Building Loading - Wind Exposure (1982 ANSI, 1998
ASCE 7, 1999 BOCA, 1996 BOCA, 1993 BOCA, 1996 NCST,
1994 NCST, OBBC, 1994 SFL, JBSA, CONN, 2001 FL, 2001 FL
(HVHZ), 2000 IBC)
(Revised: 04/01/08)
Exposure A: Large city centers with at least 50% of the buildings
having a height in excess of 70 feet. Use of this exposure category shall be
limited to those areas for which terrain representative of Exposure A prevails
in the upwind direction for a distance of at least one-half mile or 10 times
the height of the building or structure, whichever is greater. Possible
channeling effects or increased velocity pressures due to the building or
structure being located in the wake of adjacent buildings shall be taken into
account.
Exposure
B: Urban and suburban areas, wooded areas, or
terrain with numerous closely spaced obstructions having the size of
single-family dwellings or larger. Use of this exposure category shall be
limited to those areas for which terrain representative of Exposure B prevails
in the upwind direction for a distance of at least 1500 feet or 10 times the
height of the building or structure, whichever is greater.
Exposure
C: Open terrain with scattered obstructions
having heights generally less than 30 feet. This category includes flat, open
country and grasslands.
Exposure
D: Flat, unobstructed coastal areas directly
exposed to wind flowing over large bodies of water. This exposure shall be used
for those areas representative of Exposure D extending inland from the
shoreline a distance of 1500 feet or 10 times the height of the building or
structure, whichever is greater.
See also:
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Building Loading - Wind Load