STRUCTURAL GLASS FACADES - USC School of Architecture

Similar to the mast of a sailing yacht, pin-connected bracing
struts extend from the center mast to cable or rod bracing
stays, and act to stiffen the mast. Short-span systems can use
masts braced on 2 opposing sides to form a 2-dimensional
truss element (Figure 6.5), which can then be placed at each
glazing grid module. Equally simple cable bracing can be used
to stiffen the trusses laterally. Long-span systems can use
trusses braced on 3 or 4 sides set at some multiple of the
glass grid module, with horizontal mast or cable trusses
spanning between them to match the glazing grid (note that
horizontal cable trusses would require heavy boundary
structure to resolve prestress loads). Glazing support is
typically provided by one set of the bracing struts extending
out to define the glazing plane and provide attachment for the
glass system.
Design Considerations
Aesthetics: System designs can very considerably, but mast
Figure 6.5 Mast truss
cable-braced on two
sides.
trusses typically present a predominant, yet elegant, exposed structure. Some designers
prefer a dominant structural presence, to feature the structure rather than minimize it. This
system provides an excellent opportunity for this kind of aesthetic treatment.
Transparency (and control): Very good; the transparency of mast truss systems is
significantly more than simple truss systems, but still less than the tension-based systems.
The enhanced transparency is largely a result of lifting the glazing plane away from the
structure. This invariably has the affect of lightening the structural system and increasing the
perception of transparency to the envelope. Sunlight control issues start to get more
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