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New research aims to solve NZ-specific construction issue

A four-year research project investigating solutions to strengthen precast concrete hollow-core floors prone to earthquake damage will publish its findings to assist developers.

The ReCast Project, led by experts from the Universities of Canterbury and Auckland with funding from the Earthquake Commission (EQC), the Building Research Association of New Zealand, and Concrete NZ, has been testing and verifying solutions to the issue that was magnified by recent earthquakes.

Results will be published in the Structural Engineering Society NZ (SESOC) journal to provide builders and engineers with a cost-effective solution to retrofitting buildings.

“We focused on the least complex and most affordable retrofit solutions, tested them, verified them and developed design guidance for the different technologies,” ReCast Project Coordinator Nicholas Brooke said.

Issues with hollow-core floors were emphasised after the November 2016 Kaikoura earthquake that caused significant damage in Wellington, where $NZ947 million ($AUD874.01 million) worth of insurance claims were made to commercial properties in the city.

“This research is incredibly valuable and detailed, and we hope it will give engineers and building owners, especially in the Wellington area, the confidence to start repairing a building instead of demolishing them,” EQC Chief Resilience and Research Officer Jo Horrocks said.

Dr Horrocks says the recommendations will help prevent New Zealanders from feeling the brunt of future earthquakes.

“New Zealand has suffered devastating impacts from earthquakes over the past 11 years, but from that trauma we have learned a huge amount and developed world-leading science and engineering solutions.”

“We will continue to fund excellent research like this, because we know it saves lives and protects property,” she said.

Despite their proclivity to earthquake damage, precast hollow-core floors have been used prevalently by New Zealand’s construction industry since the 1980s.

“The rest of the world was not so excited about hollow-core floors, so this is really a distinct New Zealand issue,” said Mr Brooke.

Professor Des Bull at the University of Canterbury says the prevalence of hollow-core floors throughout New Zealand’s architecture is a major concern and thanked the EQC for allowing researchers to assess solutions.

The project was praised for its unique collaboration, with both universities contributing four PhD students and one masters degree student to the study.

“It was truly a unique collaboration with PhD students from Canterbury working in the Auckland lab and vice versa, which we believe had not happened previously to anything like the same extent,” Mr Brooke said.

The results are the largest journal published in SESOC, with 11 articles and over 200 designs provided to engineers.

“It is the culmination of 25 years of research, building on the work of Des Bull and funding by EQC, that will be hugely valuable to seismic engineers in New Zealand and abroad,” Mr Brooke said.