Bridges

The adoption of integral construction for bridges incorporating Super-T girders is becoming increasingly common in New Zealand. In addition to the whole-of-life advantages to the bridge owner of eliminating bearings and deck joints, constructors are becoming aware that with careful construction planning, integral construction also offers savings in program and cost. Integral construction can also provide benefits for the seismic resistance of structures.However, the adoption of integral construction also considerably increases the complexity of the analysis and design of the bridge. As with any form of construction, approaches to analysis and design take some time to gain general acceptance within the bridge design community, from bridge owners, and to be adequately catered for in owner’s requirements. A dominant feature of the NZ Transport Agency’s Waterview Connection project in Auckland is the Great North Road motorway to motorway (SH20 to SH16) interchange. The interchange ramps include four separate significantly curved viaducts varying in height and ranging in length from 225 m to 500 m. With almost 1.7 km of ramp construction to complete, the Waterview Connection Alliance carefully investigated the available structural forms and concluded that integral Super-T construction offered the best value-for-money outcome. The viaduct superstructures are fully integral with all substructures apart from abutments and a portal pier at the mid-length of one viaduct.With design complete and construction of the viaducts well advanced, and also integrating lessons from other projects, this paper offers the designer’s perspective on integral Super-T design and construction in the New Zealand environment. The paper outlines key aspects of analysis and design methodology and describes construction details developed to optimise constructability. It concludes with a review of the requirements of the NZ Transport Agency Bridge Manual and recommendations on how these could be improved to more efficiently make use of this durable and resilient construction form.