The Timber Wave Lee Franck Structural and Civil Engineer EPFL Ove Arup and Partners Ltd

Abundance and properties of American Red Oak

Structural elements of the Timber Wave

Description of the structural system

The annual London Design Festival (LDF) creates a platform for designers to explore materials in new ways. The LDF, in partnership with the American Hardwood Export Council (AHEC), challenged Arup and Amanda Levete Architects (AL_A) to design a temporary installation that would dem-onstrate both the strength and beauty of American Red Oak, an abundant timber with excellent structural properties, but much underused within Europe.

The sculpture was to be located outside the entrance to the listed Victoria and Albert Museum in London, as part of the 2011 Festival, for a period of approximately 6 weeks. It had to echo the form and scale of the museums entrance, but be built from small sections to create an installation that was visually lightweight.

The final structural system comprises a 12m high self-supporting arch made from a three-dimensional truss of curved, laminated timber elements.

The curvature of the waves were to demand a continual inter-play between architect and engineer, whereby the larger the waves, the larger and more expensive the members became, not only because they needed to carry larger moments and shears due only to their shape, but also because ever thinner laminates of red oak were needed to achieve the tighter cur-vatures. At the same time as fine tuning the member curva-tures, every effort was made to optimize the overall wave geometry using a parametrical geometrical model in order to achieve the lightest possible members.

The project was completed on budget and within a tight timeframe largely due to a very close and successful collabo-ration between the engineers, the architects and the fabrica-tors. The structural design of each of the 500 elements has been pushed to the limits to create the delicate tracery which demonstrates the strength of the material and the unique po-tential of timber to form complex geometries. It is the first time that American Red Oak has been used structurally on such a large scale.

Early concept models

1. Delivery of 20m3 of 1 inch thick boards 3. Application of glue onto the boards 5. Connection rods are bonded into chords 7. Delivery to site in prefabricated sections

2. Boards are saw cut into 6mm thick laminates 4. Laminates are pressed into shape 6. Chord ends are finger jointed 8. Installation under temporary works

Axial Forces within the Timber Wave Deflections of the Timber Wave

Geometrical model generated by the software Rhino and Grasshopper and used by the structural engineers to test the impact of geometrical parameters on the structural behaviour

3D parametrical model generated by the architects and coupled to the engineers structural model to visualize the impact of the geometrical parameters

Allowable eccentricities in braces provided by the structural engineers to the architects to inform the design of the Timber Wave

The idealised node, where the centre lines of every incoming element coincide exactly, was unachievable in practice. Early guidelines were given to the architect

to minimise eccentricities at the node.

Designed by: Lee Franck, Alice Blair, Andrew Lawrence, Ed Clark (Arup) Fred Pittman, YooJin Kim, Ho-Yin Ng (AL_A)

Fabricated and built by: Cowley Timberwork For the London Design Festival 2011

Supported by the American Hardwood Export Council