PROFIS ENGINEERING
Figure 5.1c. breakout at y- edge
Figure 5.1d. breakout at x- edge
Summary( for this example) of ACI 318 Shear Concrete Breakout Provisions for an Irregular Anchor Layout
Reference [ 37 ]. Anchor 1 is closest to the y- edge. The spacing between anchors 1 and 2( s y1-2) and anchors 2 and 3( s y2-3) is greater than c a1, 1y, so Case 1 / Case 2 provisions are relevant with respect to shear concrete breakout at the y- edge. The y component of the shear load( V ua, y) is therefore assumed to be distributed proportionately on anchors 1, 2 and 3. The design concrete breakout strength( ϕV cb, nn) for anchors 1, 2 and 3 is checked versus the y component of the shear load assumed to act on each anchor, respectively. The design calculations can be summarized as follows:
• assume 0.33V ua, y, acts on anchor 1 check( 0.33V ua, y / ϕV cb, 1y) ≤ 1.0
• assume 0.67V ua, y, acts on anchor 2 check( 0.67V ua, y / ϕV cb, 2y) ≤ 1.0
• assume 1.0V ua, y, acts on anchor 3 check( 1.0V ua, y / ϕV cb, 3y) ≤ 1.0
MAX {( 0.33V ua, y / ϕV cb, 1y);( 0.67V ua, y / ϕV cb, 2y);( 1.0V ua, y / ϕV cb, 3y)} controls the design with respect to shear concrete breakout towards the y- edge.
Reference [ 37 ]. Anchor 1 is closest to the x- edge. The spacing between anchors 1 and 6( s x1-6) and anchors 6 and 4( s y6-4) is less than c a1, 1x, so Case 3 provisions are relevant with respect to shear concrete breakout at the x- edge. The x component of the shear load( V ua, x) is assumed to act only on anchor 1. The design concrete breakout strength for anchor 1( ϕV cb, 1x) is checked versus 1.0V ua, x. The design calculations can be summarized as follows:
• assume 1.0V ua, x, acts on anchor 1 check( 1.0V ua, x / ϕV cb, 1x) ≤ 1.0( 1.0V ua, x / ϕV cb, 1x) controls the design with respect to shear concrete breakout towards the x- edge. The overall design for shear concrete breakout is controlled by the highest utilization for both edges:
•
greater of MAX {( 0.33V ua, y / ϕV cb, 1y);( 0.67V ua, y / ϕV cb, 2y);( 1.0V ua, y / ϕV cb, 3y)} and( 1.0V ua, x / ϕV cb, 1x) controls the design for shear concrete breakout.
October 2025 37