Long and narrow cable supported bridges subjected to wind load

Ph.D. project by Søren Vestergaard Larsen.
The project comprises a comparative investigation of aerodynamic properties of long and narrow cable supported bridges of different design.
A new cable-stayed system denoted a spatial cable system formed an important part of the project. The spatial system consists of four inclined cable planes giving both vertical and lateral support to the girder.
The spatial system is compared to a conventional earth anchored suspension system and a cable-stayed system both with two vertical cable planes. These systems render primarily vertical and torsional support to the girder. However, the earth anchored system will when laterally deflected induce restoring forces due to the "pendulum effect".
The aerodynamic properties were tested by section model tests and full bridge model tests. The latter was based on a 13 m long model with dimensions found by scaling down in 1:100 a bridge with an 800 m main span and two 250 m side spans. The girder width was chosen at 1/100 of the span.
The investigations clearly indicated that the spatial system is superior to the two others, both with regards to the 'static' sidesway and to aerodynamic stability. It was even possible to achieve sufficient aerodynamic stability with a bluff (rectangular) girder in the spatial cable system.