In April 2000, The National Trust installed the new £50 000 Carrick-a-Rede Rope Bridge, to span the 18m wide, 24m deep chasm between the mainland and Carrick-a-Rede Island. There has been a bridge across this chasm since the 1600s and it is now one of Northern Ireland's most popular tourist attractions (Fig 1). Given the local weather conditions the bridge is taken down and re-erected annually.
Scott Wilson was asked to design the new bridge without compromising the existing unique form, to take account of modern health and safety considerations in usage and to find a way of safe annual erection. Although the new bridge may not be considered complex in pure engineering terms, its unique situation and unusual design nevertheless proved challenging, not least because there are no codes of practice which apply specifically to rope bridges.
The following paper outlines the unique challenges that were faced in designing a footbridge to include generous sway and vibration.
David McGlade, MA (Hons) MEng (Cantab)