Imagine Auckland in the early 1960s. The Newmarket Viaduct was just an idea. Now, the Newmarket Viaduct stands before us. It’s more than just concrete and steel. It’s a testament to innovative engineering.
This seven-lane viaduct carries the Southern Motorway. It soars over the Newmarket suburb. The Newmarket Viaduct stretches 700 meters long. At its highest, it reaches 20 meters.
Back in 1966, its opening marked a milestone. It was New Zealand’s first pair of balanced cantilever bridges. The cost then was NZ$2.26 million. Its design was groundbreaking. It had long spans and an s-curve. The varying superelevation added to its complexity.
Constructed from 1962 to 1966, it became the largest pre-stressed concrete bridge. Initially, engineers considered steel girders. Concrete won due to the high costs of importing and maintaining steel.
However, the original Newmarket Viaduct had a weakness. It was built to lower earthquake standards. It could only withstand a 1 in 500-year return period earthquake. A quake as common as one in 200 years could significantly damage it. Temperature stresses caused cracking. This was between the black bitumen coat and the light-colored concrete beams. Additional pre-stressed cables were added. Light-colored stone chips were placed on the bitumen to fix this issue.
Traffic increased to over 200,000 vehicles a day. This is more than the Auckland Harbour Bridge. This made the Newmarket Viaduct replacement necessary. The old viaduct had low safety barriers. In 2004, a truck even fell off. It landed on its roof 15 meters below. The viaduct was a prohibited route for overweight vehicles. This forced more trucks through city streets.
Major repairs were considered. But the structure wasn’t easy to strengthen. A new structure was decided. It would last over 100 years. The new Newmarket Viaduct cost NZ$150 million.
Construction had to minimize traffic flow. A new four-lane viaduct was built first. It was built for southbound traffic. It was placed northeast of the existing structure. Then the old southbound lanes were demolished. Three new northbound lanes were built in the gap. Finally, the old northbound lanes were demolished.
The new Newmarket Viaduct is designed to withstand a 2,500-year return period earthquake. The new structure uses segmented construction. It’s built from 468 pre-cast concrete sections. These sections were made in East Tāmaki. A lifting gantry truss moved them into place.
The new viaduct also features better noise protection. Noise-absorbing asphalt and concrete crash barriers were added. Partial noise walls were also installed. There’s even a volcanic-themed walkway. It runs from Gillies Avenue down to Newmarket.
Construction began in 2007. The first foundations were for the southbound part. A 140-meter-long launching gantry was erected. The southbound addition was finished by the end of 2010. The northbound section took until March 2012.
The replacement work was completed in March 2013. The demolition work won the Civils Demolition Award in 2012.
The Newmarket Viaduct stands as a symbol of progress. It shows how Auckland has grown. Its story is one of innovation and resilience.