Heads up:
There are no amended sections in this chapter.
This chapter shall apply to the design of nonprestressed and prestressed slabs reinforced for flexure in two directions, with or without beams between supports, including (a) through (d):
(a) Solid slabs
(b) Slabs cast on stayinplace, noncomposite steel deck
(c) Composite slabs of concrete elements constructed in separate placements but connected so that all elements resist loads as a unit
(d) Twoway joist systems in accordance with 8.8
A slab system shall be permitted to be designed by any procedure satisfying equilibrium and geometric compatibility, provided that design strength at every section is at least equal to required strength, and all serviceability requirements are satisfied. The direct design method of 8.10 or the equivalent frame method of 8.11 is permitted for design where applicable.
The effects of concentrated loads and openings shall be considered in design.
Slabs prestressed with an average effective compressive stress less than 125 psi shall be designed as nonprestressed slabs.
A drop panel in a nonprestressed slab, where used to reduce the minimum required thickness in accordance with 8.3.1.1 or the quantity of deformed negative moment reinforcement at a support in accordance with 8.5.2.2, shall satisfy (a) and (b):
(a) The drop panel shall project below the slab at least onefourth of the adjacent slab thickness.
(b) The drop panel shall extend in each direction from the centerline of support a distance not less than onesixth the span length measured from centertocenter of supports in that direction.
Design properties for concrete shall be selected to be in accordance with Chapter 19.
Design properties for steel reinforcement shall be selected to be in accordance with Chapter 20.
Materials, design, and detailing requirements for embedments in concrete shall be in accordance with 20.7.
For nonprestressed slabs without interior beams spanning between supports on all sides, having a maximum ratio of longtoshort span of 2, overall slab thickness h shall not be less than the limits in Table 8.3.1.1, and shall be at least the value in (a) or (b), unless the calculated deflection limits of 8.3.2 are satisfied:
(a) Slabs without drop panels as given in 8.2.4... 5 in.
(b) Slabs with drop panels as given in 8.2.4........ 4 in.
Table 8.3.1.1—Minimum thickness of nonprestressed twoway slabs without interior beams (in.)^{[1]}
f_{y}, psi^{[2]}  Without drop panels^{[3]}  With drop panels^{[3]}  

Exterior panels  Interior panels  Exterior panels  Interior panels  
Without edge beams  With edge beams^{[4]}  Without edge beams  With edge beams^{[4]}  
40,000  ℓ_{n}/33  ℓ_{n}/36  ℓ_{n}/36  ℓ_{n}/36  ℓ_{n}/40  ℓ_{n}/40 
60,000  ℓ_{n}/30  ℓ_{n}/33  ℓ_{n}/33  ℓ_{n}/33  ℓ_{n}/36  ℓ_{n}/36 
75,000  ℓ_{n}/28  ℓ_{n}/31  ℓ_{n}/31  ℓ_{n}/31  ℓ_{n}/34  ℓ_{n}/34 
^{[1]}ℓ_{n} is the clear span in the long direction, measured facetoface of supports (in.).
^{[2]}For f_{y} between the values given in the table, minimum thickness shall be calculated by linear interpolation.
^{[3]}Drop panels as given in 8.2.4.
For nonprestressed slabs with beams spanning between supports on all sides, overall slab thickness h shall satisfy the limits in Table 8.3.1.2, unless the calculated deflection limits of 8.3.2 are satisfied.
Table 8.3.1.2—Minimum thickness of nonprestressed twoway slabs with beams spanning between supports on all sides
α_{fm}^{[1]}  Minimum h, in.  

α_{fm} ≤ 0.2 
8.3.1.1 applies

(a)  
0.2 < α_{fm} ≤ 2.0  Greater of:  (b)^{[2],[3]}  
5.0  (c)  
α_{fm} > 2.0  Greater of:  (d)^{[2],[3]}  
3.5  (e) 
^{[1]}α_{fm} is the average value of α_{f} for all beams on edges of a panel and α_{f} shall be calculated in accordance with 8.10.2.7.
^{[2]}ℓ_{n} is the clear span in the long direction, measured facetoface of beams (in.).
^{[3]}β is the ratio of clear spans in long to short directions of slab.
If single or multipleleg stirrups are used as shear reinforcement, the slab thickness shall be sufficient to satisfy the requirements for d in 22.6.7.1.
Immediate and timedependent deflections shall be calculated in accordance with 24.2 and shall not exceed the limits in 24.2.2 for twoway slabs given in (a) through (c):
(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 longtoshort span exceeding 2.0
(c) Prestressed slabs
For nonprestressed composite concrete slabs satisfying 8.3.1.1 or 8.3.1.2, deflections occurring after the member becomes composite need not be calculated. Deflections occurring before the member becomes composite shall be investigated, unless the precomposite thickness also satisfies 8.3.1.1 or 8.3.1.2.
For nonprestressed slabs, ε_{t} shall be at least 0.004.
Prestressed slabs shall be designed as Class U with . Other stresses in prestressed slabs immediately after transfer and at service loads shall not exceed the permissible stresses in 24.5.3 and 24.5.4.
Required strength shall be calculated in accordance with the factored load combinations in Chapter 5.
Required strength shall be calculated in accordance with the analysis procedures given in Chapter 6. Alternatively, the provisions of 8.10 for the direct design method shall be permitted for the analysis of nonprestressed slabs and the provisions of 8.11 for the equivalent frame method shall be permitted for the analysis of nonprestressed and prestressed slabs, except 8.11.6.5 and 8.11.6.6 shall not apply to prestressed slabs.
For prestressed slabs, effects of reactions induced by prestressing shall be considered in accordance with 5.3.11.
For a slab system supported by columns or walls, dimensions c_{1}, c_{2}, and ℓ_{n} shall be based on an effective support area. The effective support area is the intersection of the bottom surface of the slab, or drop panel or shear cap if present, with the largest right circular cone, right pyramid, or tapered wedge whose surfaces are located within the column and the capital or bracket and are oriented no greater than 45 degrees to the axis of the column.
A middle strip is a design strip bounded by two column strips.
For slabs built integrally with supports, M_{u} at the support shall be permitted to be calculated at the face of support, except if analyzed in accordance with 8.4.2.2.
For slabs analyzed using the direct design method or the equivalent frame method, M_{u} at the support shall be located in accordance with 8.10 or 8.11, respectively.
The fraction of factored slab moment resisted by the column, γ_{f}M_{sc}, shall be assumed to be transferred by flexure, where γ_{f} shall be calculated by:
(8.4.2.3.2) 
The effective slab width b_{slab} for resisting γ_{f}M_{sc} shall be the width of column or capital plus 1.5h of slab or drop panel on either side of column or capital.
For nonprestressed slabs, where the limitations on v_{ug} and ε_{t} in Table 8.4.2.3.4 are satisfied, γ_{f} shall be permitted to be increased to the maximum modified values provided in Table 8.4.2.3.4, where v_{c} is calculated in accordance with 22.6.5, and v_{ug} is the factored shear stress on the slab critical section for twoway action due to gravity loads without moment transfer.
Table 8.4.2.3.4—Maximum modified values of γ_{f} for nonprestressed twoway slabs
Column location  Span direction  v_{ug}  ε_{t} (within b_{slab})  Maximum modified γ_{f} 

Corner column  Either direction  ≤0.5ϕv_{c}  ≥0.004  1.0 
Edge column  Perpendicular to the edge  ≤0.75ϕv_{c}  ≥0.004  1.0 
Parallel to the edge  ≤0.4ϕv_{c}  ≥0.010  
Interior column  Either direction  ≤0.4ϕv_{c}  ≥0.010 
Concentration of reinforcement over the column by closer spacing or additional reinforcement shall be used to resist moment on the effective slab width defined in 8.4.2.3.2 and 8.4.2.3.3.
The fraction of M_{sc} not calculated to be resisted by flexure shall be assumed to be resisted by eccentricity of shear in accordance with 8.4.4.2.
For slabs built integrally with supports, V_{u} at the support shall be permitted to be calculated at the face of support.
Sections between the face of support and a critical section located d from the face of support for nonprestressed slabs and h/2 from the face of support for prestressed slabs shall be permitted to be designed for V_{u} at that critical section if (a) through (c) are satisfied:
(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.
Slabs reinforced with stirrups or headed shear stud reinforcement shall be evaluated for twoway shear at critical sections in accordance with 22.6.4.2.
Slabs reinforced with shearheads shall be evaluated for twoway shear at critical sections in accordance with 22.6.9.8.
For twoway shear with factored slab moment resisted by the column, factored shear stress v_{u} shall be calculated at critical sections in accordance with 8.4.4.1. Factored shear stress v_{u} corresponds to a combination of v_{ug} and the shear stress produced by γ_{v}M_{sc}, where γ_{v} is given in 8.4.4.2.2 and M_{sc} is given in 8.4.2.3.1.
The fraction of M_{sc} transferred by eccentricity of shear, γ_{v}M_{sc}, shall be applied at the centroid of the critical section in accordance with 8.4.4.1, where:
γ_{v} = 1 — γ_{f}  (8.4.4.2.2) 
The factored shear stress resulting from γ_{v}M_{sc} shall be assumed to vary linearly about the centroid of the critical section in accordance with 8.4.4.1.
For each applicable factored load combination, design strength shall satisfy ϕS_{n} ≥ U, including (a) through (d). Interaction between load effects shall be considered.
(a) ϕM_{n} ≥ M_{u} at all sections along the span in each direction
(b) ϕM_{n} ≥ γ_{f}M_{sc} within b_{slab} as defined in 8.4.2.3.3
(c) ϕV_{n} ≥ V_{u} at all sections along the span in each direction for oneway shear
(d) ϕv_{n} ≥ v_{u} at the critical sections defined in 8.4.4.1 for twoway shear
ϕ shall be in accordance with 21.2.
M_{n} shall be calculated in accordance with 22.3.
In calculating M_{n} for nonprestressed slabs with a drop panel, the thickness of the drop panel below the slab shall not be assumed to be greater than onefourth the distance from the edge of drop panel to the face of column or column capital.
In calculating M_{n} for prestressed slabs, external tendons shall be considered as unbonded unless the external tendons are effectively bonded to the slab along its entire length.
For oneway shear, where each critical section to be investigated extends in a plane across the entire slab width, V_{n} shall be calculated in accordance with 22.5.
For twoway shear, v_{n} shall be calculated in accordance with 22.6.
Openings of any size shall be permitted in slab systems if shown by analysis that all strength and serviceability requirements, including the limits on deflections, are satisfied.
As an alternative to 8.5.4.1, openings shall be permitted in slab systems without beams in accordance with (a) through (d).
(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 oneeighth 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 onefourth 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.
A minimum area of flexural reinforcement, A_{s,min}, shall be provided near the tension face in the direction of the span under consideration in accordance with Table 8.6.1.1.
Table 8.6.1.1—A_{s,min} for nonprestressed twoway slabs
Reinforcement type  f_{y}, psi  A_{s,min}, in.^{2}  

Deformed bars  < 60,000  0.0020A_{g}  
Deformed bars or welded wire reinforcement  ≥ 60,000  Greater of:  
0.0014A_{g} 
For prestressed slabs, the effective prestress force A_{ps}f_{se} shall provide a minimum average compressive stress of 125 psi on the slab section tributary to the tendon or tendon group. For slabs with varying cross section along the slab span, either parallel or perpendicular to the tendon or tendon group, the minimum average effective prestress of 125 psi is required at every cross section tributary to the tendon or tendon group along the span.
For slabs with bonded prestressed reinforcement, total quantity of A_{s} and A_{ps} shall be adequate to develop a factored load at least 1.2 times the cracking load calculated on the basis of f_{r} defined in 19.2.3.
For slabs with both flexural and shear design strength at least twice the required strength, 8.6.2.2 need not be satisfied.
For prestressed slabs, a minimum area of bonded deformed longitudinal reinforcement, A_{s,min}, shall be provided in the precompressed tension zone in the direction of the span under consideration in accordance with Table 8.6.2.3.
Table 8.6.2.3—Minimum bonded deformed longitudinal reinforcement A_{s,min} in twoway slabs with bonded or unbonded tendons
Region  Calculated f_{t} after all losses, psi  A_{s,min}, in.^{2}  

Positive moment  Not required  (a)  
(b)^{[1],[2],[4]}  
Negative moment at columns  0.00075A_{cf}  (c)^{[3],[4]} 
^{[1]}The value of f_{y} shall not exceed 60,000 psi.
^{[2]}N_{c} is the resultant tensile force acting on the portion of the concrete cross section that is subjected to tensile stresses due to the combined effects of service loads and effective prestress.
^{[3]}A_{cf} is the greater gross crosssectional area of the slabbeam strips of the two orthogonal equivalent frames intersecting at a column of a twoway slab.
^{[4]}For slabs with bonded tendons, it shall be permitted to reduce A_{s},_{min} by the area of the bonded prestressed reinforcement located within the area used to determine N_{c} for positive moment, or within the width of slab defined in 8.7.5.3(a) for negative moment.
Splice lengths of deformed reinforcement shall be in accordance with 25.5.
Bundled bars shall be detailed in accordance with 25.6.
For nonprestressed solid slabs, maximum spacing s of deformed longitudinal reinforcement shall be the lesser of 2h and 18 in. at critical sections, and the lesser of 3h and 18 in. at other sections.
At exterior corners of slabs supported by edge walls or where one or more edge beams have a value of α_{f} greater than 1.0, reinforcement at top and bottom of slab shall be designed to resist M_{u} per unit width due to corner effects equal to the maximum positive M_{u} per unit width in the slab panel.
Factored moment due to corner effects, M_{u}, shall be assumed to be about an axis perpendicular to the diagonal from the corner in the top of the slab and about an axis parallel to the diagonal from the corner in the bottom of the slab.
Reinforcement shall be provided for a distance in each direction from the corner equal to onefifth the longer span.
Reinforcement shall be placed parallel to the diagonal in the top of the slab and perpendicular to the diagonal in the bottom of the slab. Alternatively, reinforcement shall be placed in two layers parallel to the sides of the slab in both the top and bottom of the slab.
Where a slab is supported on spandrel beams, columns, or walls, anchorage of reinforcement perpendicular to a discontinuous edge shall satisfy (a) and (b):
(a) Positive moment reinforcement shall extend to the edge of slab and have embedment, straight or hooked, at least 6 in. into spandrel beams, columns, or walls
(b) Negative moment reinforcement shall be bent, hooked, or otherwise anchored into spandrel beams, columns, or walls, and shall be developed at the face of support
Where a slab is not supported by a spandrel beam or wall at a discontinuous edge, or where a slab cantilevers beyond the support, anchorage of reinforcement shall be permitted within the slab.
For slabs without beams, reinforcement extensions shall be in accordance with (a) through (c):
(a) Reinforcement lengths shall be at least in accordance with Fig. 8.7.4.1.3a, 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. 8.7.4.1.3a shall be based on the longer span.
(c) Bent bars shall be permitted only where the depthtospan ratio permits use of bends of 45 degrees or less.
All bottom deformed bars or deformed wires within the column strip, in each direction, shall be continuous or spliced with full mechanical, full welded, or Class B tension splices. Splices shall be located in accordance with Fig. 8.7.4.1.3a.
At least two of the column strip bottom bars or wires in each direction shall pass within the region bounded by the longitudinal reinforcement of the column and shall be anchored at exterior supports.
In slabs with shearheads where it is not practical to pass the bottom bars through the column in accordance with 8.7.4.2.2, at least two bottom bars or wires in each direction shall pass through the shearhead as close to the column as practicable and be continuous or spliced with full mechanical, full welded, or Class B tension splices. At exterior columns, the bars or wires shall be anchored at the shearhead.
External tendons shall be attached to the slab in a manner that maintains the specified eccentricity between the tendons and the concrete centroid through the full range of anticipated member deflections.
If bonded deformed longitudinal reinforcement is required to satisfy flexural strength or for tensile stress conditions in accordance with Eq. (8.6.2.3(b)), the detailing requirements of 7.7.3 shall be satisfied.
Bonded longitudinal reinforcement required by Eq. (8.6.2.3(c)) shall be placed in the top of the slab, and shall be in accordance with (a) through (c):
(a) Reinforcement shall be distributed between lines that are 1.5h outside opposite faces of the column support.
(b) At least four deformed bars, deformed wires, or bonded strands shall be provided in each direction.
(c) Maximum spacing s between bonded longitudinal reinforcement shall not exceed 12 in.
Posttensioned anchorage zones shall be designed and detailed in accordance with 25.9.
Posttensioning anchorages and couplers shall be designed and detailed in accordance with 25.8.
Length of deformed reinforcement required by 8.6.2.3 shall be in accordance with (a) and (b):
(a) In positive moment areas, length of reinforcement shall be at least ℓ_{n}/3 and be centered in those areas
(b) In negative moment areas, reinforcement shall extend at least ℓ_{n}/6 on each side of the face of support
Except as permitted in 8.7.5.6.3, at least two tendons with ^{1}/_{2} in. diameter or larger strand shall be placed in each direction at columns in accordance with (a) or (b):
(b) Tendons shall be anchored within the region bounded by the longitudinal reinforcement of the column, and the anchorage shall be located beyond the column centroid and away from the anchored span.
Slabs with tendons not satisfying 8.7.5.6.1 shall be permitted if bonded bottom deformed reinforcement is provided in each direction in accordance with 8.7.5.6.3.1 through 8.7.5.6.3.3.
Minimum bottom deformed reinforcement A_{s} in each direction shall be the greater of (a) and (b):
(a)  (8.7.5.6.3.1a) 
(b)  (8.7.5.6.3.1b) 
where b_{w} is the width of the column face through which the reinforcement passes.
Bottom deformed reinforcement calculated in 8.7.5.6.3.1 shall pass within the region bounded by the longitudinal reinforcement of the column and shall be anchored at exterior supports.
Bottom deformed reinforcement shall be anchored to develop f_{y} beyond the column or shear cap face.
Singleleg, simpleU, multipleU, and closed stirrups shall be permitted as shear reinforcement.
If stirrups are provided, location and spacing shall be in accordance with Table 8.7.6.3.
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 
Headed shear stud reinforcement shall be permitted if placed perpendicular to the plane of the slab.
The overall height of the shear stud assembly shall be at least the thickness of the slab minus the sum of (a) through (c):
(a) Concrete cover on the top flexural reinforcement
(b) Concrete cover on the base rail
(c) Onehalf the bar diameter of the flexural tension reinforcement
Headed shear stud reinforcement location and spacing shall be in accordance with Table 8.7.7.1.2.
Table 8.7.7.1.2—Shear stud location and spacing limits
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 22.6.5.4  3d/4  
Parallel to column face  Spacing between adjacent shear studs on peripheral line nearest to column face  All  2d 
Nonprestressed twoway joist construction consists of a monolithic combination of regularly spaced ribs and a top slab designed to span in two orthogonal directions.
Width of ribs shall be at least 4 in. at any location along the depth.
Overall depth of ribs shall not exceed 3.5 times the minimum width.
Clear spacing between ribs shall not exceed 30 in.
V_{c} shall be permitted to be taken as 1.1 times the values calculated in 22.5.
For structural integrity, at least one bottom bar in each joist shall be continuous and shall be anchored to develop f_{y} at the face of supports.
Reinforcement area perpendicular to the ribs shall satisfy slab moment strength requirements, considering load concentrations, and shall be at least the shrinkage and temperature reinforcement area in accordance with 24.4.
Slab thickness over fillers shall be at least the greater of onetwelfth the clear distance between ribs and 1.5 in.
For calculation of shear and negative moment strength, it shall be permitted to include the vertical shells of fillers in contact with the ribs. Other portions of fillers shall not be included in strength calculations.
If fillers not complying with 8.8.2.1 or removable forms are used, slab thickness shall be at least the greater of onetwelfth the clear distance between ribs and 2 in.
In slabs constructed with liftslab methods where it is impractical to pass the tendons required by 8.7.5.6.1 or the bottom bars required by 8.7.4.2 or 8.7.5.6.3 through the column, at least two posttensioned tendons or two bonded bottom bars or wires in each direction shall pass through the lifting collar as close to the column as practicable, and be continuous or spliced with full mechanical, full welded, or Class B tension splices. At exterior columns, the reinforcement shall be anchored at the lifting collar.
Twoway slabs satisfying the limits in 8.10.2 shall be permitted to be designed in accordance with this section.
Variations from the limitations in 8.10.2 shall be permitted if demonstrated by analysis that equilibrium and geometric compatibility are satisfied, the design strength at every section is at least equal to the required strength, and serviceability conditions, including limits on deflection, are met.
Circular or regular polygonshaped supports shall be treated as square supports with the same area.
There shall be at least three continuous spans in each direction.
Successive span lengths measured centertocenter of supports in each direction shall not differ by more than onethird the longer span.
Panels shall be rectangular, with the ratio of longer to shorter panel dimensions, measured centertocenter of supports, not to exceed 2.
All loads shall be due to gravity only and uniformly distributed over an entire panel.
Total factored static moment M_{o} for a span shall be calculated for a strip bounded laterally by the panel centerline on each side of the centerline of supports.
The absolute sum of positive and average negative M_{u} in each direction shall be at least:
(8.10.3.2) 
In Eq. (8.10.3.2), ℓ_{n} is the clear span length in the direction that moments are considered, shall extend from face to face of columns, capitals, brackets, or walls, and shall be at least 0.65ℓ_{1}.
In Eq. (8.10.3.2), if the transverse span of panels on either side of the centerline of supports varies, ℓ_{2} shall be taken as the average of adjacent transverse spans.
In Eq. (8.10.3.2), if the span adjacent and parallel to a slab edge is being considered, the distance from edge to panel centerline shall be substituted for ℓ_{2}.
In an interior span, M_{o} shall be distributed as follows: 0.65M_{o} to negative moment and 0.35M_{o} to positive moment.
In an end span, M_{o} shall be distributed in accordance with Table 8.10.4.2.
Table 8.10.4.2—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  
Interior negative  0.75  0.70  0.70  0.70  0.65 
Positive  0.63  0.57  0.52  0.50  0.35 
Exterior negative  0  0.16  0.26  0.30  0.65 
Critical section for negative M_{u} shall be at the face of rectangular supports.
Negative M_{u} shall be the greater of the two interior negative M_{u} calculated for spans framing into a common support unless an analysis is made to distribute the unbalanced moment in accordance with stiffnesses of adjoining elements.
Edge beams or edges of slabs shall be designed to resist in torsion their share of exterior negative M_{u}.
The column strip shall resist the portion of interior negative M_{u} in accordance with Table 8.10.5.1.
Table 8.10.5.1—Portion of interior negative M_{u} in column strip
α_{f1}ℓ_{2}/ℓ_{1}  ℓ_{2}/ℓ_{1}  

0.5  1.0  2.0  
0  0.75  0.75  0.75 
≥1.0  0.90  0.75  0.45 
Note: Linear interpolations shall be made between values shown.
The column strip shall resist the portion of exterior negative M_{u} in accordance with Table 8.10.5.2.
Table 8.10.5.2—Portion of exterior negative M_{u} in column strip
α_{f1}ℓ_{2}/ℓ_{1}  β_{t}  ℓ_{2}/ℓ_{1}  

0.5  1.0  2.0  
0  0  1.0  1.0  1.0 
≥2.5  0.75  0.75  0.75  
≥1.0  0  1.0  1.0  1.0 
≥2.5  0.90  0.75  0.45 
Note: Linear interpolations shall be made between values shown. β_{t} is calculated using Eq. (8.10.5.2a), where C is calculated using Eq. (8.10.5.2b).
(8.10.5.2a)  
(8.10.5.2b) 
In addition to moments calculated according to 8.10.5.7.1, beams shall resist moments caused by factored loads applied directly to the beams, including the weight of the beam stem above and below the slab.
That portion of negative and positive factored moments not resisted by column strips shall be proportionately assigned to corresponding half middle strips.
Each middle strip shall resist the sum of the moments assigned to its two half middle strips.
A middle strip adjacent and parallel to a wallsupported edge shall resist twice the moment assigned to the half middle strip corresponding to the first row of interior supports.
Columns and walls built integrally with a slab system shall resist moments caused by factored loads on the slab system.
At an interior support, columns or walls above and below the slab shall resist the factored moment calculated by Eq. (8.10.7.2) in direct proportion to their stiffnesses unless a general analysis is made.
M_{sc} = 0.07[(q_{Du}+ 0.5q_{Lu})ℓ_{2}ℓ_{n}^{2} — q_{Du}'ℓ_{2}'(ℓ_{n}')^{2}]  (8.10.7.2) 
where q_{Du}', ℓ_{2}', and ℓ_{n}' refer to the shorter span.
Beams between supports shall resist the portion of shear in accordance with Table 8.10.8.1 caused by factored loads on tributary areas in accordance with Fig. 8.10.8.1.
Table 8.10.8.1—Portion of shear resisted by beam
α_{f1}ℓ_{2}/ℓ_{1}  Distribution coefficient 

0  0 
≥1.0  1.0 
Note: Linear interpolation shall be made between values shown.
Fig. 8.10.8.1—Tributary area for shear on an interior beam.
In addition to shears calculated according to 8.10.8.1, beams shall resist shears caused by factored loads applied directly to the beams, including the weight of the beam stem above and below the slab.
It shall be permitted to account for the contribution of metal column capitals to stiffness, resistance to moment, and resistance to shear.
It shall be permitted to neglect the change in length of columns and slabs due to direct stress, and deflections due to shear.
The structure shall be modeled by equivalent frames on column lines taken longitudinally and transversely through the building.
Frames adjacent and parallel to an edge shall be bounded by that edge and the centerline of the adjacent panel.
Analysis of each equivalent frame in its entirety shall be permitted. Alternatively, for gravity loading, a separate analysis of each floor or roof with the far ends of columns considered fixed is permitted.
The moment of inertia of slabbeams from the center of the column to the face of the column, bracket, or capital shall be assumed equal to the moment of inertia of the slabbeam at the face of the column, bracket, or capital divided by the quantity (1 — c_{2}/ℓ_{2})^{2}, where c_{2} and ℓ_{2} are measured transverse to the direction of the span for which moments are being determined.
Variation in moment of inertia along the axis of slabbeams shall be taken into account.
It shall be permitted to use the gross crosssectional area of concrete to determine the moment of inertia of slabbeams at any cross section outside of joints or column capitals.
Variation in moment of inertia along the axis of columns shall be taken into account.
It shall be permitted to use the gross crosssectional area of concrete to determine the moment of inertia of columns at any cross section outside of joints or column capitals.
Torsional members shall be assumed to have a constant cross section throughout their length consisting of the greatest of (a) through (c):
(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.
At exterior supports without brackets or capitals, the critical section for negative M_{u} in the span perpendicular to an edge shall be taken at the face of the supporting element.
At exterior supports with brackets or capitals, the critical section for negative M_{u} in the span perpendicular to an edge shall be taken at a distance from the face of the supporting element not exceeding onehalf the projection of the bracket or capital beyond the face of the supporting element.
Circular or regular polygonshaped supports shall be assumed to be square supports with the same area for location of critical section for negative design moment.