Concrete Slab Design
Minimum thickness for 2-way Slabs
The minimum thickness for 2-way slabs is broken up into multiple parts which have been detailed below:
For slabs without red interior beams (between supports) having a ratio of the long span to short span of less than 2:
- Slabs without drop panels = 5"
- Slabs with drop panels = 4"
- Drop panels are described in section 13.2.5 of the ACI 318-05
| Table 1: Min. Thickness of Slabs without interior beams | ||||||
| fy (psi) | Without Drop Panels(b) | With Drop Panels(b) | ||||
| Exterior Panels | Interior Panels | Exterior Panels | Interior Panels | |||
| Without Edge Beams | With Edge Beams(a) | Without Edge Beams | With Edge Beams(a) | |||
| 40,000 | ln/33 | ln/36 | ln/36 | ln/36 | ln/40 | ln/40 |
| 60,000 | ln/30 | ln/33 | ln/33 | ln/33 | ln/36 | ln/36 |
| 75,000 | ln/28 | ln/31 | ln/31 | ln/31 | ln/34 | ln/34 |
where:
ln = the length of clear span in the long direction (face to face)
fy the yield strength of the rebar
\alpha_f = {E_{cb}I_b\over {E_{cs}I_s}}
fy the yield strength of the rebar
\alpha_f = {E_{cb}I_b\over {E_{cs}I_s}}
|
Notes: (b) A definition of a drop panel has been provided here. All conditions of the drop panel must be met to validate using these numbers. If fy falls between the values provided in the table, minimum thickness can be found from linear interpolation |
For slabs with red interior beams (between supports) having a ratio of the long span to short span of less than 2:
To be inserted...
References
- American Concrete Institute, "ACI 318", 2005