Estimating in Building Construction

Concrete 95

FIGURE 10.6.Volume in Bells 50-Degree Angle (top) and 60-Degree Angle (bottom).

EXAMPLE 10–3 DRILLED PIER

From the small commercial building example found in Appendix A,
there are three identical drilled piers with the following dimensions:

Shaft diameter 18 inches

Bell diameter 42 inches

Angle of bell 60 degrees

Formula 10-1

Height of Bell on Reamed Footing

Formula 10-2

Height of Bell on Reamed Footing

From the given dimensions the bell height is

or

H1.732¿

Htan(60°)a

3.5¿1.5¿

2

b

H1.732–

H

sin(60°)a

3.5¿1.5¿

2

b

sin(90°60°)

Htan(A)a

B 5

2

b

H

sin(A)

B 5

2

sin(90A)

Once the bell height (H) is found, Formula 10-3 or 10-4 can be

used to determine the volume of the belled portion of the footing.

Formula 10-3

Volume of Bell

Formula 10-4

Volume of Bell

The bell volume is as follows:

or

Volume of bell8.96 cf

Volume of bell

1.732¿

12

(1.5¿^2 3.5¿^2 1.5¿3.5¿)

Volume of bell

H

12

(S^2 B^2 SB)

Volume of bell8.96 cf

a

3.5¿1.5¿)1.732¿

4

bbb

a 2 aa

(21.5¿)3.5¿

6

Volume of bella b

1.5¿^2 1.732¿

4

b

Volume of bell

H

12

(S^2 B^2 SB)

a

(BS)H

4

bbb

Volume of bella

S^2 H

4

ba 2 aa

2 SB

6

b