Section 18.9.3.3 Support Two Way Minimum Reinforcement
For span segment strips, this criteria is only applied at the face of support.
For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support.
For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location further than L/6 from a support.
For a span with no supports (as determined by the declaration of supports in the design strip segment), this criterion is never applied.
See "Minimum Reinforcement" above for details regarding which slab/beam face (top or bottom) that the reinforcement will have the reinforcement added.
For strict adherence to ACI 318-99 this criterion should only be used for two-way slabs of uniform thickness ( RAM Concept uses it for all slabs declared as "two-way"; section 18.9.2 should be used for two-way slabs that do not have a uniform thickness. Under ACI 318-02 and IBC 2000 it is acceptable to use this criterion for all two-way slabs.)
Acf is calculated as the maximum of the cross section area and the cross section depth times the span length. This will not always exactly match the code requirement
The location of bonded reinforcement (the 1.5 h requirement) is not checked.
The number of bars ("4 bars or wires") is not checked.
User defined reinforcement on the appropriate face and bonded post-tensioning that is on the appropriate side of the centroid is counted toward the requirement. Vector components are taken of reinforcement and bonded post-tensioning that is not orthogonal to the cross section.
No check is made to ensure that the structure is post-tensioned.