Client: Whangarei District Council

Contractor: Transfield / McConnell Dowell JV

Status: Completed 2013

The Steel Composite bridge is 265m long with nine 25m-long spans and two 20m-long end spans on each side of the central navigation channel of the Hatea River. The Bridge has a lifting Bascule span over the navigation channel which can be raised to allow vessels taller than 7.5m to transit the bridge.
 
The main deck consists of a Steel ladder arrangement with two longitudinal U-Girders and transoms creating a structural configuration for supporting the precast deck. Careful attention to detail allowed the fixed spans to be constructed quickly and efficiently and with precision.

The opening mechanism is based on a traditional rolling bascule, which consists of two steel J-shaped Beams supporting a light weight orthotropic road deck and two cantilever footways with an aluminum decking system. The J-Beams roll back on a Track and Rack mechanism and are raised by two Hydraulic cylinders with upper sections providing the balancing counterweight. As advantageous as the counterweights were, they presented a unique design problem. There were now enormous masses sitting high in the sky atop relatively slender and flexible J-beams. A finite element model was created to examine the natural frequency of the J-beams, which facilitated an assessment of vortex shedding. The model concluded that such vibrations would not be a significant issue.
 
The bascule span presented an interesting complication for the seismic design philosophy. Structurally, and mechanically, the best decision for the bascule span was to keep the two structures separate. The only solution was a complete air gap between the two structures.

The engineering excellence displayed in this project was the seamless integration of civil, structural, mechanical, electrical and hydraulic engineering into an architectural form to create a visually stunning and Iconic bridge, totally embraced by the local community.