Timber in new civic build proves strong, resilient

A contractor working on the civic construction site in Ashburton guides a CLT panel into place.

The building material in Ashburton’s new new civic building has been given the nod of approval by a University of Canterbury research project.

New research has demonstrated cross-laminated timber (CLT) walls are feasible and cost-competitive with steel or concrete systems in low-rise buildings and offer significant environmental benefits.

Associate Professor Minghao Li and his PhD student Ben Moerman have been testing large CLT shear walls in the university’s structural engineering laboratory to find out how these multi-storey walls behave in significant earthquakes.

“We loaded the walls horizontally to create a similar scenario of multi-storey CLT buildings in big earthquakes like the ones in Christchurch,that the weight of timber is only one-fifth of concrete, meaning much lower earthquake loads, but has similar strength as concrete.

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

The research team designed innovative high capacity connections to resist earthquake forces and protect the integrity of the timber walls.

“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,” Moerman said.

CLT can be seen on Ashburton’s new civic build site on the corner of Baring Square and Havelock Street. Most of the structural timber walls are standing which will allow the floors above the ground floor to be installed and the concrete topping slabs poured.

Ashburton District Council business support group manager Paul Brake said the benefits of CLT can be realised in the precision of the product during the manufacturing process.

“Speed – or the high degree of planning and accuracy allows installation to proceed at a faster pace as the majority of the problems have been worked through prior to any work starting on site.

“Safety – materials spend less time exposed to the elements usually, and also it reduces the time that workers are at height or undertaking activities using power tools; and environmental – timber has very different properties to concrete and steel with regards its carbon footprint, manufacturing process, acoustic properties, performance during its life and its end of life uses,” he said.

CLT is not the only sustainable feature or new technology in the building. “Hydrothermal energy will heat and cool the building in the majority making this a more energy-efficient building with better running costs over its life.

“The process involves drilling into aquifers deep below Ashburton and extracting water that is at a constant temperature all year round and using that for heating in winter and cooling in summer.

“The water is not consumed in any way in this process and it is then returned back to the ground under Ashburton,” Mr Brake said.

~By Daniel Tobin