Bridges

State Highway 25A Taparahi slipped in late January 2023 following a large rainfall event. The 115 m long, 20 m deep slip severed a vital connection between Kopu, Hikuai, and the wider Coromandel region. To quickly reconnect the communities required an innovative, collaborative approach. This led to a joint effort by NZ Transport Agency Waka Kotahi (NZTA), McConnell Dowell, Fulton Hogan, Tonkin+Taylor, and Beca bringing new thinking to designing and constructing a reliable solution. The final solution involved a 124m long, 3-span steel composite girder bridge.

The objective of the team was to open the road as quickly as possible, and what makes this project truly remarkable is the accelerated timeline - from award to an operational highway in less than seven months, a feat that typically takes up to 24 months.

A key approach to this rapid delivery was the focus on adopting a Design for Manufacture and Assembly (DfMA) approach to the design and construction of the bridge. The DfMA approach aimed to maximise off-site works and minimise on-site construction with the objective to gain benefits in programme, risk reduction, health and safety, environmental impact, and quality. Standardised bridge components were developed with early material decisions to allow for prompt procurement, modular construction, and off-site manufacturing, minimising both time and costs and improving construction safety. An innovative example of this approach was to use a full-thickness precast concrete bridge deck unit system without an in-situ topping, which significantly reduced on-site construction activities, resulting in time savings, improved quality, and improved construction safety with less working at height.

This paper will cover the key innovations, methods and lessons learned from the project, that resulted in increased productivity, reliability, quality, and the successful delivery in a record-setting programme.