Deformation and force characteristics of double-cable suspension bridges

A double-cable suspension bridge has broad application prospects. As a kind of suspension bridge, it is a flexible structure with small overall stiffness, structural deformation induced by live loads is a major concern in the design of double-cable suspension bridges. Deformation and force characteristics of double-cable suspension bridges were studied in this paper, a theoretical analysis method is proposed for calculating the main cable's horizontal force increment and vertical deformation under live load (concentrated and half-span uniform loads) of the double-cable system. Finite element models (FEMs) were established to verify the proposed formulas, and the comparison of formula solutions with FEM solutions revealed good agreement. The effects of key design parameters on the force and deformation were studied; and the deformation and force characteristics of double -cable suspension bridges were compared with those of traditional single-cable suspension bridges. Results showed that the ratio of the horizontal force increments of the two cables caused by the live load is mainly determined by the sag-to-span ratio of these cables. The sag-to-span ratio and the proportion of dead load distributed to the double cables affect the main cable deflection. Increasing the proportion of dead load borne by the top cable or reducing the sag-to-span ratio can increase the gravity stiffness of a double-cable system.