WikiEngineer :: Structural :: Minimum Thickness for 1-way Slabs

Concrete Slab Design

Minimum Thickness:

For structures that will not be damaged by significant deflections, the minimum thickness of a slab can be obtained by the following chart ^[1]. These equations work for normal weight concrete with f_y = 60,000 psi steel.

Table 1: Solid 1-way slabs
Types of Construction	Min. Thickness (t)
simply supported	l_c/20
one end continuous	l_c/24
both ends continuous	l_c/28
cantilever	l_c/10

Table 2: Beams or ribbed 1-way slabs
Types of Construction	Min. Thickness (t)
simply supported	l_c/16
one end continuous	l_c/18.5
both ends continuous	l_c/21
cantilever	l_c/8

where:

l_c = the clear span between supports ^[2]

For lightweight concrete:

lightweight concrete factor = λ = 1.65-.005*w_c
lightweight concrete min. thickness = λ* t_{(from above table)}

where:

w_c= wt. of lightweight concrete (b/w 90 and 120 pcf)

For f_y other than 60,000 psi:

steel strength factor = β = 0.4 + f_y/100,000
steel strength concrete min. thickness = β* t_{(from above table)}

where:

f_y= the strength of the reinforcing steel

References

American Concrete Institute, "ACI 318", 2005
- Found in ACI 318 Table 9.5(a)
American Concrete Institute, "ACI 318", 2005
- Found in ACI 318 8.7.3