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Each building and structure shall be assigned a structural occupancy category in accordance with Table 1604.5.

TABLE 1604.5
STRUCTURAL OCCUPANCY/RISK CATEGORY AND IMPORTANCE FACTORS
STRUCTURAL
OCCUPANCY/ RISK
CATEGORYa
NATURE OF OCCUPANCY/RISK
I Buildings and other structures that represent a low hazard to human life in the event of failure including, but not limited to:
  1. Agricultural facilities
  2. Certain temporary facilities
  3. Minor storage facilities
II Buildings and other structures except those listed in Structural Occupancy/Risk Categories I, III and IV
III Buildings and other structures that represent a substantial hazard to human life in the event of failure including, but not limited to:
  1. Buildings and other structures whose primary occupancy is public assembly with an occupant load greater than 300.
  2. Buildings and other structures containing elementary school, secondary school or day-care facilities with an occupant load greater than 250.
  3. Buildings and other structures containing adult education facilities, such as colleges and universities with an occupant load greater than 500.
  4. Group I-2 occupancies with an occupant load of 50 or more resident patients but not having surgery or emergency treatment facilities.
  5. Group I-3 occupancies.
  6. Any other occupancy with an occupant load greater than 5,000a.
  7. Power-generating stations, water treatment for potable water, waste-water treatment facilities and other public utility facilities not included in Structural Occupancy/Risk Category IV.
  8. Buildings and other structures not included in Structural Occupancy/Risk Category IV containing sufficient quantities of toxic or explosive substances to be dangerous to the public if released.
IV Buildings and other structures designed as essential facilities including, but not limited to:
  1. Group I-2 occupancies having surgery or emergency treatment facilities.
  2. Fire, rescue, ambulance and police stations and emergency vehicle garages.
  3. Designated earthquake, hurricane or other emergency shelters.
  4. Designated emergency preparedness, communication, and operation centers and other facilities required for emergency response.
  5. Power-generating stations and other public utility facilities required as emergency backup facilities for Structural Occupancy/Risk Category IV structures.
  6. Structures containing highly toxic materials as defined by Section 307 where the quantity of the material exceeds the maximum allowable quantities of Table 307.7(2).
  7. Aviation control towers, air traffic control centers and emergency aircraft hangars.
  8. Buildings and other structures having critical national defense functions.
  9. Water storage facilities and pump structures required to maintain water pressure for fire suppression.
  1. For purposes of occupant load calculation, occupancies required by Table 1004.1.1 to use gross floor area calculations shall be permitted to use net floor areas to determine the total occupant load.
1604.5.1 Multiple Occupancies
Where a building or structure is occupied by two or more occupancies not included in the same structural occupancy category, it shall be assigned the classification of the highest structural occupancy category corresponding to the various occupancies. Where buildings or structures have two or more portions that are structurally separated, each portion shall be separately classified. Where a separated portion of a building or structure provides required access to, required egress from or shares life safety components with another portion having a higher structural occupancy category, both portions shall be assigned to the higher structural occupancy category.
1604.5.2 Importance Factors
Importance factors for snow, wind and seismic loads shall be determined in accordance with Table 1604.5.2 based on the Structural Occupancy Category or Risk Category assigned in accordance with Table 1604.5.

TABLE 1604.5.2 IMPORTANCE FACTORS

STRUCTURAL
OCCUPANCY/RISK
CATEGORY
SNOW
IMPORTANCE
FACTOR, I
WIND
IMPORTANCE
FACTOR, I
SEISMIC
IMPORTANCE
FACTOR, I
I 0.80 0.87 1.00
II 1.00 1.00 1.00
III 1.10 1.15 1.25
IV 1.20 1.15 1.50

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