Two-Way Slab Design Limits
The minimum slab thickness is controlled and reported automatically according to Table 22.214.171.124 for flat slabs.
The minimum slab thickness is controlled and reported automatically according to Table 126.96.36.199 for beam-to-slabs.
For nonprestressed slabs not satisfying 8.3.1, immediate and time-dependent deflection is calculated according to 24.2 and is not exceed the limits in 24.2.
h = overall thickness, height, or depth of member, in.
ln = length of clear span measured face-to-face of supports, in.
fy = specified yield strength for nonprestressed reinforcement, psi
αfm = average value of αf for all beams on edges of a panel
Minimum slab thickness
There are two different slab thickness limits according to flat slab and beam-to-slab.
Flat slab thickness limit
For nonprestressed flat slabs having a maximum ratio of long-to-short span of 2, overall slab thickness h is not less than the limits in Table 188.8.131.52, and is at least the value in a and b, if the calculated deflection limits of 8.3.2 are not provided:
a) Slabs without drop panels = 5 in.
b) Slabs with drop panels = 4 in.
Note: Deflection is determined with a reduced modulus of rupture fr= 5√f’c for fy exceeding 80 000 psi.
Beam-to-slab thickness limit
For nonprestressed beam-to-slabs, overall slab thickness h provide the limits in Table 184.108.40.206, if the calculated deflection limits of 8.3.2 are not provided.
Calculated deflection limits
According to 8.3.2, immediate and time-dependent deflections is determined in accordance with 24.2. Deflections should not exceed the limits in 24.2.2 for nonprestressed slabs not provided 8.3.1, nonprestressed slabs without interior beams spanning between the supports on all sides and having a ratio of long-to-short span exceeding 2.0 and prestressed slabs.
Reinforcement strain limit in nonprestressed slabs
It’s automatically designed according to Strength Reduction Factors.