For the duration of September’s London Design Festival and a month after, the imposing Portland stone Gothic Revival entrance of the Victoria & Albert Museum will all but disappear behind the Timber Wave, an intricate latticework spiral arch made of myriad sections of laminated American red oak. You can’t help but feel Prince Albert himself would have approved.

Queen Victoria’s consort was, of course, patron of the 1851 Great Exhibition in the original Crystal Palace. Here  architects, designers, engineers and industrialists pushed the boundaries of their disciplines, experimented with new manufacturing and construction methods and materials, and took existing ones in whole new directions. The Wave has similar objectives.

Collaboration
One of the key partners in the project is the American Hardwood Export Council (AHEC), an organisation with the dual role of promoting US hardwoods and helping develop their applications worldwide. In this task European director David Venables is a particular advocate of harnessing the creative juices of architects and designers. This has already led to a string of collaborations that have triggered a design press buzz continent-wide, including two at previous London Design Festivals. In 2008 AHEC teamed up with architect David Adjaye on Sclera, an outdoor pavilion built behind the Royal Festival Hall using 1,500 solid and laminated tulipwood boards. This one ticked multiple boxes for AHEC. It highlighted the creative possibilities of tulipwood, which is generally used in painted joinery and mouldings, and, thanks to the input of timber treatment specialist Osmose, it challenged the perception that it is an interior-use only species. AHEC estimates it also generated US$2m of free publicity.

Last year’s partnership was with Established & Sons design director Sebastian Wrong and artist Richard Woods. Again using tulipwood, they created foyer seating at the V&A by laminating and colouring multiple tiers of timber. Besides further underlining its design potential, Bench Press also flagged up its sustainability. The wood was recycled from the 30 tonnes of tulipwood Wrong used in his Pelota partitions at the Milan Furniture Fair.

Working with such creatives, said Venables, has created an “extraordinary chain reaction” for AHEC and US hardwood. “It really is seeing us leap from one thing to the next and work in a way and profile we haven’t done before. People are now coming to us very receptive to trying new things.”

Main attraction
While he waxes lyrical about these previous projects, Venables believes Timber Wave will top them all. “It looks certain to be the main attraction for the London Design Festival, not just for the fact that the design is very challenging, but  because, thanks to Festival director Ben Evans making it happen, it will be on Cromwell Road at the front entrance of the V&A. It will be seen by hundreds of thousands of passers-by for the six weeks it will be on show.”

The rest of the team behind Timber Wave are architect Amanda Levete of AL_A, engineers Arup and specialist wood construction contractor Cowley Timberwork. According to them, it will also fulfil AHEC’s other objective of sparking new perspectives on working with, designing and building in timber. AHEC put forward American red oak to Levete and Arup to “explore its use in an outdoor and structural context”. The species is still not widely known in Europe, but in the US is ubiquitous in construction and furniture. It also has the added environmental appeal of being North America’s most abundant hardwood.

Strength-to-weight ratio
Previous testing at BRE commissioned by AHEC and Arup had also shown that red oak’s density and straight grain made it twice as strong as softwood with a “strength-to-weight ratio better than steel”. The inherent resilience of the timber was enhanced by Cowley taking the original 25mm random width boards, slicing them up and bonding the material back together to create more than 2,000 laminated components.

“Timber is strongest when stressed parallel to the cells or fibres and the design called for curved components,” said Cowley Timberworks’ Peter Hogg. “By creating the highly stressed chords from thin laminates, we were able to curve the fibres to follow the lines of force and we also used less material than cutting from a solid section would have done.” In laminated wood, he added, the effect of knots and other natural defects is localised to one laminate, further improving structural performance.

According to Levete, the inspiration for the actual design of the 12m high by 16m wide Wave was the “multi-layered, ornamental” museum entrance itself. “Repetition of motif is very much part of the V&A’s didactic tradition and the form reflects the existing conical arch, while the wooded steps and landing the Timber Wave blends into  also mirror the original entrance,” she said.

The structure
The Wave’s structural system comprises a self-supporting arch made from a three-dimensional truss of curved elements. It has six outer and five inner chords, with diagonal braces in between and the components fixed together with stainless steel connectors. The chords comprise 77 laminated sections made from 1,600 pieces of timber. These are mainly in axial tension or compression with bending because they are curved and were formed in the lamination process for
maximum axial strength.

The connection designs were demanding

The forces in the diagonal sections are much smaller, so these were CNC-cut from straight laminated members, as were the ties connecting the outer chords to each other, because their sections vary from circular to square along their length.

In total the Wave comprises 460 of these bracing elements.

Andrew Lawrence of Arup described the project as one of the most complex he’s worked on. “It’s based on simple structural principles, but the curved members, complex three-dimensional geometry and use of material with strength characteristics that vary naturally with orientation, made it highly challenging to analyse structurally and design. Understanding the timber element fabrication and the limits on thickness and depth of components this would entail, was essential to the process.”

Connection designs
The connection designs were also demanding and went through many iterations to achieve the right balance of structural capability, aesthetics, cost and ease of use. “Fitting up to eight timber elements at each node, meant the load paths through the connection had to be considered carefully as the idealised node was actually quite different to the real one,” said Lawrence.

The partners agreed, however, that the challenges taught them valuable lessons in working with timber. “Besides structural efficiency and sculptural quality, buildability has been one of the main drivers in design and we’ve worked closely with AL_A and Arup to develop the most appropriate fabrication methods, with minimum on-site assembly,” said Hogg.

“The project also allowed AL_A to develop a set of bespoke digital tools, including writing bespoke scripting, for producing accurate, changeable live models,” said Levete. “We’ve used these in new ways of collaborating with the engineers and contractors.”

The Timber Wave, she added, also demonstrated the strength and workability of timber in general and American red oak in particular. “We’ve been impressed with the quality of the material, its structural properties and the extent of the various fabrication techniques available. It’s three storeys high, reflecting the grand proportions of the entrance arch, so it’s visible from long views as you approach the museum along Cromwell Road.”

The finished structure, pre-assembled into manageable sections, took around a week to erect on site. Because of the V&A’s Grade-1 listed status, it cannot be attached to the building, only fixed to the steps. Other than that it has to be fully self-supporting, so has undergone an optimisation process to make it stable under wind loads, with kentledge used to ballast the base.

It was officially unveiled by the US ambassador on September 19 and will stay in place until October 15.

Construction is based on simple structural principles, but complex three-dimensional geometry made the project very challenging

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