suspension bridge configurations remain unclear. This paper presents an analysis of three-tower suspension bridges with spans ranging from 1500 to 2500 m, using a simplified calculation method for a bi-cable system and incorporating the elastic deformation of hangers. The effects of the top cable load distribution factor, tower stiffness, sag-to-span ratio, and side-to-main span ratio on static performance are examined, and reasonable value ranges for each parameter are proposed.
Li et al. (2026) studied this question.