Page 219 - Civil Engineering Formulas

154 CHAPTER FIVE

Counterfort

A A

Toe
Heel

(a) Section B-B

B

B

(b) Plan A-A
FIGURE 5.6 Counterfort retaining wall. (a) Vertical
section. (b) Horizontal section.

Shear unit stress on a horizontal section of a counterfort may be computed
from v V /bd, where b is the thickness of the counterfort and d is the hori-
c
1
zontal distance from face of wall to main steel,
M
V 1 V (tan tan ) (5.120)
d

where V shear on section
M bending moment at section
angle earth face of counterfort makes with vertical
angle wall face makes with vertical

For a vertical wall face, 0 and V V (M/d)tan . The critical section
1
for shear may be taken conservatively at a distance up from the base equal to d
sin cos , where d is the depth of counterfort along the top of the base.