Design guide for considering concrete breakout in shear using ACI 318 anchoring-to-concrete provisions October 2025 | Page 159

PROFIS ENGINEERING

Nominal Concrete Breakout Strength in Shear( V cbg)

Check shear towards to the x- edge from Col 1,3.

V b = 7 l e d a

0.2 d a λ a f ′ c c a1

1.5

CASE 3 c a1 is taken from anchor 3 and V ua, col 1, 3 = 1.0V ua, x

ACI 318-19 Eq.( 17.7.2.2.1a)

l e = MIN h e f | 8d a = 3.25 in h ef = 3.25 in CONTROLS d a = 0.5 in 8d a = 4.0 in normal weight concrete: λ = 1.0 → λ a = 1.0 ACI 318-19 Table 17.2.4.1

V b = [( 7)( 3.25 in / 0.5 in) 0. 2( 0.5 in) 0. 5 ]( 1.0)( 3000 psi) 0. 5( 3.2 in) 1. 5

= 2257 lb V b = 9λ a f ′ c c a1

1.5 f’ c = 3000 psi

ACI 318-19 Eq.( 17.7.2.2.1b)

c a1, row 56 = 3.2 in

V cbg =

V b =( 9)( 1.0)( 3000 psi) 0. 5( 3.2 in) 1. 5 = 2822 lb check: design V b = MIN { 2257 lb; 2822 lb } = 2257 lb Shear towards the y- edge

A Vc A Vc0 ψ ec, V ψ ed, V ψ c, V ψ h, V ψ parallel, V V b

V cbg, row 56 =( 71.04 in 2 / 46.08 in 2)( 0.963)( 1.0)( 1.0)( 1.0)( 1.0)( 2257 lb)

V cbg =

A Vc A Vc0

= 3351 lb Shear parallel to y- edge

ψ ec, V ψ ed, V ψ c, V ψ h, V ψ parallel, V V b

V cbg, row 12 =( 71.04 in 2 / 46.08 in 2)( 0.963)( 1.0)( 1.0)( 1.0)( 2.0)( 2257 lb)

= 6702 lb ψ parallel, V = 2.0

V b = 2257 lb

Nominal Concrete Pryout Strength in Shear( V cpg) ACI 318-19 Section 17.7.3

There are 6 anchors in tension and 6 anchors in shear → calculate V cpg using N cbg for 6 anchors.

NOTE:

Pryout is a shear load. Calculate N cbg for pryout using shear eccentricity values. reference page 156: N cbg = 13,709 lb ψ ec, N = 0.895 N cbg, modified = N cbg / ψ ec, N = 15,317 lb e c, x = 0.185 in ψ ec, Vx = 0.963 e c, y = 0.185 in ψ ec, Vy = 0.963 N cbg, pryout = N cbg, modified)( ψ ec, Vx)( ψ ec, Vy) = 14,205 lb

V cpg = k cp N cbg ACI 318-19 Eq.( 17.7.3.1b) h ef = 3.25 in → k cp = 2.0 for h ef ≥ 2.5 in V cpg =( 2.0)( 14,205 lb) = 28,410 lb

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