Load Analysis - Tensile Fabric Structures: Design, Analysis, and Construction - page 102

6.7 System Components

Tensile membrane structures typically consist of many components. Successful
projects require the designer to evaluate the load and performance criteria of the
overall system and of each component.

6.7.1 Fabric

Membrane strength is typically measured prior to fabrication, shipping and
installation. The allowable design loads for membranes are very sensitive to the type
of material used, consistency and quality control of the manufactured membrane, the
duration of load, long-term weather degradation, fabrication techniques and potential
damage during construction. All of these factors tend to reduce the installed available
strength. The consequences of membrane failure may range from incidental loss of
weather protection to catastrophic structural failure. Typical membrane
characteristics are discussed more fully in Chapter 3, The Material Characteristics of
Fabrics.

6.7.2 Cables

Cables are available in a wide range of sizes, strengths, wire lay and materials. The
most common cables are galvanized wire rope used extensively in construction
rigging. The aircraft and marine industries support a wide range of small to modest
sized stainless steel cables. Although their primary market may not be for building
construction, many of these cables can be successfully adapted. Whenever cables are
used in association with a tensile membrane structure, the designer must consider the
type of load, the duration of load, the potential for creep, corrosion protection and
other factors as necessary. Cable manufacturers typically identify the minimum
breaking strengths for each size and type of cable they supply. The following strength
criteria, taken from ASCE Standard 19-96, provide a starting point in identifying
suitable cable strengths:

a. Breaking Strength > 2.2 T 1

(6.7.2-1)

b. Breaking Strength > 2.2 T 2

(6.7.2-2)

c. Breaking Strength > 2.0 T 3

(6.7.2-3)

d. Breaking Strength > 2.0 T 4

(6.7.2-4)

e. Breaking Strength > 2.0 T 5

(6.7.2-5)

where:

T 1 = Cable tension due to D + P
T 2 = Cable tension due to D + P + (Lr or S or R)
T 3 = Cable tension due to D + P + (W or E).
T 4 = Cable tension due to D + P + L + (Lr or S or R) + (W or E)
T 5 = Cable Tension due to C = erection components of D, L, P and W.