FIGURE 30
following calculations demonstrate, the theoretical cutoff point lies at y = 11 ft 7 in (3.531
m), where M = 218,400 in-lb (24,674.8 N-m); d = 4.5 + 10(11.58/16.5) = 11.52 in
(292.608 mm); As = 218,400/[20,0OO (0.874)(11.52)] = 1.08 in^2 (6.968 cm^2 ). This is ac-
ceptable. Also, T= 3930 Ib (17,480.6 N); u = 101 lb/in^2 (696.4 kPa). This is acceptable.
From the ACI Code, anchorage - 12(9/8) - 13.5 in (342.9 mm).
The alternate bars will therefore be terminated at 6 ft 1 in (1.854 m) above the top of
the base. The Code requires that special precautions be taken where more than half the
bars are spliced at a point of maximum stress. To circumvent this requirement, the short
bars can be extended into the footing; therefore only the long bars require splicing.
For the dowels, wallow - 0.75(235) = 176 lb/in^2 (1213.5 kPa); length of lap = 1.00
(20,000)/[176(3.5)] = 33 in (838.2 mm).
- Design the heel
Let V and M denote the shear and bending moment, respectively, at section D. Case 1:
surcharge extending to G—downward pressure;? = 16,5(130) + 1.5(150) = 2370 lb/ft^2
(113.5 kPa); V= 6.5[2370 - »/2(2244 + 171)] = 7560 Ib (33,626.9 N); M= 12(6 5)^2 [V 2 x
2370 - %(2244 + 2 x Hl)] = 383,000 in-lb (43,271.3 N-m).
verticals
stop above base
dowels
verticals
stop
horizontals
verticals
verticals
