Talking timber

By - , Build 170

BRANZ Structural Engineer David Carradine comes to the role of President of the New Zealand Timber Design Society as the use of engineered timber is expanding here and around the world. He tells Build why this is.

Q. What results have you seen from your work as an experimental researcher in timber structures?

I have engaged in research on a broad range of structural timber systems including heavy timber framing incorporating structural insulated panels (SIPs), log structures, post-tensioned timber, multi-storey light timber frame and wood-plastic composite materials. This research aims to push the envelope of what can be done with timber-based products and systems, and many have found their way into buildings in one way or another.

For me, the objective is always to incorporate the most suitable systems into a building to maximise the properties of the materials. The continued development of cutting-edge timber-based materials provides increased opportunities to use timber throughout the built environment.

Q. Engineered timber such as CLT and LVL have an increasingly high profile. Why and what are some projects where it has been used?

Engineered wood products such as CLT, LVL and glue-laminated timber are being used more for larger buildings due to the excellent structural performance that can be achieved. Timber is less dense than other materials, which decreases the seismic loads on a building and allows for smaller foundations than heavier materials.

The global drive for more timber in larger buildings has led to research programmes incorporating the wide array of timber materials within multi-storey buildings. This has resulted in leaps in innovation for timber buildings with 18-storey examples built in Europe and North America.

New Zealand developed post-tensioned buildings have popped up throughout the country, including the Kaikoura District Council building. These buildings incorporate CLT and LVL within the structure and performed very well during the 2016 Kaikoura earthquake. Examples have also shown up overseas – for example in Switzerland and in the US with the Peavy building at Oregon State University.

Q. You were a judge in the 2018 NZ Wood Resene Timber Design Awards. What stood out?

The most difficult part of judging the Timber Design Awards was choosing which projects were superior, because there were so many inspiring examples of timber use and the innovation was truly impressive.

Multi-storey projects were on the increase, with more of these larger buildings using timber. This is a signal that architects and engineers are embracing timber as a building material and realising its potential to create robust and meaningful buildings.

Q. You were elected as the new President of the New Zealand Timber Design Society (TDS). What did this mean to you and what plans do you have?

This appointment has been very gratifying in that the timber design community has the confidence in my abilities to guide the Society at a time of increasing awareness and uptake of timber materials for buildings.

As more demand is placed on designers, it is critical that information is available to enable professionals to make educated choices and develop quality designs using the full spectrum of timber-based materials. That is a focus for the Society.

With the new timber design standard for New Zealand currently out for public comment, it is also critical that TDS spreads the word. DZ NZS/AS 1720.1 Timber structures – Part 1: Design methods is hugely important for the timber design community, and TDS will be making efforts to provide input on its development and will also conduct workshops once the final standard is out. The workshops will inform designers of the changes made from the previous versions of NZS 3603 Timber structures standard and how to navigate the new standard NZS/AS 1720.1, which is integrated with the Australian timber design standard.

Q.Is timber, as a natural product,likely to be used to help the building industry response to climate change and limit greenhouse gas emissions?

Timber has enormous potential to reduce greenhouse gas emissions as it becomes more commonly used for large multi-storey buildings globally. It also has other performance-related benefits increasing its appeal as part of the built environment of the future. Most buildings are combinations of materials, so timber won’t solve all the problems, however when used within well-executed building systems, it can play a significant role in moving towards more sustainable and high-performance structures.

Q. Anything else you would like to add?

It is a very exciting time for timber buildings throughout the world and New Zealand as the use of timber-based products throughout the building sector continues to gain momentum. New Zealand has a significant timber resource,and continued development utilising this resource within the built environment is a great way of adding value to an inspiring natural material.

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