Heads up: There are no amended sections in this chapter.
This chapter shall apply to reinforcement details, including:

(a) Minimum spacing

(b) Standard hooks, seismic hooks, and crossties

(c) Development of reinforcement

(d) Splices

(e) Bundled reinforcement

(f) Transverse reinforcement

(g) Post-tensioning anchorages and couplers

Provisions of 25.9 shall apply to anchorage zones for post-tensioned tendons.
For parallel nonprestressed reinforcement in a horizontal layer, clear spacing shall be at least the greatest of 1 in., db, and (4/3)dagg.
For parallel nonprestressed reinforcement placed in two or more horizontal layers, reinforcement in the upper layers shall be placed directly above reinforcement in the bottom layer with a clear spacing between layers of at least 1 in.
For longitudinal reinforcement in columns, pedestals, struts, and boundary elements in walls, clear spacing between bars shall be at least the greatest of 1.5 in., 1.5db, and (4/3)dagg.
For pretensioned strands at ends of a member, minimum center-to-center spacing s shall be the greater of the value in Table 25.2.4, and [(4/3)dagg + db].

Table 25.2.4—Minimum center-to-center spacing of pretensioned strands at ends of members

fci', psi Nominal strand diameter, in. Minimum s
< 4000 All 4db
≥ 4000 < 0.5 in. 4db
0.5 in. 1-3/4 in.
0.6 in. 2 in.
For pretensioned wire at ends of a member, minimum center-to-center spacing s shall be the greater of 5db and [(4/3)dagg + db].
Reduced vertical spacing including bundling of prestressed reinforcement shall be permitted in the middle portion of a span.
Standard hooks for the development of deformed bars in tension shall conform to Table 25.3.1.

Table 25.3.1—Standard hook geometry for development of deformed bars in tension

Type of standard hook Bar size Minimum inside bend diameter, in. Straight extension[1] ext, in. Type of standard hook
90-degree hook No. 3 through No. 8 6db 12db
No. 9 through No. 11 8db
No. 14 and No. 18 10db
180-degree hook No. 3 through No. 8 6db Greater of 4db and 2.5 in.
No.9 through No. 11 8db
No.14 and No. 18 10db

[1]A standard hook for deformed bars in tension includes the specific inside bend diameter and straight extension length. It shall be permitted to use a longer straight extension at the end of a hook. A longer extension shall not be considered to increase the anchorage capacity of the hook.

Minimum inside bend diameters for bars used as transverse reinforcement and standard hooks for bars used to anchor stirrups, ties, hoops, and spirals shall conform to Table 25.3.2. Standard hooks shall enclose longitudinal reinforcement.

Table 25.3.2—Minimum inside bend diameters and standard hook geometry for stirrups, ties, and hoops

Type of standard hook Bar size Minimum inside bend diameter, in. Straight extension[1] ext, in. Type of standard hook
90-degree hook No. 3 through No. 5 4db Greater of 6db and 3 in.
No. 6 through No. 8 6db 12db
135-degree hook No. 3 through No. 5 4db Greater of 6db and 3 in.
No. 6 through No. 8 6db
180-degree hook No. 3 through No. 5 4db Greater of 4db and 2.5 in.
No.6 Through No. 8 6db

[1]A standard hook for stirrups, ties, and hoops includes the specific inside bend diameter and straight extension length. It shall be permitted to use a longer straight extension at the end of a hook. A longer extension shall not be considered to increase the anchorage capacity of the hook.

Minimum inside bend diameters for welded wire reinforcement used as stirrups or ties shall not be less than 4db for deformed wire larger than D6 and 2db for all other wires. Bends with inside diameter of less than 8db shall not be less than 4db from nearest welded intersection.
Seismic hooks used to anchor stirrups, ties, hoops, and crossties shall be in accordance with (a) and (b):

(a) Minimum bend of 90 degrees for circular hoops and 135 degrees for all other hoops

(b) Hook shall engage longitudinal reinforcement and the extension shall project into the interior of the stirrup or hoop

Crossties shall be in accordance with (a) through (e):

(a) Crosstie shall be continuous between ends

(b) There shall be a seismic hook at one end

(c) There shall be a standard hook at other end with minimum bend of 90 degrees

(d) Hooks shall engage peripheral longitudinal bars

(e) 90-degree hooks of two successive crossties engaging the same longitudinal bars shall be alternated end for end, unless crossties satisfy 18.6.4.3 or 25.7.1.6.1

Calculated tension or compression in reinforcement at each section of a member shall be developed on each side of that section by embedment length; hook, headed deformed bar, mechanical device, or a combination thereof.
Hooks and heads shall not be used to develop bars in compression.
Development lengths do not require a strength reduction factor ϕ.
The values of used to calculate development length shall not exceed 100 psi.
Development length d for deformed bars and deformed wires in tension shall be the greater of (a) and (b):

(a) Length calculated in accordance with 25.4.2.2 or 25.4.2.3 using the applicable modification factors of 25.4.2.4

(b) 12 in.

For deformed bars or deformed wires, d shall be calculated in accordance with Table 25.4.2.2.

Table 25.4.2.2Development length for deformed bars and deformed wires in tension

Spacing and cover No. 6 and smaller bars and deformed wires No. 7 and larger bars
Clear spacing of bars or wires being developed or lap spliced not less than db, clear cover at least db, and stirrups or ties throughout d not less than the Code minimum
or
Clear spacing of bars or wires being developed or lap spliced at least 2db and clear cover at least db
Other cases
For deformed bars or deformed wires, d shall be calculated by:
(25.4.2.3a)

in which the confinement term (cb + Ktr)/db shall not exceed 2.5, and

(25.4.2.3b)

where n is the number of bars or wires being developed or lap spliced along the plane of splitting. It shall be permitted to use Ktr = 0 as a design simplification even if transverse reinforcement is present.

For the calculation of d, modification factors shall be in accordance with Table 25.4.2.4.

Table 25.4.2.4—Modification factors for development of deformed bars and deformed wires in tension

Modification factor Condition Value of factor
Lightweight λ Lightweight concrete 0.75
Lightweight concrete, where fct is specified In accordance with 19.2.4.3
Normalweight concrete 1.0
Epoxy[1] ψe Epoxy-coated or zinc and epoxy dual-coated reinforcement with clear cover less than 3db or clear spacing less than 6db 1.5
Epoxy-coated or zinc and epoxy dualcoated reinforcement for all other conditions 1.2
Uncoated or zinc-coated (galvanized) reinforcement 1.0
Size ψs No. 7 and larger bars 1.0
No. 6 and smaller bars and deformed wires 0.8
Casting position[1] ψt More than 12 in. of fresh concrete placed below horizontal reinforcement 1.3
Other 1.0

[1]The product ψtψe need not exceed 1.7.

Development length dh for deformed bars in tension terminating in a standard hook shall be the greater of (a) through (c):

(a) with ψe, ψc, ψr, and λ given in 25.4.3.2.

(b) 8db

(c) 6 in.

For the calculation of dh, modification factors shall be in accordance with Table 25.4.3.2. Factors ψc and ψr shall be permitted to be taken as 1.0. At discontinuous ends of members, 25.4.3.3 shall apply.

Table 25.4.3.2—Modification factors for development of hooked bars in tension

Modification factor Condition Value of factor
Lightweight λ Lightweight concrete 0.75
Normalweight concrete 1.0
Epoxy ψe Epoxy-coated or zinc and epoxy dualcoated reinforcement 1.2
Uncoated or zinc-coated (galvanized) reinforcement 1.0
Cover ψc For No. 11 bar and smaller hooks with side cover (normal to plane of hook) ≥ 2-1/2 in. and for 90-degree hook with cover on bar extension beyond hook ≥ 2 in. 0.7
Other 1.0
Confining reinforcement ψr[2] For 90-degree hooks of No. 11 and smaller bars
(1) enclosed along dh within ties or stirrups[1] perpendicular to dh at s ≤ 3db, or
(2) enclosed along the bar extension beyond hook including the bend within ties or stirrups[1] perpendicular to ext at s ≤ 3db
0.8
For 180-degree hooks of No. 11 and smaller bars enclosed along dh within ties or stirrups[1] perpendicular to dh at s ≤ 3db
Other 1.0

[1]The first tie or stirrup shall enclose the bent portion of the hook within 2db of the outside of the bend.

[2]db is the nominal diameter of the hooked bar.

For bars being developed by a standard hook at discontinuous ends of members with both side cover and top (or bottom) cover to hook less than 2-1/2 in., (a) through (c) shall be satisfied:

(a) The hook shall be enclosed along dh within ties or stirrups perpendicular to dh at s ≤ 3db

(b) The first tie or stirrup shall enclose the bent portion of the hook within 2db of the outside of the bend

(c) ψr shall be taken as 1.0 in calculating dh in accordance with 25.4.3.1(a)

where db is the nominal diameter of the hooked bar.

Use of heads to develop deformed bars in tension shall be permitted if conditions (a) through (g) are satisfied:

(a) Bar shall conform to 20.2.1.3

(b) Bar fy shall not exceed 60,000 psi

(c) Bar size shall not exceed No. 11

(d) Net bearing area of head Abrg shall be at least 4Ab

(e) Concrete shall be normalweight

(f) Clear cover for bar shall be at least 2db

(g) Clear spacing between bars shall be at least 4db

Development length dt for headed deformed bars in tension shall be the greatest of (a) through (c):

(a) , with ψe given in 25.4.4.3 and value of fc' shall not exceed 6000 psi

(b) 8db

(c) 6 in.

Modification factor ψe in 25.4.4.2(a) shall be 1.2 for epoxy-coated or zinc and epoxy dual-coated bars and 1.0 for uncoated or zinc-coated (galvanized) bars.
Any mechanical attachment or device capable of developing fy of deformed bars shall be permitted, provided it is approved by the building official in accordance with 1.10. Development of deformed bars shall be permitted to consist of a combination of mechanical anchorage plus additional embedment length of the deformed bars between the critical section and the mechanical attachment or device.
Development length d for welded deformed wire reinforcement in tension measured from the critical section to the end of wire shall be the greater of (a) and (b), where wires in the direction of the development length shall all be deformed D31 or smaller.

(a) Length calculated in accordance with 25.4.6.2

(b) 8 in.

For welded deformed wire reinforcement, d shall be calculated from 25.4.2.2 or 25.4.2.3, times welded deformed wire reinforcement factor ψw from 25.4.6.3 or 25.4.6.4. For epoxy-coated welded deformed wire reinforcement meeting 25.4.6.3, it shall be permitted to use ψe = 1.0 in 25.4.2.2 or 25.4.2.3.
For welded deformed wire reinforcement with at least one cross wire within d that is at least 2 in. from the critical section, ψw shall be the greater of (a) and (b), and need not exceed 1.0:

(a)

(b)

where s is the spacing between the wires to be developed.

For welded deformed wire reinforcement with no cross wires within d or with a single cross wire less than 2 in. from the critical section, ψw shall be taken as 1.0.
Where any plain wires, or deformed wires larger than D31, are present in the welded deformed wire reinforcement in the direction of the development length, the reinforcement shall be developed in accordance with 25.4.7.
Zinc-coated (galvanized) welded deformed wire reinforcement shall be developed in accordance with 25.4.7.
Development length d for welded plain wire reinforcement in tension measured from the critical section to the outermost cross wire shall be the greater of (a) and (b) and shall require a minimum of two cross wires within d.

(a) Length calculated in accordance with 25.4.7.2

(b) 6 in.

d shall be the greater of (a) and (b):

(a) spacing of cross wires + 2 in.

(b) , where s is the spacing between the wires to be developed, and λ is given in Table 25.4.2.4.

Development length d of pretensioned seven-wire strands in tension shall be in accordance with (a) and (b):
  (a) (25.4.8.1)

(b) If bonding of a strand does not extend to end of member, and design includes tension at service loads in the precompressed tension zone, d calculated by Eq. (25.4.8.1) shall be doubled.

Seven-wire strand shall be bonded at least d beyond the critical section except as provided in 25.4.8.3.
Embedment less than d shall be permitted at a section of a member, provided the design strand stress at that section does not exceed values obtained from the bilinear relationship defined by Eq. (25.4.8.1).
Development length dc for deformed bars and deformed wires in compression shall be the greater of (a) and (b)

(a) Length calculated in accordance with 25.4.9.2

(b) 8 in.

dc shall be the greater of (a) and (b), using the modification factors of 25.4.9.3:

(a)

(b) 0.0003fyψrdb

For the calculation of dc, modification factors shall be in accordance with Table 25.4.9.3, except ψr shall be permitted to be taken as 1.0.

Table 25.4.9.3—Modification factors for deformed bars and wires in compression

Modification factor Condition Value of factor
Lightweight λ Lightweight concrete 0.75
Lightweight concrete, if fct is specified In accordance with 19.2.4.3
Normalweight concrete 1.0
Confining reinforcement ψr

Reinforcement enclosed within (1),
(2), (3), or (4):

  1. a spiral
  2. a circular continuously wound tie with db1/4 in. and pitch 4 in.
  3. No. 4 bar or D20 wire ties in accordance with 25.7.2 spaced ≤ 4 in. on center
  4. hoops in accordance with 25.7.4 spaced ≤ 4 in. on center
0.75
Other 1.0
Reduction of development lengths defined in 25.4.2.1(a), 25.4.3.1(a), 25.4.6.1(a), 25.4.7.1(a), and 25.4.9.1(a) shall be permitted by use of the ratio (As,required)/(As,provided), except where prohibited by 25.4.10.2. The modified development lengths shall not be less than the respective minimums specified in 25.4.2.1(b), 25.4.3.1(b), 25.4.3.1(c), 25.4.6.1(b), 25.4.7.1(b), and 25.4.9.1(b).
A reduction of development length in accordance with 25.4.10.1 is not permitted for (a) through (e).

(a) At noncontinuous supports

(b) At locations where anchorage or development for fy is required

(c) Where bars are required to be continuous

(d) For headed and mechanically anchored deformed reinforcement

(e) In seismic-force-resisting systems in structures assigned to Seismic Design Categories D, E, or F

Lap splices shall not be permitted for bars larger than No. 11, except as provided in 25.5.5.3.
For contact lap splices, minimum clear spacing between the contact lap splice and adjacent splices or bars shall be in accordance with the requirements for individual bars in 25.2.1.
For noncontact splices in flexural members, the transverse center-to-center spacing of spliced bars shall not exceed the lesser of one-fifth the required lap splice length and 6 in.
Reduction of development length in accordance with 25.4.10.1 is not permitted in calculating lap splice lengths.
Lap splices of bundled bars shall be in accordance with 25.6.1.7.
Tension lap splice length st for deformed bars and deformed wires in tension shall be in accordance with Table 25.5.2.1, where d shall be in accordance with 25.4.2.1(a).

Table 25.5.2.1—Lap splice lengths of deformed bars and deformed wires in tension

As,provided/As,required[1] over length of splice Maximum percent of As spliced within required lap length Splice type st
≥ 2.0 50 Class A Greater of: 1.0d and 12 in.
100 Class B Greater of: 1.3d and 12 in.
< 2.0 All cases Class B

[1]Ratio of area of reinforcement provided to area of reinforcement required by analysis at splice location.

If bars of different size are lap spliced in tension, st shall be the greater of d of the larger bar and st of the smaller bar.
Tension lap splice length st of welded deformed wire reinforcement in tension with cross wires within the lap splice length shall be the greater of 1.3d and 8 in., where d is calculated in accordance with 25.4.6.1(a), provided (a) and (b) are satisfied:

(a) Overlap between outermost cross wires of each reinforcement sheet shall be at least 2 in.

(b) Wires in the direction of the development length shall all be deformed D31 or smaller

If 25.5.3.1(a) is not satisfied, st shall be calculated in accordance with 25.5.2.
If 25.5.3.1(b) is not satisfied, st shall be calculated in accordance with 25.5.4.
If the welded deformed wire reinforcement is zinc-coated (galvanized), st shall be calculated in accordance with 25.5.4.
Tension lap splice length st of welded plain wire reinforcement in tension between outermost cross wires of each reinforcement sheet shall be at least the greatest of (a) through (c):

(a) s + 2 in.

(b) 1.5d

(c) 6 in.

where s is the spacing of cross wires and d is calculated in accordance with 25.4.7.2(b).

If As,provided/As,required ≥ 2.0 over the length of the splice, st measured between outermost cross wires of each reinforcement sheet shall be permitted to be the greater of (a) and (b).

(a) 1.5d

(b) 2 in.

where d is calculated by 25.4.7.2(b).

Compression lap splice length sc of No. 11 or smaller deformed bars in compression shall be calculated in accordance with (a) or (b):

(a) For fy ≤ 60,000 psi: sc is the greater of 0.0005fydb and 12 in.

(b) For fy > 60,000 psi: sc is the greater of (0.0009fy — 24) db and 12 in.

For fc' < 3000 psi, the length of lap shall be increased by one-third.

Compression lap splices shall not be used for bars larger than No. 11, except as permitted in 25.5.5.3.
Compression lap splices of No. 14 or No. 18 bars to No. 11 or smaller bars shall be permitted and shall be in accordance with 25.5.5.4.
Where bars of different size are lap spliced in compression, sc shall be the greater of dc of larger bar calculated in accordance with 25.4.9.1 and sc of smaller bar calculated in accordance with 25.5.5.1 as appropriate.
For bars required for compression only, transmission of compressive stress by end bearing of square-cut ends held in concentric contact by a suitable device shall be permitted.
End-bearing splices shall be permitted only in members containing closed stirrups, ties, spirals, or hoops.
Bar ends shall terminate in flat surfaces within 1.5 degrees of a right angle to the axis of the bars and shall be fitted within 3 degrees of full bearing after assembly.
A mechanical or welded splice shall develop in tension or compression, as required, at least 1.25fy of the bar.
Welding of reinforcing bars shall conform to 26.6.4.
Mechanical or welded splices need not be staggered except as required by 25.5.7.4.
Splices in tension tie members shall be made with a mechanical or welded splice in accordance with 25.5.7.1. Splices in adjacent bars shall be staggered at least 30 in.
Groups of parallel reinforcing bars bundled in contact to act as a unit shall be limited to four in any one bundle.
Bundled bars shall be enclosed within transverse reinforcement. Bundled bars in compression members shall be enclosed by transverse reinforcement at least No. 4 in size.
Bars larger than a No. 11 shall not be bundled in beams.
Individual bars within a bundle terminated within the span of flexural members shall terminate at different points with at least 40db stagger.
Development length for individual bars within a bundle, in tension or compression, shall be that of the individual bar, increased 20 percent for a three-bar bundle, and 33 percent for a four-bar bundle.
A unit of bundled bars shall be treated as a single bar with an area equivalent to that of the bundle and a centroid coinciding with that of the bundle. The diameter of the equivalent bar shall be used for db in (a) through (e):

(a) Spacing limitations based on db

(b) Cover requirements based on db

(c) Spacing and cover values in 25.4.2.2

(d) Confinement term in 25.4.2.3

(e) ψe factor in 25.4.2.4

Lap splices of bars in a bundle shall be based on the lap splice length required for individual bars within the bundle, increased in accordance with 25.6.1.5. Individual bar splices within a bundle shall not overlap. Entire bundles shall not be lap spliced.
Bundling of post-tensioning ducts shall be permitted if shown that concrete can be satisfactorily placed and if provision is made to prevent the prestressing steel, when tensioned, from breaking through the duct.
Stirrups shall extend as close to the compression and tension surfaces of the member as cover requirements and proximity of other reinforcement permits and shall be anchored at both ends. Where used as shear reinforcement, stirrups shall extend a distance d from extreme compression fiber.
Between anchored ends, each bend in the continuous portion of a single or multiple U-stirrup and each bend in a closed stirrup shall enclose a longitudinal bar or strand.
Anchorage of deformed bar and wire shall be in accordance with (a), (b), or (c):

(a) For No. 5 bar and D31 wire, and smaller, and for No. 6 through No. 8 bars with fyt ≤ 40,000 psi, a standard hook around longitudinal reinforcement

(b) For No. 6 through No. 8 bars with fyt > 40,000 psi, a standard hook around a longitudinal bar plus an embedment between midheight of the member and the outside end of the hook equal to or greater than , with λ as given in Table 25.4.3.2

(c) In joist construction, for No. 4 bar and D20 wire and smaller, a standard hook

Anchorage of each leg of welded plain wire reinforcement forming a single U-stirrup shall be in accordance with (a) or (b):

(a) Two longitudinal wires spaced at a 2 in. spacing along the member at the top of the U

(b) One longitudinal wire located not more than d/4 from the compression face and a second wire closer to the compression face and spaced not less than 2 in. from the first wire. The second wire shall be permitted to be located on the stirrup leg beyond a bend, or on a bend with an inside diameter of bend of at least 8db.

Anchorage of each end of a single leg stirrup of welded wire reinforcement shall be with two longitudinal wires at a minimum spacing of 2 in. in accordance with (a) and (b):

(a) Inner longitudinal wire at least the greater of d/4 or 2 in. from d/2

(b) Outer longitudinal wire at tension face shall not be farther from the face than the portion of primary flexural reinforcement closest to the face

Stirrups used for torsion or integrity reinforcement shall be closed stirrups perpendicular to the axis of the member. Where welded wire reinforcement is used, transverse wires shall be perpendicular to the axis of the member. Such stirrups shall be anchored by (a) or (b):

(a) Ends shall terminate with 135-degree standard hooks around a longitudinal bar

(b) In accordance with 25.7.1.3(a) or (b) or 25.7.1.4, where the concrete surrounding the anchorage is restrained against spalling by a flange or slab or similar member

Stirrups used for torsion or integrity reinforcement shall be permitted to be made up of two pieces of reinforcement: a single U-stirrup anchored according to 25.7.1.6(a) closed by a crosstie where the 90-degree hook of the crosstie shall be restrained against spalling by a flange or slab or similar member.
Except where used for torsion or integrity reinforcement, closed stirrups are permitted to be made using pairs of U-stirrups spliced to form a closed unit where lap lengths are at least 1.3d. In members with a total depth of at least 18 in., such splices with Abfyt ≤ 9000 lb per leg shall be considered adequate if stirrup legs extend the full available depth of member.
Ties shall consist of a closed loop of deformed bar with spacing in accordance with (a) and (b):

(a) Clear spacing of at least (4/3)dagg

(b) Center-to-center spacing shall not exceed the least of 16db of longitudinal bar, 48db of tie bar, and smallest dimension of member

Diameter of tie bar shall be at least (a) or (b):

(a) No. 3 enclosing No. 10 or smaller longitudinal bars

(b) No. 4 enclosing No. 11 or larger longitudinal bars or bundled longitudinal bars

As an alternative to deformed bars, deformed wire or welded wire reinforcement of equivalent area to that required in 25.7.2.1 shall be permitted subject to the requirements of Table 20.2.2.4a.
Rectilinear ties shall be arranged to satisfy (a) and (b):

(a) 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

(b) No unsupported bar shall be farther than 6 in. clear on each side along the tie from a laterally supported bar

Anchorage of rectilinear ties shall be provided by standard hooks that conform to 25.3.2 and engage a longitudinal bar. A tie shall not be made up of interlocking headed deformed bars.
Circular ties shall be permitted where longitudinal bars are located around the perimeter of a circle.
Anchorage of individual circular ties shall be in accordance with (a) through (c):

(a) Ends shall overlap by at least 6 in.

(b) Ends shall terminate with standard hooks in accordance with 25.3.2 that engage a longitudinal bar

(c) Overlaps at ends of adjacent circular ties shall be staggered around the perimeter enclosing the longitudinal bars

Ties to resist torsion shall be perpendicular to the axis of the member anchored by either (a) or (b):

(a) Ends shall terminate with 135-degree standard hooks or seismic hooks around a longitudinal bar

(b) In accordance with 25.7.1.3(a) or (b) or 25.7.1.4, where the concrete surrounding the anchorage is restrained against spalling

Spirals shall consist of evenly spaced continuous bar or wire with clear spacing conforming to (a) and (b):

(a) At least the greater of 1 in. and (4/3)dagg

(b) Not greater than 3 in.

For cast-in-place construction, spiral bar or wire diameter shall be at least 3/8 in.
Volumetric spiral reinforcement ratio ρs shall satisfy Eq. (25.7.3.3).
(25.7.3.3)

where the value of fyt shall not be taken greater than 100,000 psi.

Spirals shall be anchored by 1-1/2 extra turns of spiral bar or wire at each end.
Spirals are permitted to be spliced by (a) or (b):

(a) Mechanical or welded splices in accordance with 25.5.7

(b) Lap splices in accordance with 25.7.3.6 for fyt not exceeding 60,000 psi

Spiral lap splices shall be at least the greater of 12 in. and the lap length in Table 25.7.3.6.

Table 25.7.3.6—Lap length for spiral reinforcement

Reinforcement Coating Ends of lapped spiral bar or wire Lap length in.
Deformed bar Uncoated or zinc-coated (galvanized) Hook not required 48db
Epoxy-coated or zinc and epoxy dual-coated Hook not required 72db
Standard hook of 25.3.2[1] 48db
Deformed wire Uncoated Hook not required 48db
Epoxy-coated Hook not required 72db
Standard hook of 25.3.2[1] 48db
Plain bar Uncoated or zinc-coated (galvanized) Hook not required 72db
Standard hook of 25.3.2[1] 48db
Plain wire Uncoated Hook not required 72db
Standard hook of 25.3.2[1] 48db

[1]Hooks shall be embedded within the core confined by the spiral.

Hoops shall consist of a closed tie or continuously wound tie, which can consist of several reinforcement elements each having seismic hooks at both ends.
The ends of the reinforcement elements in hoops shall be anchored using seismic hooks that conform to 25.3.4 and engage a longitudinal bar. A hoop shall not be made up of interlocking headed deformed bars.
Anchorages and couplers for tendons shall develop at least 95 percent of fpu when tested in an unbonded condition, without exceeding anticipated set.
Anchorages and couplers for bonded tendons shall be located so that 100 percent of fpu shall be developed at critical sections after the post-tensioned reinforcement is bonded in the member.
In unbonded construction subject to repetitive loads, the possibility of fatigue of prestressed reinforcement in anchorages and couplers shall be considered.
Couplers shall be placed at locations approved by the licensed design professional and enclosed in housings long enough to permit necessary movements.
Anchorage regions of post-tensioned tendons shall consist of two zones, (a) and (b):

(a) The local zone shall be assumed to be a rectangular prism (or equivalent rectangular prism for circular or oval anchorages) of concrete immediately surrounding the anchorage device and any confining reinforcement

(b) The general zone includes the local zone and shall be assumed to be the portion of the member through which the concentrated prestressing force is transferred to the concrete and distributed more uniformly across the section

The local zone shall be designed in accordance with 25.9.3.
The general zone shall be designed in accordance with 25.9.4.
Compressive strength of concrete required at time of post-tensioning shall be specified as required by 26.10.
Stressing sequence shall be considered in the design process and specified as required by 26.10.
Factored prestressing force at the anchorage device, Ppu, shall exceed the least of (a) through (c), where 1.2 is the load factor from 5.3.12:

(a) 1.2(0.94fpy)Aps

(b) 1.2(0.80fpu)Aps

(c) Maximum jacking force designated by the supplier of anchorage devices multiplied by 1.2

The design of local zone in post-tensioned anchorages shall meet the requirements of (a), (b), or (c):

(a) Monostrand or single 5/8 in. or smaller diameter bar anchorage devices shall meet the bearing resistance and local zone requirements of ACI 423.7

(b) Basic multistrand anchorage devices shall meet the bearing resistance requirements of AASHTO LRFD Bridge Design Specifications, Article 5.10.9.7.2, except that the load factors shall be in accordance with 5.3.12 and ϕ shall be in accordance with 21.2.1

(c) Special anchorage devices shall satisfy the tests required in AASHTO LRFD Bridge Design Specifications, Article 5.10.9.7.3, and described in AASHTO LRFD Bridge Construction Specifications, Article 10.3.2.3

Where special anchorage devices are used, supplementary skin reinforcement shall be provided in addition to the confining reinforcement specified for the anchorage device.
Supplementary skin reinforcement shall be similar in configuration and at least equivalent in volumetric ratio to any supplementary skin reinforcement used in the qualifying acceptance tests of the anchorage device.
The extent of the general zone is equal to the largest dimension of the cross section. In the case of slabs with anchorages or groups of anchorages spaced along the slab edge, the depth of the general zone shall be taken as the spacing of the tendons.
For anchorage devices located away from the end of a member, the general zone shall include the disturbed regions ahead of and behind the anchorage devices.
Methods (a) through (c) shall be permitted for design of general zones:

(a) Strut-and-tie models in accordance with Chapter 23

(b) Linear stress analysis, including finite element analysis or equivalent

(c) Simplified equations in AASHTO LRFD Bridge Design Specifications, Article 5.10.9.6, except where restricted by 25.9.4.3.2

The design of general zones by other methods shall be permitted, provided that the specific procedures used for design result in prediction of strength in substantial agreement with results of comprehensive tests.

Simplified equations as permitted by 25.9.4.3.1(c) shall not be used for the design of a general zone if any of the situations listed in (a) through (g) occur:

(a) Member cross sections are nonrectangular

(b) Discontinuities in or near the general zone cause deviations in the force flow path

(c) Minimum edge distance is less than 1.5 times the anchorage device lateral dimension in that direction

(d) Multiple anchorage devices are used in other than one closely spaced group

(e) Centroid of the tendons is located outside the kern

(f) Angle of inclination of the tendon in the general zone is less than —5 degrees from the centerline of axis of the member, where the angle is negative if the anchor force points away from the centroid of the section

(g) Angle of inclination of the tendon in the general zone is greater than +20 degrees from the centerline of axis of the member, where the angle is positive if the anchor force points towards the centroid of the section

Three-dimensional effects shall be considered in design and analyzed by (a) or (b):

(a) Three-dimensional analysis procedures

(b) Approximated by considering the summation of effects for two orthogonal planes

Tensile strength of concrete shall be neglected in calculations of reinforcement requirements.
Reinforcement shall be provided in the general zone to resist bursting, spalling, and longitudinal edge tension forces induced by anchorage devices, as applicable. Effects of abrupt changes in section and stressing sequence shall be considered.
For anchorage devices located away from the end of the member, bonded reinforcement shall be provided to transfer at least 0.35Ppu into the concrete section behind the anchor. Such reinforcement shall be placed symmetrically around the anchorage device and shall be fully developed both behind and ahead of the anchorage device.
If tendons are curved in the general zone, bonded reinforcement shall be provided to resist radial and splitting forces, except for monostrand tendons in slabs or where analysis shows reinforcement is not required.
Reinforcement with a nominal tensile strength equal to 2 percent of the factored prestressing force shall be provided in orthogonal directions parallel to the loaded face of the anchorage zone to limit spalling, except for monostrand tendons in slabs or where analysis shows reinforcement is not required.
For monostrand anchorage devices for 1/2 in. or smaller diameter strands in normalweight concrete slabs, reinforcement satisfying (a) and (b) shall be provided in the general zone, unless a detailed analysis in accordance with 25.9.4.3 shows that this reinforcement is not required:

(a) Two horizontal bars at least No. 4 in size shall be provided parallel to the slab edge. They shall be permitted to be in contact with the front face of the anchorage device and shall be within a distance of h/2 ahead of each device. Those bars shall extend at least 6 in. either side of the outer edges of each device.

(b) If the center-to-center spacing of anchorage devices is 12 in. or less, the anchorage devices shall be considered as a group. For each group of six or more anchorage devices, n + 1 hairpin bars or closed stirrups at least No. 3 in size shall be provided, where n is the number of anchorage devices. One hairpin bar or stirrup shall be placed between each anchorage device and one on each side of the group. The hairpin bars or stirrups shall be placed with the legs extending into the slab perpendicular to the edge. The center portion of the hairpin bars or stirrups shall be placed perpendicular to the plane of the slab from 3h/8 to h/2 ahead of the anchorage devices.

Maximum design tensile stress in reinforcement at nominal strength shall not exceed the limits in Table 25.9.4.5.1.

Table 25.9.4.5.1—Maximum design tensile stress in reinforcement

Type of reinforcement Maximum design tensile stress
Nonprestressed reinforcement fy
Bonded, prestressed reinforcement fpy
Unbonded, prestressed reinforcement fse + 10,000
Compressive stress in concrete at nominal strength shall not exceed 0.7λfci', where λ is defined in 19.2.4.
If concrete is confined by spirals or hoops and the effect of confining reinforcement is documented by tests and analysis, it shall be permitted to use an increased value of compressive stress in concrete when calculating the nominal strength of the general zone.
Prestressing reinforcement shall not be stressed until compressive strength of concrete, as indicated by tests of cylinders cured in a manner consistent with curing of the member, is at least 2500 psi for single-strand or bar tendons or at least 4000 psi for multistrand tendons unless 25.9.4.5.5 is satisfied.
Provisions of 25.9.4.5.4 need not be satisfied if (a) or (b) is satisfied:

(a) Oversized anchorage devices are used to compensate for a lower concrete compressive strength

(b) Prestressing reinforcement is stressed to no more than 50 percent of the final prestressing force

Selection of reinforcement size, spacing, cover, and other details for anchorage zones shall make allowances for tolerances on fabrication and placement of reinforcement; for the size of aggregate; and for adequate placement and consolidation of the concrete.
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