STRUCTURAL GLASS FACADES - USC School of Architecture

Span/Depth (L/d) characteristics: The depth of the flat
nets is minimal; a flat net spanning 100 ft. (30m) can
easily have a depth under 1 ft. (300mm), or roughly a
span to depth ration of 100. Double-curved nets are
locally shallow, but have an overall depth comprised of
the maximum displacement between the opposing
curvatures, called the sag.
Typical deflection criteria: Cable nets have the highest
relative deflections; deflection criteria is typically in the
range of L/45 to L/5O. The necessary control of
deflections results in design complexity to minimize
Figure 6.13 Rocker arm detail on
New Beijing Poly Plaza cable net;
SOM architect, (Gritth 2007b).
prestress loads. Flat nets are geometrically simple but
deflections are high. The added stability provided by the
double-curved nets significantly reduces the prestress
requirements necessary to limit deflections, reducing the demands on the boundary steel,
but at considerably added complexity to the cable net.
Pre-tension requirements: This consideration renders design efforts to minimize prestress
forces of paramount importance. High prestress loads impact boundary structure. Cable nets
may be impractical for renovation projects unless boundary support requirements can be
efficiently met.
Reaction Loads: As discussed here, high prestress requirements result in high reaction
loading which must be accommodated by the boundary structure.
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