A competition was launched by New Plymouth District Council in 2007 for the opportunity to design and build an iconic bridge that was to be 'simultaneously utilitarian and beautiful' . Te Rewa Rewa bridge was to be built under a fixed price contract and was necessary to provide an important commuter connection between the city of New Plymouth and the other suburb of Bell Block via the award-winning Coastal Walkway. What's more, the location was on a site historically significant to the indigenous Maori people, giving access to a sacred site where many Maori people died defending their homes in past battles. From the windswept site, three bodies of water can be viewed in a single vista; The Waiwhakaiho River, Lake Rotomanu and the Tasman Sea. There was to be minimal disturbance to the river, for both environmental and cultural reasons - ruling out temporary and permanent piers in the water.

The winning entry was from contractor Whitaker Civil Engineering. Its designed as both a memorial and sculptural bridge, to honour the dead and the sacred status of the land it led to. Firstly the deck was aligned to the summit of the sacred mountain, Taranaki. Secondly, the skewed arch over the deck forms a gateway to signify to the observer that they are entering or leaving sacred land. Thirdly the series of curved ribs connect the windward side of the deck to the arch, to capture a sense of the prevailing wind. Fourthly, the open and white superstructure frames the natural vistas and is an intriguing form in changing light and shadow conditions.

The finished bridge deck has a clear span of almost 69m, and is 3.25m wide. It sits 4.5m above normal water level and was built to be clear of floods and debris flows during volcanic eruptions, and to allow access for emergency vehicles. The Crown of the arch is nearly 10m above the bridge deck.

ARTHUR C HAYDEN MEDAL

Sponsored by Bridge Design & Engineering magazine, this medal recognises a single recent outstanding achievement in bridge engineering, demonstrating vision and innovation in special use bridges.

Judges comments:

"eye catching...this is a bridge you simply cannot ignore"

"it's beautiful...I have never seen anything like this..."

The bridge is highly asymmetrical and not surprisingly, its fundamental mode of vibration is torsional, with a frequency of 1.3Hz. To overcome possible torsional excitation due to wind and pedestrian loading, a series of time history analyses were performed with SAP2000 to determine the likely behaviour. These indicated that the vertical and horizontal accelerations and  the amplitudes of the deck would be within acceptable limits. In reality the modelling proved to be slightly conservative with smaller deck amplitudes being observed.

The torsional stiffness of the most critical side of the deck is controlled by the combined horizontal and vertical stiffness of the deck and arch structure respectively; the inherent torsional stiffness of the three main tubes- and the balustrades form Virendeel trusses to stiffen each edge of the precast concrete deck.

The superstructure was fabricated in factory, then transported to the site as a single 85m-long, 85t element. One end of the superstructure was placed on two 30T excavator bases that were coupled together and towed across the shallow river by a crane base. This method avoided temporary staging in the waterway and very high-capacity cranes.