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EQC research may shake up construction, forestry industries

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Timber wall seismic testing undertaken by the University of Canterbury could have far-reaching implications for New Zealand’s construction and forestry industries, as well as the nation’s quest to become a carbon-neutral economy, the Earthquake Commission (EQC) says.

The research demonstrated cross-laminated timber (CLT) walls are feasible if fitted with special dowels, and cost-competitive with steel or concrete systems in low-rise buildings, offering significant environmental benefits.

The findings, from EQC-funded research by the university’s Associate Professor Minghao Li and his team, produced “stunning results for construction and environment,” EQC said.

Professor Li and his PhD student Ben Moerman tested large CLT shear walls to find out how the multi-storey walls behave in significant earthquakes. They loaded the walls horizontally to create a similar scenario to Christchurch.

The weight of timber is only one-fifth of concrete, meaning much lower earthquake loads, but engineered timber has similar strength as concrete.

“With the right connections, CLT buildings can be really strong and resilient in an earthquake,” Mr Li said.

The research team designed innovative high-capacity connections to resist earthquake forces and protect the integrity of the timber walls and tested connections that tie the walls to the foundations to study their performance in an earthquake.

They found steel dowels in the connections would bend to absorb energy and prevent the walls from being significantly damaged or collapsing. After an earthquake, the dowels can be replaced, leaving buildings equally as strong as before.

EQC says the research has major environmental implications as New Zealand’s building industry contributes around 20% of the country’s carbon footprint.

“If we can put more wood from sustainable plantations into buildings, we can lock carbon into those buildings for at least 50 years, which will have great benefits for New Zealand to achieve our carbon-neutral goals,” Mr Li said.

Mr Li also says the speed of construction may help make timber a cost-competitive building solution as the walls are pre-fabricated off-site.

“You only need a handful of staff to put the walls together, so you make savings and can build much faster by using timber.”

The construction industry contributes around 40% of global carbon dioxide emissions.