New research by a New Zealand university team has revealed that cross-laminated timber (CLT) walls are feasible, strong and cost-competitive with steel or concrete systems for low-rise buildings, all while offering environmental benefits. This could help New Zealand’s construction industry and the country in reaching their carbon-neutral goals.
The research was done by associate professor Minghao Li and his team at the University of Canterbury (UC), who have been testing large CLT shear walls and trying to find out how they behave in earthquake scenarios.
“We loaded the walls horizontally to create a similar scenario of multi-storey CLT buildings in big earthquakes like the ones in Christchurch,” explained Li. He also pointed out that 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.”
The team also designed high-capacity connections to resist earthquake forces and protect the integrity of the timber walls, as PhD student in the team, Ben Moerman, explained: “We have tested those large-capacity connections that tie the walls down to the foundations to study their performance in an earthquake. The main benefit is that after an earthquake you can simply replace the dowels and the buildings will be just as strong as they were before the earthquake.”
The construction industry in New Zealand contributes around 20% of the country’s carbon footprint, while the global construction industry contributes 40% of global CO2 emissions. “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,” said Li.
Li further acknowledged that engineered timber might now be more expensive than other materials, the speed of construction and limited resources required may also make timber a cost-competitive building solution: “The walls are pre-fabricated off-site and you only need a handful of staff to put the walls together, so you make savings and can build much faster by using timber.”