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:

Building Loading - Wind Load