STRUCTURAL GLASS FACADES - USC School of Architecture

Durability and Maintenance: The concern here is for the painted steel finish. If the structure
is interior to the façade the system should easily have a ten-year lifespan with minimal
maintenance. However, industry warranties for paint finish are typically for only one year. A
longer warranty period can be included in the project specifications.
Sustainability: General parity between systems.
Structural Performance
Spanning capacity: Trusses in the 20 to 70 ft. range are very economical. Longer spans are
achievable. Truss design may become more complex as a means to reduce the depth of
system.
Span/Depth (L/d) characteristics: L/d = 10 to 15.
Typical deflection criteria: L/175.
Pre-tension requirements: Typically not required. Lateral bracing and internal truss bracing
may require simple pre-tensioning to a snug-tight condition.
Reaction Loads: Trusses can be hung or base-loaded. Hung trusses can be lighter, but
require heavy steel overhead support. Systems are typically base loaded, and not designed
to support the roof, meaning the truss-top connection detail must be designed to transfer
out-of-plane lateral loads from the facade into the roof structure, but not pick up any vertical
dead or live loads from the roof structure. Roof deflections relative to the façade must be
carefully analyzed. Reaction loads are in the normal range for any long-spanning closed
system as a function of tributary area of the spanning elements.
Structural Efficiency (strength to weight): Trusses are moderately efficient as structural
systems.
214