Building Design and Construction Handbook - Merritt - Ventech!

9.76 SECTION NINE
TABLE 9.17 Minimum Slab Thickness, in, for Various Fire-Resistive Ratings
Type of concrete
Fire-resistive rating
1 hour 2 hours 3 hours
Normal weight concrete
Top slab thickness*
Siliceous aggregate 3.5 5.0 6.2
Carbonate aggregate 3.2 4.6 5.7
Structural lightweight concrete
Top slab thickness*
Sand-lightweight 2.7 3.8 4.6
Lightweight 2.5 3.6 4.4
* From Table 7-7-C-C in Uniform Building Code Std. 7-7 or Table 709.2.2.1 in Standard Building Code.
TABLE 9.18 Minimum and Maximum Reinforcement for One-Way Concrete Slabs
Slab
thickness
h, in
Area A s
in 2 /ft
Minimum reinforcement*
Bar size and
spacing, in
Weight‡
psf
Area A s
in 2 /ft
Maximum reinforcement†
Bar size and
spacing, in
Weight‡
psf
4 0.086 No. 3 @ 12 � 0.38 0.552 No. 6 @ 9 1 ⁄2 1.90
4 1 ⁄2 0.097 No. 3 @ 13 1 ⁄2 0.33 0.648 No. 6 @ 8 2.25
5 0.108 No. 3 @ 12 0.38 0.744 No. 6 @ 7 2.58
5 1 ⁄2 0.119 No. 3 @ 11 0.41 0.840 No. 6 @ 6 3.00
6 0.130 No. 4 @ 18 0.45 0.924 No. 7 @ 7 1 ⁄2 3.27
6 1 ⁄2 0.140 No. 4 @ 17 0.49 1.020 No. 7 @ 7 3.50
7 0.151 No. 4 @ 15 1 ⁄2 0.52 1.104 No. 8 @ 8 1 ⁄2 3.77
7 1 ⁄2 0.162 No. 4 @ 14 1 ⁄2 0.55 1.200 No. 8 @ 7 1 ⁄2 4.27
8 0.173 No. 4 @ 13 1 ⁄2 0.59 1.284 No. 9 @ 9 4.53
8 1 ⁄2 0.184 No. 4 @ 13 0.62 1.380 No. 9 @ 8 1 ⁄2 4.80
9 0.194 No. 4 @ 12 0.67 1.476 No. 9 @ 8 5.10
* For Grade 60 reinforcement. Minimum area As � 0.0018bh, where b � slab width and h � slab
thickness.
†For � 3000 psi; no compression reinforcement; 0.75 �b � 0.016; and 3 ⁄4 in concrete cover (not
ƒ�c exposed to weather). Maximum area As � 0.016bd, where d � effective depth of slab.
‡ Weight is based on the bar size and spacing for a 1-ft wide by 1-ft length of slab. No transverse
reinforcement is included in the weight.
� This spacing for a 4-in slab is the maximum spacing for flexure but can be increased to 18 in for
temperature and shrinkage reinforcement.
if the slab meets ACI 318 Building Code requirements for approximate frame analysis
with uniform loads.
For development (bond) of reinforcement, see Art. 9.49.
Shear. Shear strength is usually not critical in one-way slabs carrying uniform
loads, but the ACI 318 Building Code requires that it be investigated (see Art.
9.47).