Municipal Code of Chicago § 14B-16-1601 General.
14B-16-1601 General.
The provisions of Section 1601 of IBC are adopted by reference without modification.
STRUCTURAL DESIGN
Municipal Code of Chicago tit. 14B, ch. 14B-16
in effectMunicipal Code of Chicago § 14B-16-1602 Notations.
14B-16-1602 Notations.
The provisions of Section 1602 of IBC are adopted by reference without modification.
Municipal Code of Chicago § 14B-16-1603 Construction documents.
14B-16-1603 Construction documents.
The provisions of Section 1603 of IBC are adopted by reference with the following modifications:
1. Revise the exception to Section 1603.1 by deleting item 5.
2. Revise the first two sentences of Section 1603.1.3 to read:
"The ground snow load, Pg, shall be indicated. The following additional information shall also be provided, regardless of whether snow loads govern the design of the roof:"
3. Revise item 6 in Section 1603.1.3 to read:
"6. Drift surcharge load(s), Pd."
4. Revise item 1 in Section 1603.1.4 to read:
"1. Basic design wind speed, V, miles per hour or allowable stress design wind speed, Vasd, as determined in accordance with Section 1609.3.1."
5. Add a new item 6 to Section 1603.1.4 to read:
"6. Design base shear(s)."
6. Revise Section 1603.1.5 by inserting the following between items 6 and 7:
"The following information shall be shown for structures assigned to seismic design category B, C or D:"
7. Delete Section 1603.1.7.
8. Delete Section 1603.1.9.
Municipal Code of Chicago § 14B-16-1604 General design requirements.
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)
Municipal Code of Chicago § 14B-16-1605 Load combinations.
14B-16-1605 Load combinations.
The provisions of Section 1605 of IBC are adopted by reference with the following modifications:
1. Revise item 1 in the first paragraph of Section 1605.1 to read:
"1. The load combinations specified in Section 1605.2 or 1605.3.1."
2. Delete item 3 in the third paragraph of Section 1605.1.
3. Revise Section 1605.1.1 by replacing "registered design professional" with "registered geotechnical engineer."
4. Delete the first sentence of Section 1605.2.1.
5. Revise Section 1605.3 by deleting "or 1605.3.2."
6. Delete the first sentence of Section 1605.3.1.2.
7. Delete Section 1605.3.2 and its subsections.
Municipal Code of Chicago § 14B-16-1606 Dead loads.
14B-16-1606 Dead loads.
The provisions of Section 1606 of IBC are adopted by reference with the following modification:
1. Revise Section 1606.2 to read:
"1606.2 Design dead load.
For purposes of design, the actual weights of materials of construction and fixed equipment shall be used. In the absence of definite information, values used shall be approved by the building official."
Municipal Code of Chicago § 14B-16-1607 Live loads.
14B-16-1607 Live loads.
The provisions of Section 1607 of IBC are adopted by reference with the following modifications:
1. Revise Table 1607.1 by replacing “OCCUPANCY OR USE” with “FUNCTION OR USE” in the heading of the first column.
1.1. Revise row 2 of Table 1607.1 to read:
2. Access floor systemsOffice useTelecommunication equipment area | 50100 | 2,0002,000
2. Revise row 4 of Table 1607.1 by inserting an entry for "Dressing rooms" with a value of "40."
3. Revise row 5 of Table 1607.1 to read:
5. Porches, exterior balconies, decks and similar structures hAccessible from a single dwelling unitAll others | 60100 | 300 f300 f
4. Revise row 9 of Table 1607.1 by adding "including associated kitchens" in the first column.
5. Revise row 13 of Table 1607.1 be deleting the entry for "on single family dwellings only."
6. Revise row 21 of Table 1607.1 to read:
21. Mechanical Rooms | 125 p | –
7. Revise row 22 of Table 1607.1 to read:
22. OfficesCorridors above first floorFile rooms other than high-density filesTelecommunication equipment areasLobbies and first-floor corridorsOffices and associated work areas, meeting rooms, break rooms, reception areas, and similar nonpublic gathering areas | 80100125 p10050 | 2,000––2,0002,000
8. Revise row 25 of Table 1607.1 to read:
25. ResidentialGroup R-3, R-4 and R-5 occupanciesUninhabitable attics without storage iUninhabitable attics with storage i, j, k All other areasGroup R-1 and R-2 occupanciesPrivate rooms and corridors serving themPublic rooms m and corridors serving them | 10204040100 | –
9. Revise row 26 of Table 1607.1 by deleting "except one- and two-family dwellings" and replacing "Occupiable roofs" with "Occupiable rooftops."
10. Revise row 27 of Table 1607.1 by adding an entry for "Shops" with a uniform value of "100" and concentrated value of "2,000."
11. Revise row 30 of Table 1607.1 by replacing "One- and two-family" with "Group R-5 (interior)."
12. Revise row 31 of Table 1607.1 to read:
31. Storage (shall be designed for heavier loads if required for anticipated storage)HeavyLightTelecommunications equipment areas | 250 n125 n100 p | –
13. Revise note d to Table 1607.1 by replacing "an approved method" with "an accepted engineering practice."
14. Revise note k to Table 1607.1 by replacing "habitable attics and sleeping rooms" with "all other areas."
15. Revise note l to Table 1607.1 to read:
"l. Areas of occupiable rooftops accessible from a single dwelling unit shall be designed in accordance with Row 5. Areas of roofs with vegetation and not intended for occupancy shall be designed in accordance with Section 1607.13.3."
16. Add a new note p to Table 1607.1 to read:
"p. Where actual fixed equipment loads are known, permanent aisles shall be allowed to be designed for a live load of 40 pounds per square foot and equipment areas shall be allowed to be designed for the actual dead loads."
17. Revise Section 1607.2 to read:
"1607.2 Loads not specified.
For occupancies or uses not designated in Table 1607.1, the live load shall be approved by the building official."
18. Revise item 1 in Section 1607.7.2 to read:
"1. The actual operational loads, including outrigger reactions and contact areas of the vehicles."
19. Revise the exception to Section 1607.7.3 by deleting "and are approved by the building official."
20. Revise exception 1 to Section 1607.8.1 to read:
"1. For Group R-5 occupancies and within individual dwelling units, only the single concentrated load required by Section 1607.8.1.1 shall be applied."
21. Revise Section 1607.9 to replace "an approved method" with "an accepted engineering practice."
21.1. Revise Section 1607.10.4 to read:
"1607.10.4 Fall arrest, lifeline, and rope descent system anchorages.
In addition to any other applicable live loads, fall arrest, lifeline, and rope descent system anchorages and structural elements that support these anchorages shall be designed for a live load of not less than 3,100 pounds (13.8 kN) for each attached line, in any direction that the load can be applied. Anchorages of horizontal lifelines and the structural elements that support these anchorages shall be designed for the maximum tension that develops in the horizontal lifeline from these live loads."
22. Revise Section 1607.13 to delete "and marquees."
23. Revise Section 1607.13.2 to delete "and marquees."
24. Revise Section 1607.13.3 to read:
"1607.13.3 Occupiable rooftops.
Occupiable rooftops and vegetative roofs are permitted to have their uniformly distributed live loads reduced in accordance with Section 1607.11 for floors."
25. Delete Section 1607.15.2.
(Amend Coun. J. 2-19-20, p. 14473, Art. II, § 73; Amend Coun. J. 10-7-20, p. 21791, Art. II, § 28; Amend Coun. J. 1-26-22, p. 43756, Art. II, § 17; Amend Coun. J. 1-24-24, p. 8634, Art. IV, § 5)
Municipal Code of Chicago § 14B-16-1608 Snow loads.
14B-16-1608 Snow loads.
The provisions of Section 1608 of IBC are adopted by reference with the following modifications:
1. Revise Section 1608.2 to read:
"1608.2 Ground snow load.
The ground snow load to be used in determining the design snow loads for roofs shall be 25 pounds per square foot (1.20 kN/ m2)."
2. Delete all figures and tables included in Section 1608.
Municipal Code of Chicago § 14B-16-1609 Wind loads.
14B-16-1609 Wind loads.
The provisions of Section 1609 of IBC are adopted by reference with the following modifications:
1. Revise Section 1609.1.1 to read:
"1609.1.1 Determination of wind loads.
Wind loads on every building or structure shall be determined in accordance with Chapters 26 to 30 of ASCE 7. The basic design wind speed, V, and the exposure category for a site shall be determined in accordance with Section 1609. Wind shall be assumed to come from any horizontal direction and wind pressures shall be assumed to act normal to the surface considered.
Exceptions:
1. [Reserved.]
2. Buildings of Group R-3, R-4 or R-5 occupancy using the provisions of AWC WFCM (including buildings containing up to 3 dwelling units).
3. Buildings of Group R-3, R-4 or R-5 occupancy using the provisions of AISI S230 (including buildings containing up to 3 dwelling units).
4. Designs using NAAMM FP 1001.
5. Designs using TIA-222 for antenna-supporting structures and antennas, provided that the horizontal extent of Topographic Category 2 escarpments in Section 2.6.6.2 of TIA-222 shall be 16 times the height of the escarpment.
6. Wind tunnel tests in accordance with ASCE 49 and Sections 31.4 and 31.5 of ASCE 7.
7. Wind loads determined in accordance with Chapter 28 of ASCE 7 shall only be allowed for buildings containing only Group F, S or U occupancies.
8. Wind loads determined in accordance with Section 1609.6.
The wind speeds in Section 1609.3 are basic design wind speeds, V. Allowable stress design wind speeds, Vasd, from Section 1609.3.1 shall be used when the provisions of the standards referenced in Exceptions 4 and 5 are used."
2. Delete Section 1609.1.1.1.
3. Add a new Section 1609.1.2 to read:
"1609.1.2 Special investigations.
Special investigations shall be required to determine wind loads for buildings and other structures with a mean roof height exceeding 400 feet (122 m). Special investigations shall be required to determine wind loads for buildings and other structures with a mean roof height of 400 feet (122 m) or less and having irregular shapes, response characteristics or site locations with shielding or channeling effects that warrant special consideration."
4. Delete Section 1609.2 and its subsections and tables.
5. Revise Section 1609.3 to read:
"1609.3 Basic design wind speed.
The basic design wind speed, V, for nominal design 3-second gust wind speeds at 33 feet (10 m) above ground for exposure category C for the determination of the wind loads shall be as follows:
1. The basic design wind speed, V, for use in the design of Risk Category I structures shall be 101 mph (45 m/s).
2. The basic design wind speed, V, for use in the design of Risk Category II structures shall be 107 mph (48 m/s).
3. The basic design wind speed, V, for use in the design of Risk Category III structures shall be 114 mph (51 m/s).
4. The basic design wind speed, V, for use in the design of Risk Category IV structures shall be 119 mph (53 m/s)."
6. Delete all figures and tables included in Section 1609.3.
7. Revise Section 1609.3.1 to read:
"1609.3.1 Wind speed conversion.
Where required, the basic design wind speeds of Section 1609.3 shall be converted to allowable stress design wind speeds, Vasd, using Equation 16-33."
8. Revise the Description of V in Equation 16-33 to read:
"V = Basic design wind speed determined from Section 1609.3."
9. Delete Table 1609.3.1.
10. Revise Section 1609.4.2 by deleting the second sentence describing Surface Roughness D.
11. Insert a new Section 1609.6 to read:
"1609.6 Alternative wind loads for enclosed structure with mean roof height of 60 feet or less.
Where the mean roof height of a structure is 60 feet (18.3 m) or less, wind loads on the main windforce-resisting system and on components and cladding shall be permitted to be determined in accordance with Section 1609.6, provided the following conditions are met:
1. The structure is classified as "enclosed" in accordance with Chapter 26 of ASCE 7.
2. Both the windward and leeward wind loads are transmitted by roof and vertically spanning wall assemblies, through continuous floor and roof diaphragms, to the main windforce-resisting system.
3. The longest horizontal dimension of the structure is no more than five times the shortest horizontal dimension of the structure.
4. The structure has no unusual geometrical irregularity in spatial form.
5. The structure does not have response characteristics that make it subject to across-wind loading, vortex shedding, or instability caused by galloping or flutter.
6. The structure does not have a site location for which channeling effects or buffeting in the wake of upwind obstructions warrant special consideration.
1609.6.1 Main windforce-resisting system.
The load due to wind pressure, W, on the main windforce-resisting system shall be based on exposure category and risk category as indicated in Table 1609.6.1.
TABLE 1609.6.1
LOAD DUE TO WIND PRESSURE ON MAIN WINDFORCE-RESISTING SYSTEM c, d, e, f, g
EXPOSURE CATEGORY | LOAD DUE TO WIND PRESSURE (pounds per square foot)
Risk Category
I or II | III | IV
B | 25 | 28 | 31
C | 32 | 37 | 40
D | 38 | 43 | 46
For SI: 1 pound per square foot = 0.0479 kN/ m 2
a. Exposure category shall be determined in accordance with Section 1609.4.3.
b. Risk category shall be determined in accordance with Section 1604.5.
c. Wind loads shall use the following load cases (see ASCE 7, Chapter 27):
Case 1: 100 percent of the design wind pressure acting on the projected area perpendicular to each principal axis of the structure, considered separately for each principal axis.
Case 2: 75 percent of the design wind pressure acting on the projected area perpendicular to each principal axis of the structure, in conjunction with a torsional moment resulting from this wind pressure acting at an eccentricity equal to 15 percent of the building width, considered separately for each principal axis.
Case 3: Wind loading as defined in Case 1 but considered to act simultaneously on each principal axis at 75 percent of the value specified in Case 1.
Case 4: Wind loading as defined in Case 2 but considered to act simultaneously on each principal axis at 75 percent of the value specified in Case 2.
d. For buildings that include parapets, additional parapet load shall be applied in accordance with ASCE 7, Section 27.3.4.
e. For the main windforce-resisting system of a roof, the values shall be multiplied by 1.0 for negative (uplift) pressure and 0.3 for positive (downward) pressure. (See Section 1609.6.2 for components and cladding.)
f. All wind loads are ultimate wind loads (W) and shall be utilized in load combinations using strength or load and resistance factor design per Section 1605.2. Where required, service level loads may be obtained by dividing the values in the table by 1.6, however these service level loads shall not be used for either method of load combination prescribed in Section 1605.2 or 1605.3.1.
g. Projecting elements such as flag poles, sign structures, tanks and towers shall be designed in accordance with ASCE 7.
1609.6.2 Components and cladding.
The load due to wind pressure, W, on components and cladding shall be the values in Table 1609.6.1 multiplied by the multiplier provided in Table 1609.6.2.
TABLE 1609.6.2
MULTIPLIERS TO DETERMINE COMPONENTS AND CLADDING WIND PRESSURE
CONDITION | MULTIPLIER k
Flat Roof (less than 7° slope) | Sloped Gable Roof j
Wall (field) a | 1.2 | 1.2
Wall (corner) a, c | 1.4 | 1.4
Roof (field) b | 1.0 h | 2.0
Roof (edge) b | 2.3 d, h | 3.0 f, i
Roof (corner) b | 3.2 e, h | 3.6 g, i
For SI: 1 foot = 304.8 mm, 1 degree = 0.017 rad.
a. Wall pressures shall act toward (positive) or away (negative) from the surface.
b. Roof pressures shall be considered as acting away (negative) from the surface.
c. Wall corners shall be defined as a distance from the corner equal to the lesser of 0.1 times the least horizontal dimension or 0.4 times the height in both directions (minimum 3 feet).
d. Flat roof edges shall be defined as a distance from the roof edge of 1.2 times the height.
e. Flat roof corners shall be defined as a distance from each roof corner of 0.6 times the height (for a width of 0.2 times the height).
f. Sloped gable roof edges shall be defined as a distance from the roof edge equal to the lesser of 0.1 times the least horizontal dimension or 0.4 times the height (minimum 3 feet) from the roof edge.
g. Sloped gable roof corners shall be defined as a distance from any roof corner or peak equal to the lesser of 0.1 times the least horizontal dimension or 0.4 times the height (minimum 3 feet) in both directions.
h. For overhangs on flat roofs utilize the flat roof multipliers above (includes pressure contribution from both upper and lower surface).
i. For overhangs on sloped gable roofs, increase the sloped gable roof multipliers above by 30 percent (includes pressure contribution from both upper and lower surface).
j. Loads above shall not apply to hip roofs (Refer to Chapter 30 of ASCE 7).
k. Resulting wind loads are ultimate wind loads and shall be utilized in load combinations using strength or load and resistance factor design per Section 1605.2 or converted in accordance with Section 1609.3.1.
(Amend Coun. J. 2-19-20, p. 14473, Art. II, § 74; Amend Coun. J. 6-25-21, p. 32180, Art. II, § 24)
Municipal Code of Chicago § 14B-16-1610 Soil lateral loads.
14B-16-1610 Soil lateral loads.
The provisions of Section 1610 of IBC are adopted by reference with the following modifications:
1. Revise Section 1610.1, excluding the exception, to read:
"1610.1 General.
Foundation walls and retaining walls shall be designed to resist lateral soil loads. Soil loads specified in Table 1610.1 shall be used as the minimum design lateral soil loads unless determined otherwise by a geotechnical investigation in accordance with Section 1803. Foundation walls and other walls in which horizontal movement is restricted at the top shall be designed for at-rest pressure. Retaining walls free to move and rotate at the top shall be permitted to be designed for active pressure. Design lateral pressure from surcharge loads shall be added to the lateral earth pressure load. Foundation walls shall be designed to support the weight of the full hydrostatic pressure of undrained backfill unless a drainage system is installed in accordance with Sections 1805.4.2 and 1805.4.3. Where a portion or the whole of the adjacent soil is below a free-water surface, computations shall be based on the weight of the soil diminished by buoyancy, plus full hydrostatic pressure."
2. Replace Table 1610.1 as follows:
TABLE 1610.1
LATERAL SOIL LOAD
LATERAL PRESSURE | DESIGN LATERAL SOIL LOAD a (pounds per square foot per foot of depth)
Active pressure | 45
At rest pressure | 60
For SI: 1 pound per square foot per foot of depth = 0.157 kPa/m, 1 foot = 304.8 mm.
Municipal Code of Chicago § 14B-16-1611 Rain loads.
14B-16-1611 Rain loads.
The provisions of Section 1611 of IBC are adopted by reference with the following modifications:
1. Revise the last sentence of Section 1611.1 to read:
"The design rainfall shall be based on a 100-year hourly rainfall rate of 4.03 inches (102 mm)."
2. Delete figures accompanying Section 1611.1.
3. Delete Equation 16-35.
(Amend Coun. J. 2-19-20, p. 14473, Art. II, § 75)
Municipal Code of Chicago § 14B-16-1612 Flood design.
14B-16-1612 Flood design.
The provisions of Section 1612 of IBC are not adopted. The following language is adopted as Section 1612:
"1612. FLOOD DESIGN.
1612.1 General.
Development in special flood hazard areas shall comply with Chapter 16-6 of the Municipal Code."
Municipal Code of Chicago § 14B-16-1613 Earthquake loads.
14B-16-1613 Earthquake loads.
The provisions of Section 1613 of IBC are adopted by reference with the following modifications:
1. Revise the exceptions to Section 1613.1 to read:
"Exceptions:
1. Buildings and structures assigned to Seismic Design Category A shall comply with Section 1613.4.
2. Group R-3 and R-5 occupancies.
3. The seismic force-resisting system of wood-frame buildings of light-frame construction that conform to the provisions of Section 2308 are not required to be analyzed as specified in this section.
4. Agricultural and industrial storage structures intended only for incidental human occupancy.
5. Structures that require special consideration of their response characteristics and environment that are not addressed by this code or ASCE 7 and for which other regulations provide seismic criteria, such as vehicular bridges, electrical transmission towers, hydraulic structures, buried utility lines and their appurtenances and nuclear reactors.
6. References within ASCE 7 to Chapter 14 shall not apply, except as specifically required herein."
2. Revise Section 1613.2 to read:
"1613.2 Seismic ground motion values.
Seismic ground motion values shall be determined in accordance with this section.
1613.2.1 Acceleration parameters.
The acceleration parameters shall be: mapped 0.2 sec. spectral response acceleration (5% of critical damping, Site Class B) Ss = 0.125 g and mapped 1.0 sec. spectral response acceleration (5% of critical damping, Site Class B) S1 = 0.066.
1613.2.2 Site class definitions.
Based on the site soil properties, the site shall be classified as Site Class A, B, C, D, E or F in accordance with Chapter 20 of ASCE 7. The site class shall reflect the soil conditions that affect the ground motion input to the structure.
Where the soil properties are not known in sufficient detail to determine the site class, Site Class D, subjected to the requirements of Section 1613.2.3, shall be used unless the building official or a registered geotechnical engineer determines that Site Class E or F soils are present at the site.
Where site investigations that are performed in accordance with Chapter 20 of ASCE 7 reveal rock conditions consistent with Site Class B, but site-specific velocity measurements are not made, the site coefficients Fa and Fv shall be taken at unity (1.0).
1613.2.3 Site coefficients and adjusted maximum considered earthquake spectral response acceleration parameters.
The maximum considered earthquake spectral response acceleration for short periods, SMS, and at 1-second period, SM1, adjusted for site class effects and five-percent damped design spectral response acceleration at short periods, SDS, and at 1-second period, SD1 shall be as provided in Table 1613.2.3.
Where the simplified design procedure of ASCE 7 Section 12.14 is used, these values shall be determined in accordance with ASCE 7 Section 12.14.8.1.
TABLE 1613.2.3
SEISMIC DESIGN PARAMETERS
Site Class | Maximum Spectral Response Accelerations | Design Spectral Response Accelerations | Seismic Design Category
Risk Category
SMS | SM1 | SDS | SD1 | I, II or III | IV
Site Class | Maximum Spectral Response Accelerations | Design Spectral Response Accelerations | Seismic Design Category
Risk Category
SMS | SM1 | SDS | SD1 | I, II or III | IV
A | 0.100 | 0.053 | 0.067 | 0.035 | A | A
B | 0.113 | 0.053 | 0.075 | 0.035 | A | A
C | 0.163 | 0.099 | 0.108 | 0.066 | A | A
D | 0.200 | 0.155 | 0.133 | 0.103 | B a | C
E | 0.300 | 0.277 | 0.200 | 0.185 | C | D
F | note b | note b | note b | note b | note c
a. The structure shall be assigned to Seismic Design Category A where the mean roof height does not exceed 60 feet (18.3 m) and the horizontal distance between vertical elements of the seismic force-resisting system does not exceed 40 feet (12.2 m).
b. Values shall be determined in accordance with Section 11.4.8 of ASCE 7.
c. Determine in accordance with ASCE 7.
1613.2.4 [Reserved.]
1613.2.5 Determination of seismic design category.
Structures shall be assigned to a Seismic Design Category in accordance with Table 1613.2.3.
1613.2.5.1 [Reserved.]
1613.2.5.2 Simplified design procedure.
Where the alternate simplified design procedure of ASCE 7 is used, the seismic design category shall be determined in accordance with ASCE 7."
3. Revise the last sentence of Section 1613.3 to read:
"In structures assigned to Seismic Design Category C or D, ballasted nonpenetrating systems shall be designed to accommodate seismic displacement determined by nonlinear response-history or other engineering analysis or shake-table testing, using input motions consistent with ASCE 7 lateral and vertical seismic forces for nonstructural components on roofs."
4. Insert a new Section 1613.4 to read:
"1613.4 Seismic design requirements for buildings assigned to Seismic Design Category A.
Buildings and other structures assigned to Seismic Design Category A need only comply with the requirements of this section. Nonstructural components of buildings and structures in Seismic Design Category A are exempt from seismic design requirements.
Exception: Tanks assigned to Risk Category IV shall satisfy the freeboard requirements of Section 15.6.5.1 of ASCE 7.
1613.4.1 General.
All structures shall be provided with a continuous load path in accordance with the requirements of Section 1613.4.2 and shall have a complete lateral force-resisting system with adequate strength to resist the forces indicated in Section 1613.4.3. All members of the structural system shall be connected to their supporting members in accordance with Section 1613.4.4. Structural walls shall be anchored to diaphragms and supports in accordance with Section 1613.4.5. The effects on the structure and its components caused by the forces stipulated in this section shall be taken as the notional load, N, and combined with the effects of other loads in accordance with the load combinations of Section 1605. Where material resistance depends on load duration, notional loads are permitted to be taken as having a duration of 10 minutes.
1613.4.2 Load path connections.
All parts of the structure between separation joints shall be interconnected to form a continuous path to the lateral force-resisting system, and the connections shall be capable of transmitting the lateral forces induced by the parts being connected. Any smaller portion of the structure shall be tied to the remainder of the structure with elements having the strength to resist a force of not less than 5% of the portion’s weight.
1613.4.3 Lateral forces.
Each structure shall be analyzed for the effects of static lateral forces applied independently in each of two orthogonal directions. In each direction, the static lateral forces at all levels shall be applied simultaneously. For purposes of analysis, the force at each level shall be determined using Equation 16-36a.
Fx = 0.01Wx (Equation 16-36a)
where:
Fx = The design lateral force applied at level x.
Wx = the portion of the total dead load of the structure, D, located or assigned to level x.
1613.4.4 Connection to supports.
A positive connection for resisting a horizontal force acting parallel to the member shall be provided for each beam, girder or truss either directly to its supporting elements or to slabs designed to act as diaphragms. Where the connection is through a diaphragm, the member’s supporting element shall also be connected to the diaphragm. The connection shall have the strength to resist a force of 5% of the unfactored dead load plus live load reaction imposed by the supported member on the supporting member.
1613.4.5 Anchorage of structural walls.
Walls that provide vertical load bearing or lateral shear resistance for a portion of the structure shall be anchored to the roof and all floors and members that provide lateral support for the wall or that are supported by the wall. The anchorage shall provide a direct connection between the walls and the roof or floor construction. The connections shall be capable of resisting a strength level horizontal force perpendicular to the plane of the wall equal to 0.2 times the weight of the wall tributary to the connection, but not less than 5 psf (0.24 kN/m2)."
(Amend Coun. J. 7-24-19, p. 3646, § 33; Amend Coun. J. 2-19-20, p. 14473, Art. II, § 76)
Municipal Code of Chicago § 14B-16-1614 Atmospheric ice loads.
14B-16-1614 Atmospheric ice loads.
The provisions of Section 1614 of IBC are adopted by reference with the following modification:
1. Revise Section 1614.1 to read:
"1614.1 General.
Ice-sensitive structures shall be designed for atmospheric ice loads in accordance with Chapter 10 of ASCE 7."
Municipal Code of Chicago § 14B-16-1615 IBC Section 1615.
14B-16-1615 IBC Section 1615.
The provisions of Section 1615 of IBC are not adopted.
Municipal Code of Chicago § 14B-16-1616 Structural integrity.
14B-16-1616 Structural integrity.
The provisions of Section 1616 of IBC are adopted by reference without modification.
Source: City of Chicago, Municipal Code of Chicago (American Legal Publishing, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/chicago/latest/chicago_il/0-0-0-2666290Fetched: 10/24/2026