Italics are used for text within Sections1903 through 1905 of this code to indicate provisions that differ from ACI 318.
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 post-tensioning tendons.
- For structures assigned to Seismic Design Category D, E or F, a statement if slab on grade is designed as a structural diaphragm.
Concrete shall be assigned to exposure classes in accordance with the durability requirements of ACI 318 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, maximum cementitious admixtures, minimum air-entrainment and minimum specified concrete compressive strength requirements of ACI 318 based on the exposure classes assigned in Section 1904.1.
TABLE 1904.2
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 slabs | 2,500 | 2,500 | 2,500a |
Basement wallsc, foundation walls, exterior walls and other vertical concrete surfaces exposed to the weather | 2,500 | 3,000b | 3,000b |
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 |
- 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.
- Concrete shall be air entrained in accordance with ACI 318.
- Structural plain concrete basement walls are exempt from the requirements for exposure conditions of Section 1904.2.
- For garage floor slabs where a steel trowel finish is used, the total air content required by ACI 318 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.
FIGURE 1904.2
WEATHERING PROBABILITY MAP FOR CONCRETEa, b, c
- Lines defining areas are approximate only. Local areas can be more or less severe than indicated by the region classification.
- A "severe" classification is where weather conditions encourage or require the use of deicing chemicals or where there is potential for a continuous presence of moisture during frequent cycles of freezing and thawing. A "moderate" classification is where weather conditions occasionally expose concrete in the presence of moisture to freezing and thawing, but where deicing chemicals are not generally used. A "negligible" classification is where weather conditions rarely expose concrete in the presence of moisture to freezing and thawing.
- Alaska and Hawaii are classified as severe and negligible, respectively.
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 PRECAST STRUCTURAL WALL. A precast wall complying with the requirements of Chapters 1 through 18.
ORDINARY REINFORCED CONCRETE STRUCTURAL WALL. A cast-in-place wall complying with the requirements of Chapters 1 through 18.
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-tothickness 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 21.1.1.3 and 21.1.1.7 to read as follows:
(a) Ordinary moment frames shall satisfy 21.2.
(b) Ordinary reinforced concrete structural walls and ordinary precast structural walls need not satisfy any provisions in Chapter 21.
(c) Intermediate moment frames shall satisfy 21.3.
(d) Intermediate precast structural walls shall satisfy 21.4.
(e) Special moment frames shall satisfy 21.5 through 21.8.
(f) Special structural walls shall satisfy 21.9.
(g) Special structural walls constructed using precast concrete shall satisfy 21.10.
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, 21.4.6 and 21.4.7 to read as follows:
1. Wall piers that satisfy 21.13.
2. Wall piers along a wall line within a story where other shear wall segments provide lateral support to the wall piers and such segments have a total stiffness of at least six times the sum of the stiffnesses of all the wall piers.
Modify ACI 318, Section 21.9, by deleting Section 21.9.8 and replacing with the following:
1. Wall piers that satisfy 21.13.
2. Wall piers along a wall line within a story where other shear wall segments provide lateral support to the wall piers and such segments have a total stiffness of at least six times the sum of the stiffnesses of all the wall piers.
Modify ACI 318, Section 21.10.2, to read as follows:
Modify ACI 318, Section 21.12.1.1, to read as follows:
Modify ACI 318, Section 22.6, by adding new Section 22.6.7 to read as follows:
(a) 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 22.6.6.5.
(b) Horizontal reinforcement at least 0.20 square inch (129 mm2) in cross-sectional area shall be provided:
1. Continuously at structurally connected roof and floor levels and at the top of walls;
2. At the bottom of load-bearing walls or in the top of foundations where doweled to the wall; and
3. At a maximum spacing of 120 inches (3048 mm).
Delete ACI 318, Section 22.10, and replace with the following:
(a) Structural plain concrete basement, foundation or other walls below the base are permitted in detached one- and two-family dwellings three stories or less in height constructed with studbearing walls. In dwellings assigned to Seismic Design Category D or E, the height of the wall shall not exceed 8 feet (2438 mm), the thickness shall not be less than 71/2 inches (190 mm), and the wall shall retain no more than 4 feet (1219 mm) of unbalanced fill. Walls shall have reinforcement in accordance with 22.6.6.5.
(b) Isolated footings of plain concrete supporting pedestals or columns are permitted, provided the projection of the footing beyond the face of the supported member does not exceed the footing thickness.
(c) Plain concrete footings supporting walls are permitted, provided the footings have at least two continuous longitudinal reinforcing bars. Bars shall not be smaller than No. 4 and shall have a total area of not less than 0.002 times the gross cross-sectional area of the footing. For footings that exceed 8 inches (203 mm) in thickness, a minimum of one bar shall be provided at the top and bottom of the footing. Continuity of reinforcement shall be provided at corners and intersections.
1. In Seismic Design Categories A, B and C, detached one- and two-family dwellings three stories or less in height constructed with stud-bearing walls, are permitted to have plain concrete footings without longitudinal reinforcement.
2. 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.
3. 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 318-08 Sections D.3.3.4 through D.3.3.6 and add Section D3.3.7 to read as follows:
Exceptions:
1. 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.
2. D.3.3.4 need not apply and the design shear strength in accordance with D.6.2.1(c) need not be computed for anchor bolts attaching wood sill plates of bearing or nonbearing walls of light-frame wood structures to foundations or foundation stem walls provided all of the following are satisfied:
2.1. The allowable in-plane shear strength of the anchor is determined in accordance with AF&PA NDS Table 11E for lateral design values parallel to grain.
2.2. The maximum anchor nominal diameter is 5/8 inch (16 mm).
2.3. Anchor bolts are embedded into concrete a minimum of 7 inches (178 mm).
2.4. Anchor bolts are located a minimum of 13/4 inches (45 mm) from the edge of the concrete parallel to the length of the wood sill plate.
2.5. Anchor bolts are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the wood sill plate.
2.6. The sill plate is of 2-inch or 3-inch nominal thickness.
3. Section D.3.3.4 need not apply and the design shear strength in accordance with Section D.6.2.1(c) need not be computed for anchor bolts attaching cold-formed steel track of bearing or nonbearing walls of light-frame construction to foundations or foundation stem walls provided all of the following are satisfied:
3.1. The maximum anchor nominal diameter is 5/8 inch (16 mm).
3.2. Anchors are embedded into concrete a minimum of 7 inches (178 mm).
3.3. Anchors are located a minimum of 13/4 inches (45 mm) from the edge of the concrete parallel to the length of the track.
3.4. Anchors are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the track.
3.5. The track is 33 to 68 mil designation thickness.
4. In light-frame construction, design of anchors in concrete shall be permitted to satisfy D.3.3.7.
1. 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.
2. 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:
The design and construction of structural plain concrete, both cast-in-place and precast, shall comply with the minimum requirements of ACI 318, as modified in Section 1905.
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.
- 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 1908.2. Where anchors are subject to combined shear and tension, the following relationship shall be satisfied:
(Ps / Pt )5/3 + (Vs / Vt ) 5/3 ≤ 1 | (Equation 19-1) |
where:
Ps | = | Applied tension service load, pounds (N). |
Pt | = | Allowable tension service load from Table 1908.2, pounds (N). |
Vs | = | Applied shear service load, pounds (N). |
Vt | = | Allowable shear service load from Table 1908.2, pounds (N). |
TABLE 1908.2
ALLOWABLE SERVICE LOAD ON EMBEDDED BOLTS (pounds)
BOLT DIAMETER (inches) | MINIMUM EMBEDMENT (inches) | EDGE DISTANCE (inches) | SPACING (inches) | MINIMUM CONCRETE STRENGTH (psi) | |||||
f 'c = 2,500 | f 'c = 3,000 | f 'c = 4,000 | |||||||
Tension | Shear | Tension | Shear | Tension | Shear | ||||
1/4 | 21/2 | 11/2 | 3 | 200 | 500 | 200 | 500 | 200 | 500 |
3/8 | 3 | 21/4 | 41/2 | 500 | 1,100 | 500 | 1,100 | 500 | 1,100 |
1/2 | 4 | 3 | 6 | 950 | 1,250 | 950 | 1,250 | 950 | 1,250 |
4 | 5 | 6 | 1,450 | 1,600 | 1,500 | 1,650 | 1,550 | 1,750 | |
5/8 | 41/2 | 33/4 | 71/2 | 1,500 | 2,750 | 1,500 | 2,750 | 1,500 | 2,750 |
41/2 | 61/4 | 71/2 | 2,125 | 2,950 | 2,200 | 3,000 | 2,400 | 3,050 | |
3/4 | 5 | 41/2 | 9 | 2,250 | 3,250 | 2,250 | 3,560 | 2,250 | 3,560 |
5 | 71/2 | 9 | 2,825 | 4,275 | 2,950 | 4,300 | 3,200 | 4,400 | |
7/8 | 6 | 51/4 | 101/2 | 2,550 | 3,700 | 2,550 | 4,050 | 2,550 | 4,050 |
1 | 7 | 6 | 12 | 3,050 | 4,125 | 3,250 | 4,500 | 3,650 | 5,300 |
11/8 | 8 | 63/4 | 131/2 | 3,400 | 4,750 | 3,400 | 4,750 | 3,400 | 4,750 |
11/4 | 9 | 71/2 | 15 | 4,000 | 5,800 | 4,000 | 5,800 | 4,000 | 5,800 |
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 1905.1.9 and 1905.1.10, provided they are within the scope of Appendix D.
The strength design of anchors that are not within the scope of Appendix D of ACI 318, and as amended in Sections 1905.1.9 and 1905.1.10, shall be in accordance with an approved procedure.
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.
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 permit holder shall make available to the building official a job log with the following minimum items.
- Cast density recordings/hour.
- Product evaluation for application.
- Date and job locations identified.
- Results of any field test conducted.
Lightweight insulating concrete shall be poured over bottom slotted galvanized (G-90) steel decking as follows; cellular, 0.5-percent open; hybrid, 0.75-percent open, aggregate, 1.5-percent open. No lightweight insulating concrete shall be poured over a painted or nongalvanized steel deck.
1. Lightweight insulating concrete over structural concrete slabs, twin tees, precast units or other non-venting substrates shall be vented to allow the escape of excess moisture.
Insulation board with lightweight insulating concrete shall conform to Type I expanded polystyrene insulation as defined in ASTM C 578.
- Packaged insulation board delivered to the job site shall comply with the provisions of Section 2603.2.
- Installation of insulating board in conjunction with lightweight insulating concrete shall comply with uplift requirements set forth in Section 1609 (Section 1620 for the High-Velocity Hurricane Zone). Insulation panels shall be placed in a minimum 1/8-inch (3.2 mm) slurry of insulating concrete while the material is still in a plastic state. The insulating concrete shall be cast over the insulation boards according to the insulating concrete manufacturer's product approval. Insulation panels shall be provided with holes and/or slots for keying and venting.