Design of a Stress Ribbon Glulam Footbridge Across a Steep Forest Torrent

Abstract

<p>For the Xitou area of National Taiwan University Experimental Forest, a nature conservation area in central Taiwan, our design team was tasked with developing a proposal for a wood footbridge, connecting pedestrian paths on either side of a steep torrent. Selected among various alternatives, our design consists of a stress ribbon glulam deck tensioned over two fan-shaped supports. These are themselves composed of curved glulam members and shaped like the leaves of a ginkgo tree. The pattern is prolonged in the wood lattice work of the guardrail. Combined foundations connect the bridge abutment and pier to each side, helping to balance out lateral forces. To permit the use of Japanese cedar sourced from the local forest, the glulam members are dimensioned to a relatively low allowable bending stress of 80 kgf/cm². Lessening their visual impact, most steel plate connectors are slotted into the glulam members. The bridge was finished in March and will be opened to the public in May. The resulting bridge is relatively high above the torrent, passing over the pedestrian path to one side. In addition to keeping the bridge clear of typhoon floods, this will let hikers experience crossing over and passing under the bridge, offering views from above and along the torrent. The paper will tell the story of how this design evolved, from early concept development to construction. The authors developed this design as part of their undergraduate course of study at the Department of Civil Engineering of National Taiwan University.</p>