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30 ST MARY AXE

FARSHID MOUSSAVI

All of us, when we see a painting, are bound to be

reminded of a hundred-and-one things which

influence our likes and dislikes.

E.H. Gombrich

The Square Mile in the City of London is dominated by dry

repetitions of the conventional office blockvertically

extruded, horizontally striatedmingled with the weighty

presence of its historical institutions. The Gherkin,

as St Mary Axe is popularly known, has a distinctiveshape and circular plan that immediately set it apart from

the orthogonal towers around it. The buildings extra-

ordinary form leaves us bewildered as to what in the way

of precedents or prototypes may have inspired it and what

type of construction or functional requirements may have

determined it. But on further analysis we discover that its

utterly unique expression is the product of a complex of

multivalent parameters, transversally interlinked through

its physical assemblage in ways that deliberately

contradict our expectations. The double-glazed, circular

outer envelope incorporates a diagrid structural system,

a single-glazed inner envelope, and asterisk-shaped floorplates. Each floor is rotated five degrees from the floor

below, generating six atria in the form of triangular prisms

that spiral around the building, admitting daylight and

allowing for air circulation in the offices. It is in the zone

between the single-glazed inner envelope and the double-

glazed exterior envelope that the different elements

imbricate and the expected outward expression of the

buildings internal functions dissolves. This generates

a kind of incomprehension, reducing the viewers

perception of how the building works to speculation and

technological fantasy.

Vertical support for the building is provided by a

series of intersecting, two-story-high A-frames that makeup a steel diagrid structure that is highly efficient in resist-

ing wind forces. Fire regulations required that these A-

frames, composed of circular sections, be wrapped in

fireproof aluminum casings. In the Hearst Towerin New

York, the casings are the same shape as the structural

sections, to express the working structure, but here they

are kite-shaped in section, with the two pairs of adjacent

sides unequal in length. This allows the outline of the

structural sections to be stretched to connect directly with

the thin, blade-like glazing mullions that project beyond

the glazing panels and support the exterior glazed

envelope. If the casings were rhomboidal, rectangular,or square, the structural members would not dissolve

seamlessly into the glazing mullions. In addition, as the

two longer sides of the casings are oriented toward the

exterior, the depth of the visible structure is foreshort-

ened, making it seem far more slender than it is and

further distorting our perception of how it works. The

encased diagonal members, placed end to end, are also

painted white, while the horizontal crossbars are painted

Harvard Design Magazine

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black. As a result, from the exterior the structure readsas a diamond rather than a triangular pattern, again

obscuring our understanding of it.

This strategy of obfuscation continues in the interior.

On the perimeter of every other floor, hoops encircle the

building in line with the nodes or junctions of the diagrid

members, counteracting the horizontal spread of the

structure and binding the whole together. The kite-

shaped profile of these hoops causes them to disappear

next to the diagrid assemblage. In addition, the floors,

because of their asterisk shape, touch the perimeter at

only six points, so no continuous horizontal floor plates

are visible on the exterior. They spring up along thefacade, appearing and disappearing; when they do touch,

they are camouflaged by the crossbars and perimeter

hoops. Thus it is almost impossible to read the location

of the floor platestheir presence is no more expressed

than the thickness of the glazing mullions subdividing the

large white diamonds.

Together, the diagrid and hoop structures of St

Mary Axedisguise not only the towers interior horizontal

striation by floor plates but also its vertical load distri-bution. They form an exoskeleton that distributes vertical

loads along the diagonal lines of the steel members,

eliminating the need for columns in the interior. While it

is undeniable that a column-free space offers many

advantages, it seems unlikely, in the case of St Mary

Axe, that this solution was prompted by a desire to

engineer the most efficient office space possible. After all,

offices are more flexible when they can accommodate

changing layouts over time, and neither a circular plan

nor an asterisk-shaped plan could ever be as flexible as a

square one, even if its six wings, by introducing rect-

angular segments into an otherwise round volume, makeit easier to create cellular offices. The decision to combine

a circular exterior envelope with an asterisk-shaped floor

plan was in fact made as much for the sake of exterior

optical effects as for efficiency.

St Mary Axewas designed not only from the inside

out but also from the outside in. The requirements of

these two approaches are, however, entirely different.

Whereas column-free space, naturally ventilated offices,

15th floor plan. Courtesy Foster + Partners

Opposite:Detailofsteeldiagridstructure

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and breakout spaces are needed in the interior, the

exterior has to provide open public space while mitigating

the effects of the buildings large scale within its historical

setting. The circular footprint of the tower is compact,

maximizing the public realm at ground level and reducingthe amount of wind deflected to the street. This compres-

sed footprint bulges outward from the ground up,

reaching its optimum floor-plate size on the sixth floor,

and increases marginally as it approaches the twenty-

first, after which it tapers inward toward the apex. The

result is a conical tower rather than a rectangular block,

and this shape allows for the required amount of office

space without overpowering the neighboring buildings,

which are lower in height. Furthermore, compared with a

similarly sized tower, St Mary Axeappears infinitely

more slender, yet the slight bulging and tapering also give

it a sense of weight. Had the circular plan simply been

extruded, there would certainly have been a sense ofgravity but not of weight.

The play with optical illusions continues on the

surface of the tower. Its conical envelope is clad in

triangular glass panels that, owing to the curvature of the

towers profile, are tilted either toward the sky or toward

the ground. The panels reflect the light differently as the

sun moves around the building, creating a flickering

effect, and shimmering argyle patterns appear on the

Detail of steel diagrid structure

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59 St Mary Axe

surface of the envelope. But the optical drama of the

glazing does not stop here. Two different colors of glass

panels are used: the areas fronting the diagonal atria

spiraling around the building are wrapped in gray-tinted,high-performance glass, while the office areas are

wrapped in clear glass with a low-performance coating.

The gray-tinted glass was selected to reduce solar gain,

but as it winds and twists its way around the bullet-like

form of the building, it appears to spiral around its axis of

gravity and lends the tower a sense of potential energy

and acceleration.

The tower, in fact, makes it impossible for us to remain

passive, as it presents us with a whole series of para-

doxes. It transmits the sensation of heaviness but also of

a delicate lattice, the sensation of verticality but also of

twisting. It is fully glazed, yet instead of an affect ofintangibility it transmits that of a tactile argyle knit. The

sensation of conicality is unlike that of any other tower.

The diagonality that is triggered by the spiraling strips of

gray-tinted glass defies any sense of horizontal striation

or the stacking that we commonly associate with towers.

The lack of apparent correlation between the exterior

argyle pattern and the interior offices renders it scaleless.

And it is this multiplicity of affects that is so perplexing

and that gives St Mary Axea dream-like quality. The

twisting reminds us of roller coasters or the slides in water

parks, or even Carsten Hllers giant slide installations.

The latticing reminds us of baskets or fishnet tights. Theconicality reminds us of rockets or gherkins. The argyle

pattern recalls Scotland, socks, Pringle,knitting patterns,

intarsia, harlequin-patterned floors or furniture. It is no

wonder that the Gherkin is only one of many nicknames

that have been attached to this polysemic building.

Great buildings such as this one, however, have

little to do with aesthetic populism. Instead, they take

conventional architectural elementsshape, materials

and size of the components, construction system,

lighting, ventilation, acoustics, planning of activities

and assemble them in unexpected ways. In doing so,

they transcend signification and meaning to generatenew subjectivities. The multiplicity of affects that we

experience at St Mary Axeis very different from any

we are familiar with. As an affective break with the

conventional office tower, it is an example of an architec-

ture of a-signifyingsemioticsnot designed to commun-

icate meaning but to probe our cognitive and social

environment. It challenges our common sense, and this is

what makes it so compelling.

Detail of glazing panels

2012

bythePresidentandFellowsofHarvard

College.Allrightsreserved.

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