PROFIS ENGINEERING
Extrapolating ACI 318 Provisions
Extrapolating ACI 318 Shear Provisions for Irregular Anchor Layouts
Figure 5.1a. ACI 318 Provisions- s y1-2 and s y2-3 > c a1, 1y
Reference
[ 35 ] above. Consider shear concrete breakout towards the y- edge for anchors 1, 2 and 3. Anchor 1 is the closest anchor to the y- edge. If the spacing in the y direction between anchors 1 and 2( s y1-2) and anchors 2 and 3( s y2-3) is greater than the distance of anchor 1 to the y- edge( c a1, 1y), Case 1 / Case 2 provisions are relevant for calculating shear concrete breakout because a complete concrete failure surface can develop towards the y- edge from each of these anchors.
Nominal concrete breakout strength( V cb, nn) is calculated for anchor 1( V cb, 1y), anchor 2( V cb, 2y) and anchor 3( V cb, 3y). The design concrete breakout strength for each anchor( ϕV cb, nn) is checked versus the shear load assumed to act on each anchor. Since Case 1 / Case 2 provisions are relevant, assume the y component of the shear load( V ua, y) is distributed proportionally among anchors 1, 2 and 3.
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.
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