Canada Street Bridge | Auckland, New Zealand | 2015

Architects: Monk Mackenzie Architects & Novare Design, GHD
Client: New Zealand Transport Agency
Contractor: Hawkins Infrastructure
Steel Fabricators: PFS Engineering

The Canada Street Cycle Bridge is a spectacular realisation of the NZTA’s vision to provide world-class cycling infrastructure with this new cycle bridge currently being constructed at Central Motorway Junction in central Auckland. This bridge provides a missing link in Auckland’s cycle network and provides a new seamless transition for cyclists between Newton Road (Upper Queen Street) and Union Street.

The superstructure is composed of a unique inverted triangular shaped steel orthotropic deck box girder. The bridge has a total length of 160m. The bridge curves from its landing on the existing Nelson Street off-ramp, spans over the Southbound lanes of SH1 and subsequently turns to weave its way alongside the Northern shoulder of SH1 to meet the bottom of Canada Street. The complex layout of the bridge was guided primarily by the fact that it has to function as a cycle bridge. As a result, due to tight site constraints it has to curve in plan in a number of locations to facilitate a smooth change of direction for cyclists, avoid site obstructions but also avoid encroaching over SH1.

Due to the curving nature of the bridge, a box girder type span was adopted due to its inherently efficient ability to deal with the effects of torsion. It proved to be the most efficient way of dealing with the in plan curvature and possible eccentric live loading on the bridge deck.

An architecturally striking triangular shape was adopted for the main pier located adjacent to SH1. This pier supports the main span of bridge as it crosses over SH1. A complex vertically tapering pier geometry was adopted in order to exhibit an effortless transition from the bridges superstructure to substructure.

The remaining bridge piers located on the North side of SH1 have a rhombic shape at the base. This shape transitions into a “splay” at the top of the pier in order cradle the deck overhead.

As the bridge spans one of the busiest sections of the NZ road network it was essential for Novare Design to devise a construction sequence/methodology that would minimise all traffic interruptions during the bridge construction. The selection of pre-fabricated bridge piers and deck segments made it possible to lift all elements of the bridge into place. It also restricts all road closures to night time while still maintaining an ambitious construction schedule.

Due to the unique shape of the deck, in-plan curvature and long length of the bridge, the bridges complex dynamic behaviour was analysed using state-of-the-art finite element analysis software. This analysis investigated affects such as local distortion, warping stresses and out-of-plane stresses induced in the bridge deck due to the complex curvature. Dynamic time history analyses was also undertaken to investigate the behaviour of the bridge under pedestrian traffic loading.