Modular by necessity – Bracklinn Falls footbridge

Abstract

Bracklinn Falls is situated in a gorge surrounded by ancient woodland within the Loch Lomond and the Trossachs National Park. The park authority required a replacement footbridge to cross the gorge and to provide views of the falls. However, access for construction plant and materials was extremely difficult, with the sole access by way of a steep and sharp-cornered path. The construction and access constraints drove the development of a new modular system and governed the structural and aesthetic design for the new footbridge. The resulting structure consists of perforated panels, formed from single sheets of weathering steel folded into a z-shape. These panels were bolted to cross-frames and assembled to create a half-through beam that spans 21.4 m. The scheme achieved an A+ rating under the ‘structural carbon for bridges’ (SCORBs) system (Archer and Green, 2021). The structure was assembled bay by bay and push launched along a set of temporary rails, then jacked onto the permanent bearings. By using a folding process, the modular system minimised welding and hence fabrication time. The system is in the process of being developed for repeated use at other locations, and forms an attractive ‘flat-packed’ modular alternative for difficult to access locations.