Researchers in New Zealand develop a new 'rocking' technology for earthquake-resilient bridges

A new “rocking” technology that could make bridges more resilient to earthquakes has been developed by researchers in New Zealand. Their so-called ‘low-damage solution’ has a series of rocking bridge columns that move with seismic shocks, leaving bridges with little to no damage compared to conventional building methods despite the fact that it allows large displacements.

More than 900 bridges were damaged during the Kaikōura earthquake on New Zealand’s South Island in 2016. Roads and railway lines were also destroyed, disrupting the transport network. After visiting the area, the researchers understood the need to know how low-damage rocking systems performed in different soil conditions.

Alessandro Palermo, Professor in Structural Engineering and Materials at University of Canterbury (UC), said current bridge design often prevented collapse in an earthquake but did not prevent significant damage which was time-consuming to fix. The UC experts hoped their solution would minimise such damage, or allow for rapid repairs. The research is being led by UC Civil Engineering PhD student and chartered bridge engineer Sabina Piras, under the supervision of Palermo and associate professor Gabriele Chiaro at UC’s College of Engineering.

“When an earthquake occurs, the column rocks over the foundation,” said Piras. “The joint where the rocking motion happens is designed and detailed 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, in comparison to current construction methods that can take months or even years to fix or rebuild.”

Alessandro Palermo says that this technology makes bridges more resilient. The researchers have developed flexible columns made of high-strength steel that move during an earthquake. They act like giant rubber bands to bring bridge supports back into position. Conventional steel bars are also used to dissipate seismic energy, reducing the impact of a powerful tremor.

“This special steel, which is usually placed in the middle of the column, is actually working as a rubber band. So, during the earthquake this high-strength steel is actually trying to bring the pier back to the original position," Palermo said.  "And we are actually trying to combine these resilience-solutions - seismic resilience-solutions - with accelerated bridge construction. How can we actually build bridges faster and at the same time (be) resilient? This system allows (us) to do that.”