Two-Way Slab Design Strength
Both flexural moment and shear strength is controlled automatically according to 126.96.36.199.
Dimensions of the cross-section should be satisfy ACI Eq. (188.8.131.52). It’s automatically controlled and users are warned if the rule is not satisfied.
Mu = factored flexural moment at section, lb
Mn = nominal flexural strength at section, in.
Msc = factored slab moment that is resisted by the column at a joint, in.-lb
f'c = specified comprehensive strength of concrete, psi
Ac-sh = area of concrete used to determine shear stress, in2
Ag = gross area of concrete section, in2
bw = web width or diameter of circular section, in.
d = distance from extreme compression fiber to centroid of longitudinal tension reinforcement, in.
h = overall thickness, height, or depth of member, in.
s = center-to-center spacing transverse reinforcement, in
Vc = nominal shear strength provided by concrete, lb
Vn = nominal shear strength, lb
Vs = nominal shear strength provided by shear reinforcement, lb
Vu = factored shear force at section, lb
γf = factor used to determine the fraction of Msc transferred by slab flexure at slab-column connections
To design two-way slab under flexural moment, two-way slab design strength is provided ΦSn ≥ U. Both flexural moment and shear strength is controlled according to 184.108.40.206.
ΦMn ≥ Mu at all sections along the span in each direction
ΦMn ≥ γfMsc within bslab 220.127.116.11.3 (flat slab)
ΦVn ≥ Vu at all sections along the span in each direction for one-way shear
Φvn ≥ vu at the critical sections defined 18.104.22.168 for two-way shear (flat slab)
Φ is automatically designed according to Strength Reduction Factors.
Mn is determined according to 22.3 as nominal flexural strength Mn is calculated as shown below. Detailed information: Flexural Strength
For one-way shear Vn is determined according to 22.5. Nominal one-way shear strength at a section, Vn, is calculated by eq. 22.214.171.124.
The shear strength is based on an average shear stress over the effective cross section, bwd. Therefore dimensions of the cross-section should be satisfy ACI Eq. (126.96.36.199). Detailed information: One-Way Shear Strength
For two-way shear vn is determined according to 22.6.
Openings in slab systems
ACI 188.8.131.52 are provided, when an opening is placed at least 4h from the face of a column, concentrated load or reaction area. Detailed information: Two-Way Shear Strength .