Loads - Tensile Fabric Structures: Design, Analysis, and Construction - page 52

9. As of this writing there is no Load Resistance Factor Design standard
methodology for tensile membrane structures. As a consequence of their non-
linear behavior LRFD methodology can result in significant difference in
design outcome from Allowable Stress Design.
10. As with other structures, some thought should be given to load combinations
to produce the most unfavorable effects for a given structural system and its
components.
Other than these challenges, determination of appropriate design loading is the same
as for other structures and systems.
4.2 Dead Loads
These structures are typically very lightweight. Commonly employed fabric
membrane materials have a unit weight of 8 N/m 2 to 24 N/m 2 (0.17 to 0.50 psf). Film
materials such as ETFE are lighter. Generally, any attached equipment such as
lighting speakers or architectural features may best be considered as live load and
included or excluded from load combinations as necessary to produce maximum
demand.
4.3 Live Loads
Tensile membrane structures are most commonly employed in roof and building
envelope applications or for partially or fully open canopies. Where and if used in
other applications live loads per the jurisdiction's building code must be employed.
For roof applications the standard live load per ASCE 7 is dependent upon the
tributary area supported by the member in question and the roof slope. An exception
is noted for “awnings and canopies of fabric construction supported by a lightweight
rigid skeleton structure” for which the minimum live load is 240 N/m 2 (5 psf). There
are requirements for single point loads, most notable a 1.33 kN (300 lb) point load
for roof surfaces subject to maintenance workers.
Not including the exception for fabric awnings and canopies, tensile membrane
structure roofs are subject to live load reductions. However, the concept of tributary
area is not directly applicable to most tensile membrane structures as a large
percentage of the system, indeed the entire structure can be engaged in resisting even
a single concentrated load. In consideration of the fabric membrane, the “tributary
area” can be considered as the region affected by load application and in all but quite
small structures or where the membrane is used in discrete panels, this area will be
greater than the 56 m 2 (600 ft 2 ) required to reduce the minimum live load to 580 N/
m 2 (12 psf).
4.4 Wind Loads
Wind produces the governing loading for many tensile membrane structures. Wind