SPECTRAL ANALYSIS OF THE RESPONSE OF KESSOCK BRIDGE TO VORTEX SHEDDING

Kessock Bridge is a cable stayed bridge that crosses the Beauly Firth to the North of Inverness. The crossing has a total length of 1052 m with a main span of 240m supported on 21 planes of cables in an harp configuration. The steel deck has an open cross section and is continuous throughout the 1052 m crossing. During the design of the bridge, wind tunnel tests were carried out by the University of Glasgow. These predicted that the bridge would suffer large amplitude response due to vortex shedding for wind speeds in the region of 20 ms-1. Large amplitude response was recorded on the actual structure both during construction and soon after opening. As a result a set of tuned mass dampers were installed on the bridge to limit the first mode response to an acceptable level. However, these dampers showed only limited success and several episodes of large amplitude response were subsequently recorded and reported. (A) For the covering abstract see IRRD E100250.