There have been many instances of aircraft hangars' roof systems
being damaged during high winds, yet other buildings' roof systems
at an airport and in nearby communities were not damaged.
Obviously, the wind did not target the hangars' roof systems, so
why did damage occur? The answer lies with the unique
characteristics of aircraft hangars, which many roof system
designers do not recognize. Following is some information about
these unique characteristics and how they contribute to
wind-related roof system damage, as well as design solutions that
can be implemented to avoid or minimize damage.
A distinguishing characteristic of hangars is location. Because
an airport's surrounding terrain typically is flat, vegetation is
low and there are few nearby buildings, virtually all hangars are
in Exposure C as defined in ASCE 7, "Minimum Design Loads for
Buildings and Other Structures."
ASCE 7 defines three common exposure classifications: B (urban,
suburban and wooded areas); C (open terrain with scattered
obstructions and shorelines in hurricane-prone areas); and D
(shorelines exposed to wind flowing over open water for a distance
of at least 1 mile [1.6 km]). A building's exposure classification
strongly influences its wind load. For example, for an enclosed
building (a building whose exterior envelope is relatively
air-impermeable), the uplift loads on roof systems in Exposure C
are 40 percent greater than those in Exposure B, and the loads in
Exposure D are 66 percent greater than those in Exposure B. Because
of a terrain's influence on wind loads, a windstorm delivers about
40 percent higher uplift loads to roof systems on most airport
buildings versus loads delivered to buildings in nearby...
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