Reformatted according to Frosch comment #13 (note this … · 2017-08-05 · 49 6.2.1.2.1 — For ASTM A615, A706, A996, and A955 deformed bars with fy less than 50 60,000 psi, yield

ACI 318-14 Chapter 6 Code, Approved Version, 2012-09-10

1

Reformatted according to Frosch comment #13 (note this change in 1 numbering results in associated modfications to these references 2 in other chapters). 3

6.2 Nonprestressed reinforcing bars and wire 4 6.2.1 Material properties 5 6.2.2 Design properties 6 6.3 Prestressing strands, wires, and bars 7 6.2.1 Material properties 8 6.2.2 Design properties 9 6.4 Structural steel, pipe, and tubing for composite columns 10 6.2.1 Material properties 11 6.2.2 Design properties 12 13 CR063 – Modified to address results LB 12-2 as Approved ACI 318 Main Summer 2012. Highlighted text with underline strikeout denotes substantive changes to ACI 318-11 as approved. Y: 15 C: 12 N: 12 (negatives addressed or withdrawn) A: 2 14

Approved ACI 318 Summer Meeting in Detroit June 15, 2012 15 16 CHAPTER 6 — STEEL REINFORCEMENT PROPERTIES AND 17 DURABILITY 18 19 6.1 — Scope 20 21 6.1.1 — Provisions of this chapter shall apply to steel reinforcement and govern 22

(a) material properties; 23 (b) properties to be used for design; and 24 (c) durability requirements for reinforcement including minimum specified cover 25

requirements. <~> 26 27 6.1.2 — Construction requirements for the placement and protection of steel reinforcement and 28 embedments shall conform to 23.xx.xx and shall be included in contract documents in 29 accordance with 23.yy.yy. <~> 30 31 The references above to be updated when Chapter 23 is completed. This chapter has been updated to be consistent with ACI 318-11. 32 6.2 —Nonprestressed bars and wires 33


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34 6.2.1 — Material properties 35 36 6.2.1.1 — Nonprestressed bars and wires shall be deformed, except plain bars or wires are 37 permitted for use in spirals. <3.5.1> 38 39 6.2.1.2 — Deformed bars shall conform to (a), (b), (c), (d), or (e). 40

(a) ASTM A615 – carbon steel 41 (b) ASTM A706 – low-alloy steel 42 (c) ASTM A996 – axle steel and rail steel. Bars from rail steel shall be Type R. 43 (d) ASTM A955 – stainless steel 44 (e) ASTM A1035 – low-carbon chromium steel 45 <3.5.3.1, 3.5.3.3> 46

47 Consider note in commentary that A1035 is for transverse reinforcement in 21.6.4 or spirals in 10.9.3 of ACI 318-11. This information is also included in Table 6.3.4(a)

48 6.2.1.2.1 — For ASTM A615, A706, A996, and A955 deformed bars with fy less than 49 60,000 psi, yield strength shall be taken as the stress corresponding to a strain of 0.5 50 percent; for fy of at least 60,000 psi, yield strength shall be taken as the stress corresponding 51 to a strain of 0.35 percent. < 3.5.3.2> 52 53

54 6.2.1.3 — Plain bars for spiral reinforcement shall conform to ASTM A615, A706, A955, or 55 A1035. <3.5.4.1> 56 57 6.2.1.4 — Welded deformed bar mats shall conform to ASTM A184. Deformed bars used in bar 58 mats shall conform to ASTM A615 or A706. <3.5.3.4> 59 60 6.2.1.5 — Headed deformed bars shall conform to ASTM A970 including Annex A1 61 Requirements for Class HA Head Dimensions. <3.5.9> 62 63 6.2.1.6 — Deformed wire, plain wire, welded deformed wire reinforcement, and welded plain 64 wire reinforcement shall conform to (a) or (b): 65 (a) A1064 – carbon steel 66 (b) A1022 – stainless steel 67 68

6.2.1.6.1 – For plain or deformed wire satisfying 6.2.1.6 with a specified yield strength greater 69 than 60,000 psi, yield strength shall be taken as the stress corresponding to a strain of 0.35 70 percent. <ACI 318-11 3.5.3.5, 3.5.3.6, 3.5.3.7, 3.5.3.10, 3.5.4.2> 71

72 6.2.1.6.2 – Deformed wire sizes D-4 through D-31 shall be permitted. 73 74 6.2.1.6.3 – Deformed wire sizes larger than D-31 shall be permitted in welded wire 75 reinforcement if treated as plain wire for calculation of development and splice lengths in 76 accordance with 21.4.7 and 21.5.4, respectively. <3.5.3.6, 3.5.3.7, 3.5.3.11> 77


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78 6.2.1.6.4 — Spacing of welded intersections in welded wire reinforcement in direction of 79 calculated stress shall not exceed (a) or (b) except as permitted for welded wire reinforcement 80 used as stirrups in accordance with 21.8.1. <3.5.3.6, 3.5.3.7, 3.5.3.10> 81

(a) 16 in. for welded deformed wire reinforcement, and 82 (b) 12 in. for welded plain wire reinforcement. 83

84 6.2.2 — Design properties 85 86 6.2.2.1 — For nonprestressed bars and wires, the stress below fy shall be taken as Es times steel 87 strain. For strains greater than that corresponding to fy, stress shall be considered independent of 88 strain and equal to fy. <10.2.4.10> 89 90 6.2.2.2 — Modulus of elasticity, Es, for nonprestressed bars and wires shall be permitted to be 91 taken as 29,000,000 psi. <8.5.2> 92 93 6.2.2.3 — Yield strength for nonprestressed bars and wires for use in design calculations shall be 94 based on the grade of reinforcement specified by the licensed design professional and shall not 95 exceed the values given in 6.2.2.4 for the associated applications. <~> 96 97 6.2.2.4 — Types of nonprestressed bars and wires to be specified for particular structural 98 applications shall be in accordance with Table 6.2.2.4(a) for deformed reinforcement and Table 99 6.2.2.4(b) for plain reinforcement. <ACI 318-11 3.5.1; 3.5.3.3; 3.5.4.1; 9.4; 10.9.3; 11.4.2; 100 11.5.3.4; 11.6.6; 19.3.2; 21.1.5.1; 21.1.5.2; 21.1.5.4; and 21.1.5.5> 101 102

Table 6.2.2.4(a) —Nonprestressed deformed bars and wires 103

Usage Application

Maximumvalue of fy or fyt

permitted for design

calculations, psi

Applicable ASTM Specification

DeformedBars

DeformedWires

Welded wire

Welded

bar mats

Flexure, axial force, and

shrinkage and temperature

Special seismic systems

60,000 A615†, A706

Not permitted

Not

permitted

A184§ (a)

Other 80,000

A615, A706, A955, A996

A1064, A1022

A1064, A1022

A184§ (b)

Lateral support of longitudinal bars

or

Concrete confinement

Special seismic systems

100,000

A615, A706, A955, A996, A1035

A1064, A1022

A1064†, A1022†

Not permitted (c)

Spirals 100,000

A615, A706, A955, A996,

A1064, A1022

Not permitted

Not permitted (d)


4

A1035

Other 80,000

A615, A706, A955, A996

A1064, A1022

A1064, A1022

Not permitted (e)

Shear

Spirals 60,000

A615, A706, A955, A996

A1064, A1022

Not permitted

Not permitted (f)

Shear friction 60,000

A615, A706, A955, A996

A1064, A1022

A1064, A1022

Not permitted (g)

Stirrups, ties, hoops

60,000

A615, A706, A955, A996

A1064, A1022

A1064, A1022

(welded plain wire)

Not permitted (h)

80,000 Not permitted

Not permitted

A1064, A1022

(welded deformed

wire)

Not permitted (i)

Torsion Longitudinal

and transverse

60,000

A615, A706, A955, A996

A1064, A1022

A1064, A1022

Not permitted (j)

† ASTM A615 Grades 40 and 60 reinforcement conforming to 6.3.5 shall be permitted.<21.1.5.2> §Welded bar mats shall be permitted to be assembled using A615 or A706 deformed bars. <3.5.3.4> † A1064, A1022 is only permitted where it is wrapped around the element, not where the weld is being called upon to resist shear in response to confinement or lateral buckling action. <~>

104


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Table 6.2.2.4(b) —Nonprestressed plain bars and wires 105

Usage Application

Maximum value of fy or fyt

permitted for design

calculations, psi


Plain Bars Plain Wires

Lateral support of

longitudinal bars

or

Concrete confinement

Spirals in

special seismic systems

100,000

A615, A706, A955, A1035

A1064, A1022 (a)

Spirals

100,000

A615, A706, A955, A1035

A1064, A1022

(b)

Shear Spirals 60,000 A615, A706, A955, A1035 A1064, A1022 (c)

Torsion in nonprestressed

beams Spirals 60,000 A615, A706,

A955, A1035 A1064, A1022 (d)

106 6.2.2.5 — ASTM A615 Grades 40 and 60 deformed reinforcement shall be permitted for 107 longitudinal reinforcement in special seismic systems if the actual yield strength based on mill 108 tests does not exceed fy by more than 18,000 psi and ratio of the actual tensile strength to the 109 actual yield strength is at least 1.25. <21.1.5.2> 110 111 6.3 — Prestressing strands, wires, and bars 112 113 6.3.1 — Material properties 114 115 6.3.1.1 — Prestressing reinforcement shall conform to (a), (b), or (c): <3.5.6.1> 116

(a) ASTM A416 – strand 117 (b) ASTM A421 – wire including Supplementary Requirement S1 “Low-Relaxation Wire 118

and Relaxation Testing” 119 (c) ASTM A722 – high-strength bar 120

121 122 6.3.1.2 — Prestressing sStrands, wires, and bars that do not conform to not specifically listed in 123 ASTM A421, A416, or A722 are permitted provided they conform to minimum requirements of 124 these specifications and are shown by test or analysis not to impair the performance of the 125 member. and do not have properties that make them less satisfactory than those listed in ASTM 126


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A416, A421 or A722. <Strikeout underline shown as approved in CB030 ACI 318 Spring 2012; 127 3.5.6.2> 128 129 6.3.2 — Design properties 130 131 6.3.2.1 — Modulus of elasticity, Ep, for prestressing reinforcement shall be determined from 132 tests or as reported by the manufacturer. <8.5.3> <~> 133 134 NOTE: Consider including information in the commentary on default values for Ep. 135 6.3.2.2 — Tensile strength, fpu, for use in design calculations shall be based on the grade or type 136 of prestressing reinforcement specified by the licensed design professional and shall not exceed 137 the values given in Table 6.3.2.2. <3.5.6.1> <3.5.6.2> <18.1.1> <21.1.5.3> 138 139

Table 6.3.2.2 — Prestressing strands, wires, and bars 140

Type

Maximum value of fpu permitted for design

calculations, psi


Strand (stress-relieved and low-relaxation) 270,000 A416 (a)

Wire (stress-relieved and low-relaxation) 250,000

A421 (b) A421 including Supplementary Requirement S1 “Low-Relaxation

Wire and Relaxation Testing”

(c)

High-strength bar 150,000 A722 (d) 141


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Comment from Bondy to be considered for inclusion in commentary: ASTM A421 specifies tensile strengths of 235,000 to 250,000 psi depending on the diameter and type of the wire. For the most common diameter, perhaps the ONLY diameter ever used in the US (0.25”) ASTM A421 specifies a tensile strength of 240,000 psi. Also consider including in commentary: There are two grades of strand Gr 250 and Gr 270. 142 143 6.3.2.3—Stress in bonded prestressed reinforcement at nominal flexural strength, fps 144 145 6.3.2.3.1 — As an alternative to a more accurate determination of fps based on strain 146 compatibility, values of fps calculated in accordance with Eq. (6.3.2.3.1) shall be permitted for 147 members with bonded prestressed reinforcement if 0.5se puf f≥ . If compression reinforcement is 148 considered for the calculation of fps by Eq. (6.3.2.3.1), 6.3.2.3.1(a) and 6.3.2.3.1(b) shall apply. 149 <18.7.2> 150 151

( )1

1 p pu yps pu p

c p c

f fdf ff d f

γρ ρ ρ

β

⎧ ⎫⎡ ⎤⎪ ⎪′= − + −⎢ ⎥⎨ ⎬′ ′⎢ ⎥⎪ ⎪⎣ ⎦⎩ ⎭ (6.3.2.3.1)

152

where pγ is in accordance with Table 6.3.2.3.1<18.7.2> 153 Table 6.3.2.3.1 Values of pγ for use in Eq. (6.3.2.3.1) 154

py puf / f pγ ≥ 0.80 0.55 ≥ 0.85 0.40 ≥ 0.90 0.28

155 156

6.3.2.3.1(a) — If d′ exceeds 0.15dp, the compression reinforcement shall be neglected in 157 Eq. (6.3.2.3.1). <18.7.2> 158 159 6.3.2.3.1(b) — If compression reinforcement is included in Eq. (6.3.2.3.1) the term 160

( )pu yp

c p c

f fdf d f

ρ ρ ρ⎡ ⎤

′+ −⎢ ⎥′ ′⎢ ⎥⎣ ⎦ shall not be taken less than 0.17. <18.7.2> 161

162 6.3.2.3.2 — For pretensioned strands, the strand design stress at sections of members located 163 within a distance ℓd from the free end of strand shall not exceed that calculated in accordance 164 with 21.4.8.4. <12.9.1.1> 165 166 6.3.2.4—Stress in unbonded prestressed reinforcement at nominal flexural strength, fps 167 168


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6.3.2.4.1 — As an alternative to a more accurate determination of fps based on strain 169 compatibility, values of fps calculated in accordance with Table 6.3.2.4.1 shall be permitted to be 170 used for members prestressed with unbonded tendons if 0.5se puf f≥ . <18.7.2> 171 172

Table 6.3.2.4.1 — Approximate values of fps at nominal flexural 173 strength for unbonded tendons 174

ℓn/h fps

≤ 35

The least of:

cse

p

f 'f ,ρ

+ +10 000100 (a)

(fse + 60,000) (b)

fpy (c)

> 35

The least of:

cse

p

f 'f ,ρ

+ +10 000300 (d)

(fse + 30,000) (e)

fpy (f) 175 6.3.2.5 —Permissible tensile stresses in prestressed reinforcement 176 177 6.3.2.5.1 — The tensile stress in prestressed reinforcement during and immediately after 178 stressing shall not exceed the limits in Table 6.3.1.5.1. <18.5.1> 179 180


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Table 6.3.2.5.1 — Maximum permissible tensile stresses in 181 prestressed reinforcement 182

Stage Location Maximum tensile stress

During stressing At jacking end

Least of:

0.94fpy (a)

0.80fpu (b) Maximum tensile

stress recommended by the manufacturer of

prestressing reinforcement steel

or anchorage devices Maximum jacking

force recommended by the supplier of

anchorage device

(c)

Immediately after force

transfer

At post-

tensioning anchorage devices

and couplers

0.70fpu (d)

183 6.3.2.6 —Prestress losses 184 185 6.3.2.6.1 —Prestress losses shall be considered in calculation of the effective tensile stress in the 186 prestressed reinforcement, fse, and shall include: <18.6.1> 187 188

(a) Prestressed reinforcement seating at transfer; 189 (b) Elastic shortening of concrete; 190 (c) Creep of concrete; 191 (d) Shrinkage of concrete; and 192 (e) Relaxation of prestressed reinforcement; and 193 (f) Friction loss due to intended or unintended curvature in post-tensioning tendons. 194

195 6.3.2.6.2 — Calculated friction loss in post-tensioning tendons shall be based on experimentally 196 determined wobble and curvature friction coefficients. < 18.6.2.2> 197 198 6.3.2.6.3 – Where loss of prestress in a member is anticipated due to connection of the member 199 to adjoining construction, such loss of prestress shall be included in design calculations. 200 <18.6.3> 201 202 6.4 —Structural steel, pipe, and tubing for composite columns 203


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204 6.4.1— Material properties 205 206 6.4.1.1— Structural steel other than steel pipe or tubing used with reinforcing bars in composite 207 columns with concrete encasing a steel core shall conform to (a), (b), (c), (d), or (e). <3.5.7.1> 208 209

(a) ASTM A36 – carbon steel; 210 (b) ASTM A242 – high-strength low-alloy steel; 211 (c) ASTM A572 – high-strength, low-alloy, columbium-vanadium steel; 212 (d) ASTM A588 – high-strength, low-alloy, 50 ksi steel; 213 (e) ASTM A992 – structural shapes. 214

215 6.4.1.2—Steel pipe or tubing used in composite columns to encase a concrete core shall conform 216 to (a), (b) or (c). <3.5.7.2> 217 218

(a) ASTM A53 Grade B – black steel, hot-dipped, zinc-coated; 219 (b) ASTM A500 – cold-formed, welded, seamless; 220 (c) ASTM A501 – hot-formed, welded, seamless. 221

222 6.4.2— Design properties 223 224 6.4.2.1 —For structural steel in composite columns, maximum value of fy used in design 225 calculations shall be in accordance with the appropriate ASTM specifications in 6.4.1. <~> 226 227 6.4.2.2 —For structural steel used in composite columns with a structural steel core, with 228 laterally tied or spirally reinforced concrete around a structural steel core, maximum value of fy 229 used in design calculations shall not exceed 50,000 psi. <10.13.7.1> <10.13.8.1> 230 231 6.5 — Headed shear stud reinforcement 232 233 6.5.1— Headed shear stud reinforcement and stud assemblies shall conform to ASTM A1044. 234 <3.5.5.1> 235 236 Note: The value for fyt was added to fit the flow of information provided in this chapter. Negatives brought up in CR062 were persuasive to move this material back to the commentary. 237 6.6 — Anchors for connections to concrete 238 239 6.6.1 — Material properties and design requirements for anchors used as connections to concrete 240 shall comply with provisions of Chapter 19.<D.1> 241 242 6.7 —Discontinuous deformed steel fiber reinforcement 243 244


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6.7.1 —Discontinuous steel fiber reinforcement for concrete shall be deformed and shall 245 conform to ASTM A820. Fibers shall have a length-to-diameter ratio of not smaller than 50 and 246 not greater than 100. <3.5.8> 247 248 6.7.2 — Discontinuous deformed steel fibers conforming to 22.5.5 shall be permitted only for 249 resisting shear under conditions specified in 13.6.3.1. <3.5.1> 250 251 Note: 6.7.2 as modified above was balloted and approved as CD022 ACI 318 Summer 2012. Note: Suggested commentary for R6.7.2 (318-11 Section R3.5.1) —For other applications where it is desired to account for the strength or ductility provided by fibers, 1.10 provides a procedure for approval. 252 6.8 — Provisions for durability of steel reinforcement 253 254 6.8.1 — Specified concrete cover 255 256 6.8.1.1 —Unless the general building code requires a greater concrete cover for fire protection, 257 the specified concrete cover shall not be less than required in 6.8. <7.7.1> <7.7.8> 258 259 6.8.1.2 — It shall be permitted to consider all concrete floor finishes as part of required cover for 260 nonstructural purposes. <8.14.2> 261 262 263 264 265 266 6.8.1.3 —Specified concrete cover requirements 267 268 6.8.1.3.1 —Nonprestressed cast-in-place concrete members shall have specified concrete cover 269 for reinforcement at least that given in Table 6.8.1.3.1. <7.7.1> 270 271

Note: The second half of ACI 318‐08 8.14.2 “or total thickness for nonstructural considerations” was not included with this section, and should be relocated to a more appropriate location in the code.


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Table 6.8.1.3.1 — Specified concrete cover for cast-in-place nonprestressed concrete members 272

Concrete exposure Member Reinforcement

Specified Cover

in.

Cast against and permanently in contact with ground

All All 3 (a)

Exposed to weather or in contact with ground

All

No. 6 through No. 18 bars 2 (b) No. 5 bar, W31 or D31 wire, and smaller 1-1/2 (c)

Not exposed to weather or in contact with ground

Slabs, joists and walls

No. 14 and No. 18 bars 1-1/2 (d) No. 11 bar and smaller 3/4 (e)

Beams, columns, pedestals and tension ties

Primary reinforcement, stirrups, ties, spirals and hoops

1-1/2 (f)

273 6.8.1.3.2 —Cast-in-place prestressed concrete members shall have specified concrete cover for 274 reinforcement, ducts and end fittings at least that given in Table 6.8.1.3.2. <7.7.2> 275 276

Table 6.8.1.3.2 — Specified concrete cover for cast-in-place prestressed concrete members 277


Specified Cover

in.

Cast against and permanently in contact with ground

All All 3 (a)


Slabs, joists and walls All 1 (b)

All other All 1-1/2 (c)


Slabs, joists and walls All 3/4 (d)

Beams, columns and tension ties

Primary reinforcement 1-1/2 (e) Stirrups, ties, spirals and hoops 1 (f)

278 6.8.1.3.3 —Precast nonprestressed or prestressed concrete members manufactured under plant 279 conditions shall have specified concrete cover for reinforcement, ducts, and end fittings at least 280 that given in Table 6.8.1.3.3. <7.7.3> 281 282


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Table 6.8.1.3.3 — Specified concrete cover for precast nonprestressed or prestressed concrete 283 members manufactured under plant conditions 284


Specified Cover

in.


Walls

No. 14 and No. 18 bars; Tendons larger than 1-1/2 in. diameter 1-1/2 (a)

No. 11 bars and smaller; W31 and D31 wire and smaller; Tendons and strands 1-1/2 in. diameter and smaller

3/4 (b)

All other

No. 14 and No. 18 bars; Tendons larger than 1-1/2 in. diameter 2 (c)

No. 6 through No. 11 bars; Tendons and strands larger than 5/8 in. diameter through 1-1/2 in. diameter

1-1/2 (d)

No. 5 bar, W31 or D31 wire, and smaller; Tendons and strands 5/8 in. diameter and smaller

1-1/4 (e)


Slabs, joists and walls

No. 14 and No. 18 bars; Tendons larger than 1-1/2 in. diameter 1-1/4 (f)

Tendons and strands 1-1/2 in. diameter and smaller 3/4 (g)

No. 11 bar, W31 or D31 wire, and smaller 5/8 (h)

Beams, columns, pedestals and tension ties

Primary reinforcement

Greater of db and 5/8

and need not exceed 1-1/2

(i)

Stirrups, ties, spirals and hoops 3/8 (j) 285 286 6.8.1.3.4 —For bundled bars, specified concrete cover shall not be less than the smaller of (a) 287 and (b), and for concrete cast against and permanently in contact with ground, the specified 288 cover shall be 3 in. <7.7.4> 289

(a) the equivalent diameter of the bundle 290 (b) 2 in. 291

292 6.8.1.3.5— For headed shear stud reinforcement, specified concrete cover for the heads or base 293 rails shall be at least that required for the reinforcement in the member. <7.7.5> 294 295 6.8.1.3.6— For pipes, conduits and fittings, specified concrete cover shall be at least 1-1/2 in. for 296 concrete exposed to weather or in contact with ground; and at least ¾ in. for concrete not 297 exposed to weather or in contact with ground. <6.3.10> 298 299 Remove ACI 318-11 <6.3.10> cover for pipes, conduits and fittings from Chapter 6 as per


14

Seguirant N #152. Pipes, conduits and fittings do not fit the definition of reinforcement. This section is already in Chapter 23. Consider adding information in the commentary about other cover concerns in the code. 300 6.8.1.4 —Specified concrete cover requirements for corrosive environments 301 302 6.8.1.4.1 — In corrosive environments or other severe exposure conditions, the specified 303 concrete cover shall be increased as deemed necessary and specified by the licensed design 304 professional. The applicable requirements for concrete based on exposure categories in 5.3 shall 305 be satisfied, or other protection shall be provided. <ACI 318-11 7.7.6> 306 307 6.8.1.4.2 —For prestressed concrete members classified as Class T or C in 10.5.2 and exposed to 308 corrosive environments or other severe exposure categories such as those defined in 5.3, the 309 specified concrete cover shall be at least 1.5 times the cover for prestressed reinforcement 310 required by 6.8.1.3.2 for cast-in-place prestressed concrete members and 6.8.1.3.3 for precast 311 concrete members. <7.7.6.1> 312 313 6.8.1.4.3 —The increased cover requirement of 6.8.1.4.2 need not be satisfied if the 314 precompressed tensile zone is not in tension under sustained loads. <7.7.6.1> 315 316 6.8.2 — Nonprestressed coated reinforcement 317 318 6.8.2.1 — Nonprestressed coated reinforcement shall conform to Table 6.8.2.1. <3.5.3.8> 319 <3.5.3.9> 320 321

Table 6.8.2.1— Nonprestressed coated reinforcement 322

Type of Coating

Applicable ASTM Specifications

Bar Wire Welded wire

Zinc-Coated (Galvanized) A767 Not

permitted A1060 (a)

Epoxy-Coated A775 or A934 A884 A884 (b)

Zinc and Epoxy Dual-Coated A1055 Not

permittedNot

permitted (c)

323 6.8.2.2 — Deformed bars to be zinc-coated (galvanized), epoxy-coated, or zinc and epoxy dual-324 coated shall conform to 6.2.1.2 (a), (b) or (c). < 3.5.3.8> 325 326 6.8.2.3 —Wire and welded wire reinforcement to be epoxy-coated shall conform to 6.2.1.6(a). 327 <3.5.3.9> 328 329 Note: Consider adding information in the commentary about other corrosion-resistant reinforcement (e.g., stainless steel, etc.) 330 6.8.3 —Corrosion protection for unbonded prestressing reinforcement 331


15

332 6.8.3.1 — Unbonded prestressing reinforcement shall be encased in sheathing, and the space 333 between the strand and the sheathing shall be completely filled with a suitable material 334 formulated to inhibit corrosion. Sheathing shall be watertight and continuous over the entire 335 length to be unbonded. <18.16.1> <18.16.2> 336 337 6.8.3.2 — For applications in corrosive environments, the sheathing shall be connected to all 338 stressing, intermediate, and fixed anchorages in a watertight fashion. <18.16.3> 339 340 6.8.3.3 — Unbonded single-strand tendons shall be protected against corrosion in accordance 341 with ACI 423.7. <18.16.4> 342 343 6.8.4 — Corrosion protection for grouted tendons 344 345 6.8.4.1 — Ducts for grouted tendons shall be mortar grout-tight and nonreactive with concrete, 346 prestressing reinforcement, grout, and corrosion inhibitor. <18.17.1> 347 348 6.8.4.2 — Ducts shall be maintained free of ponded water if members to be grouted are exposed 349 to temperatures below freezing prior to grouting. <18.17.4> 350 351 6.8.4.3 — Ducts for grouted single-wire, single-strand, or single-bar tendons shall have an inside 352 diameter at least 1/4 in. larger than the diameter of the prestressing reinforcement. <18.17.2> 353 354 6.8.4.4 — Ducts for grouted multiple wire, multiple strand, or multiple bar tendons shall have an 355 inside cross-sectional area at least two times the cross-sectional area of the prestressing 356 reinforcement. <18.17.3> 357 358 6.8.5 — Corrosion protection for post-tensioning anchorages, couplers, and end fittings. 359 360 6.8.5.1 — The licensed design professional shall detail Anchorages, couplers, and end fittings 361 shall be protected to provide long-term resistance to corrosion to resist long-term corrosion. 362 <18.21.4> 363 364 6.8.6 — Corrosion protection for external post-tensioning anchorages, couplers, and end 365 fittings. 366 367 6.8.6.1— External tendons and tendon anchorage regions shall be protected against corrosion. 368 <18.22.4> 369 370 371

318-14 Chapter 6 Commentary, Approved 2013-03-19

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Chapter 6 Commentary was approved at ACI 318 Main meeting in San Antonio, Tuesday, January 15th. It is to be posted for 30-day review. Ballot History: Chapter 6 Commentary was balloted in LB 12-8 as CR064. The result was Y/C/N/A: 17/13/8/3 N: Becker, Cleland, Fiorato, Frosch, Parra, Rabbat, Seguirant, Wyllie A: Barth, Ghosh, Hwang The negative ballots were resolved at the ACI 318 Main meeting in Toronto. The final document needed approval by ACI 318Main, but overall vote was not completed at the main meeting, so the commentary was sent out for approval in LB12-10. Note, to resolve Fiorato’s negative, he requested that “total thickness” of floor in existing 8.14.2 is addressed in appropriate chapter (e.g., as it relates to serviceability). See note associated with 6.8.1.2. This note is provided to ensure that the text is picked up by the appropriate chapter. Chapter 6 Commentary was reviewed in LB 12-10 as CR065. The result was Y/C/N/A: 20/9/7/2 N: Dolan, Fiorato, Frosch, Holland, Moehle, Seguirant, Wyllie A: Ghosh, Wood The negative ballots and comments were resolved at the ACI 318 Main meeting in San Antonio. The document is to be posted for 30-day review. The yellow highlighted changes shown below are those made to address the negatives and comments associated with LB12-10. 1 2 3 CHAPTER 6 — STEEL REINFORCEMENT PROPERTIES AND DURABILITY 4 Commentary 5 6 R6.1.1 — Materials permitted for use as reinforcement are specified. Other metal elements, such as 7 inserts, anchor bolts, or plain bars for dowels at isolation or contraction joints, are not normally 8 considered to be [2] reinforcement under the provisions of this Code. Fiber-reinforced polymer (FRP) 9 reinforcement is not addressed in this Code. ACI Committee 440 has developed guidelines for the use of 10 FRP reinforcement.3.2, 3.3 <Part of R3.5.1> <R3.5.1> 11 12 R6.2 — Nonprestressed bars and wires 13 14 R6.2.1 — Material properties 15 16 R6.2.1.2 — Low-alloy steel deformed bars conforming to ASTM A706 are intended for applications 17 where controlled tensile properties, restrictions on chemical composition to enhance weldability, or both, 18 are required. 19 20 Rail-steel deformed bars used with this Code are required to conform to ASTM A996 including the 21 provisions for Type R bars. Type R bars are required to meet more restrictive provisions for bend tests 22 than other types of rail steel. 23 24


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Stainless steel deformed bars are used in applications where high corrosion resistance or controlled 25 magnetic permeability are required. The physical and mechanical property requirements for stainless steel 26 bars under ASTM A955 are the same as those for carbon-steel bars under ASTM A615. <R3.5.3.1> 27 28 Low-carbon chromium steel is a high-strength material that is permitted for use as transverse 29 reinforcement for confinement in special earthquake-resistant structural systems and spirals in columns. 30 See Tables 6.2.2.4(a) and (b). ASTM A1035 provides requirements [3] for bars of two minimum yield 31 strength levels, 100,000 psi, and 120,000 psi designated as Grade 100 and Grade 120, respectively, but 32 only Grade 100 is permitted by a maximum fyt of 100,000 psi is permitted for design calculations in this 33 Code. [4,5,6] 34 35 R6.2.1.2.1 — The ASTM specifications require that yield strength be determined by the offset method 36 (0.2 percent offset) and also include, for bars with fy of 60,000 psi or more greater [7], the additional 37 requirement that the stress corresponding to a tensile strain of 0.35 percent be at least fy. The 0.35 percent 38 strain limit is necessary to ensure that the assumption of an elasto-plastic stress-strain curve in 6.2.2.1 will 39 not lead to unconservative [8] values of the member strength. Therefore, the Code defines yield strength 40 in terms of the stress corresponding to a strain of 0.5 percent for fy less than 60,000 psi and the stress 41 corresponding to a strain of 0.35 percent for fy of 60,000 psi or more greater [7]. <R3.5.3.2> 42 43 Note to staff: In approved version of Code Chapter 6, Line 89, change 10.2.4.10 to 10.2.4. 44 R6.2.1.3 — Plain bars are permitted only for spiral reinforcement either [10] used as transverse 45 reinforcement for compression members columns [12], transverse reinforcement for torsion, or and [11] 46 confining reinforcement for splices. <R3.5.4> 47 48 R6.2.1.5 — The limitation to Class HA head dimensions from Annex A1 of ASTM A970 is due to a lack 49 of test data for headed deformed bars that do not meet Class HA dimensional requirements. Heads not 50 conforming to Class HA limits on bar deformation obstructions and bearing face features could cause 51 unintended splitting forces in the concrete that may not be characteristic of the heads used in the tests that 52 were the basis for 21.4.4. For heads conforming to Class HA dimensional requirements, the net bearing 53 area of the head can be assumed to be equal to the gross area of the head minus the area of the bar. This 54 assumption may not be valid for heads not conforming to Class HA dimensional requirements. <R3.5.9> 55 56 R6.2.1.6 — Plain wire is permitted only for spiral reinforcement and in welded plain [13]wire 57 reinforcement, which is considered deformed. Stainless steel wire and stainless steel welded wire 58 reinforcement are used in applications where high corrosion resistance or controlled magnetic 59 permeability is required. The physical and mechanical property requirements for deformed stainless steel 60 wire and deformed and plain welded wire reinforcement under ASTM A1022 are the same as those for 61 deformed wire, deformed welded wire reinforcement, and plain welded wire reinforcement under ASTM 62 A1064. <R3.5.3.10> 63 64 R6.2.1.6.1 — Welded plain and deformed wire reinforcement is made of wire conforming to ASTM 65 A1064, which specifies a minimum yield strength of 70,000 psi. The Code has assigned a yield strength 66 value of 60,000 psi, but makes provision for the use of higher yield strengths provided the stress 67 corresponds to a strain of 0.35 percent. See Tables 6.2.2.4(a) and (b). <R3.5.3.6, R3.5.3.7> 68 69 R6.2.1.6.2 — An upper limit is placed on the size of deformed wire because tests show that D-45 wire 70 will achieve only approximately 60 percent of the bond strength in tension given by Eq. (21.4.2.3.a).3.5 71 <R3.5.3.5> 72 73


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R6.2.2 — Design properties 74 75 R6.2.2.1 — For deformed reinforcement, it is reasonably accurate to assume that the stress in 76 reinforcement is proportional to strain below the specified yield strength fy. The increase in strength due 77 to the effect of strain hardening of the reinforcement is neglected for strength calculations. In strength 78 calculations, the force developed in tension or compression reinforcement is calculated as: 79 if εs < εy (yield strain) 80

81 if εs ≥ εy 82

83 where εs is the value from the strain diagram at the location of the reinforcement. <R10.2.4> 84 85 Note substantial change proposed to be made to table in Chapter 6: Change the heading in Table 6.2.2.4(a) to “Nonprestressed deformed reinforcement bars and wires” Because it includes welded wire reinforcement, which is not clear from the current heading Change the heading in Table 6.2.2.4(b) to “Nonprestressed plain spiral reinforcement bars and wires” Because it makes it consistent with proposed change to title of Table 6.2.2.4(a) and also makes clear it is only to be used for spiral reinforcement. 86 R6.2.2.4 —Tables 6.2.2.4(a) and (b) limit the maximum values of yield strength to be used in design 87 calculations for nonprestressed deformed reinforcement and nonprestressed plain spiral reinforcement, 88 respectively. [Added this sentence to provide better flow.] 89 90 In Table 6.2.2.4(a), for deformed reinforcement in special moment frames and special structural walls, the 91 use of longitudinal reinforcement with strength substantially higher than that assumed in design will lead 92 to higher shear and bond stresses at the time of development of yield moments. These conditions may 93 lead to brittle failures in shear or bond and should be avoided even if such failures may occur at higher 94 loads than those anticipated in design. Therefore, a ceiling limit [20] is placed on the actual yield strength 95 of the steel [see 6.2.2.5]. ASTM A706 for low-alloy steel reinforcing bars now includes both Grade 60 96 and Grade 80; however, only Grade 60 is generally [22] permitted because of insufficient data to confirm 97 applicability of existing code provisions for structures using the higher grade. Section 20.2.1.7 permits 98 alternative material such as ASTM A706 Grade 80 if results of tests and analytical studies are presented 99 in support of its use. <Part of R21.1.5> [23] For flexural members beams [24] the deflection provisions 100 of 10.2 and the limitations on distribution of flexural reinforcement of 10.3 become increasingly critical 101 as fy increases. <R9.4> [reordered this to be more consistent with Table 6.2.2.4(a).] 102 103 Limits on tThe maximum values value of yield strength for calculation purposes is limited to 100,000 psi 104 to be used for both nonprestressed deformed reinforcement and plain spiral reinforcement in Tables 105 6.2.2.4(a) and (b), respectively, when used for lateral support of longitudinal [30] bars or for concrete 106 confinement. spirals and spirals in special seismic earthquake-resistant structural [29] systems are allowed 107 to be designed with yield strengths of 100,000 psi [25]. The research10.27-10.29 used to enable that supports 108 [32] this limit for confinement is given in References 10.27-10.29. <R10.9.3> For reinforcement in 109 special moment frames and special structural walls, the research that indicated that higher yield strengths 110 can be used effectively as for [34] confinement reinforcement is given in References 21.9-21.11. < From 111 R21.1.5 below.> 112 113 Limiting the values of fy and fyt used in design of for [36] deformed and plain spiral shear reinforcement 114 to 60,000 psi and welded wire reinforcement to 80,000 psi for welded wire reinforcement (see Table 115 6.2.2.4(a)) and plain spiral shear reinforcement to 60,000 psi (see Table 6.2.2.4(b)) provides a control on 116

s s s s sA f A E ε=

s s s yA f A f=


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diagonal inclined [38] crack width. The higher yield strength for welded deformed wire reinforcement is 117 based on References 11.18-11.20. The research that has indicated that the performance of higher-strength 118 welded deformed wire reinforcement as shear reinforcement has been satisfactory is given in References 119 11.18-11.20. [35] In particular, full-scale beam tests described in Reference 11.19 indicated that the 120 widths of inclined shear cracks at service load levels were less for beams reinforced with smaller-121 diameter welded deformed wire reinforcement cages designed on the basis of a yield strength of 75,000 122 psi than beams reinforced with deformed Grade 60 stirrups. <R11.4.2> 123 124 Limiting the values of fy and fyt used in design of deformed and plain spiral torsion reinforcement (see 125 Tables 6.2.2.4(a) and (b)) [40] to 60,000 psi provides a control on diagonal crack width. <R11.5.3.4> 126 127 Note to staff: Fix reference in Chapter 6 Table 6.2.2.4(a) footnote to reference 6.3.5 6.2.2.5 [41] 128 R6.2.2.5 — The requirement for the tensile strength to be greater than the yield strength of the 129 reinforcement by a factor of 1.25 is based on the assumption that the capability of a structural member to 130 develop inelastic rotation capacity is a function of the length of the yield region along the axis of the 131 member. In interpreting experimental results, the length of the yield region has been related to the relative 132 magnitudes of nominal probable and yield moments.21.8 According to this interpretation, the greater the 133 ratio of nominal probable [42] to yield moment, the longer the yield region. Members with reinforcement 134 not satisfying this condition can also develop inelastic rotation, but their behavior is sufficiently different 135 to exclude them from direct consideration on the basis of rules derived from experience with members 136 reinforced with strain-hardening steel. <Part of R21.1.5> 137 138 R6.3 — Prestressing strands, wires, and bars 139 140 R6.3.1 — Material properties 141 142 Fix Code side 6.3.1.1

Reason: Missing reference to ASTM A 421 wire excluding the low-relaxation wire supplement. See commentary and Table 6.3.2.2 which has a separate line for ASTM 421 and ASTM 421 including supplement.

6.3.1.1 — Prestressing reinforcement shall conform to (a), (b), or (c), or (d): <3.5.6.1> (a) ASTM A416 – strand (b) ASTM A421 - wire (b) (c) ASTM A421 – low-relaxation wire including Supplementary Requirement S1 “Low-Relaxation Wire and Relaxation Testing” (c) (d) ASTM A722 – high-strength bar <3.5.6.1> 143 R6.3.1.1 — Because low-relaxation prestressing steel reinforcement [45] is addressed in a supplementary 144 requirement to ASTM A421, which applies only when low-relaxation material is specified, the 145 appropriate ASTM reference is listed as a separate entity. <R3.5.6.1> 146 147 R6.3.2 — Design properties 148 149 R6.3.2.1 — Default values of Ep between 28,500,000 and 29,000,000 psi are commonly used for design 150 purposes. More precise accurate [46] values based on tests or manufacturer’s reports may be needed for 151 elongation checks during stressing. 152 153 Reason: ACI 318-11 21.1.5.3 limits prestressing steel resisting earthquake-induced flexural and axial


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loads in frame members and in precast structural walls to ASTM A416 or A722. This is not clear from 6.3.2.2 so it should be clarified. Proposed changes: 6.3.2.2 — Tensile strength, fpu, for use in design calculations shall be based on the grade or type of prestressing reinforcement specified by the licensed design professional and shall not exceed the values given in Table 6.3.2.2. Prestressing reinforcement in members resisting earthquake-induced moment, axial force, or combinations a combination of both [49] shall conform to ASTM A416 or A722. <3.5.6.1> <3.5.6.2> <18.1.1> <21.1.5.3> 154 R6.3.2.2 — ASTM 416 specifies two grades of strand tensile strength, 250,000 and 270,000 psi ksi [52]. 155 <Proposed commentary from Bondy.> 156 157 ASTM A421 specifies tensile strengths of 235,000, 240,000 and 250,000 psi depending on the diameter 158 and type of wire. For the most common diameter, 0.25in., ASTM A421 specifies a tensile strength of 159 240,000 psi. <Proposed commentary from Bondy.> 160 161 R6.3.2.3—Stress in bonded prestressed reinforcement at nominal flexural strength, fps 162 163 R6.3.2.3.1 — Use of [53] Equation (6.3.2.3.1) may underestimate the strength of beams with high 164 percentages of reinforcement and, for more accurate evaluations of their strength, the strain compatibility 165 and equilibrium method should be used. Use of Eq. (6.3.2.3.1) is appropriate when all of the prestressed 166 reinforcement is in the tension zone. When part of the prestressed reinforcement is in the compression 167 zone, a strain compatibility and equilibrium method should be used. 168 169 The γp term in Eq. (6.3.2.3.1) and Table 6.3.2.3.1 reflects the influence of different types of prestressing 170 reinforcement on the value of fps. Table R6.3.2.3.1 associates the shows prestressed reinforcement type 171 withand the associated ratio of [54] fpy/fpu.<Beginning of R18.7.2> 172

Table R6.3.2.3.1 Ratio of fpy/fpu associated with Reinforcement Type 173 Prestressed Reinforcement Type fpy/fpu

High-strength prestressing bars

ASTM A722 Type I (Plain) [184] ≥ 0.85

ASTM A722 Type II (Deformed) [184] ≥ 0.80

Stress-relieved strand and wire

ASTM A416 ASTM A421

≥ 0.85

Low-relaxation strand and wire

ASTM A416 ASTM A421

≥ 0.90

174 The ρ’ term in Eq. (6.3.2.3.1) reflects the increased value of fps obtained when compression reinforcement 175 is provided in a beam with a large reinforcement index. <R18.7.2> The compression reinforcement may 176 be conservatively neglected when using Eq. (6.3.2.3.1) by taking ρ’ as zero. If the term [ρp (fpu/fc′) + 177 (d/dp) (fy/ fc′) (ρ – ρ′)] in Eq. (6.3.2.3.1) is small, the neutral axis depth is small, the compression 178 reinforcement does not develop its yield strength, and Eq. (6.3.2.3.1) becomes unconservative. This is the 179 reason why the term [ρp (fpu/fc′) + (d/dp) (fy/ fc′) (ρ – ρ′)] may not be taken less than 0.17 if compression 180 reinforcement is taken into account when computing fps. By taking ρ’ as zero, then the term [ρp (fpu/fc′) + 181


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(d/dp) (fy/ fc′) (ρ)] may be less than 0.17 and an increased and correct value of fps is obtained. <R18.7.2> 182 [58] 183 184 R6.3.2.3.1(a) — When d′ is large, the strain in compression reinforcement can be considerably less than 185 its yield strain. In such a case, the compression reinforcement does not influence fps as favorably as 186 implied by Eq. (6.3.2.3.1). For this reason, if d’exceeds 0.15dp, the applicability of Eq. (6.3.2.3.1) is 187 limited to beams in which d’ is less than or equal to 0.15dp applicable only if the compression 188 reinforcement is neglected [62]. <Portion of R18.7.2> 189 190 R6.3.2.3.1(b) — The ρ’ term in Eq. (6.3.2.3.1) reflects the increased value of fps obtained when 191 compression reinforcement is provided in a beam with a large reinforcement index. <R18.7.2> If When 192 the term [ρp (fpu/fc′) + (d/dp) (fy/ fc′) (ρ – ρ′)] in Eq. (6.3.2.3.1) is small, the neutral axis depth is small, the 193 compressive reinforcement does not develop its yield strength, and Eq. (6.3.2.3.1) becomes 194 unconservative. For this reason, the term [ρp (fpu/fc′) + (d/dp) (fy/ fc′) (ρ – ρ′)] in Eq. (6.3.2.3.1) may not be 195 taken less than 0.17 if compression reinforcement is taken into account when calculating fps. <Portion of 196 R18.7.2> The compression reinforcement may be conservatively neglected when using Eq. (6.3.2.3.1) by 197 taking ρ’ as zero, in which case the term [ρp (fpu/fc′) + (d/dp) (fy/ fc′) (ρ)] may be less than 0.17 and an 198 increased and correct acceptable value of fps is obtained. <R18.7.2> [58] 199 200 Fix references to Code side 6.3.2.3.2

Reason: Correct reference.

6.3.2.3.2 — For pretensioned strands, the strand design stress at sections of members located within a distance ℓd from the free end of strand shall not exceed that calculated in accordance with 21.4.8.4 21.4.8.3. <12.9.1.1> 201 R6.3.2.4 — Stress in unbonded prestressed reinforcement at nominal flexural strength, fps 202 203 R6.3.2.4.1 —The term [fse + 10,000 + fc′/(300 ρp)] reflects results of tests on members with unbonded 204 tendons and span-to-depth ratios greater than 35 (one-way slabs, flat plates, and flat slabs).18.11 These tests 205 also indicate that the term [fse + 10,000 + fc′/(100 ρp)], formerly used for all span-depth ratios, 206 overestimates the amount of stress increase in such members. Although these same tests indicate that the 207 moment strength of those shallow members designed using [fse + 10,000 + fc′/(100 ρp)] meets the factored 208 load strength requirements, this reflects the effect of the Code requirements for minimum bonded 209 reinforcement, as well as the limitation on concrete tensile stress that often controls the amount of 210 prestressing force provided. <Portion of R18.7.2> 211 <R18.7.2> 212 213 R6.3.2.5 — Permissible tensile stresses in prestressed reinforcement 214 215

216 Fix references to Code side 6.3.2.5.1

Reason: Correct reference.

6.3.2.5.1 — The tensile stress in prestressed reinforcement during and immediately after stressing shall not exceed the limits in Table 6.3.1.5.16.3.2.5.1. <18.5.1>

217 218 R6.3.2.5.1 — Because of the high yield strength of low-relaxation wire and strand strand and wire [67] 219 meeting the requirements of ASTM A416 and A421 including Supplementary Requirement S1 220


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“Low-Relaxation Wire and Relaxation Testing” [68], it is appropriate to specify permissible stresses 221 in terms of specified minimum ASTM yield strength along with the specified minimum ASTM tensile 222 strength. 223 224 Because of the higher allowable initial prestressing steel stresses permitted since the 1983 Code, final 225 stresses can be greater. For structures subject to corrosive conditions or repeated loadings, limiting the 226 final stress should be considered consideration should be given to limiting the final stress [70]. <R18.5.1> 227 228 R6.3.2.6 —Prestress losses 229 230 R6.3.2.6.1 — For an explanation of how to calculate prestress losses, see References 18.6 through 18.9. 231 Reasonably accurate estimates of prestress losses can be calculated in accordance with the 232 recommendations in Reference 18.9, which include consideration of initial stress level (0.7fpu or higher), 233 type of steel (stress-relieved or low-relaxation wire, strand, or bar), exposure conditions, and type of 234 construction (pretensioned, bonded post-tensioned, or unbonded post-tensioned). 235 236 Actual losses, greater or smaller than the computed values, have little effect on the design strength of the 237 member, but affect service load behavior (deflections, camber, cracking load) and connections. At service 238 loads, overestimation of prestress losses can be almost as detrimental as underestimation, because the 239 former can result in excessive camber and horizontal movement. <R18.6.1> 240 241 R6.3.2.6.2 — Estimation of friction losses in post-tensioned tendons is addressed in Reference 18.10. 242 Values of the wobble and curvature friction coefficients to be used for the particular types of prestressing 243 reinforcement and particular types of ducts should be obtained from the manufacturers of the tendons. An 244 unrealistically low estimate of the friction loss can lead to improper camber, or potential deflection, of the 245 member and inadequate prestress. Overestimation of the friction may result in extra prestressing force. 246 This could lead to excessive camber and excessive shortening of a member. If the friction factors are 247 determined to be less than those assumed in the design, the tendon stressing should be adjusted to provide 248 only that prestressing force in the critical portions of the structure required by the design. 249 250 When safety or serviceability of the structure may be involved, the acceptable range of prestressing 251 reinforcement jacking forces or other limiting requirements should either be given or approved by the 252 licensed design professional in conformance with the permissible stresses of 6.3.2.5 and 10.5. <R18.6.2> 253 254 R6.4 — Structural steel, pipe, and tubing for composite columns 255 256 R6.4.1 — Material properties 257 258 R6.4.2 — Design properties 259 260 R6.4.2.2 — The design yield strength of the steel core should be limited to that which would not generate 261 spalling of the concrete. It has been assumed that axially compressed concrete will not spall at strains less 262 than 0.0018. The yield strength of 0.0018 × 29,000,000, or 52,000 psi, represents an upper limit of the 263 useful maximum steel stress. <1st paragraph of R10.13.8> 264 265 R6.5 — Headed shear stud reinforcement 266 267 R6.5.1 — The configuration of the studs for headed shear stud reinforcement differs from the 268 configuration of the headed-type shear studs prescribed in Section 7 of AWS D1.1 and referenced for use 269 in Chapter 19 of this Code (Fig. R6.5.1). Ratios of the head to shank cross-sectional areas of the AWS 270 D1.1 studs range from about 2.5 to 4. In contrast, ASTM A1044 requires the area of the head of headed 271


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shear reinforcement studs to be at least 10 times the area of the shank. Thus, the AWS D1.1 headed studs 272 are not suitable for use as headed shear stud reinforcement. The base rail, where provided, anchors one 273 end of the studs; ASTM A1044 specifies material width and thickness of the base rail that are sufficient to 274 provide the required anchorage without yielding for stud shank diameters of 0.375, 0.500, 0.625, and 275 0.750 in. In ASTM A1044, the minimum specified yield strength of headed shear studs is 51,000 psi. 276 <The value for fyt was added to fit the flow of information provided in this chapter. Negatives brought up 277 in CR062 were persuasive to move this material back to the commentary.> 278 279 280

281 Fig. R6.5.1 — Configurations of stud heads Need to change figure 282 <R3.5.5> 283 284 R6.7 — Discontinuous deformed steel fiber reinforcement 285 286 R6.7.1 — Deformations in steel fibers enhance mechanical anchorage with the concrete. The lower and 287 upper limits for the fiber length-to-diameter ratio are based on available test data.3.6 Because data are not 288 available on the potential for corrosion problems due to galvanic action, the use of deformed steel fibers 289 in members reinforced with stainless-steel bars or galvanized steel bars is not recommended. <R3.5.8> 290 291 NOTE: Code Section 6.7.2 was modified by ballot and approved as CD022 at ACI 318 Summer 2012 meeting. Suggested commentary 6.7.2 — Discontinuous deformed steel fibers conforming to 22.5.5 22.3.5 shall be permitted for resisting shear under conditions specified in 13.6.3.1. <3.5.1> 292 R6.7.2 —For other applications where it is desired to account for the strength or ductility provided by 293 fibers, 1.10 provides a procedure for approval. For other applications where it is desired to use 294 discontinuous deformed steel fibers, Section 1.10 provides a procedure for approval. [75,76] 295 296 R6.8 — Provisions for durability of steel reinforcement 297 298 R6.8.1 — Specified concrete cover 299 This section addresses concrete cover over reinforcement and does not include requirements for concrete 300 cover over embedments such as pipes, conduits and fittings, which are addressed in 23.6. <ACI 318-11 301 6.3.10 cover for pipes, conduits and fittings was eliminated from ACI 318-14 Chapter 6 based on a 302 negative by Seguirant. He suggested adding information in the commentary of Chapter 6 about other 303 cover concerns in the Code.> 304 305 R6.8.1.1 — Concrete cover as protection of reinforcement against weather and other effects is measured 306 from the concrete surface to the outermost surface of the reinforcement to which the cover requirement 307 applies. Where concrete cover is prescribed for a class of structural members, it is measured to the outer 308 edge of stirrups, ties, or spirals if transverse reinforcement encloses main bars; to the outermost layer of 309

STAFF – The head diameter is 2x the shank diameter. Fix figure so it is in appropriate scale.


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bars if more than one layer is used without stirrups or ties; to the metal end fitting or duct on of post-310 tensioneding prestressing steeltendons [79]; or to the outermost part of the head on headed bars. 311 312 The condition “exposed to weather or in contact with ground” refers to direct exposure to moisture 313 changes and not just to temperature changes. Slab or [80] soffits are not usually considered directly 314 exposed unless subject to alternate wetting and drying, including that due to condensation conditions or 315 direct leakage from exposed top surface, run off, or similar effects. 316 317 Alternative methods of protecting the reinforcement from weather may be provided if they are equivalent 318 to the additional concrete cover required by the Code. When approved by the building official under the 319 provisions of 1.10, reinforcement with alternative protection from the weather may not have concrete 320 cover not less than the cover required for reinforcement not exposed to weather. [81] 321 322 Development length provisions given in Chapter 21 are a function of bar cover over the reinforcement. In 323 some cases, order to meet needs requirements for development length, it may be necessary to use larger 324 than minimum cover greater than the minimums specified in 6.8.1. [82] <R7.7> 325 326 Note: 6.8.1.2 — It shall be permitted to consider concrete floor finishes as part of required cover for nonstructural purposes. <8.14; 8.14.2> <The second half of ACI 318-08 8.14.2 “or total thickness for nonstructural considerations” was not included with this section, and should be relocated to a more appropriate location in the code.> 327 R6.8.1.2 —Concrete floor finishes may be considered for nonstructural purposes such as cover for 328 reinforcement and fire protection. Provisions should be made, however, to ensure that the concrete finish 329 will not spall off, thus resulting in decreased cover. Furthermore, considerations for development of 330 reinforcement requires require [86] minimum monolithic concrete cover in accordance with 21.4. 331 <R8.14> 332 333 R6.8.1.3 — Specified concrete cover requirements 334 335 R6.8.1.3.3 — The lesser cover thicknesses for precast construction reflect the greater control for 336 proportioning, placing, and curing inherent in precasting. The term “manufactured under plant 337 conditions” does not specifically imply that precast members should be manufactured in a plant. 338 Structural elements precast at the job site will also qualify under this section if the control of form 339 dimensions, placing of reinforcement, quality control of concrete, and curing procedures [88] are equal to 340 that normally expected in a plant. 341 342 Concrete cover to pretensioned strand as described in this section is intended to provide minimum 343 protection against weather and other effects. Such cover may not be sufficient to transfer or develop the 344 stress in the strand, and it may be necessary to increase the cover accordingly. <R7.7.3> 345 346 R6.8.1.3.5 —Concrete cover requirements for headed shear stud reinforcement are illustrated in See 347 Figure R6.8.1.3.5. <Paraphrased portion of R7.7.5, other information in R7.7.5 should be located in 348 Chapter 9 on Sectional Strength or appropriate member chapters.> 349

350

351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371

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R6.8.2.1 — Zinc-coated (hot-dipped [92] galvanized) reinforcing bars (ASTM A767), epoxy-coated 372 reinforcing bars (ASTM A775 and A934), and zinc and epoxy dual-coated reinforcing bars (ASTM 373 A1055) are used in applications where corrosion resistance of reinforcement is of particular concern. 374 They have typically been used such as [91] in parking structures, bridge structures, and other highly 375 corrosive environments. <R3.5.3.8> 376 377 R6.8.3 — Corrosion protection for unbonded prestressing reinforcement 378 379 R6.8.3.1 —Material for corrosion protection of unbonded prestressing [93] reinforcement should have the 380 properties identified in Section 5.1 of Reference 18.29. <R18.16.1> 381 382 Typically, sheathing is a continuous, seamless, high-density polythylene material that is extruded directly 383 onto the coated prestressing reinforcement [95]. <R18.16.2> 384 385 R6.8.4 — Corrosion protection for grouted tendons 386 387 R6.8.4.2 — Water in ducts may cause distress to the surrounding concrete upon freezing. When 388 prestressing reinforcement is [97] present, ponded water in ducts should also be avoided. A corrosion 389 inhibitor should be used to provide temporary corrosion protection if prestressing reinforcement is 390 exposed to prolonged periods of moisture in the ducts before grouting.18.30 <R18.17.4> 391 392 R6.8.5 — Corrosion protection for post-tensioning anchorages, couplers, and end fittings. 393 394 R6.8.5.1 — For recommendations regarding protection, see Sections 4.2 and 4.3 of Reference 18.11 and 395 Sections 3.4, 3.6, 5, 6, and 8.3 of Reference 18.29. <R18.21.4> 396 397 398 Fix associated heading on code side.

Reason: Heading on code side should be consistent with commentary heading.

6.8.6 — Corrosion protection for external post-tensioning anchorages, couplers, and end fittings. 399 400 R6.8.6 — Corrosion protection for external post-tensioning anchorages, couplers, and end fittings. 401 402 R6.8.6.1 — Permanent corrosion protection can be achieved by a variety of methods. The corrosion 403 protection provided should be suitable to the environment in which the tendons are located. Some 404 conditions will require that the prestressing reinforcement be protected by concrete cover or by cement 405 grout in polyethylene or metal tubing; other conditions will permit the protection provided by coatings 406 such as paint or grease. Corrosion protection methods should meet the fire protection requirements of the 407 General Building Code, unless the installation of external post-tensioning is to only improve 408 serviceability. <R18.22.4> 409 410

Documents

Reformatted according to Frosch comment #13 (note this … · 2017-08-05 · 49 6.2.1.2.1 — For ASTM A615, A706, A996, and A955 deformed bars with fy less than 50 60,000 psi, yield