2.0 SHEAR
2.1 Concrete Breakout Failure Mode
Variables ψ parallel , V
Variables ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
ψ parallel , V
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
A
V cb
= 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
( c ) For shear force parallel to an edge V cb or V cbg shall be permitted to be twice the value of the shear calculated by Eq . ( 17.7.2.1a ) or ( 17.7.2.1b ), respectively , with the shear assumed to act perpendicular to the edge and with ψ ed , V taken equal to 1.0 .
( d ) For anchors located at a corner , the limiting nominal concrete breakout strength shall be calculated for each edge , and the lesser value shall be used .
ACI 318 anchoring-to-concrete provisions for concrete breakout in shear are predicated on failure occurring at a fixed edge when a shear load acts towards that edge . Consideration must also be given to concrete breakout failure in shear when the shear load acts parallel to a fixed edge . Per ACI 318-19 Section 17.7.2.1 ( c ), when shear load acts parallel to a fixed edge , the nominal concrete breakout strength for the anchorage ( V cb or V cbg
) is calculated as if the load acts towards that edge , but the calculated values for either V cb or V cbg are multiplied by 2 .
PROFIS Engineering considers concrete breakout failure for shear towards an edge and shear parallel to an edge via a modification factor that it designates
ψ parallel , V
. If the nominal concrete breakout strength ( V cb or V cbg
) is being calculated for shear load applied towards a fixed edge , PROFIS Engineering calculates ( V cb or V cbg
) using a modified Eq . ( 17.7.2.1a ) or Eq . ( 17.7.2.1b ) that includes the PROFIS Engineering parameter “ ψ parallel , V
”, with ψ parallel , V = 1.0 .
V cb
=
A Vc ψed , V ψ c , V ψ h , V
V b
( 17.7.2.1a )
A Vc0
( PROFIS Engineering )
PROFIS Engineering includes an additional modification factor ( ψ parallel , V ) when calculating V cb per Eq . ( 17.7.2.1a ) and V cbg per Eq . ( 17.7.2.1b ). For the example below , shear perpendicular to ( i . e . towards ) the y- edge and shear parallel to the x + edge need to be considered with respect to concrete breakout failure . PROFIS Engineering calculates V cbg for both conditions .
PROFIS Engineering calculates V cbg for the y- edge using ψ parallel , V
= 1.0 .
V cb
=
A Vc ψed , V ψ c , V ψ h , V ψ parallel , V
V b
A Vc0
V cb
=
A Vc ψed , V ψ c , V ψ h , V ψ parallel , V
V b
A Vc0
If the nominal concrete breakout strength ( V cb or V cbg
) is being calculated for shear load applied parallel to a fixed edge , PROFIS Engineering calculates ( V cb or V cbg
) using a modified Eq . ( 17.7.2.1a ) or Eq . ( 17.7.2.1b ) that includes the PROFIS Engineering parameter “ ψ parallel , V
”, with ψ parallel , V = 2.0 .
V cbg
= A Vc ψ ec , V ψ ed , V ψ c , V ψ h , V
V b
( 17.7.2.1b )
A Vc0
( PROFIS Engineering )
PROFIS Engineering calculates V cbg for the x + edge using ψ parallel , V
= 2.0 .
V cbg
= A Vc ψ ec , V ψ ed , V ψ c , V ψ h , V ψ parallel , V
V b
A Vc0
V cbg
= A Vc ψ ec , V ψ ed , V ψ c , V ψ h , V ψ parallel , V
V b
A Vc0
If a corner application is being considered with shear load acting towards one of the corner edges , PROFIS Engineering calculates V cb or V cbg for shear towards that edge and V cb or V cbg for shear parallel to the other edge . The results for the smallest calculated V cb or V cbg value are shown in the report .
If a corner application is being considered with shear load acting at an angle to the corner edges , PROFIS Engineering calculates V cb or V cbg for shear towards each edge and V cb or V cbg for shear parallel to each edge . The calculated V cb or
V cbg value for each edge is checked against the shear load component being considered for that edge , and the results for the highest utilization ( V ua
/ ϕV n
) are shown in the report .
Reference the Equations and Results sections of the PROFIS Engineering report for more information on the following parameters :
• V cb
: nominal concrete breakout strength in shear for a single anchor
• V cbg
: nominal concrete breakout strength in shear for a group of anchors in shear
• V ua
: factored shear load
• ϕ ( V cb or V cbg
): design concrete breakout strength in shear
190 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions