- Compute the footing settlement
Combine Eqs. 31 and 32 to obtain
HCC log (0-2/(T 1 )
" i!«.(33)
Solving gives s = 14(0.274) log (2022/1884)7(1 + 0.84) = 0.064 ft = 0.77 in (19.558 mm).
DETERMINATION OF FOOTING SIZE
BY HOUSEL'S METHOD
A square footing is to transmit a load of 80 kips (355.8 kN) to a cohesive soil, the settle-
ment being restricted to
5
A in (15.9 mm). Two test footings were loaded at the site until
the settlement reached this value. The results were
Footing size Load, Ib (N)
1 ft 6 in x 2 ft (45.72 x 60.96 cm) 14,200 (63,161.6)
3 ft x 3 ft (91.44 x 91.44 cm) 34,500 (153,456.0)Applying House!'s method, determine the size of the footing in plan.Calculation Procedure:
- Determine the values of p and s corresponding to the allowable
settlement
Housel considers that the ability of a cohesive soil to support a footing stems from two
sources: bearing strength and shearing strength. This concept is embodied in
W = Ap +Ps (34)where W = total load; A = area of contact surface; P = perimeter of contact surface; p =
bearing stress directly below footing; s = shearing stress along perimeter.
Applying the given data for the test footings gives: footing 1, A = 3 ft^2 (2787 cm^2 ),
P = 1 ft (2.1 m); footing 2, A = 9 ft^2 (8361 cm^2 ), P = 12 ft (3.7 m). Then 3>p + Is = 14,200;
9p + Us = 34,500; p = 2630 lb/ft^2 (125.9 kPa); s = 900 Ib/lin ft (13,134.5 N/m).
- Compute the size of the footing to carry the specified load
Let jc denote the side of the footing. Then, 263Ox^2 + 900(4*) = 80,000; x = 4.9 ft (1.5 m).
Make the footing 5 ft (1.524 m) square.
APPLICATION OF PILE-DRIVING FORMULA
A 16 x 16 in (406.4 x 406.4 mm) pile of 3000-lb/m^2 (20,685-kPa) concrete, 45 ft (13.7 m)
long, is reinforced with eight no. 7 bars. The pile is driven by a double-acting steam ham-
mer. The weight of the ram is 4600 Ib (20,460.8 N), and the energy delivered is 17,000
ft-lb (23,052 J) per blow. The average penetration caused by the final blows is 0.42 in