Simplified Design for Structural Walls - Simplified Design of Reinforced Concrete Buildings - page 199

(1) Determine factored shear force. Use ACI Eq. (9-4) for wind loads only

V u = 1.6(160) = 256 kips

(2) Determine φ V c and maximum allowable φ V n

From Table 6-5 φ V c = 7.3 10 = 73 kips

φ V n = 36.4 10 = 364 kips

Wall cross section is adequate (V u < maximum φ V n ); however, shear reinforcement is determined from

ACI Eq. (11-29) must be provided (V u > φ V c ).

(3) Determine required horizontal shear reinforcement

φ V s = V u - φ V c = 256 - 73 = 183 kips

φ V s = 183/10 = 18.3 kips/ft length of wall

Select horizontal bars from Table 6-4

For No. 5 @ 7 in., φ V s = 19.1 kips/ft > 18.3 kips/ft O.K.

s max = 18 in. > 7 in. O.K.

Use No. 5 @ 7 in. horizontal reinforcement

Note: The use of minimum shear reinforcement No. 4 @ 10 in (Table 6-3) for an 8 in. wall thickness
is not adequate:

φ V s = 8.6 kips/ft only (Table 6-4).

(4) Determine required vertical shear reinforcement

ρ ˜ = 0.0025 + 0.5(2.5 - h w /˜ w )( ρ t - 0.0025)

= 0.0025 + 0.5(2.5 - 2)(0.0055 - 0.0025)
= 0.0033

where h w /˜ w = 20/10 = 2

ρ t = A vh /s 2 h = 0.31/(8 7) = 0.0055

Required A vn /s 1 = ρ ˜ h = 0.0033 8 = 0.026 in. 2 /in.

For No. 5 bars: s 1 = 0.31/0.026 = 11.9 in. < 18 in. O.K.

Use No. 5 @ 12 in. vertical reinforcement.