Chapter 19 Concrete
Section 1901 General
1901.1 Scope.
The provisions of this chapter shall govern the materials, quality control, design and construction of concrete used in structures.
1901.2 Plain and reinforced concrete.
Structural concrete shall be designed and constructed in accordance with the requirements of this chapter and ACI 318 as supplemented in Section 1905 of this code.
1901.2.1 Structural concrete with GFRP reinforcement.
Cast-in-place structural concrete internally reinforced with glass fiber reinforced polymer (GFRP) reinforcement conforming to ASTM D7957 and designed in accordance with ACI CODE 440.11 shall be permitted where fire-resistance ratings are not required and only for structures assigned to Seismic Design Category A.
1901.3 Anchoring to concrete.
Anchoring to concrete shall be in accordance with ACI 318 as supplemented in Section 1905, and applies to cast-in (headed bolts, headed studs and hooked J- or L-bolts), post-installed expansion (torque-controlled and displacement-controlled), undercut, screw, and adhesive anchors.
1901.5 Construction documents.
The construction documents for structural concrete construction shall include:
- 1.
The specified compressive strength of concrete at the stated ages or stages of construction for which each concrete element is designed.
- 2.
The specified strength or grade of reinforcement.
- 3.
The size and location of structural elements, reinforcement and anchors.
- 4.
Provision for dimensional changes resulting from creep, shrinkage and temperature.
- 5.
The magnitude and location of prestressing forces.
- 6.
Anchorage length of reinforcement and location and length of lap splices.
- 7.
Type and location of mechanical and welded splices of reinforcement.
- 8.
Details and location of contraction or isolation joints specified for plain concrete.
- 9.
Minimum concrete compressive strength at time of posttensioning.
- 10.
Stressing sequence for posttensioning tendons.
- 11.
For structures assigned to Seismic Design Category D, E or F, a statement if slab on grade is designed as a structural diaphragm.
1901.7 Tolerances for structural concrete.
Where not indicated in construction documents, structural tolerances for concrete structural elements shall be in accordance with this section.
1901.7.1 Cast-in-place concrete tolerances.
Structural tolerances for cast-in-place concrete structural elements shall be in accordance with ACI 117.
Exceptions:
- 1.
Group R-3 detached one- or two-family dwellings are not required to comply with this section.
- 2.
Shotcrete is not required to comply with this section.
Section 1902 Coordination of Terminology
1902.1 General.
Coordination of terminology used in ACI 318 and ASCE/SEI 7 shall be in accordance with Section 1902.1.1.
1902.1.1 Design displacement.
Design displacement shall be the Design Earthquake Displacement, δDE, defined in ASCE/SEI 7 Section 12.8.6.3. For diaphragms that can be idealized as rigid in accordance with ASCE/SEI 7 Section 12.3.1.2, δdi, displacement due to diaphragm deformation corresponding to the design earthquake, is permitted to be taken as zero.
Section 1903 Specifications for Tests and Materials
Section 1904 Durability Requirements
1904.1 Structural concrete.
Structural concrete shall conform to the durability requirements of 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).
1904.2 Nonstructural concrete.
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.
Section 1905 Seismic Requirements
1905.2 ACI 318 Section 2.3.
Modify existing definitions and add the following definitions to ACI 318 Section 2.3:
CAST-IN-PLACE CONCRETE EQUIVALENT DIAPHRAGM.
DETAILED PLAIN CONCRETE STRUCTURAL WALL.
ORDINARY PLAIN CONCRETE STRUCTURAL WALL.
ORDINARY PRECAST STRUCTURAL WALL.
ORDINARY REINFORCED CONCRETE STRUCTURAL WALL.
PRECAST CONCRETE DIAPHRAGM.
A diaphragm constructed with precast concrete components, with or without a cast-in-place topping, that includes the use of discrete connectors or joint reinforcement to transmit diaphragm forces.
1905.3 Intermediate precast structural walls.
Intermediate precast structural walls shall comply with Section 18.5 of ACI 318 and this section.
1905.3.1 Connections designed to yield.
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.
1905.4 Foundations designed to resist earthquake forces.
Foundations resisting earthquake-induced forces or transferring earthquake-induced forces between a structure and the ground shall comply with the requirements of Section 18.13 of ACI 318 and other applicable provisions of ACI 318 unless modified by Chapter 18.
1905.5 Detailed plain concrete structural walls.
Detailed plain concrete structural walls are walls conforming to the requirements of ordinary plain concrete structural walls and Section 1905.5.1.
1905.5.1 Reinforcement.
Reinforcement shall be provided as follows:
- 1.
Vertical reinforcement of not less than 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 Section 14.6.1 of ACI 318.
- 2.
Horizontal reinforcement of not less than 0.20 square inch (129 mm2) in cross-sectional area shall be provided:
- 2.1.
Continuously at structurally connected roof and floor levels and at the top of walls.
- 2.2.
At the bottom of load-bearing walls or in the top of foundations where doweled to the wall.
- 2.3.
At a maximum spacing of 120 inches (3048 mm).
- 2.1.
Reinforcement at the top and bottom of openings, where used in determining the maximum spacing specified in Item 2.3, shall be continuous in the wall.
1905.6 Structural plain concrete.
Structural plain concrete elements shall comply with this section in lieu of Section 14.1.4 of ACI 318.
1905.6.1 Seismic Design Categories A and B.
In structures assigned to Seismic Design Category A or B, 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.
1905.6.2 Seismic Design Categories C, D, E and F.
Structures assigned to Seismic Design Category C, D, E or F shall not have elements of structural plain concrete, except as follows:
- 1.
Structural plain concrete basement, foundation or other walls below the base as defined in ASCE/SEI 7 are permitted in detached one- and two-family dwellings three stories or less in height constructed with stud-bearing 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 be not less than 7 1/2 inches (190 mm), and the wall shall retain not more than 4 feet (1219 mm) of unbalanced fill. Walls shall have reinforcement in accordance with Section 14.6.1 of ACI 318.
- 2.
Isolated footings of plain concrete supporting pedestals or columns are permitted, provided that the projection of the footing beyond the face of the supported member does not exceed the footing thickness.
Exception: In detached one- and two-family dwellings three stories or less in height, the projection of the footing beyond the face of the supported member is permitted to exceed the footing thickness.
- 3.
Plain concrete footings supporting walls are permitted, provided that the footings have not fewer than 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, not fewer than one bar shall be provided at the top and bottom of the footing. Continuity of reinforcement shall be provided at corners and intersections.
Exceptions:
- 1.
Where assigned to Seismic Design Category 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, not fewer than one bar shall be provided at the top of the stemwall and at the bottom of the footing.
- 3.
Footings cast monolithically with a slab-on-ground shall have not fewer than one No. 4 bar at the top and bottom of the footing or one No. 5 bar or two No. 4 bars in the middle third of the footing depth.
- 1.
1905.7 Design requirements for anchors.
For the design requirements for anchors, Sections 1905.7.1 and 1905.7.2 provide exceptions that are permitted to ACI 318.
1905.7.2 Anchors in shear.
The following exceptions are permitted to ACI 318 Section 17.10.6.2:
Exceptions:
- 1.
For the calculation of the in-plane shear strength of anchor bolts attaching wood sill plates of bearing or nonbearing walls of light-frame wood structures to foundations or foundation stemwalls, the in-plane shear strength in accordance with Sections 17.7.2 and 17.7.3 of ACI 318 need not be computed and Section 17.10.6.3 of ACI 318 shall be deemed to be satisfied provided that all of the following are met:
- 1.1.
- 1.2.
The maximum anchor nominal diameter is 5/8 inch (16 mm).
- 1.3.
Anchor bolts are embedded into concrete not less than 7 inches (178 mm).
- 1.4.
Anchor bolts are located not less than 1¾ inches (45 mm) from the edge of the concrete parallel to the length of the wood sill plate.
- 1.5.
Anchor bolts are located not less than 15 anchor diameters from the edge of the concrete perpendicular to the length of the wood sill plate.
- 1.6.
The sill plate is 2-inch (51 mm) or 3-inch (76 mm) nominal thickness.
- 2.
For the calculation of the in-plane shear strength of anchor bolts attaching cold-formed steel track of bearing or nonbearing walls of light-frame construction to foundations or foundation stemwalls, the in-plane shear strength in accordance with Sections 17.7.2 and 17.7.3 of ACI 318 need not be computed and 17.10.6.3 shall be deemed to be satisfied provided that all of the following are met:
Allowable in-plane shear strength of exempt anchors, parallel to the edge of concrete, shall be permitted to be determined in accordance with AISI S100 Section J3.3.1.
- 2.1.
The maximum anchor nominal diameter is 5/8 inch (16 mm).
- 2.2.
Anchors are embedded into concrete a minimum of 7 inches (178 mm).
- 2.3.
Anchors are located a minimum of 1 3/4 inches (45 mm) from the edge of the concrete parallel to the length of the track.
- 2.4.
Anchors are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the track.
- 2.5.
The track is 33 to 68 mil (0.84 mm to 1.73 mm) designation thickness.
- 2.1.
- 3.
In light-frame construction bearing or nonbearing walls, shear strength of concrete anchors less than or equal to 1 inch (25 mm) in diameter attaching sill plate or track to foundation or foundation stemwalls need not satisfy Sections 17.10.6.3(a) through (c) when the design strength of the anchors is determined in accordance with Section 17.7.2.1(c) of ACI 318.
Section 1906 Footings for Light-Frame Construction
1906.1 Plain concrete footings.
For Group R-3 occupancies and buildings of other occupancies less than two stories above grade plane of light-frame construction, the required thickness of plain concrete footings is permitted to be 6 inches (152 mm), provided that the footing does not extend more than 4 inches (102 mm) on either side of the supported wall.
Section 1907 Slabs-On-Ground
1907.1 Structural slabs-on-ground.
Structural concrete slabs-on-ground shall comply with all applicable provisions of this chapter. Slabs-on-ground shall be considered structural concrete where required by ACI 318 or where designed to transmit either of the following:
- 1.
Vertical loads or lateral forces from other parts of the structure to the soil.
- 2.
Vertical loads or lateral forces from other parts of the structure to foundations.
1907.2 Nonstructural slabs-on-ground.
Nonstructural slabs-on-ground shall be required to comply with Sections 1904.2, 1907.3 and 1907.4. Portions of the nonstructural slabs-on-ground used to resist uplift forces or overturning shall be designed in accordance with accepted engineering practice throughout the entire portion designated as dead load to resist uplift forces or overturning.
1907.3 Thickness.
The thickness of concrete floor slabs supported directly on the ground shall be not less than 31/2 inches (89 mm).
1907.4 Vapor retarder.
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:
- 1.
For detached structures accessory to occupancies in Group R-3, such as garages, utility buildings or other unheated facilities.
- 2.
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.
- 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.
- 4.
For driveways, walks, patios and other flatwork that will not be enclosed at a later date.
- 5.
Where approved based on local site conditions.