(a) Solid slabs
(b) Slabs cast on stay-in-place, noncomposite steel deck
(d) Two-way joist systems in accordance with 8.8
(a) The drop panel shall project below the slab at least one-fourth of the adjacent slab thickness.
|fy, psi||Without drop panels||With drop panels|
|Exterior panels||Interior panels||Exterior panels||Interior panels|
|Without edge beams||With edge beams||Without edge beams||With edge beams|
ℓn is the clear span in the long direction, measured face-to-face of supports (in.).
For fy between the values given in the table, minimum thickness shall be calculated by linear interpolation.
Slabs with beams between columns along exterior edges. Exterior panels shall be considered to be without edge beams if αf is less than 0.8. The value of αf for the edge beam shall be calculated in accordance with 220.127.116.11.
|αfm||Minimum h, in.|
|αfm ≤ 0.2||
|0.2 < αfm ≤ 2.0||Greater of:||(b),|
|αfm > 2.0||Greater of:||(d),|
ℓn is the clear span in the long direction, measured face-to-face of beams (in.).
β is the ratio of clear spans in long to short directions of slab.
(a) Nonprestressed slabs not satisfying 8.3.1
(b) Nonprestressed slabs without interior beams spanning between the supports on all sides and having a ratio of long-to-short span exceeding 2.0
(c) Prestressed slabs
Table 18.104.22.168.4—Maximum modified values of γf for nonprestressed two-way slabs
|Column location||Span direction||vug||εt (within bslab)||Maximum modified γf|
|Corner column||Either direction||≤0.5ϕvc||≥0.004||1.0|
|Edge column||Perpendicular to the edge||≤0.75ϕvc||≥0.004||1.0|
|Parallel to the edge||≤0.4ϕvc||≥0.010|
|Interior column||Either direction||≤0.4ϕvc||≥0.010|
(a) Support reaction, in direction of applied shear, introduces compression into the end regions of the slab.
(b) Loads are applied at or near the top surface of the slab.
(c) No concentrated load occurs between the face of support and critical section.
|γv = 1 — γf||(22.214.171.124.2)|
(a) ϕMn ≥ Mu at all sections along the span in each direction
(b) ϕMn ≥ γfMsc within bslab as defined in 126.96.36.199.3
(c) ϕVn ≥ Vu at all sections along the span in each direction for one-way shear
(d) ϕvn ≥ vu at the critical sections defined in 188.8.131.52 for two-way shear
(a) Openings of any size shall be permitted in the area common to intersecting middle strips, but the total quantity of reinforcement in the panel shall be at least that required for the panel without the opening.
(b) At two intersecting column strips, not more than one-eighth the width of column strip in either span shall be interrupted by openings. A quantity of reinforcement at least equal to that interrupted by an opening shall be added on the sides of the opening.
(c) At the intersection of one column strip and one middle strip, not more than one-fourth of the reinforcement in either strip shall be interrupted by openings. A quantity of reinforcement at least equal to that interrupted by an opening shall be added on the sides of the opening.
(d) If an opening is located within a column strip or closer than 10h from a concentrated load or reaction area, 184.108.40.206 for slabs without shearheads or 220.127.116.11 for slabs with shearheads shall be satisfied.
Table 18.104.22.168—As,min for nonprestressed two-way slabs
|Reinforcement type||fy, psi||As,min, in.2|
|Deformed bars||< 60,000||0.0020Ag|
|Deformed bars or welded wire reinforcement||≥ 60,000||Greater of:|
|Region||Calculated ft after all losses, psi||As,min, in.2|
|Positive moment||Not required||(a)|
|Negative moment at columns||0.00075Acf||(c),|
The value of fy shall not exceed 60,000 psi.
For slabs with bonded tendons, it shall be permitted to reduce As,min by the area of the bonded prestressed reinforcement located within the area used to determine Nc for positive moment, or within the width of slab defined in 22.214.171.124(a) for negative moment.
(a) Reinforcement lengths shall be at least in accordance with Fig. 126.96.36.199.3a, and if slabs act as primary members resisting lateral loads, reinforcement lengths shall be at least those required by analysis.
(b) If adjacent spans are unequal, extensions of negative moment reinforcement beyond the face of support in accordance with Fig. 188.8.131.52.3a shall be based on the longer span.
(c) Bent bars shall be permitted only where the depth-to-span ratio permits use of bends of 45 degrees or less.
(b) At least four deformed bars, deformed wires, or bonded strands shall be provided in each direction.
(a) In positive moment areas, length of reinforcement shall be at least ℓn/3 and be centered in those areas
(b) In negative moment areas, reinforcement shall extend at least ℓn/6 on each side of the face of support
|Direction of measurement||Description of measurement||Maximum distance or spacing, in.|
|Perpendicular to column face||Distance from column face to first stirrup||d/2|
|Spacing between stirrups||d/2|
|Parallel to column face||Spacing between vertical legs of stirrups||2d|
|Direction of measurement||Description of measurement||Condition||Maximum distance or spacing, in.|
|Perpendicular to column face||Distance from column face to first peripheral line of shear studs||All||d/2|
|Constant spacing between peripheral lines of shear studs||Nonprestressed slab with||3d/4|
|Nonprestressed slab with||d/2|
|Prestressed slabs conforming to 184.108.40.206||3d/4|
|Parallel to column face||Spacing between adjacent shear studs on peripheral line nearest to column face||All||2d|
Table 220.127.116.11—Distribution coefficients for end spans
|Exterior edge unrestrained||Slab with beams between all supports||Slab without beams between interior supports||Exterior edge fully restrained|
|Without edge beam||With edge beam|
Note: Linear interpolations shall be made between values shown. βt is calculated using Eq. (18.104.22.168a), where C is calculated using Eq. (22.214.171.124b).
|Msc = 0.07[(qDu+ 0.5qLu)ℓ2ℓn2 — qDu'ℓ2'(ℓn')2]||(126.96.36.199)|
where qDu', ℓ2', and ℓn' refer to the shorter span.
Note: Linear interpolation shall be made between values shown.
(a) A portion of slab having a width equal to that of the column, bracket, or capital in the direction of the span for which moments are being determined.
(b) For monolithic or fully composite construction, the portion of slab specified in (a) plus that part of the transverse beam above and below the slab.