Newmarket Connection Project, New Zealand

The Newmarket Viaduct in Auckland is the busiest stretch of motorway in New Zealand. It was built in the mid 1960s under the Auckland urban motorways project. The concerns about its inability to comply with the earthquake standards and to cater to the increasing traffic have called for the expansion of the viaduct.

As the Newmarket Viaduct is unable to be widened, a complete deconstruction and replacement of the viaduct has been opted as a solution. The viaduct will be replaced with a new wider structure by December 2012. The three-lane eastern southbound section was opened for traffic in September 2010.

In 2009, the Newmarket Viaduct carried 161,490 vehicles a day, of which southbound and northbound sections carried 83,117 and 78,373 vehicles a day respectively.

Newmarket connection project

The $215m Newmarket connection project is a four-stage replacement for the Newmarket Viaduct (motorway flyover). It is funded by the New Zealand Transport Agency. The project began in June 2009 and is scheduled to be completed in about 49 months.

Stage one of the expansion will add a four-lane southbound bridge beside the existing southbound section. The existing southbound viaduct will be dismantled in stage two to make way for a new bridge to be built in stage three.

Stage four will involve the demolition of the existing northbound sections and relocation of the northbound traffic to a new three-lane structure.

The project also includes realignment of the on/off-ramps and urban design and landscaping initiatives at Newmarket. It will also improve pedestrian links around the area.

The new northbound section will not be widened for many reasons. One of the main reasons is to avoid congestion into the recently upgraded Spaghetti Junction (CMJ). Another reason is that the northbound section carries less traffic than the southbound and it is not necessary to widen the section as the bridge itself does not cause congestion in comparison with the southbound.

Widening of the southbound section of the roadway will reduce the congestion at one section but will transfer that congestion to northbound section, thus giving less benefits from the project.

Bridge construction

The existing viaduct is a balanced cantilever box girder bridge. The staged construction or deconstruction process is possible because the bridge consists of two individual structures. The deconstruction process will remove the deck segments from the existing bridge in a balanced cantilever sequence by using the same equipment throughout the construction process.

Temporary bracing is being installed to support the remaining viaduct once half of it is removed, in order to withstand the extra loads inherent in the deconstruction process. The bracing will not only act as a support but also improve the seismic stability of the existing structure for the balance of its useful life. An overhead launching gantry of 800t is being used in the construction and deconstruction activity.

The new bridge is being constructed by precast match-cast segmental balanced cantilever method which involves placing of bridge decks equally either side of the columns until they meet in the middle. There are no adjacent columns provided at the two ends and spans will be completed by using temporary supports.

The new viaduct bridge will include 468 bridge segments and 24 (2×12) columns. The segments may look identical but each one is uniquely designed for its specific position. Each segment weighing approximately 80t is built in pre-cast yard at East Tamaki and transported to the site. The balance supports consisting over 90t of steel and concrete are installed around each column to address temporary imbalances during the construction. Approximately 4,200t of reinforced steel and 30,000m³ of concrete will be used in the construction.

Newmarket connection project contractors

The project is being executed by the Northern Gateway Alliance (NGA) Newmarket team consisting of several key players such as NZ Transport Agency, Fulton Hogan, Leighton Contractors, VSL NZ, BECA, URS, Tonkin & Taylor and Boffa Miskell.

Beca-Opus was appointed by The New Zealand Transport Agency (NZTA) to conduct environmental assessments and obtain necessary approvals for the project.