Civil Engineering Reference
In-Depth Information
Periodic inspection by the manufacturer or other qualified personnel is recommended.
The scope of such inspections should generally include checking for abrasion of the
fabric at interfaces with other elements.
8.8 Cost Issues
Interest in tensioned fabric structures is often based in part on the assumption that
“tent” construction is inexpensive. In reality, the cost of fabric structures varies
widely, and their expense relative to alternative roof systems is dependent on the type
of roof with which they are compared and, in some cases, the desire of the owner to
make an iconic or other architectural statement. Measured in dollars per square foot
of plan area, exclusive of foundations or other supporting structure, the cost of a
custom permanent tensile fabric structure generally varies between $700 and
$1700/m
2
. Standardized structures may cost as little as $250/m
2
. Some of the
parameters affecting tensioned fabric structure cost are discussed in the paragraphs
below.
8.8.1 Material Choices
Certain knit materials and lightweight fabrics using vinyl-coated polyester or other
materials are typically low in cost, but generally unsuitable for structures of
substantial size that are subject to significant environmental loading. Polyester-based
materials offer the lowest cost structural fabric, while fiberglass and expanded PTFE
materials command a substantial cost premium. The difficulty in handling the strong
but brittle fiberglass fabrics results in higher costs for erection of membranes using
this material.
8.8.2 Symmetry and Repetition
By designing structures with symmetry about one or more axes, and by providing
repetitive modules, analysis, patterning, and fabrication costs can all be significantly
reduced.
8.8.3 Scale
Because membrane structure dead load is generally small and because the cost of
fabricated fabric does not vary dramatically with increases in fabric stress, cost per
unit plan area does not rise as dramatically with increase in span as it does with
conventional construction.
8.8.4 Structural Efficiency
Design choices that result in efficient structural behavior can yield significant
economies. For example, reasonable fabric curvature is required in order to limit
fabric stress and cable force, and to achieve stability under wind load. Increased
curvature results in an increase in the height of the structure, which can in turn cause
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