14B-16-1604  General design requirements.
The provisions of Section 1604 of IBC are adopted by reference with the following modifications:
1.   Revise Section 1604.2 to read:
1604.2 Strength.
Buildings and other structures, and parts thereof, shall be designed and constructed to support the factored loads in load combinations defined in this code without exceeding the appropriate strength limit states for the materials of construction. Alternatively, buildings and other structures, and parts thereof, shall be designed and constructed to support the nominal loads in load combinations defined in this code without exceeding the appropriate specified allowable stresses for the materials of construction.
Loads and forces for occupancies or uses not covered in this chapter shall be approved by the building official.”
2.   Revise Section 1604.5, including the exception, to read:
1604.5 Risk category.
Each building and structure shall be assigned a risk category in accordance with Table 1604.5. Where a referenced standard specifies an occupancy category, the risk category shall not be taken as lower than the occupancy category specified therein. Where a referenced standard specifies that the assignment of a risk category be in accordance with ASCE 7, Table 1.5-1, Table 1604.5 shall be used in lieu of ASCE 7, Table 1.5-1.”
3.   Replace Table 1604.5 as shown:
TABLE 1604.5
RISK CATEGORY OF BUILDINGS AND OTHER STRUCTURES
 
RISK CATEGORY
NATURE OF OCCUPANCY
I
Structures that represent a low hazard to human life in the event of failure, including but not limited to:
   •   Agricultural buildings.
   •   Minor storage structures.
II
Structures except those listed in Risk Categories I, III and IV.
III
Structures that represent a substantial hazard to human life in the event of failure, including but not limited to:
   •   Buildings containing one or more Group A occupancies with a combined occupant load in Group A occupancies greater than 1,000.a
   •   Buildings containing Group E occupancies with an occupant load greater than 500.a
   •   Buildings containing Group I-2, Condition 1 occupancies with 50 or more care recipients.
   •   Buildings containing Group I-2, Condition 2 occupancies not providing emergency surgery or emergency treatment.
   •   Buildings containing Group I-3 occupancies.
   •   Any other building with an occupant load greater than 5,000.a
   •   Power-generating stations, water treatment facilities for potable water, wastewater treatment facilities and other public utility structures not included in Risk Category IV.
   •   Structures not included in Risk Category IV containing quantities of toxic or explosive materials that exceed maximum allowable quantities per control area as given in Table 307.1(1) or 307.1(2) or per outdoor control area in accordance with the Chicago Fire Prevention Code; and are sufficient to pose a threat to the public if released.b
IV
Structures designated as essential facilities, including but not limited to:
   •   Buildings containing Group I-2, Condition 2 occupancies providing emergency surgery or emergency treatment.
   •   Buildings containing fire, rescue, ambulance and police stations and emergency vehicle garages.
   •   Buildings containing earthquake, hurricane or other emergency shelters.
   •   Designated emergency preparedness, communications and operations centers and other structures required for emergency response.
   •   Power-generating stations and other utility structures providing emergency backup for Risk Category IV structures.
   •   Structures containing quantities of highly toxic materials that: exceed maximum allowable quantities per control area as given in Table 307.1(2) or per outdoor control area in accordance with the Chicago Fire Prevention Code; and are sufficient to pose a threat to the public if released.b
   •   Aviation control towers, air traffic control centers and emergency aircraft hangars.
   •   Structures having critical public safety or national defense functions.
   •   Water storage and pump structures required to maintain water pressure for fire suppression.
 
a.   Occupant load shall be determined in accordance with Table 1004.5.
b.   Where approved by the fire code official, the classification of structures as Risk Category III or IV based on their quantities of toxic, highly toxic or explosive materials is permitted to be reduced to Risk Category II, provided that it can be demonstrated by a hazard assessment in accordance with Section 1.5.3 of ASCE 7 that a release of the hazardous materials is not sufficient to pose a threat to the public.
4.   Delete the exception to Section 1604.5.1.
5.   Revise Section 1604.7 by replacing “approved” with “accepted.”
6.   Revise Section 1604.8.3 to read:
1604.8.3 Decks, porches, exterior balconies and similar structures.
Where supported by attachment to an exterior wall, decks, porches, exterior balconies and similar structures shall be positively anchored to the primary building structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive connection to the primary building structure cannot be verified, decks, porches, exterior balconies and similar structures shall be self-supporting. Connections of decks, porches, exterior balconies and similar structures with cantilevered framing members to exterior walls or other framing members shall be designed for both of the following:
1.   The reactions resulting from the dead load and live load specified in Table 1607.1, or the snow load specified in Section 1608, in accordance with Section 1605, acting on all portions of the structure.
2.   The reactions resulting from the dead load and live load specified in Table 1607.1, or the snow load specified in Section 1608, in accordance with Section 1605, acting on the cantilevered portion of the structure, and no live load or snow load on the remaining portion of the structure.”
7.   Delete Section 1604.10.
(Amend Coun. J. 2-19-20, p. 14473, Art. II, § 72)