2.0 SHEAR
2.1 Concrete Breakout Failure Mode
Equations A Vc0
Equations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
A Vc0
= 4.5c a1
2
17.7.2.1 Nominal concrete breakout strength in shear , V cb of a single anchor or V cbg of an anchor group satisfying 17.5.1.3.1 , shall be calculated in accordance with ( a ) through ( d ): ( a ) For shear force perpendicular to the edge on a single anchor
V cb
=
A Vc ψed , V ψ c , V ψ h , V
V b
( 17.7.2.1a )
A Vc0
( b ) For shear force perpendicular to the edge on an anchor group
V cbg
= A Vc ψ ec , V ψ ed , V ψ c , V ψ h , V
V b
( 17.7.2.1b )
A Vc0
17.7.2.1.3 A Vc0 is the projected area for a single anchor in a deep member with a distance from edges of at least 1.5c a1 in the direction perpendicular to the shear . It shall be permitted to calculate A Vc0 by Eq . ( 17.7.2.1.3 ), which gives the area of the base of a half-pyramid with side length parallel to the edge of 3c a1 and a depth of 1.5c a1 .
A Vc0
= 4.5c a1
2
( 17.7.2.1.3 )
A vc0 is a modification factor that defines an idealized area of influence assumed to develop in concrete when a shear load acts towards a fixed edge on a single anchor without any perpendicular edge distance influences , any adjacent anchor spacing , in a concrete member of infinite thickness . A Vc calculations are predicated on the parameter c a1
, which is assumed to be the distance in the direction of the applied shear load from the anchor to the fixed edge . ACI anchoring-to-concrete provisions do not set a maximum limit on the value for c a1
.
Minimum edge distance values ( c min
) are given in ACI 318-19 Section 17.9.2 and in post-installed anchor approvals . The geometry for A Vc0 is modeled as the base of a truncated pyramid defined by projected distances of 1.5c a1 perpendicular to the direction of the applied shear load , and down from the surface of the concrete . Therefore , the idealized area defined by A Vc0 equals ( 1.5c a1
+ 1.5c a1 )*( 1.5c a1
) or 4.5c a12 . The calculated value for
A Vc0 will always equal 4.5c a12
. The figure below illustrates how A Vc0 is calculated .
A Vc0
= ( 1.5c a1
+ 1.5c a1 ) ( 1.5c a1
)
= ( 4.5c a1
) 2 where : c min
≤ c a1
Reference the Variables section of the PROFIS Engineering report for more information on c a1
.
Reference the Calculations section of the PROFIS Engineering report for more information on A Vc0
.
168 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions