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Title: Section 1907  •  Size: 42844

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SECTION 1907 - DETAILS OF REINFORCEMENT

1907.0 Notations.

d = distance from extreme compression fiber to centroid of tension reinforcement, inches (mm).

= nominal diameter of bar, wire or prestressing strand, inches (mm).

= specified yield strength of nonprestressed reinforcement, psi (MPa).

= development length, inches (mm). See Section 1912.

1907.1 Standard Hooks. ``Standard hook'' as used in this code is one of the following:

1907.1.1 One-hundred-eighty-degree bend plus 4 extension, but not less than 2 1/2 inches (64 mm) at free end of bar.

1907.1.2 Ninety-degree bend plus 12 extension at free end of bar.

1907.1.3 For stirrup and tie hooks:

1. No. 5 bar and smaller, 90-degree bend plus 6 extension at free end of bar, or

2. No. 6, No. 7 and No. 8 bar, 90-degree bend, plus 12 extension at free end of bar, or

3. No. 8 bar and smaller, 135-degree bend plus 6 extension at free end of bar.

4. For stirrup and tie hooks in Seismic Zones 3 and 4, refer to the hoop and crosstie provisions of Section 1921.1 and the transverse reinforcement.

1907.2 Minimum Bend Diameters.

1907.2.1 Diameter of bend measured on the inside of the bar, other than for stirrups and ties in sizes No. 3 through No. 5, shall not be less than the values in Table 19-B.

1907.2.2 Inside diameter of bends for stirrups and ties shall not be less than 4 for No. 5 bar and smaller. For bars larger than No. 5, diameter of bend shall be in accordance with Table 19-B.

1907.2.3 Inside diameter of bends in welded wire fabric (plain or deformed) for stirrups and ties shall not be less than 4 for deformed wire larger than D6 and 2 for all other wires. Bends with inside diameter of less than 8 shall not be less than 4 from nearest welded intersection.

1907.3 Bending.

1907.3.1 All reinforcement shall be bent cold, unless otherwise permitted by the building official.

1907.3.2 Reinforcement partially embedded in concrete shall not be field bent, except as shown on the design drawings or permitted by the building official.

1907.4 Surface Conditions of Reinforcement.

1907.4.1 At the time concrete is placed, metal reinforcement shall be free from mud, oil or other nonmetallic coatings that decrease bond.

1907.4.2 Metal reinforcement, except prestressing tendons, with rust, mill scale or a combination of both, shall be considered satisfactory, provided the minimum dimensions (including height of deformations) and weight of a hand-wire-brushed test specimen are not less than applicable specification requirements.

1907.4.3 Prestressing tendons shall be clean and free of oil, dirt, scale, pitting and excessive rust. A light oxide is permissible.

1907.5 Placing Reinforcement.

1907.5.1 Reinforcement, prestressing tendons and ducts shall be accurately placed and adequately supported before concrete is placed, and shall be secured against displacement within tolerances of this section.

1907.5.2 Unless otherwise approved by the building official, reinforcement, prestressing tendons and prestressing ducts shall be placed within the following tolerances:

1907.5.2.1 Tolerance for depth d, and minimum concrete cover in flexural members, walls and compression members shall be as follows:

TOLERANCE ON
d
TOLERANCE ON MINIMUM
CONCRETE COVER
d 8 in. (203 mm)
± 3/8 in. (9.5 mm)
- 3/8 in. (9.5 mm)
d > 8 in. (203 mm)
± 1/2 in. (13 mm)
- 1/2 in. (13 mm)

except that tolerance for the clear distance to formed soffits shall be minus 1/4 inch (6.4 mm) and tolerance for cover shall not exceed minus one third the minimum concrete cover required by the approved plans or specifications.

1907.5.2.2 Tolerance for longitudinal location of bends and ends of reinforcement shall be ± 2 inches (± 51 mm) except at discontinuous ends of members where tolerance shall be ± 1/2 inch(± 13 mm).

1907.5.3 Welded wire fabric (with wire size not greater than W5 or D5) used in slabs not exceeding 10 feet (3048 mm) in span may be curved from a point near the top of slab over the support to a point near the bottom of slab at midspan, provided such reinforcement is either continuous over, or securely anchored at, support.

1907.5.4 Welding of crossing bars shall not be permitted for assembly of reinforcement.

EXCEPTIONS: 1. Reinforcing steel not required by design.

2. When specifically approved by the building official, welding of crossing bars for assembly purposes in Seismic Zones 0, 1 and 2 may be permitted, provided that data are submitted to the building official to show that there is no detrimental effect on the action of the structural member as a result of welding of the crossing bars.

1907.6 Spacing Limits for Reinforcement.

1907.6.1 The minimum clear spacing between parallel bars in a layer shall be but not less than 1 inch (25 mm). See also Section 1903.3.2.

1907.6.2 Where parallel reinforcement is placed in two or more layers, bars in the upper layers shall be placed directly above bars in the bottom layer with clear distance between layers not less than 1 inch (25 mm).

1907.6.3 In spirally reinforced or tied reinforced compression members, clear distance between longitudinal bars shall not be less than 1.5 or less than 1 1/2 inches (38 mm). See also Section 1903.3.2.

1907.6.4 Clear distance limitation between bars shall apply also to the clear distance between a contact lap splice and adjacent splices or bars.

1907.6.5 In walls and slabs other than concrete joist construction, primary flexural reinforcement shall not be spaced farther apart than three times the wall or slab thickness, or 18 inches (457 mm).

1907.6.6 Bundled bars.

1907.6.6.1 Groups of parallel reinforcing bars bundled in contact to act as a unit shall be limited to four bars in one bundle.

1907.6.6.2 Bundled bars shall be enclosed within stirrups or ties.

1907.6.6.3 Bars larger than No. 11 shall not be bundled in beams.

1907.6.6.4 Individual bars within a bundle terminated within the span of flexural members shall terminate at different points with at least 40 stagger.

1907.6.6.5 Where spacing limitations and minimum concrete cover are based on bar diameter , a unit of bundled bars shall be treated as a single bar of a diameter derived from the equivalent total area.

1907.6.7 Prestressing tendons and ducts.

1907.6.7.1 Clear distance between pretensioning tendons at each end of a member shall not be less than 4 for wire, or 3 for strands. See also Section 1903.3.2. Closer vertical spacing and bundling of strands may be permitted in the middle portion of a span.

1907.6.7.2 Posttensioning ducts may be bundled if it is shown that concrete can be satisfactorily placed and if provision is made to prevent the tendons, when tensioned, from breaking through the duct.

1907.7 Concrete Protection for Reinforcement.

1907.7.1 Cast-in-place concrete (nonprestressed). The following minimum concrete cover shall be provided for reinforcement:

MINIMUM COVER,
inches (mm)
1.
Concrete cast against and permanently exposed to earth 3 (76)
2.
Concrete exposed to earth or weather:

No. 6 through No. 18 bar
No. 5 bar, W31 or D31 wire, and smaller


2 (51)
1 1/2 (38)
3.
Concrete not exposed to weather or in contact with ground:

Slabs, walls, joists:

No. 14 and No. 18 bar
No. 11 bar and smaller

1 1/2 (38)
3/4 (19)
Beams, columns:

Primary reinforcement, ties, stirrups, spirals

1 1/2 (38)
Shells, folded plate members:

No. 6 bar and larger
No. 5 bar, W31 or D31 wire, and smaller


3/4 (19)
1/2 (13)

1907.7.2 Precast concrete (manufactured under plant control conditions). The following minimum concrete cover shall be provided for reinforcement:

MINIMUM COVER,
inches (mm)
1.
Concrete exposed to earth or weather:

Wall panels:

No. 14 and No. 18 bar
No. 11 bar and smaller

Other members:

No. 14 and No. 18 bar
No. 6 through No. 11 bar
No. 5 bar W31 or D31 wire, and smaller

1 1/2 (38)
3/4 (19)

2 (51)
1 1/2 (38)
1 1/4 (32)

2.
Concrete not exposed to weather or in contact with ground:

Slabs, walls, joists:

No. 14 and No. 18 bar
No. 11 bar and smaller



1 1/4 (32)
5/8 (16)
Beams, columns:

Primary reinforcement



but not less than 5/8 (16) and need not exceed 1 1/2 (38)
Ties, stirrups, spirals

Shells, folded plate members:

No. 6 bar and larger
No. 5 bar, W31 or D31 wire, and smaller

3/8 (9.5)



5/8 (16)
3/8 (9.5)

1907.7.3 Prestressed concrete.

1907.7.3.1 The following minimum concrete cover shall be provided for prestressed and nonprestressed reinforcement, ducts and end fittings, except as provided in Sections 1907.7.3.2 and 1907.7.3.3.

MINIMUM COVER,
inches (mm)
1.
Concrete cast against and permanently exposed to earth 3 (76)
2.
Concrete exposed to earth or weather:

Wall panels, slabs, joists
Other members


1 (25)
1 1/2 (32)
3.
Concrete not exposed to weather or in contact with ground:

Slabs, walls, joists
Beams, columns:

Primary reinforcement
Ties, stirrups, spirals


3/4 (19)

1 1/2 (38)
1 (25)

Shells, folded plate members:

No. 5 bars, W31 or D31 wire, and smaller
Other reinforcement


3/8 (9.5)
but not less than 3/4 (19)

1907.7.3.2 For prestressed concrete members exposed to earth, weather or corrosive environments, and in which permissible tensile stress of Section 1918.4.2, Item 2, is exceeded, minimum cover shall be increased 50 percent.

1907.7.3.3 For prestressed concrete members manufactured under plant control conditions, minimum concrete cover for nonprestressed reinforcement shall be as required in Section 1907.7.2.

1907.7.4 Bundled bars. For bundled bars, minimum concrete cover shall be equal to the equivalent diameter of the bundle, but need not be greater than 2 inches (51 mm); except for concrete cast against and permanently exposed to earth, minimum cover shall be 3 inches (76 mm).

1907.7.5 Corrosive environments. In corrosive environments or other severe exposure conditions, amount of concrete protection shall be suitably increased, and denseness and nonporosity of protecting concrete shall be considered, or other protection shall be provided.

1907.7.6 Future extensions. Exposed reinforcement, inserts and plates intended for bonding with future extensions shall be protected from corrosion.

1907.7.7 Fire protection. When a thickness of cover for fire protection greater than the minimum concrete cover specified in Section 1907.7 is required, such greater thickness shall be used.

1907.8 Special Reinforcement Details for Columns.

1907.8.1 Offset bars. Offset bent longitudinal bars shall conform to the following:

1907.8.1.1 Slope of inclined portion of an offset bar with axis of column shall not exceed 1 in 6.

1907.8.1.2 Portions of bar above and below an offset shall be parallel to axis of column.

1907.8.1.3 Horizontal support at offset bends shall be provided by lateral ties, spirals or parts of the floor construction. Horizontal support provided shall be designed to resist one and one-half times the horizontal component of the computed force in the inclined portion of an offset bar. Lateral ties or spirals, if used, shall be placed not more than 6 inches (152 mm) from points of bend.

1907.8.1.4 Offset bars shall be bent before placement in the forms. See Section 1907.3.

1907.8.1.5 Where a column face is offset 3 inches (76 mm) or greater, longitudinal bars shall not be offset bent. Separate dowels, lap spliced with the longitudinal bars adjacent to the offset column faces, shall be provided. Lap splices shall conform to Section 1912.17.

1907.8.2 Steel cores. Load transfer in structural steel cores of composite compression members shall be provided by the following:

1907.8.2.1 Ends of structural steel cores shall be accurately finished to bear at end-bearing splices, with positive provision for alignment of one core above the other in concentric contact.

1907.8.2.2 At end-bearing splices, bearing shall be considered effective to transfer not more than 50 percent of the total compressive stress in the steel core.

1907.8.2.3 Transfer of stress between column base and footing shall be designed in accordance with Section 1915.8.

1907.8.2.4 Base of structural steel section shall be designed to transfer the total load from the entire composite member to the footing; or, the base may be designed to transfer the load from the steel core only, provided ample concrete section is available for transfer of the portion of the total load carried by the reinforced concrete section to the footing by compression in the concrete and by reinforcement.

1907.9 Connections.

1907.9.1 At connections of principal framing elements (such as beams and columns), enclosure shall be provided for splices of continuing reinforcement and for end anchorage of reinforcement terminating in such connections.

1907.9.2 Enclosure at connections may consist of external concrete or internal closed ties, spirals or stirrups.

1907.10 Lateral Reinforcement for Compression Members.

1907.10.1 Lateral reinforcement for compression members shall conform to the provisions of Sections 1907.10.4 and 1907.10.5 and, where shear or torsion reinforcement is required, shall also conform to provisions of Section 1911.

1907.10.2 Lateral reinforcement requirements for composite compression members shall conform to Section 1910.14. Lateral reinforcement requirements for prestressing tendons shall conform to Section 1918.11.

1907.10.3 Lateral reinforcement requirements of Sections 1907.10, 1910.14 and 1918.11 may be waived where tests and structural analyses show adequate strength and feasibility of construction.

1907.10.4 Spirals. Spiral reinforcement for compression members shall conform to Section 1910.9.3 and to the following:

1907.10.4.1 Spirals shall consist of evenly spaced continuous bar or wire of such size and so assembled as to permit handling and placing without distortion from designed dimensions.

1907.10.4.2 For cast-in-place construction, size of spirals shall not be less than 3/8-inch (9.5 mm) diameter.

1907.10.4.3 Clear spacing between spirals shall not exceed 3 inches (76 mm) or be less than 1 inch (25 mm). See also Section 1903.3.2.

1907.10.4.4 Anchorage of spiral reinforcement shall be provided by one and one-half extra turns of spiral bar or wire at each end of a spiral unit.

1907.10.4.5 Splices in spiral reinforcement shall be lap splices of 48, but not less than 12 inches (305 mm) or welded.

1907.10.4.6 Spirals shall extend from top of footing or slab in any story to level of lowest horizontal reinforcement in members supported above.

1907.10.4.7 Where beams or brackets do not frame into all sides of a column, ties shall extend above termination of spiral to bottom of slab or drop panel.

1907.10.4.8 In columns with capitals, spirals shall extend to a level at which the diameter or width of capital is two times that of the column.

1907.10.4.9 Spirals shall be held firmly in place and true to line.

1907.10.5 Ties. Tie reinforcement for compression members shall conform to the following:

1907.10.5.1 All nonprestressed bars shall be enclosed by lateral ties, at least No. 3 in size for longitudinal bars No. 10 or smaller, and at least No. 4 in size for Nos. 11, 14 and 18 and bundled longitudinal bars. Deformed wire or welded wire fabric of equivalent area may be used.

1907.10.5.2 Vertical spacing of ties shall not exceed 16 longitudinal bar diameters, 48 tie bar or wire diameters, or least dimension of the compression member.

1907.10.5.3 Ties shall be arranged such that every corner and alternate longitudinal bar shall have lateral support provided by the corner of a tie with an included angle of not more than 135 degrees and a bar shall be not farther than 6 inches (152 mm) clear on each side along the tie from such a laterally supported bar. Where longitudinal bars are located around the perimeter of a circle, a complete circular tie may be used.

1907.10.5.4 Ties shall be located vertically not more than one half a tie spacing above the top of footing or slab in any story and shall be placed as provided herein to not more than one half a tie spacing below the lowest horizontal reinforcement in members supported above.

1907.10.5.5 Where beams or brackets frame from four directions into a column, ties may be terminated not more than 3 inches (76 mm) below lowest reinforcement in shallowest of such beams or brackets.

1907.10.5.6 Column lateral ties shall be as specified in Section 1907.1.3, Item 3.

1907.11 Lateral Reinforcement for Flexural Members.

1907.11.1 Compression reinforcement in beams shall be enclosed by ties or stirrups satisfying the size and spacing limitations in Section 1907.10.5 or by welded wire fabric of equivalent area. Such ties or stirrups shall be provided throughout the distance where compression reinforcement is required.

1907.11.2 Lateral reinforcement for flexural framing members subject to stress reversals or to torsion at supports shall consist of closed ties, closed stirrups, or spirals extending around the flexural reinforcement.

1907.11.3 Closed ties or stirrups may be formed in one piece by overlapping standard stirrup or tie end hooks around a longitudinal bar, or formed in one or two pieces lap spliced with a Class B splice (lap of 1.3 ), or anchored in accordance with Section 1912.13.

1907.12 Shrinkage and Temperature Reinforcement.

1907.12.1 Reinforcement for shrinkage and temperature stresses normal to flexural reinforcement shall be provided in structural slabs where the flexural reinforcement extends in one direction only.

1907.12.1.1 Shrinkage and temperature reinforcement shall be provided in accordance with either Section 1907.12.2 or 1907.12.3 below.

1907.12.2 Deformed reinforcement conforming to Section 1903.5.3 used for shrinkage and temperature reinforcement shall be provided in accordance with the following:

1907.12.2.1 Area of shrinkage and temperature reinforcement shall provide at least the following ratios of reinforcement area to gross concrete area, but not less than 0.0014:
1. Slabs where Grade 40 or 50 deformed bars are used
0.0020
2. Slabs where Grade 60 deformed bars or welded wire fabric (smooth or deformed) are used
0.0018
3. Slabs where reinforcement with yield stress exceeding
60,000 psi (413.7 MPa) measured at a yield strain of 0.35 percent is used

For SI:

1907.12.2.2 Shrinkage and temperature reinforcement shall be spaced not farther apart than five times the slab thickness, or 18 inches (457 mm).

1907.12.2.3 At all sections where required, reinforcement for shrinkage and temperature stresses shall develop the specified yield strength in tension in accordance with Section 1912.

1907.12.3 Prestressing tendons conforming to Section 1903.5.5 used for shrinkage and temperature reinforcement shall be provided in accordance with the following:

1907.12.3.1 Tendons shall be proportioned to provide a minimum average compressive stress of 100 psi (0.69 MPa) on gross concrete area using effective prestress, after losses, in accordance with Section 1918.6.

1907.12.3.2 Spacing of prestressed tendons used for shrinkage and temperature reinforcement shall not exceed 6 feet (1829 mm).

1907.12.3.3 When the spacing of prestressed tendons used for shrinkage and temperature reinforcement exceeds 54 inches (1372 mm), additional bonded shrinkage and temperature reinforcement conforming with Section 1907.12.2 shall be provided between the tendons at slab edges extending from the slab edge for a distance equal to the tendon spacing.

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