Abstract

The design of multi-span cable-stayed bridges requires the control of horizontal displacements on

the towers head when unbalanced loads are applied on deck. There are several strategies to

reduce these displacements, being one of them the use of crossing stay cables in a central section

of each main span. Based on this bridge typology, a general methodology to obtain the optimum

cable system has been developed. Number of cables, anchor position of cables on the deck, cable

areas and presstressing forces are considered design variables simultaneously into the

optimization process. Each cable anchor position is associated to an independent design variable,

allowing overlapping stay cables, different spacing of cables along the deck as well as different

number of cables on each side of the same tower. Queensferry Crossing has been chosen as

application example where the final design achieves an important saving in cable steel.

Keywords: multi-span; cable-stayed bridge; crossing stay cables; optimum design; overlapping stay

system