The Aluminum rods of British Pavilion in Shanghai are void or soild?

Sunday, September 26, 2010

Osnaburgh Street Pavilion by Carmody Groarke, London, UK





By Rob Gregory

Carmody Groarke’s refined, stainless steel Osnaburgh Pavilion. Photography by Luke Hayes

Commissioned by developer British Land and designed while Carmody Groarke was working on sculptor Antony Gormley’s 2007 installation Blind Light, this new pavilion, near Regent’s Park in London, shares a number of similarities to Gormley’s work. Like many of his figures (such as Quantum Cloud, 1999, on the banks of the Thames), its structure is made entirely from square hollow sections of stainless steel. And as a study in place-making, Carmody Groarke - which also designed the cluster of vertical pillars commemorating the 2005 London bombings (AR August 2009) - has extended Gormley’s investigation into the spatial potential of identical uniform elements.

The architect has applied similar working practices, through the production of hand-made prototypes and through an acknowledged reliance upon structural engineers, to achieve this vision; one that in this instance was predicted ‘would not stand up’ by the consulting engineer who sat on the 2007 Architecture Foundation competition jury. Despite this scepticism, however, Carmody Groarke captivated the jury with its exquisite model (a brass etching comprising 1,200 rods, each 0.5mm in diameter) and, together with collaborators, set about the task of scaling up the concept without losing any of its refinement or lustre.

In doing so, the challenge was not simply to address the extremely high slenderness ratio of the 258 50 x 50mm sections that reach 8 metres up, like toothbrush bristles, to align the wafer-thin 3mm plate steel roof with the soffits of neighbouring colonnades. Or indeed, how to make the pavilion capable of providing all of the piazza’s ambient lighting. The architect also had to address health and safety concerns that presented scenarios such as what would happen if a posse of lairy revellers attempted to discover the structure’s resonant frequency.

The engineer’s description of the challenges were more sophisticated: addressing the pavilion’s sway-sensitivity, the non-linear stress strain characteristics of stainless steel, and any possible excitation from ‘galloping, vortex shedding and interaction vortex shedding’. In other words, how to stop external forces causing the columns to resonate to the point of destruction, as seen in the failure of the Tacoma Narrows Bridge in the US in 1940. Set in the gap between two huge Terry Farrell office buildings and facing due west, the effect of wind was critical.

Following extensive wind tunnel tests, columns were arranged to shelter each other from prevailing winds. With no cross bracing, however, the structure could still sway, and it was insufficient to simply cluster the bristles more densely, as described (principally for composition purposes) in the architect’s original design. Instead, spanning between the slim 50mm-thick rigid roof lattice and a 250mm-deep subterranean bolt cage, each column had to be fitted with an internal damper so that when shaken, little or no disturbance would be transferred to adjacent sections. In their final form, the dampers comprise silicone cloaked steel rods, freely suspended inside each column. When the column begins to vibrate, silicone collides with stainless steel, absorbing sufficient energy to ensure the responding movement is controlled.

As demonstrated by architect Andy Groarke, when an individual column is manhandled it is easy to achieve a 100mm deflection, but apparently impossible for this to visibly affect the adjacent columns.

With Arup silencing structural sceptics, Carmody Groarke applied its trademark finesse to the project, including bespoke LED fittings with a colour-matched gel that produces a rich brass glow, and extraordinarily tight coordination tolerances, whereby at the base of each column a 50 x 50mm grid of granite cobble is resolved with perfect accuracy.

The only shortcoming with the pavilion is that there isn’t quite enough of it. Smaller than the original competition-winning scheme, the scale fails to compete with the dominance of the Farrell offices, and with only one clearing and a single route - conventionally signalled by standard dropped kerbs - the potential for passers-by to spontaneously interact with and meander through the field of columns seems less convincing in reality.

That said, it is exquisite - and in anticipation of building on a larger scale, Carmody Groarke has proved its technical and artistic capacity to take a project from charming concept to convincing reality. It is also testament to the practice’s ambition and know-how, showing how to make the most of a relatively conventional brief by not only giving the client something that went beyond the original commission (which called for a café), but also by creating an opportunity to pursue its own architectural interests. The outcome is a beautiful structure that extends the tradition of the belvedere, bandstand and folly in an undeniably contemporary way.

Architect Carmody Groarke, London, UK
Project manager M3 Consulting
Engineer Arup
Landscape architect EDCO
Lighting design Maurice Brill
Lighting Designcontractor Bovis
Sub contractor Skanska
Specialist sub contractor Sheetfabs, Nottingham

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