PROFIS ENGINEERING
Table 27. Interaction
Tri-Linear: N ua ϕN n
+ V ua ϕV n
≤ 1.2 Case 3: = 0.051 + 0.937 = 0.988 < 1.2
Case 2: = 0.051 + 0.469 = 0.52 < 1.2
Parabolic: N 5 5
ua 3 V ua +
3 ≤ 1. 0 Case 3 =( 0. 051) 5 / 3 +( 0.937) ϕN n ϕV 5 / 3 = 0.9 < 1.0 n
ACI 318-19 Eq.( 17.8.3)
Ref. ACI 318-19 commentary R17.8.
Case 2 =( 0.051) 5 / 3 +( 0.469) 5 / 3 = 0.29 < 1.0
SUMMARY
• Consider shear concrete breakout for anchor rows 1, 2 and 3.
• PROFIS Engineering considers a maximum of three anchor rows / columns with respect to shear concrete breakout calculations.
• Shear load acts eccentric with respect to the centroid of the anchor group.
• Shear load creates a torsion moment on the anchorage.
• Calculate resultant shear load( V ua, res), or fraction thereof, and check vs. concrete breakout strength( ϕV cbg)
• Reference page 108.
• Assume shear load acts towards the y- edge.
• x direction anchor spacing in each row is less than 3c a1, row 1
• Anchors in each row act as a group.
• y direction anchor spacing between row 1 and row 2 is less than c a1, row 1
• ACI 318 Case 3 provisions are relevant for row 1 and row 2.
• Calculate concrete breakout( ϕV cbg) from row 1 using c a1, row 1.
• Assume 1.0V ua, res acts on row 1( conservative assumption) neglects load on row 3
• Check ϕV cbg, row 1 vs. 1.0V ua, res
• y direction anchor spacing in between row 2 and row 3 is greater than c a1, row 1
• ACI 318 Case 1 / Case 2 provisions are relevant for row 1 and row 3.
• Calculate concrete breakout( ϕV cbg) from row 3 using c a1, row 3.
• Calculate concrete breakout( ϕV cbg) from row 1 using c a1, row 1.
• Assume V ua, res is distributed between row 1 and row 3
• Check ϕV cbg, row 3 vs. 1.0V ua, res
• Check ϕV cbg, row 1 vs. 0.5V ua, res
• Reasonable design assumption in lieu of conservative assumption.
• For concrete pryout calculations, ϕV cpg is checked vs. V ua(= 10,000 lb).
• Reference page 108.
•( N ua / ϕN cbg) controls the design with respect to tension failure modes
• Tension / shear interaction is satisfied: fastening satisfies ACI 318-19 provisions.
For more information on extrapolating ACI 318 shear concrete breakout provisions, reference Equal Number of Anchors and Unequal Spacing( page 10) in the design guide. For more information on calculating resultant shear load when eccentricity exists, reference Eccentric Shear Load( page 60) in the design guide.
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