44 | Rachel Graham Water of Leith design a winner DC Structures Studio REGIONAL DEVELOPMENT STEEL DETAILING IS A BUSINESS BASED ON TRUST Talk to us for all your Steel Detailing, Precast Drafting & BIM Services Contact: info@steeldetailing.co.nz | 021 190 9255 | www.steeldetailing.co.nz Dan Crocker loves bridges, and better yet he gets to design them. Dan has always loved bridges and his wife jokes that if he ever won the lottery, he’d probably just design them for free. Dan is the bridge architect and lead bridge engineer for DC Structures Studio in Cambridge. The Water of Leith Cable Stayed Bridge in Dunedin, designed by DC Structures Studio, has just been recognised in the 2022 NZ Bridge Awards, taking out the Design Excellence Award. The bridge is a 45-metre foot and cycle bridge crossing the Water of Leith river and just a stone’s throw from the Forsyth Barr Stadium and the marina. It is a cable-stay bridge with spiral strand cables attached to a 22-metre high “inverted Y” shape steel tower. The bridge was completed at the end of 2018. With the sea just off in the distance and yachts moored in the marina, the design of the bridge echoes its surroundings with the cables looking like a sail might blossom out at any moment. Dan says he loves a project with lots of constraints, and this project was perfect for his team. “We had to navigate over the Leith, had to avoid the existing walls that were designated as historical, and avoid loading an underground culvert. Also the logging yard is really close to where we were trying to land. Straight away some design solutions start to point you in a certain direction, and we started to look at a cable-stay bridge and soon realised it was the best solution. “We felt the cable stay bridge was the most elegant, lightest, and it just fit the location. All those things together meant it was the right solution.” The council originally put out a tender for a “design and construct” commission for the bridge, and initially had envisioned a steel truss bridge. Dan says his team put together a proposal that was not only cost effective and elegant but also one that recognized the importance of sustainability. The bridge conceived by DC Structure Studio removed 30 tonnes of steel – compared to the truss bridge originally proposed by Council - and actively replaced this with sustainable materials such as FSC accredited timber and recycled decking. In what he thinks is a New Zealand first, the deck is made of 93% recycled plastic and is supported by FSC accredited glulaminated timber beams. The balustrade is also made of glulaminated timber and is teamed with stainless steel top rail and infill mesh, a combination of materials that showcase the wood beautifully and calls to the maritime heritage of the adjacent marina. He says, as well as looking beautiful and being cost-effective, increasing the amount of timber and incorporating recycled decking to reduce the steel also reduced the overall carbon footprint of the project. It is this strong focus on sustainable material choices – along with other technical specialisms - that led to the recent success in the NZ Bridge Awards with the bridge receiving the prestigious Design Excellence Award and being noted as a “benchmark for how sustainable design can be done with cost-effective and elegant outcomes”. The award-winning Water of Leith Cable Stayed Bridge in Dunedin. Photo: STW Studio
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