Simplified Design for Footings - Simplified Design of Reinforced Concrete Buildings - page 227

Table 7-4 Minimum Compression Lap Splice Length for Grade 60 Bars*

Bar
Size

Lap Splice Length
(in.)

# 4 15

# 5 19

# 6 23

# 7 26

# 8 30

# 9 34

#10 38

#11 42

'

* t f 3000 psi

c

7.6.2 Horizontal Force Transfer at Base of Column

ACI 11.6.7 permits permanent compression to function like shear friction reinforcement. For all practical cases in
ordinary buildings, the column dead load will be more than enough to resist any column shear at the top of the footing.

For normalweight concrete the horizontal force V u to be transferred cannot exceed the smallest of φ (0.2f' c A c ),

φ 1600 A c in pounds where A c is gross area of column(ACI 11.6.5). For a column

concrete strength › = 4000 psi, this maximum force is equal to

(480 + 0.08f' c )A c and φ

(800A c ). Dowels required to transfer
horizontal force must have full tensile anchorage into the footing and into the column (ACI 11.6.8). The values
given in Table 8-1 and 8-5 can be modified by the appropriate factors given in ACI 12.2.

φ

7.7 EXAMPLE: REINFORCED CONCRETE FOOTING DESIGN

Design footings for the interior columns of Building No. 2 (5-story flat plate). Assume base of footings located
5 ft below ground level floor slab (see Fig. 7-8). Permissible soil pressure q a = 6 ksf.

Top of floor slab
at ground level

Figure 7-8 Interior Footing for Building No. 2