Bridges

The NZ Transport Agency's $1.4 billion Waterview Connection in Auckland is the largest roading project ever undertaken in New Zealand. One of the dominant features of the project is the Great North Road motorway to motorway (SH20 to SH16) interchange (GNRI). The interchange ramps incorporate four separate significantly curved viaducts varying in height (up to 20m above SH16) and ranging in length from 225m to 500m. The substructures typically consist of reinforced concrete hammerhead type cross heads supported on single pier columns and single piles. However, a number of variations were necessitated by restrictions on pier positions, including some portal type piers and some ‘tabletop' piers. The viaduct superstructures utilise precast Super-Tee girders made fully integral with all substructures, apart from abutments and a portal pier at the mid-length of one viaduct. Delayed stitch pours at some piers were utilised to reduce creep and shrinkage demands on end piers to acceptable levels. The superstructures were constructed using a self-launching gantry, over one of the busiest motorways in Auckland.

With the construction of the bridges successfully completed, the first part of this paper offers the designer's perspective on the challenges posed by the design and construction of long integral Super-Tee bridges utilising gantry-erected girders, outlining key analysis and design considerations. The second part describes the construction of the ramps, including construction challenges, construction methodology and construction details developed to optimise constructability.

The paper concludes with lessons learned from the design and construction of these significant structures.