Published: 21 September 2016

Elegant solutions

Bridges, Structural Awards, Timber

(Above image copyright BuroHappold)

Joe Darcy, a Graduate Member of the Institution, has been a practising structural engineer for four years. Here he talks about his career and his work on the STIHL Treetop Walkway in Westonbirt, Gloucestershire – a 280m long structure standing on 57 pairs of crossing timber legs. The Walkway has been shortlisted in The Structural Awards 2016 ‘Pedestrian Bridges’ category.

Growing up as the son of two architects, I had an exposure to the built environment from an early age, now I can’t enter a building without wondering how it was built. I have always had a passion and enjoyment for problem solving and design, so structural engineering, where we create elegant solutions to architectural challenges, was the career for me.  

The STIHL Treetop Walkway is a great example of structural engineers delivering elegant solutions, and a project where we collaborated closely with the architects. We communicated on a very regular basis to develop solutions that balanced their vision with practicality and cost.

The walkway’s signature crossing timber legs are a good example: The orientation of the legs crossing in pairs was an architectural feature, the choice of material and spacing was driven by the and the double taper (cigar shape) profile of the legs increased structural efficiency. Engineers and architects work closer together than ever before to achieve maximum efficiency on a project and push the boundaries of design. The STIHL Treetop Walkway enables users to engage with trees and increase their appreciation of the work that is done to protect and maintain their environment. 

Children on the walkway - (image copyright Paul Broom)

There were a number of unique challenges involved with the project: The client was keen to provide users with as interactive an experience as possible, and in two locations wanted them to experience movement similar to that of a tree in the wind – so we actually relaxed the natural frequency criteria of the structure to make it ‘sway’ a little.

Leisure is not normally a sector I am involved with (I came to work on this project due to its complex geometry) but it was very rewarding to work on something which clearly gives so many people enjoyment.

(Image copyright BuroHappold)

Since opening, the walkway has been very well received and helped improve visitor numbers to the arboretum in a period where historically numbers are low. Users of all ages seem to naturally head to the walkway upon arrival at the arboretum and take their time crossing it, enjoying the unique perspective, views, and various interpretations along the way. 

It was a relief to see the project finished, having worked on it for several years from design to resolving construction issues on site. I look forward to visiting in a few years’ time when the timber has weathered in and the walkway is integrated into the canopy - then the project will be truly complete.

(Image copyright BuroHappold)

Why is timber a sustainable construction material?

Timber is naturally renewable, can be locally sourced, absorbs carbon dioxide from the atmosphere, has lower emissions over its life cycle compared to other materials, has little waste in production, and can be recycled at the end of its use. 


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