Greek columns became the touchstone of this concept.. .’^8 In other
words, designers elaborate structural details in order to clarify the
expression of structural action. First, then, unelaborated structural
detailing.
The exposed first floor beams at Jussieu University, Paris, express their
internal structural actions. Steel box-beams, curved both in elevation
and plan, express the relative intensity of their bending moments (Fig.
7.26). The beams are simply supported and their elevational profiles
take on the parabolic forms of their bending moment diagrams. One
notes in passing that the architect has privileged the articulation of
bending stress rather than shear stress. Shear stress, which usually
increases linearly from a value of zero at a mid-span to reach its max-
imum value at the ends of a span, is rarely expressed. The suspended
floor trusses at Centre Pompidou, Paris, are an exception (see Fig.
7.53). Their diagonal web members increase in diameter as they approach
the truss supports in response to the increasing value of shear force.
By varying the beam flange-width in plan at the university, the beams
narrow at their ends to match the diameter of the tubular-steel columns
into which they frame. Such a high degree of column slenderness, given
that the columns support five floors, indicates their inability to resist
lateral loads and the necessity for the concrete structural cores else-
where in the building plan to provide overall stability. The level of trans-
parency provided by these small diameter columns is especially appreciated
STRUCTURAL DETAILING 145
▲ 7.26 Jussieu University, Paris, France, Edouart Albert, 1965. Beam geometry expresses
the bending moment diagram.