Bridges

The State Highway 16 Causeway Upgrade Project forms one section of the NZ Transport Agency’s Western Ring Route around Auckland, which is due to be completed by early 2017. The project improves, widens and raises approximately 4.8 km of motorway, and also safeguards it against future coastal erosion and flooding. One of the key features of the project is to widen the existing infrastructure to accommodate additional lanes of traffic. Two existing bridges on this motorway section, Whau River Bridge and Causeway Bridge, are being widened. Each of these bridges comprises two separate structures carrying traffic in opposing directions, and each structure was built originally in the 1950s/1960s and widened in the 1990s. The bridges are a mix of structural forms and present many challenges, both for the integration of further widening work and for the assessment of the existing elements to confirm structural adequacy. This paper discusses the approach taken towards the design of the bridge widening works, how Safety in Design has been taken into consideration, and how the results of assessments, including non-linear seismic ‘pushover’ analyses, have been used to confirm the functionality of the bridges in the final scheme.