(12) Determine the thickness of concrete required to carry the

shear.

Vu = 30,630 lb/in

vc = 288.5 psi

d = 30,630/288.5 = 106.2 in

(13) Determine the amount of flexural reinforcement required.

Main reinforcement:

Assume "a" block = 6 inches

As = Mub/fs (d - a/2)

Mu = 1,478,660 in-lb/in

b = 12 in

d = 106.2 in

a = assumed value of 6 in

fs = 60,000 psi

As = 1,478,660(12)/60,000(106.2 - 6/2)

= 2.87 in2/ft

a = Asfs/0.85bf'

f'c = 4,000 psi

a = 2.87(60,000)/0.85(12)(4,000)

= 4.22 in

As = 1,478,660(12)/60,000(106.2 - 4.22/2)

= 2.84 in2/ft

Amin = 0.0025bd = 0.0025(12)(106.2)

= 3.19 in2/ft

Use minimum steel: As = 3.19 in2/ft

Area of No. 11 bar = 1.56 in2

Use two No. 11 bars, top and bottom, at 12-inch spacing.

These bars should extend from one end of the foundation

to the other end (see Figure 91).

Reinforcement in other direction:

As = 0.001bTc

Tc = 110 inches

As = 0.001(12)(110)

= 1.32 in2/ft

Use one No. 10 bar, top and bottom, at 12-inch spacing.

These bars should be placed in both extensions of the

foundation (see Figure 91).

2.08-325