Simplified Design for Footings - Simplified Design of Reinforced Concrete Buildings - page 231

(c) Embedment into column:

The minimum dowel embedment length into the column must be the larger of the following:

- compression development length of No.8 column bars (› = 4000 psi) = 19 in. (Table 7-3)
- compression lap splice length of No.6 dowel bars = 23 in. (Table 7-4) (governs)

For No.6 hooked dowels, the total length of the dowels is

23 + [27 - 3 - (2 0.875)] = 45.25 in.

Use 4-No.6 dowels 3 ft-10 in.

Figure 7-9 shows the reinforcement details for the footing in the non-sway frame

4-#8 column bars

4-#6 dowels x 3'-10"
(90° standard end hook)

10-#7 bars x 9'-4"
(each way)

3" clear

9'-10" square 3" clear

Figure 7-9 Reinforcement Details for Interior Column in Building No.2 (Non-sway Frame)

7.8 ONE-STEP THICKNESS DESIGN FOR PLAIN CONCRETE FOOTINGS

Depending on the magnitude of the loads and the soil conditions, plain concrete footings may be an econom-
ical alternative to reinforced concrete footings. Structural plain concrete members are designed according t o A CI
318-11, Chapter 22. 7.2 . For normalweight plain concrete, the maximum moment design strength is
(ACI Eq. 22-2).With

5 φ ʹ f c S m

φ = 0.55 (ACI 318, Section 9.3.5)

A simplified one-step thickness design equation can be derived as follows (see Fig. 7-10):

M u ≤ 5 φ ʹ f c S m

For a one-foot design strip:

⎛
⎜

c 2
c

⎞
⎟ ≤

⎛
⎜

h 2
6

⎞
⎟

q u 5 φ ʹ f c

c 2 0.6P u c 2

A f φ ʹ

h reqd

2

= 3q u

f c = 5 φ ʹ f c