Structural Design of Helical Steel Footbridges

When it was constructed in 2004, the Greenside Place Link Bridge over Leith Street in Edinburgh became the world’s first helical steel footbridge. This landmark structure had an overall length of approximately 50m with a complex snaking geometry. Its striking design and expressive structure has been repeated in various forms a number of times in subsequent years.

It is a rare experience for an engineer to develop a new form of construction and the author was privileged not only to have led the design of the original prototype but also to have had the opportunity to develop the concept further through the ensuing Harthill Footbridge replacement project. This involved a 70m long main span crossing the busiest motorway in Scotland.

This paper examines the structural behaviour of this form of bridge and the analytical techniques necessary to undertake its conceptual and detailed design. Practical considerations in relation to the detailing, specification, fabrication and erection of the steelwork are then addressed with reference to the above3referenced projects and additional case studies.

The paper concludes with some remarks on the suitability of this intriguing structural form for various future applications as well as identifying areas for further future research and development.