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posted by martyb on Tuesday September 20 2016, @08:16AM   Printer-friendly
from the feed-the-termites! dept.

An article in The Economist makes the case for "wooden" skyscrapers:

New techniques mean that wood can now be used for much taller buildings. A handful are already going up in cities around the world. The 14-storey Treet block of flats in Bergen, Norway, is currently the tallest. But Brock Commons, an 18-storey wooden dormitory at the University of British Columbia in Canada, is due to be completed in 2017. That is when construction is expected to begin on the 21-storey Haut building in Amsterdam. Arup, a firm of engineering consultants working on the project, says it will be built using sustainable European pine. Some architects have even started designing wooden skyscrapers, like the proposed Tratoppen ("the treetop" illustrated above), a 40-floor residential tower on the drawing-board in Stockholm.

Wood has many attractions as a construction material, apart from its aesthetic qualities. A wooden building is about a quarter of the weight of an equivalent reinforced-concrete structure, which means foundations can be smaller. Timber is a sustainable material and a natural "sink" for CO2, as trees lock in carbon from the atmosphere. Tall steel-and-concrete buildings tend to have a large carbon footprint, in part because of the amount of material required to support them. Using wood could reduce their carbon footprint by 60-75%, according to some studies.

There are two main concerns about using wood to build high. The first is whether wood is strong enough. In recent years there have been big advances in "engineered" wood, such as cross-laminated timber (CLT) made from layers of timber sections glued together with their grains at right angles to one another. In much the same way that aligning carbon-fibre composites creates stronger racing cars, aircraft and golf clubs, CLT imparts greater rigidity and strength to wooden structures. A recent experiment by Skidmore, Owings & Merrill, a firm of architects, and Oregon State University, shows how strong engineered wood can be. The researchers used CLT in a hybrid form known as concrete-jointed timber. This featured an 11-metre wide CLT floor section with a thin layer of reinforced concrete spread across the surface. Thicker sections of concrete were added where the floor was supported by pillars. It was put into a giant test rig where a powerful hydraulic press pushed with increasing force onto the surface. The researchers wanted to see how the structure moved under load, but kept pressing in order to find its limits. The floor finally began to crack when the load reached a massive 82,000 pounds (37,200kg), around eight times what it was designed to support.

If you want to know what the second main concern is, you'll have to read the article. 😉


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  • (Score: 2) by butthurt on Wednesday September 21 2016, @02:00AM

    by butthurt (6141) on Wednesday September 21 2016, @02:00AM (#404624) Journal

    "Using this method, growing an individual tree into a complete chair takes anywhere from four to eight years," says a page you linked.

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