Newmarket Viaduct

Story

The Newmarket Viaduct, sometimes considered 'one of the most distinctive engineering features' of New Zealand, is a seven-lane state highway viaduct in Auckland, the country's largest city. Carrying the Southern Motorway over the Newmarket suburb area southeast of the CBD of the city, the 700 m long viaduct is up to 20 m high in places.Original structureThe viaduct was opened on 3 September 1966 at a cost of NZ$2.26 million, and was constructed as New Zealand's first pair of balanced cantilever bridges. With its long spans, the s-curvature and the varying superelevation of the motorway, it is a complex structure even today, and at the time was a ground-breaking design for New Zealand.While considered a successful design, it was built to far lower earthquake standards than those which other New Zealand structures now fulfill, being built to survive only a 1 in 500 year return period earthquake. It could have received significant damage in an earthquake as common as once in 200 years. This made the structure the weakest strategic transport infrastructure link in the Auckland area, with a potential collapse cutting off all motorway transport to the south. Also, during design, temperature stresses were not yet understood to a sufficient degree, leading to increased wear on structural elements.