Walls - Design of Reinforced Concrete - page 563

of both horizontal and vertical reinforcing, as described in Section 11.10.9 or
Chapter 14 of the Code.
9. Should V u be greater than

V c /2, shear wall reinforcing must be designed as de-
scribed in Section 11.10.9 of the Code.
10. If the factored shear force V u exceeds the shear strength V c , the value of V s is to

be determined from the following expression, in which A v is the area of the hori-
zontal shear reinforcement and s 2 is the spacing of the shear or torsional reinforc-
ing in a direction perpendicular to the horizontal reinforcing (11.10.9.1).

A v f y d

V s (ACI Equation 11-31)

s 2

11. The amount of horizontal shear reinforcing h (as a percent of the gross vertical

concrete area) shall not be less than 0.0025 (11.10.9.2).
12. The maximum spacing of horizontal shear reinforcing s 2 shall not be greater than
w /5, 3 h , or 18 in. (11.10.9.3).
13. The amount of vertical shear reinforcing n (as a percent of the gross horizontal

concrete area) shall not be less than the value given by the following equation, in
which h w is the total height of the wall (11.10.9.4).

h w
w

n 0.0025 0.5 2.5 ( h 0.0025) (ACI Section 11-32)

It shall not be less than 0.0025 but need not be greater than the required horizon-
tal shear reinforcing h .

For high walls, the vertical reinforcing is much less effective than it is in
low walls. This fact is reflected in the preceding equation, where for walls with a
height/length ratio less than 0.5, the amount of vertical reinforcing required
equals the horizontal reinforcing required. If the ratio is larger than 2.5, only a
minimum amount of vertical reinforcing is required (that is 0.0025 s 1 h ).
14. The maximum spacing of vertical shear reinforcing s 1 shall not be greater than
w /3, 3 h , or 18 in. (11.10.9.5).

EXAMPLE 18.2

c

Design the reinforced concrete wall shown in Figure 18.6 if f 3000 psi and f y 60,000 psi.

Figure 18.6