Abstract:

This paper deals with the mechanical properties of a suspension bridge with double main cables under unbalance load. The double-main cable system can be equivalent to a virtual main cable according to the distribution of the load between the top cable and the bottom cable. Under single-span load,the cable force on the load span increases,the load on the adjacent span transfers from the bottom cable to the top cable,and the sag of the virtual cable decreases,so that the cable force balances with the load span. According to the equivalent relation of the cable force between the load span and the adjacent span,the distribution ratio of the cable force loading on the top cable and the bottom cable is obtained by calculating the sag of the virtual cable. Moreover,a finite element model is established to verify the proposed theory,and the results are compared with the theoretical ones. It is found that both the deformation of the pylon and the mid-span deflection of the double-main cable system under unbalanced live loads are much less than those of the traditional suspension bridge.

Key words: double-main cable suspension bridge, virtual cable, load distribution, mechanical property