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Thursday, June 1, 2017

Is wood the new steel?

It is beginning to look as if it will be possible to build skyscrapers out of wood -- and New Zealand is a leader in the field.

From Bob Brockie in the Dominion Post

Some concrete buildings munted in the Christchurch quakes are being replaced with wooden buildings. Among them is a university building, which, at four storeys high, will be the country's tallest wooden building.
This wooden building is the brainchild of Canterbury University professor Andy Buchanan  who specialises in innovative timber construction, fire and earthquake risk, and who has spent time at the Wood Innovation and Design Centre in Canada.
Canadians got off to an early start in 2014, when they constructed an eight-storey building out of douglas fir. It was among the tallest wooden buildings in world at the time, and it has served as a model for builders everywhere.
In 2015, Norwegians built a 14-storey wooden tower comprising 62 flats, with offices and shops. In 2016, a 53-metre wooden dormitory was built at the University of British Columbia by four workers in only 70 days.
Another 30-storey building is planned for Vancouver and Austrians are currently building an 84-metre wooden building. Cambridge University architects and engineers have a 300m high wooden building on the drawing board, and which they hope to put up in London.
Plenty of two- and three-storey wooden buildings are currently being used for social housing in London.
These builders use no ordinary wood, as it is too soft and weak. Instead they cut wood into thin slices and cross-laminate them. That is to say, the sawn slices are laid on top of each other at right angles and cemented together under high pressure with resins and glues. Huge 3m by 6m blocks can be manufactured.
Enthusiasts claim that the laminated product is as strong as steel. The wood is lighter in weight so can be erected on sites too difficult for heavier concrete and steel structures. Wood is relatively inexpensive, so its buildings are 9 per cent to 14 per cent cheaper than similar conventional concrete and steel buildings.
Paradoxically, laminated wood is more fire-resistant than steel. This is because the big blocks char on the outside and this protects the structural integrity of the wood inside and, unlike steel, wood does not bend when it gets hot.
Wood is environmentally friendly because it is a lower-carbon product than concrete and steel. Used on a large scale, it is potentially useful in staving off global warming.

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