Concrete Slab Design
Flexure Design: One-Way Slab
The procedure for designing a one-way slab in flexure is the exact procedure used to design a concrete beam. Assume a tributary width of 1' and find the necessary steel required (Asr). then find the necessary spacing of the steel by:
s = {A_b\over{A_{sr}}} (12 in)
where:
s = the spacing of the rebar
Ab = the area of an individual rebar
Ab = the area of an individual rebar
Maximum spacing for the main steel [1]:
smax for slabs in flexure is the smallest of:
- 3 times the slab thickness (not depth)
- 18"
Differences in design procedures between a slab and beam:
Although the calculations to find Asr for a beam and slab are the same, some differences between the two design procedures do exist. Those differences are:
- The min. cover for the steel is 3/4".
- The minimum steel ratio is bound by the temperature and shrinkage steel. Therefore the minimum steel for beam design does not apply.
References
- American Concrete Institute, "ACI 318", 2005
- Found in section ACI 318.7.6.5