Extreme laboratory testing on an 84-year-old bridge at the University of Auckland has provided promising insights for key infrastructure across New Zealand. 

Understanding the resilience of these old bridges is important for decision-makers and planning for earthquake response, lead researcher Lucas Hogan said.  

The seismic testing was “well beyond” the displacement expected in a large earthquake, he said, and the structures performed “extremely well.” 

“The results are really important...Our testing shows that even after being exposed to the elements for over 80 years they have plenty of strength,” Mr Hogan said. "It is encouraging to know that these old bridges are still up for the job.”  

The research, funded by Toka Tu Ake EQC and QuakeCoRE, involved testing concrete bridge piers from the deconstructed Whirikono bridge south of Foxton which was replaced in 2020 by a wider structure over the Manawatū River and Moutoa floodplain. 

The bridge foundation piles had been tested in 2020 in their original location during the deconstruction phase. The project team then transported three of bridge piers to the University of Auckland where they tested the concrete under extreme conditions.  

Increasing the resilience of infrastructure is a key was to reduce the impact of natural hazards, Toka Tū Ake EQC Head of Research Natalie Balfour says. 

"When bridges and roads are unpassable, any recovery will be significantly affected as we saw in Kaikoura in 2016,” she said. 

The research team has also been exploring retrofit solutions to enhance the longevity of the old bridges by testing techniques on the remaining column from the Whirokino Bridge.  

University of Canterbury engineers developed a raft of retrofit measures based on previous research in Japan in the 1980s, including affordable solutions using steel rods and clamps to strengthen old bridges.