New Zealand researchers have found the answers to fix the distinct New Zealand construction threat of earthquake-prone precast concrete hollow-core floors.

Nicholas Brooke, the coordinator of the ReCast Project, said “The seismic issues around hollow-core floors are not new but were brought into the spotlight by the damage caused in the Wellington CBD by the Kaikōura earthquake.”

The team has spent the last four years testing and verifying retrofit solutions to strengthen buildings with precast floors, which have been widely used in New Zealand construction since the mid-1980s. The project team, led by experts from the Universities of Canterbury and Auckland and supported by funding from the Earthquake Commission, BRANZ and Concrete NZ, will publish its findings in the Structural Engineering Society NZ (SESOC) journal to provide guidance for engineers and building owners considering retrofit options for existing buildings.

“We focused on the least complex and most affordable retrofit solutions, tested them, verified them and developed design guidance for the different technologies,” says Brooke. EQC Chief Resilience and Research Officer, Dr Jo Horrocks, says “Precast hollow-core floors have been recognised as a seismic risk for many years and EQC has been eager to support any research that will tackle this issue.

“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. Many owners may have been holding off investing in repairs, in fear of having to do more repairs later, but now they can be confident a retrofit will work,” says Dr Horrocks.

A copy of the draft paper is available here.