Vibration characteristics of shallow suspension bridge with pre-tensioned cables

Cable supported structures offer an elegant and economical solution for bridging over long spans with resultant low material content and ease of construction. These structures, however, tend to be slender and flexible as the structural stiffness depends mainly on the suspending cables. In this paper a cable supported bridge model with pre-tensioned reverse profiled cables is proposed to carry out a conceptual study on the free vibration characteristics of shallow suspension pedestrian bridge structures. Effects of some structural parameters such as cable sag, cross sectional area, applied mass and pre-tensions in the reverse profiled cables have been investigated. Numerical results show that for cable supported bridges with shallow sag the lowest frequencies correspond to lateral and torsional vibration modes which are always combined together and become two types of coupled modes: coupled lateral–torsional modes, as well as coupled torsional–lateral modes. The effects of structural parameters are complex and the natural frequencies can be altered by introducing different pre-tensions in the reverse profiled cables.