The construction documents for structural concrete construction shall include:
- The specified compressive strength of concrete at the stated ages or stages of construction for which each concrete element is designed.
- The specified strength or grade of reinforcement.
- The size and location of structural elements, reinforcement and anchors.
- Provision for dimensional changes resulting from creep, shrinkage and temperature.
- The magnitude and location of prestressing forces.
- Anchorage length of reinforcement and location and length of lap splices.
- Type and location of mechanical and welded splices of reinforcement.
- Details and location of contraction or isolation joints specified for plain concrete.
- Minimum concrete compressive strength at time of posttensioning.
- Stressing sequence for posttensioning tendons.
- For structures assigned to Seismic Design Category D, E or F, a statement if slab on grade is designed as a structural diaphragm (see Section 126.96.36.199 of ACI 318).
Concrete shall be assigned to exposure classes in accordance with ACI 318, Section 4.2, based on:
- Exposure to freezing and thawing in a moist condition or deicer chemicals;
- Exposure to sulfates in water or soil;
- Exposure to water where the concrete is intended to have low permeability; and
- Exposure to chlorides from deicing chemicals, salt, saltwater, brackish water, seawater or spray from these sources, where the concrete has steel reinforcement.
Concrete mixtures shall conform to the most restrictive maximum water-cementitious materials ratios and minimum specified concrete compressive strength requirements of ACI 318, Section 4.3, based on the exposure classes assigned in Section 1904.2.
Exception: For occupancies and appurtenances thereto in Group R occupancies that are in buildings less than four stories above grade plane, normal-weight aggregate concrete is permitted to comply with the requirements of Table 1904.3 based on the weathering classification (freezing and thawing) determined from Figure 1904.3 in lieu of the requirements of ACI 318, Table 4.3.1.
MINIMUM SPECIFIED COMPRESSIVE STRENGTH (f' c)
|TYPE OR LOCATION OF CONCRETE CONSTRUCTION||MINIMUM SPECIFIED COMPRESSIVE STRENGTH (f' c at 28 days, psi)|
|Negligible exposure||Moderate exposure||Severe exposure|
|Basement wallsc and foundations not exposed to the weather||2,500||2,500||2,500a|
|Basement slabs and interior slabs on grade, except garage floor |
|Basement wallsc, foundation walls, exterior walls and other |
vertical concrete surfaces exposed to the weather
|Driveways, curbs, walks, patios, porches, carport slabs, steps and |
other flatwork exposed to the weather, and garage floor slabs
|2,500||3,000b, d||3,500b, d|
For SI: 1 pound per square inch = 0.00689 MPa.
- Concrete in these locations that can be subjected to freezing and thawing during construction shall be of air-entrained concrete in accordance with Section 1904.2.1.
- Concrete shall be air entrained in accordance with Section 1904.4.1.
- Structural plain concrete basement walls are exempt from the requirements for exposure conditions of Section 1904.3 (see Section 1909.6.1).
- For garage floor slabs where a steel trowel finish is used, the total air content required by Section 1904.4.1 is permitted to be reduced to not less than 3 percent, provided the minimum specified compressive strength of the concrete is increased to 4,000 psi.
The frequency of conducting strength tests of concrete and the minimum number of tests shall be as specified in ACI 318, Section 5.6.2.
Exception: When the total volume of a given class of concrete is less than 50 cubic yards (38 m3), strength tests are not required when evidence of satisfactory strength is submitted to the building official.
Modify existing definitions and add the following definitions to ACI 318, Section 2.2.
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 22, including 22.6.7.
ORDINARY STRUCTURAL PLAIN CONCRETE WALL. A wall complying with the requirements of Chapter 22, excluding 22.6.7.
SPECIAL STRUCTURAL WALL. A cast-in-place or precast wall complying with the requirements of 21.1.3 through 21.1.7, 21.9 and 21.10, 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.”
WALL PIER. A wall segment with a horizontal length-to-thickness ratio of at least 2.5, but not exceeding 6, whose clear height is at least two times its horizontal length.
Modify ACI 318 Sections 188.8.131.52 and 184.108.40.206 to read as follows:
220.127.116.11 – Structures assigned to Seismic Design Category A shall satisfy requirements of Chapters 1 to 19 and 22; Chapter 21 does not apply. Structures assigned to Seismic Design Category B, C, D, E or F also shall satisfy 18.104.22.168 through 22.214.171.124, as applicable. Except for structural elements of plain concrete complying with Section 1908.1.8 of the building code, structural elements of plain concrete are prohibited in structures assigned to Seismic Design Category C, D, E or F.
126.96.36.199 – 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 21 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:
- Ordinary moment frames shall satisfy 21.2.
- Ordinary reinforced concrete structural walls and ordinary precast structural walls need not satisfy any provisions in Chapter 21.
- Intermediate moment frames shall satisfy 21.3.
- Intermediate precast structural walls shall satisfy 21.4.
- Special moment frames shall satisfy 21.5 through 21.8.
- Special structural walls shall satisfy 21.9.
- Special structural walls constructed using precast concrete shall satisfy 21.10.
All special moment frames and special structural walls shall also satisfy 21.1.3 through 21.1.7.
Modify ACI 318, Section 21.4, by renumbering Section 21.4.3 to become 21.4.4 and adding new Sections 21.4.3, 21.4.5 and 21.4.6 to read as follows:
21.4.3 – 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.
21.4.4 – Elements of the connection that are not designed to yield shall develop at least 1.5 Sy.
21.4.5 – Wall piers not designed as part of a moment frame shall have transverse reinforcement designed to resist the shear forces determined from 21.3.3. Spacing of transverse reinforcement shall not exceed 8 inches (203 mm). Transverse reinforcement shall be extended beyond the pier clear height for at least 12 inches (305 mm).
Modify ACI 318, Section 21.9, by adding new Section 21.9.10 to read as follows:
21.9.10 – Wall piers and wall segments.
188.8.131.52 – Wall piers not designed as a part of a special moment frame shall have transverse reinforcement designed to satisfy the requirements in 184.108.40.206.
220.127.116.11 – Transverse reinforcement with seismic hooks at both ends shall be designed to resist the shear forces determined from 18.104.22.168. Spacing of transverse reinforcement shall not exceed 6 inches (152 mm). Transverse reinforcement shall be extended beyond the pier clear height for at least 12 inches (305 mm).
22.214.171.124 – Wall segments with a horizontal length-to-thickness ratio less than 2.5 shall be designed as columns.
Modify ACI 318, Section 21.10.2, to read as follows:
21.10.2 – Special structural walls constructed using precast concrete shall satisfy all the requirements of 21.9 for cast-in-place special structural walls in addition to Sections 21.4.2 through 21.4.4.
Modify ACI 318, Section 126.96.36.199, to read as follows:
188.8.131.52 – Foundations resisting earthquake-induced forces or transferring earthquake-induced forces between a structure and ground shall comply with the requirements of Section 21.12 and other applicable provisions of ACI 318 unless modified by Chapter 18 of the building code.
Modify ACI 318, Section 22.6, by adding new Section 22.6.7 to read as follows:
22.6.7 – Detailed plain concrete structural walls.
184.108.40.206 – Detailed plain concrete structural walls are walls conforming to the requirements of ordinary structural plain concrete walls and 220.127.116.11.
18.104.22.168 – Reinforcement shall be provided as follows:
- Vertical reinforcement of at least 0.20 square inch (129 mm2) in cross-sectional area shall be provided continuously from support to support at each corner, at each side of each opening and at the ends of walls. The continuous vertical bar required beside an opening is permitted to substitute for one of the two No. 5 bars required by 22.214.171.124.
- Continuously at structurally connected roof and floor levels and at the top of walls;
- At the bottom of load-bearing walls or in the top of foundations where doweled to the wall; and
- At a maximum spacing of 120 inches (3048 mm).
Delete ACI 318, Section 22.10, and replace with the following:
22.10 – Plain concrete in structures assigned to Seismic Design Category C, D, E or F.
22.10.1 – Structures assigned to Seismic Design Category C, D, E or F shall not have elements of structural plain concrete, except as follows:
- For foundation systems consisting of a plain concrete footing and a plain concrete stemwall, a minimum of one bar shall be provided at the top of the stemwall and at the bottom of the footing.
- Where a slab on ground is cast monolithically with the footing, one No. 5 bar is permitted to be located at either the top of the slab or bottom of the footing.
Modify ACI 318, Sections D.3.3.4 and D.3.3.5 to read as follows:
D.3.3.4 – Anchors shall be designed to be governed by the steel strength of a ductile steel element as determined in accordance with D.5.1 and D.6.1, unless either D.3.3.5 or D.3.3.6 is satisfied.
- Anchors in concrete designed to support nonstructural components in accordance with ASCE 7 Section 13.4.2 need not satisfy Section D.3.3.4.
- 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 need not satisfy Section D.3.3.4.
D.3.3.5 – Instead of D.3.3.4, the attachment that the anchor is connecting to the structure shall be designed so that the attachment will undergo ductile yielding at a force level corresponding to anchor forces no greater than the design strength of anchors specified in D.3.3.3.
- Anchors in concrete designed to support nonstructural components in accordance with ASCE 7 Section 13.4.2 need not satisfy Section D.3.3.5.
- 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 need not satisfy Section D.3.3.5.
Delete ACI 318, Section D.4.2.2, and replace with the following:
D.4.2.2 – The concrete breakout strength requirements for anchors in tension shall be considered satisfied by the design procedure of D.5.2 provided Equation D-8 is not used for anchor embedments exceeding 25 inches (635 mm). The concrete breakout strength requirements for anchors in shear with diameters not exceeding 2 inches (51 mm) shall be considered satisfied by the design procedure of D.6.2. For anchors in shear with diameters exceeding 2 inches (51 mm), shear anchor reinforcement shall be provided in accordance with the procedures of D.6.2.9.
The use of structural plain concrete shall be limited to:
- Members that are continuously supported by soil, such as walls and footings, or by other structural members capable of providing continuous vertical support.
- Members for which arch action provides compression under all conditions of loading.
- Walls and pedestals.
The use of structural plain concrete columns and structural plain concrete footings on piles is not permitted. See Section 1908.1.8 for additional limitations on the use of structural plain concrete.
Structural plain concrete walls, footings and pedestals shall be designed for adequate strength in accordance with ACI 318, Sections 22.4 through 22.8.
Exception: For Group R-3 occupancies and buildings of other occupancies less than two stories above grade plane of light-frame construction, the required edge 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 not be 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:
- For detached structures accessory to occupancies in Group R-3, such as garages, utility buildings or other unheated facilities.
- For unheated storage rooms having an area of less than 70 square feet (6.5 m2) and carports attached to occupancies in Group R-3.
- For buildings of other occupancies where migration of moisture through the slab from below will not be detrimental to the intended occupancy of the building.
- For driveways, walks, patios and other flatwork which will not be enclosed at a later date.
- Where approved based on local site conditions.
The allowable service load for headed anchors in shear or tension shall be as indicated in Table 1911.2. Where anchors are subject to combined shear and tension, the following relationship shall be satisfied:
|Ps||=||Applied tension service load, pounds (N).|
|Pt||=||Allowable tension service load from Table 1911.2, pounds (N).|
|Vs||=||Applied shear service load, pounds (N).|
|Vt||=||Allowable shear service load from Table 1911.2, pounds (N).|
ALLOWABLE SERVICE LOAD ON EMBEDDED BOLTS (pounds)
|MINIMUM CONCRETE STRENGTH (psi)|
|f' c = 2,500||f' c = 3,000||f' c = 4,000|
For SI: 1 inch = 25.4 mm, 1 pound per square inch = 0.00689MPa, 1 pound = 4.45 N.
The provisions of this section shall govern the strength design of anchors installed in concrete for purposes of transmitting structural loads from one connected element to the other. Headed bolts, headed studs and hooked (J- or L-) bolts cast in concrete and expansion anchors and undercut anchors installed in hardened concrete shall be designed in accordance with Appendix D of ACI 318 as modified by Sections 1908.1.9 and 1908.1.10, provided they are within the scope of Appendix D.
When 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. When 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: When specified by the registered design professional, 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.
The minimum thickness of reinforced gypsum concrete shall be 2 inches (51 mm) except the minimum required thickness shall be reduced to 11/2 inches (38 mm), provided the following conditions are satisfied:
- The overall thickness, including the formboard, is not less than 2 inches (51 mm).
- The clear span of the gypsum concrete between supports does not exceed 33 inches (838 mm).
- Diaphragm action is not required.
- The design live load does not exceed 40 pounds per square foot (psf) (1915 Pa).