Firm： DC Structures Studio

Type： Transport + Infrastructure › Bridge

STATUS： Built

YEAR： 2019

SIZE： 0 sqft - 1000 sqft

BUDGET： $1M - 5M

The Water of Leith Cable Stay Bridge is a 45m span x 3.5m cycle bridge designed by DC Structures Studio for Dunedin City Council. It is a cable-stay bridge with spiral strand cables attached to a 22m high “inverted Y” shape steel tower. The Water of Leith Bridge is located adjacent to the Forsyth Barr Stadium in Dunedin New Zealand and crosses the Water of Leith. The footbridge was designed and consented in the first half of 2018 and was completed in January 2019.

We believe the bridge is a much-needed industry benchmark for how sustainable choices can underpin a project and still result in elegant and cost-efficient outcomes.

> First bridge in NZ to use a 93% recycled deck.

> Our streamlined cable stayed bridge form, in combination with widespread use of FSC accredited glulaminated timber and recycled decking planks, saved 30 tonnes of steel (50%) when compared to the original Specimen Design. This is a substantial reduction in the carbon footprint of the project and underpins the overall design direction.

> Lighting design is both discrete and elegant whilst adopting industry leading “Dark Skies” design ethos to reduce impact on the wider environment.

> First bridge in NZ to use stainless steel mesh as a primary balustrade infill system.

> First bridge in NZ to be modelled (3D) and drawn (2D) using Trimble Sketchup + Trimble Layout software respectively. This substantially reduces design related overheads whilst still creating a fully 2-way integrated design process between 3D and 2D.

> Uses complex buckling analyses, historical aerodynamic wind records, and well considered liquefaction philosophies to optimize design for tangible material and cost savings for our client.

The steelwork skeleton of the main-span is encased in durable but modern and architecturally expressive glulaminated timber. Although the glulaminated timber on the Water of Leith Bridge acts structurally to carry loads between steel cross beams, it also performs a key role as the bridge’s primary architectural element by creating a visual centerpiece along with the elegant steel mast.

Choices that contribute to making this bridge “environmentally responsible” were adopted where possible. The use of timber was favoured over steel or concrete and this was derived from renewable sources. Lighting was based on low energy LED and was designed on the basis of “Dark Skies” with anti-glare light fixtures all pointing downwards to prevent unwanted light pollution. The bridge decking is constructed from boards made from 90% recycled bamboo and plastics which is a much greener and environmentally responsible alternative to tradition concrete, timber, and/or steel bridge decks.

By using traditional bridge building materials such as concrete and steel and combining them effectively with the soft modernity and sustainability offered by engineered timber and recycled composites, the Water of Leith Bridge is a truly unique cable-stay bridge which is economical, environmentally responsible, and architecturally striking.

The vision for the Water of Leith Bridge was:

"A modern bridge built from sustainable and environmentally conscious materials with a sleek design gracefully traversing the Water of Leith."