A North Island bridge that was the first in the world to feature innovative seismic strengthening technology has been named one of the country's outstanding concrete structures.
KiwiRail's South Rangitikei Viaduct, one of the North Island's tallest and longest rail bridges, on Saturday received the NZ Concrete Society's Enduring Concrete Award.
"The viaduct is one of three major pre-stressed concrete viaducts that were built on the North Island Main Trunk line (NIMT) as part of the Mangaweka deviation, which opened in 1981," says KiwiRail Acting Chief Operations Officer Henare Clarke.
"Prior to the deviation, the NIMT between Mangaweka and Utiku involved steep gradients, tight curves and narrow tunnels, making it difficult to use and maintain.
"Rather than upgrading the line, New Zealand Railways decided to re-route it across the Rangitikei River plains.
"The route crossed three major river valleys and required the three viaducts to be built, including the 315m long South Rangitikei Viaduct. It has six spans of up to 56m, and the twin leg piers which rise 76m above the river level.
"The viaduct was the first in the world to use a new type of seismic technology which allows the piers to step or rock in an earthquake, dissipating the earthquake's energy without causing any major structural damage.
"It remains a key part of KiwiRail's network, with around 110 services, including the Northern Explorer, crossing the bridge every week.
"This award is a tribute to those who built and designed the bridge, and to those who have maintained it over the years."
This Enduring Concrete Award is given every two years to recognise outstanding concrete structures or buildings greater than 25 years old.
A bronze plaque commemorating the win will be affixed to the viaduct at a later date.