Structural Design for Architecture(a)Fig. 3.33 (a) Two-way-spanning roof structure formed by
intersecting plane frameworks.
(b) Willis, Faber & Dumas office, Ipswich, England, 1974.
Foster Associates, architects; Anthony Hunt, structural
engineers. (Photo: Pat Hunt).80
In the first type of system the elements may
intersect at right angles or obliquely. The
oblique grid pattern, which is called a 'diagrid'
(Fig. 3.35), is the more efficient configuration
because the girders which span across the
corners are relatively short and can provide a
measure of support for the longer spanning
girders which run between the corners.True space frames, that is fully three-dimen-
sional structures whose fundamental units are
pyramids or tetrahedra (Fig. 3.34), allow a
more efficient use to be made of material than
in the case of the intersecting plane-frame type
because the disposition of the elements
produces a more satisfactory distribution of
internal forces. True space frameworks also can(b)