2.0 SHEAR
2.1 Concrete Breakout Failure Mode
Equations V cbg
Equations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
V cbg
= A Vc ψ ec , V ψ ed , V ψ c , V ψ h , V ψ parallel , V
V b
A Vc0
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
( 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 .
where ψ ec , V , ψ ed , V
, ψ c , V , and ψ h , V are given in 17.7.2.3 , 17.7.2.4 , 17.7.2.5 , and 17.7.2.6 respectively . PROFIS Engineering includes an additional modification factor ( ψ parallel , V
) in Eq . ( 17.5.2.1a ) and Eq .
( 17.5.2.1b ). PROFIS Engineering calculations for V cbg
:
V cbg
= A Vc ψ ec , V ψ ed , V ψ c , V ψ h , V ψ parallel , V
V b
A Vc0
PROFIS Engineering calculations for shear load acting at a corner . Check ( V ua
/ V cbg , x ) versus ( V ua
/ V cbg , y
) and take the highest utilization (%). calculate V cbg , x
ACI 318-19 provisions for concrete breakout failure in shear include two equations for calculating the “ nominal concrete breakout strength ” in shear :
• Eq . ( 17.7.2.1a ) for calculating the nominal concrete breakout strength for a single anchor in shear ( V cb
).
• Eq . ( 17.7.2.1b ) for calculating the nominal concrete breakout strength for a group of anchors in shear ( V cbg
).
Concrete breakout in shear is calculated for shear load acting towards ( i . e . perpendicular to ) a fixed edge . If shear load acts parallel to a fixed edge , Section 17.7.2.1 ( c ) requires V cb or V cbg to be calculated as if the shear load acts towards the fixed edge , and the value calculated for V cb or V cbg to be doubled . The PROFIS Engineering parameter that is designated in the report as “ ψ parallel , V
” indicates whether the software is calculating concrete breakout for shear load acting towards a fixed edge ( ψ parallel , V
= 1.0 ) or parallel to a fixed edge ( ψ parallel , V
= 2.0 ).
If a shear load acts at an angle with respect to two fixed edges , Section 17.7.2.1 ( d ) requires V cb or V cbg to be calculated with respect to each fixed edge . The calculated value for V cb or V cbg is checked against the component of the shear load that acts towards each fixed edge . PROFIS Engineering calculates V cb or V cbg for load acting towards each fixed edge as well as load acting parallel to each fixed edge . The software then checks the calculated V cb or V cbg value for each load condition ( towards the edge and parallel to the edge ) against the resultant shear load rather than the shear load component acting on each edge . This is a conservative design assumption .
Reference the Calculations section of the PROFIS Engineering report for more information on the following parameters :
A Vc
: area of influence for anchors in shear
A Vc0
: area of influence for single anchor in shear
ψ ec , V
: shear modification factor for eccentricity
ψ ed , V
: shear modification factor for edge distance
ψ h , V
: modification factor for thin slabs
V b
: basic concrete breakout strength in shear
Reference the Variables section of the PROFIS Engineering report for information on : ψ c , V
: modification factor for cracked concrete
ψ parallel , V
: modification factor for shear parallel to a fixed edge calculate V cbg , y
165 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions