50 — Build 145 — December 2014/January 2015

Commercial buildingsFEATURESECTION

NOW IS AN IDEAL TIME for a traditional material like timber to be coupled with advances in technology to create exciting contemporary buildings that can perform at least as well as any other building material.

That was the message from the 13th World Conference on Timber Engineering (WCTE) held in Quebec City, Canada, in August 2014. The conference, the premier global meeting for timber engineering, is held every 2 years.

New methods – some developed hereA significant focus was on larger timber buildings and construction methods that will allow for increased storey heights using timber. This trend is being driven by a global push to use more timber in buildings for environmental and economic reasons.

Traditional light timber framing is already used in buildings up to 6 storeys in Canada. Now, newer timber building methods such as cross-laminated timber (CLT) and post-tensioned timber – developed in New Zealand – are being considered for timber buildings up to 20 storeys and potentially more.

New options for mid-rise buildingsA big question after attending a conference like this is what can New Zealand learn from the growth in multi-storey timber buildings? There is a push to utilise value-added timber products in New Zealand, and larger timber buildings have the potential to do that.

Looking at the worldwide trend to increase timber use in larger buildings, it is clear that new timber systems provide designers with more options than ever for mid-rise buildings.

Innovative timberreaches new highs

As economic and environmental reasons drive an upsurge in commercial timber buildings, New Zealand is at the forefront of the global push to develop exciting new structural timber technologies.

BY DAVID CARRADINE, BRANZ STRUCTURAL ENGINEER

Time for timberThe conference theme was Renaissance of timber construction, with many of the keynote speeches embracing the topic.

Delegates from around the globe were present, including 27 from New Zealand – some of them from BRANZ. This provided ample opportunities to learn about trends in the design, analysis, construction and innovation of modern timber buildings.

Hybrid system of post-tensioned timber beams and concrete columns – St Elmo Courts.

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Build 145 — December 2014/January 2015 — 51

Commercial buildings FEATURESECTION

In Canada, government-funded research of about C$24 million is aimed at increasing the amount of timber used for larger multi-storey buildings. This has also led to changes in regional building codes.

In British Columbia and Quebec provinces, it has been possible for several years to build up to 6 storeys in timber. More recently, Ontario has also implemented code changes allowing timber to be used for up to 6 storeys.

Learning from othersWhile it is difficult to compare countries with different economies and populations, Canadian efforts are an example of what can be done with existing methods of timber construction. This also helps other countries develop roadmaps for utilising more timber in larger buildings.

Light timber framing, cross-laminated timber (CLT) and post-tensioned timber build-ings all have the potential to be used this way, and all were presented at WCTE 2014.

Nothing prohibits these methods being used in New Zealand. CLT is just starting here and we already have the only factory in Australasia.

and practitioners in Europe and North America, with continued research currently under way in Switzerland and Italy.

New Zealand leads in timber innovationWCTE 2014 had many examples of the strides being made towards larger and more innovative timber structures that combine a traditional material like wood with state-of-the-art structural technology.

Instead of being a follower, New Zealand is leading the charge with research and building techniques helping to pave the way in the global movement towards medium and high-rise timber buildings. For more Visit www.wcte2014.ca.

Creative projects hereFortunately, there are no limitations on heights of timber buildings in New Zealand, as long as they fulfil all the necessary Building Code performance requirements. Post-tensioned timber buildings, developed in New Zealand, have already been achieving success around the country with examples in Christchurch, Wellington, Nelson and Carterton.

The largest post-tensioned timber building to date is St Elmo Courts in Christchurch at 6 storeys. It is a hybrid structure with concrete columns and post-tensioned timber beams and floor system. It is also base isolated, which is another first for a timber building of this size.

A post-tensioned CLT building is also being constructed for the Kaikoura District Court.

These projects show that, instead of a single direction, timber buildings are moving forward in a variety of ways utilising currently available technology and materials in creative projects.

Attracting interest from abroadThe post-tensioned timber structural system has also attracted interest from researchers

The Trimble building in Christchurch (above and right) was the first here to use Pres-Lam technology.

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BRANZ guidelines comingLight timber framing is already a well understood

structural system in New Zealand. A current BRANZ

project is taking this further, developing design

guidelines for larger multi-storey light timber-frame

buildings, possibly up to 6 storeys.