TABLE 1-1 Occupancy Category of Buildings and Other Structures for Flood, Wind, Snow, Earthquake, and Ice Loads
Nature of Occupancy
Buildings and structures that represent a low hazard to human life in the event of failure including, but not limited to:
- Agriculture facilities
- Certain temporary facilities
- Minor storage facilities
Buildings and other structures except those listed in Categories I, III and IV
Buildings and other structures that represent a substantial hazard to human life in the event of failure including, but not limited to:
- Buildings and other structures where more than 300 people congregate in one area
- Buildings and other structures with day-care facilities with capacity greater than 150
- Elementary or secondary school facilities with capacity greater than 250
- Colleges & adult education facilities with a capacity greater than 500
- Health care facilities with a capacity greater than 50 resident patients but not having surgery or emergency treatment facilities
- Jails and detention facilities
Buildings and other structures, not includes in Occupancy Category IV, with potential to cause
substantial economic impact and/or mass disruption of day-to-day civilian life in event of failure,
including, but not limited to:
- Power generating stations, water treatment facilities, sewage treatment facilities, and
- Buildings and structures not included in Category IV containing sufficient quantities of toxic,
explosive, or other hazardous materials dangerous to the public if released
Buildings and other structures designated as essential facilities including, but not limited to:
- Hospitals and health care facilities having surgery or emergency treatment facilities
- Fire, rescue and police stations and emergency vehicle garages
- Designated earthquake, hurricane or other emergency shelters
- Designated emergency preparedness, communication, and operation centers and other facilities required for emergency response
- Power-generating stations and other public utility facilities required in an emergency
- Ancillary structures required foroperation of Category IV structures during an emergency
- Aviation control towers, air traffic control centers and emergency aircraft hangars
- Water storage facilities and pump structures required to maintain water pressure for fire suppression
- Buildings and other structures having critical national defense functions
- Buildings and structures containing extremelyhazardous materials where quantity of material exceeds a threshhold quantity established by authority having jurisdiction
The Topographic Factor, Kzt, accounts for effect of wind speed-up over isolated hills and escarpments (Sect. 6.5.7 and Fig. 6-4).
Kzt = (1+K1*K2*K3)^2 (Eq. 6-3), where:
H = height of hill or escarpment relative to the upwind terrain, in feet.
Lh = Distance upwind of crest to where the difference in ground elevation is
half the height of hill or escarpment, in feet.
K1 = factor to account for shape of topographic feature and maximum
K2 = factor to account for reduction in speed-up with distance upwind or
downwind of crest.
K3 = factor to account for reduction in speed-up with height above local terrain.
x = distance (upwind or downwind) from the crest to the building site, in feet.
z = height above local ground level, in feet.
The effect of wind speed-up shall not be required to be considered (Kzt = 1.0) when H/Lh < 0.2, or H < 15' for Exposures 'C' and 'D', or H < 60' for Exposure 'B'.
IMPORTANCE FACTOR, I, (ICE LOADS)
*See Section 1.5 and Table 1-1.
WIND ON ICE-COVERED STRUCTURES
Ice accreted on structural members, components, and appurte¬nances increases the projected area of the structure exposed to wind. The projected area shall be increased by adding td to all free edges of the projected area.Wind loads on this increased pro¬jected area shall be used in the design of ice-sensitive structures. Figs. 10-2 to 10-6 include 3-s gust wind speeds at 33 ft (10 m) above grade that are concurrent with the ice loads due to freezing rain. Wind loads shall be calculated in accordance with Chapter 6 as modiﬁed by Sections 10.5.1 through 10.5.5.
Disclaimer: This calculator is not intended to be used for the design of actual structures, but only for schematic (preliminary) understanding of structural design principals. For the design of an actual structure, a competent professional should be consulted.