Maximizing light
Where requiring high levels of daylight or transparency through the
building skin, architects adopt a number of stances towards structural
detailing. Maximum daylight implies reducing the silhouette or shadow of
structural members. The two most common methods are either to min-
imize structural member sizes, or to penetrate typically sized members.
Transparent structural members are also becoming increasingly popular.
Detailing to minimize structural size
Chapter 7 discusses how the dual architectural qualities of complexity
and lightness can arise where structural dimensions are minimized.
Simple calculations show that if one tension rod is replaced by two
smaller diameter rods with a combined strength equal to the original, the
area of the structural silhouette is reduced by approximately 30 per cent.
With four rods this reduction in silhouette reaches 50 per cent – the
more members, the more light, but also more visual complexity.
At 237 m long, 79 m wide and 28 m high, the vaulted Trade Fair Glass
Hall, Leipzig, was the largest single-volume glass building of the twenti-
eth century. The tubular steel exoskeletal structure consists of ten pri-
mary trusses that stabilize a grid-shell (Figs 8.13 and 8.14). Triangular in
cross-section, the arched trusses are fabricated from relatively small-
diameter steel tubes whose varied wall thicknesses reflect the intensity
of the structural actions. A resolute strategy to achieve maximum trans-
parency excluded potentially large-scale members from consideration.
As Ian Ritchie, project architect, explains:
Transparency was a key design objective. We wanted to minimize the
structural silhouette, and in fact the total area covered by structure in any174 STRUCTURE AS ARCHITECTURE
▲8.11 Recessed lights in stub columns. ▲8.12 Stadelhofen Railway Station, Zürich, Switzerland,
Santiago Calatrava, 1990. Integration of structure and artificial
lighting.