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All buildings and other structures shall be assigned a structural occupancy category, as determined by Table 1604.5. The value for snow load, wind load and seismic load importance factors shall be determined in accordance with Table 1604.5.

TABLE 1604.5
STRUCTURAL OCCUPANCY CATEGORY AND IMPORTANCE FACTORS
STRUCTURAL
OCCUPANCY
CATEGORYa
NATURE OF OCCUPANCY SEISMIC
FACTOR IE
SNOW
FACTOR IS
WIND
FACTOR IW
I Buildings and other structures that represent a low hazard to human life in the event of failure including, but not limited to:

1.00 0.8 0.87
II Buildings and other structures except those listed in Structural Occupancy Categories I, III and IV 1.00 1.0 1.00
III 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

1.25 1.1 1.15
IV Buildings and other structures designed as essential facilities including, but not limited to:

  • Hospitals and other 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 as emergency backup facilities for Structural Occupancy Category IV structures
  • Structures containing highly toxic materials as defined by Section 307 where the quantity of the mate-rial exceeds the maximum allowable quantities of Table 307.7(2)
  • Aviation control towers, air traffic control centers and emergency aircraft hangars
  • Buildings and other structures having critical national defense functions
  • Water treatment facilities required to maintain water pressure for fire suppression
1.50 1.2 1.15
  1. For the purpose of Section 1616.2, Structural Occupancy Categories I and II are considered Seismic Use Group I, Structural Occupancy Category III is considered Seismic Use Group II and Structural Occupancy Category IV is equivalent to Seismic Use Group III.
1604.5.1 Multiple Occupancies
Where a structure is used for two or more occupancies not included in the same category of Table 1604.5, the structure shall be assigned the classification of the highest structural occupancy category corresponding to the various occupancies, except as provided for in Section 1.5.1 of ASCE 7.

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