- 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.
- 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.
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.
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.
- 21.1.1.3 - 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 21.1.1.4 through 21.1.1.8, as applicable. Except for structural elements of plain concrete complying with Section 1905.1.8 of the International Building Code, structural elements of plain concrete are prohibited in structures assigned to Seismic Design Category C, D, E or F.
- 21.1.1.7 - 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.
- 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 in Seismic Design Category D, E or F shall comply with Section 1905.1.4 of the International Building Code.
- 21.4.6 - Wall piers not designed as part of a moment frame in buildings assigned to Seismic Design Category C 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).
Exceptions:
- Wall piers that satisfy 21.13.
- 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.
- 21.4.7 - Wall segments with a horizontal length-to-thickness ratio less than 2.5 shall be designed as columns.
21.9.8 - Wall piers and wall segments.
21.9.8.1 - Wall piers not designed as a part of a special moment frame shall have transverse reinforcement designed to satisfy the requirements in 21.9.8.2.
- Wall piers that satisfy 21.13.
- 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.
21.9.8.3 - Wall segments with a horizontal length-to-thickness ratio less than 2.5 shall be designed as columns.
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.
- 21.12.1.1 - 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 International Building Code.
22.6.7 - Detailed plain concrete structural walls.
22.6.7.1 - Detailed plain concrete structural walls are walls conforming to the requirements of ordinary structural plain concrete walls and 22.6.7.2.
22.6.7.2 - 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 22.6.6.5.
- Horizontal reinforcement at least 0.20 square inch (129 mm2) in cross-sectional area shall be provided:
- 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).
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:
- 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 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 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.
- 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.
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.
- 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.
Exceptions:
- 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.
- For foundation systems consisting of a plain concrete footing and a plain concrete stem wall, a minimum of one bar shall be provided at the top of the stem wall 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.
- 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.
Exceptions:
- 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.3.3.4 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:
- 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.
- The maximum anchor nominal diameter is 5/8 inch (16 mm).
- Anchor bolts are embedded into concrete a minimum of 7 inches (178 mm).
- 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.
- 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.
- The sill plate is of 2-inch or 3-inch nominal thickness.
- 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:
- The maximum anchor nominal diameter is 5/8inch (16 mm).
- Anchors are embedded into concrete a minimum of 7 inches (178 mm).
- Anchors are located a minimum of 13/4 inches (45 mm) from the edge of the concrete parallel to the length of the track.
- Anchors are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the track.
- The track is 33 to 68 mil designation thickness.
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 E3.3.1.
- In light-frame construction, design of anchors in concrete shall be permitted to satisfy D.3.3.7.
- 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.
Exceptions:
- 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.
- D.3.3.6 - As an alternative to D.3.3.4 and D.3.3.5, it shall be permitted to take the design strength of the anchors as 0.4 times the design strength determined in accordance with D.3.3.3.
- D.3.3.7 — In light-frame construction, bearing or non-bearing walls, shear strength of concrete anchors less than or equal to 1 inch (25 mm) in diameter of sill plate or track to foundation or foundation stem wall need not satisfy D.3.3.6 when the design strength of the anchors is determined in accordance with D.6.2.1(c).
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-7 is not used for anchor embedments exceeding 25 inches. The concrete breakout strength requirements for anchors in shear with diameters not exceeding 2 inches shall be considered satisfied by the design procedure of D.6.2. For anchors in shear with diameters exceeding 2 inches, shear anchor reinforcement shall be provided in accordance with the procedures of D.6.2.9.
- 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.
(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). |
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 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.