For solid nonprestressed slabs not supporting or attached to partitions or other construction likely to be damaged by large deflections, overall slab thickness h shall not be less than the limits in Table 188.8.131.52, unless the calculated deflection limits of 7.3.2 are satisfied.
Table 184.108.40.206—Minimum thickness of solid nonprestressed one-way slabs
The thickness of a concrete floor finish shall be permitted to be included in h if it is placed monolithically with the floor slab or if the floor finish is designed to be composite with the floor slab in accordance with 16.4.
For nonprestressed composite concrete slabs satisfying 7.3.1, 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 7.3.1.
Sections between the face of support and a critical section located d from the face of support for nonprestressed slabs or h/2 from the face of support for prestressed slabs shall be permitted to be designed for Vu at that critical section if (a) through (c) are satisfied:
(a) Support reaction, in direction of applied shear, introduces compression into the end region 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
If primary flexural reinforcement in a slab that is considered to be a T-beam flange is parallel to the longitudinal axis of the beam, reinforcement perpendicular to the longitudinal axis of the beam shall be provided in the top of the slab in accordance with (a) and (b). This provision does not apply to joist construction.
(a) Slab reinforcement perpendicular to the beam shall be designed to resist the factored load on the overhanging slab width assumed to act as a cantilever.
(b) Only the effective overhanging slab width in accordance with 6.3.2 need be considered.
A minimum area of shear reinforcement, Av,min, shall be provided in all regions where Vu > ϕVc. For precast prestressed hollow-core slabs with untopped h > 12.5 in., Av,min shall be provided in all regions where Vu > 0.5ϕVcw.
If shown by testing that the required Mn and Vn can be developed, 220.127.116.11 need not be satisfied. Such tests shall simulate effects of differential settlement, creep, shrinkage, and temperature change, based on a realistic assessment of these effects occurring in service.
For monolithic, cast-in-place, post-tensioned beam-and-slab construction, gross concrete area shall consist of the total beam area including the slab thickness and the slab area within half the clear distance to adjacent beam webs. It shall be permitted to include the effective force in beamtendons in the calculation of total prestress force acting on gross concrete area.
Reinforcement shall extend beyond the point at which it is no longer required to resist flexure for a distance at least the greater of d and 12db, except at supports of simply-supported spans and at free ends of cantilevers.
Flexural tension reinforcement shall not be terminated in a tension zone unless (a), (b), or (c) is satisfied:
(a) Vu ≤ (2/3)ϕVn at the cutoff point.
(b) For No. 11 bars and smaller, continuing reinforcement provides double the area required for flexure at the cutoff point and Vu ≤ (3/4)ϕVn.
(c) Stirrup area in excess of that required for shear is provided along each terminated bar or wire over a distance 3/4d from the termination point. Excess stirrup area shall be not less than 60bws/fyt. Spacings shall not exceed d/(8βb).
Adequate anchorage shall be provided for tension reinforcement where reinforcement stress is not directly proportional to moment, such as in sloped, stepped, or tapered slabs, or where tension reinforcement is not parallel to the compression face.
In slabs with spans not exceeding 10 ft, welded wire reinforcement, with wire size not exceeding W5 or D5, shall be permitted to be curved from a point near the top of slab over the support to a point near the bottom of slab at midspan, provided such reinforcement is continuous over, or developed at, the support.
At simple supports, at least one-third of the maximum positive moment reinforcement shall extend along the slab bottom into the support, except for precast slabs where such reinforcement shall extend at least to the center of the bearing length.
At simple supports and points of inflection, db for positive moment tension reinforcement shall be limited such that ℓd for that reinforcement satisfies (a) or (b). If reinforcement terminates beyond the centerline of supports by a standard hook or a mechanical anchorage at least equivalent to a standard hook, (a) or (b) need not be satisfied.
(a) ℓd ≤ (1.3Mn/Vu + ℓa) if end of reinforcement is confined by a compressive reaction
(b) ℓd ≤ (Mn/Vu + ℓa) if end of reinforcement is not confined by a compressive reaction
Mn is calculated assuming all reinforcement at the section is stressed to fy and Vu is calculated at the section. At a support, ℓa is the embedment length beyond the center of the support. At a point of inflection, ℓa is the embedment length beyond the point of inflection, limited to the greater of d and 12db.
External tendons shall be attached to the member in a manner that maintains the specified eccentricity between the tendons and the concrete centroid through the full range of anticipated member deflections.
If spacing of slab tendons exceeds 4.5 ft, additional deformed shrinkage and temperature reinforcement conforming to 24.4.3 shall be provided parallel to the tendons, except 18.104.22.168 need not be satisfied. In calculating the area of additional reinforcement, it shall be permitted to take the gross concrete area in Table 22.214.171.124 as the slab area between faces of beams. This shrinkage and temperature reinforcement shall extend from the slab edge for a distance not less than the slab tendonspacing.
Analyzing code differences
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