The research is being led by UC Civil Engineering PhD student and chartered bridge engineer Sabina Piras, who is originally from the United States.
Under the supervision of Professor Alessandro Palermo and Associate Professor Gabriele Chiaro at UC’s College of Engineering, the team has developed an alternative earthquake-resilient solution, also referred to as “low-damage”, for designing and building bridge infrastructure.
Current earthquake design philosophy prevents the collapse of bridge infrastructure as a result of a large-magnitude earthquake, but that does not mean that bridges won’t be significantly damaged, said Palermo.
Road closures and repairs can also have a significant impact, as seen in the Christchurch and Kaikōura quakes, as well as the recent flooding which saw the Ashburton River bridge closed.
The researchers have developed a solution which uses a combination of self-centring rocking bridge columns to achieve large displacements with little to no damage compared to conventional bridge columns.
A rocking column has two main structural components - one or multiple high strength bars that act like rubber bands to recentre the column, and several conventional steel bars that are detailed to dissipate energy and can be easily replaced if heavily damaged.
"The joint where the rocking motion happens is designed and detailed such that it can be easily repaired in a very short time."
The repair work on the joint could be done over one night closure, preventing major traffic disruption, she says.
The 2016 Kaikoura earthquake had a major impact on the transport network with damage, landslides and liquefaction affecting over 900 bridges.
After visiting Kaikōura, the researchers say they understood the need to know how low-damage rocking solutions perform in various soil conditions.
“It’s like driving a Ferrari on the road or rough terrain; its performance will not be the same," siad Palermo.
They investigated the influence of different soil types on the low-damage rocking column system and developed a novel and simplified testing technique to simulate this complex problem.
"The soil we build our infrastructure on varies so much throughout New Zealand, and we must understand how additional soil movements in an earthquake influence the rocking behaviour of our columns,” said Piras.
"The majority of New Zealand bridges are built on single, large-diameter piles that, although big and stiff, are still susceptible to movements in an earthquake.
"Structural bridge researchers have validated the performance of low-damage rocking bridge columns through experimental testing assuming that the foundations are fixed. However, we have recognised that this incorrectly predicts the behaviour of the system, and we are the first to study the influence of soil-foundation-structure interaction on low-damage rocking bridge columns,” she said.
The novelty of the solution stands on its simplicity to build.
“I have worked on several different, low-damage bridge systems and it seems the main barrier to implementation has been the slightly higher cost and risk associated with this novel design. I consider the Wigram-Magdala Link Bridge in Christchurch the Tesla of bridges, and would like to see more of these seismic solutions being implemented,” Palermo said.
