Italics are used for text within Sections 1903 through 1905 of this code to indicate provisions that differ from ACI 318.
Exception: For Group R-2 and R-3 occupancies not more than three stories above grade plane, the specified compressive strength, f 'c, for concrete in basement walls, foundation walls, exterior walls and other vertical surfaces exposed to the weather shall be not less than 3,000 psi (20.7 MPa).
The registered design professional shall assign nonstructural concrete a freeze-thaw exposure class, as defined in ACI 318, based on the anticipated exposure of nonstructural concrete. Nonstructural concrete shall have a minimum specified compressive strength, f 'c, of 2,500 psi (17.2 MPa) for Class F0; 3,000 psi (20.7 MPa) for Class F1; and 3,500 psi (24.1 MPa) for Classes F2 and F3. Nonstructural concrete shall be air entrained in accordance with ACI 318.
Modify existing definitions and add the following definitions to ACI 318, Section 2.3.
DESIGN DISPLACEMENT. Total lateral displacement expected for the design-basis earthquake, as specified by Section 12.8.6 of ASCE 7.
DETAILED PLAIN CONCRETE STRUCTURAL WALL. A wall complying with the requirements of Chapter 14, including 14.6.2.
ORDINARY PRECAST STRUCTURAL WALL. A precast wall complying with the requirements of Chapters 1 through 13, 15, 16 and 19 through 26.
ORDINARY REINFORCED CONCRETE STRUCTURAL WALL. A cast-in-place wall complying with the requirements of Chapters 1 through 13, 15, 16 and 19 through 26.
ORDINARY STRUCTURAL PLAIN CONCRETE WALL. A wall complying with the requirements of Chapter 14, excluding 14.6.2.
SPECIAL STRUCTURAL WALL. A cast-in-place or precast wall complying with the requirements of 18.2.4 through 18.2.8, 18.10 and 18.11, as applicable, in addition to the requirements for ordinary reinforced concrete structural walls or ordinary precast structural walls, as applicable. Where ASCE 7 refers to a "special reinforced concrete structural wall," it shall be deemed to mean a "special structural wall."
Modify ACI 318 Sections 22.214.171.124 and 126.96.36.199 to read as follows:
188.8.131.52 — Structures assigned to Seismic Design Category A shall satisfy requirements of Chapters 1 through 17 and 19 through 26; Chapter 18 does not apply. Structures assigned to Seismic Design Category B, C, D, E or F shall satisfy 184.108.40.206 through 220.127.116.11, as applicable. Except for structural elements of plain concrete complying with Section 1905.1.7 of the International Building Code, structural elements of plain concrete are prohibited in structures assigned to Seismic Design Category C, D, E or F.
18.104.22.168 — Structural systems designated as part of the seismic force-resisting system shall be restricted to those permitted by ASCE 7. Except for Seismic Design Category A, for which Chapter 18 does not apply, the following provisions shall be satisfied for each structural system designated as part of the seismic force-resisting system, regardless of the seismic design category:
Special moment frames and special structural walls shall also satisfy 18.2.4 through 18.2.8.
Modify ACI 318, Section 18.5 by adding new Section 22.214.171.124 and renumbering existing Sections 126.96.36.199 and 188.8.131.52 to become 184.108.40.206 and 220.127.116.11, respectively.
18.104.22.168 — Connections that are designed to yield shall be capable of maintaining 80 percent of their design strength at the deformation induced by the design displacement or shall use Type 2 mechanical splices.
22.214.171.124 — Elements of the connection that are not designed to yield shall develop at least 1.5 Sy.
126.96.36.199 — In structures assigned to SDC D, E or F, wall piers shall be designed in accordance with 18.10.8 or 18.14 in ACI 318.
Modify ACI 318, Section 188.8.131.52 to read as follows:
184.108.40.206 — Special structural walls constructed using precast concrete shall satisfy all the requirements of 18.10 for cast-in-place special structural walls in addition to 18.5.2.
Modify ACI 318, Section 220.127.116.11 to read as follows:
18.104.22.168 — Foundations resisting earthquake-induced forces or transferring earthquake-induced forces between a structure and ground shall comply with the requirements of 18.13 and other applicable provisions of ACI 318 unless modified by Chapter 18 of the International Building Code.
Modify ACI 318, Section 14.6 by adding new Section 14.6.2 to read as follows:
14.6.2 — Detailed plain concrete structural walls.
22.214.171.124 — Detailed plain concrete structural walls are walls conforming to the requirements of ordinary structural plain concrete walls and 126.96.36.199.
188.8.131.52 — Reinforcement shall be provided as follows:
Delete ACI 318, Section 14.1.4 and replace with the following:
14.1.4 — Plain concrete in structures assigned to Seismic Design Category C, D, E or F.
184.108.40.206 — Structures assigned to Seismic Design Category C, D, E or F shall not have elements of structural plain concrete, except as follows:
Modify ACI 318 Sections 220.127.116.11.2, 18.104.22.168.3(d) and 22.214.171.124.2 to read as follows:
126.96.36.199.2 — Where the tensile component of the strength-level earthquake force applied to anchors exceeds 20 percent of the total factored anchor tensile force associated with the same load combination, anchors and their attachments shall be designed in accordance with 188.8.131.52.3. The anchor design tensile strength shall be determined in accordance with 184.108.40.206.4.
Exception: Anchors designed to resist wall out-of-plane forces with design strengths equal to or greater than the force determined in accordance with ASCE 7 Equation 12.11-1 or 12.14-10 shall be deemed to satisfy Section 220.127.116.11.3(d).
18.104.22.168.3(d) — The anchor or group of anchors shall be designed for the maximum tension obtained from design load combinations that include E, with E increased by Ω0. The anchor design tensile strength shall be calculated from 22.214.171.124.4.
126.96.36.199.2 — Where the shear component of the strength-level earthquake force applied to anchors exceeds 20 percent of the total factored anchor shear force associated with the same load combination, anchors and their attachments shall be designed in accordance with 188.8.131.52.3. The anchor design shear strength for resisting earthquake forces shall be determined in accordance with 17.5.
Exception: For Group R-3 occupancies and buildings of other occupancies less than two stories above grade plane of light-frame construction, the required footing thickness of ACI 318 is permitted to be reduced to 6 inches (152 mm), provided that the footing does not extend more than 4 inches (102 mm) on either side of the supported wall.
The thickness of concrete floor slabs supported directly on the ground shall be not less than 31/2 inches (89 mm). A 6-mil (0.006 inch; 0.15 mm) polyethylene vapor retarder with joints lapped not less than 6 inches (152 mm) shall be placed between the base course or subgrade and the concrete floor slab, or other approved equivalent methods or materials shall be used to retard vapor transmission through the floor slab.
Exception: A vapor retarder is not required:
Where No. 5 or smaller bars are used, there shall be a minimum clearance between parallel reinforcement bars of 21/2 inches (64 mm). When bars larger than No. 5 are permitted, there shall be a minimum clearance between parallel bars equal to six diameters of the bars used. Where two curtains of steel are provided, the curtain nearer the nozzle shall have a minimum spacing equal to 12 bar diameters and the remaining curtain shall have a minimum spacing of six bar diameters.
Exception: Subject to the approval of the building official, required clearances shall be reduced where it is demonstrated by preconstruction tests that adequate encasement of the bars used in the design will be achieved.