structure a vault-like building form. Varying arch spans respond to an
irregularly shaped site. Suspended floors either hang from tension hang-
ers under the arches, or as on the street frontage, are propped off
them. This is an example of reasonably conventional arch usage where
arches are regularly spaced and aligned vertically. But at the Great
Glasshouse, Carmarthenshire, arches form a toroidal dome (Fig. 3.17).
The dome’s two constant orthogonal radii of curvature require that the
arches distant from the building’s centreline lean over in response to
the three-dimensional surface curvature. Clarity of the arched struc-
tural form is undiminished by the small diameter tubes that run longitu-
dinally to tie the arches back at regular intervals to a perimeter ring
beam. Apart from supporting the roof glazing they also prevent the
arches from buckling laterally and deflecting from their inclined planes.
Framed structures
Synthesis of architectural and structural form extends beyond curved
forms. Consider the intimate relationship between orthogonal skeletal
structural frameworks and rectilinear forms. In his discussion of the
formative 1891 Sears Roebuck Store in Chicago, Condit asserts: ‘for the
first time the steel and wrought-iron skeleton became fully and unam-
biguously the means of architectonic expression... The long west ele-
vation is developed directly out of the structural system behind it, much
as the isolated buttresses of the Gothic Cathedral serve as primary
visual elements in its indissoluble unity of structure and form.’^8
30 STRUCTURE AS ARCHITECTURE
▲ 3.17 The Great Glasshouse, Carmarthenshire, Wales, Foster and Partners, 1998.
Arched roof.
