PROFIS ENGINEERING REPORT SHEAR LOAD
Concrete Breakout Failure Mode
Calculations ψ ec , V
Calculations 318-14 Chapter 17 Provision Comments for PROFIS Engineering
ψ ec , V
17.5.2.5 The modification factor for anchor groups loaded eccentrically in shear , ψ ec , V , shall be calculated as ψ ec , V
= but ψ ec , V shall not be taken greater than 1.0 .
1
1 + 2e ́V
3c a1
( 17.5.2.5 )
If the loading on an anchor group is such that only some anchors are loaded in shear in the same direction , only those anchors that are loaded in shear in the same direction shall be considered when determining the eccentricity e ́V for use in Eq . ( 17.5.2.5 ) and for the calculation of V cbg according to Eq . ( 17.5.2.1b ).
17.5 . 2.1 The nominal concrete breakout strength in shear , V cb of a single anchor or V cbg of a group of anchors , shall not exceed : ( a ) For shear force perpendicular to the edge on a single anchor
V cb
=
A vc ψed , V ψ c , y ψ h , V
V b
( 17.5.2.1a )
A vc0
( b ) For shear force perpendicular to the edge on a group of anchors
V cbg
= A vc ψ ec , V ψ ed , V ψ c , V ψ h , V
V b
( 17.5.2.1b )
A vc0 ψ ec , V is a modification factor that is used to account for a resultant shear load that is eccentric with respect to the centroid of anchors that are loaded in shear . ψ ec , V is only considered when calculating the nominal concrete breakout strength in shear for an anchor group ( V cbg
).
The text below explains how PROFIS Engineering would determine the shear eccentricity parameter ( e ́V ) that is used to calculate ψ ec , V for an example when a torsion moment acts on four anchors . Assume a fixed edge is present in the x + direction and that concrete breakout will occur at the x + edge .
The moment creates loads in the x direction as follows :
• V 2 , x (+) on anchor 2 and V 4 , x
(+) on anchor 4
• V 1 , x ( - ) on anchor 1 and V 3 , x
( - ) on anchor 3
The moment creates loads in the y direction as follows :
• V 3 , y (+) on anchor 3 and V 4 , y
(+) on anchor 4
• V 1 , y ( - ) on anchor 1 and V 2 , y
( - ) on anchor 2 PROFIS Engineering calculates a resultant shear load ( V resultant
) from the loads acting on anchors 1-4 that influence the x + fixed edge . PROFIS Engineering would assume only loads V 2 , x and V 4 , x influence the fixed edge with respect to loads acting in the x direction . Likewise , PROFIS Engineering would assume only loads
V 3 , y and V 4 , y influence the fixed edge with respect to loads acting in the y direction .
V resultant can be calculated with these loads as shown below . Concrete breakout is assumed to occur from anchors 3 and 4 . V resultant is eccentric ( e ́V ) with respect to the centroid of these anchors . This shear eccentricity ( e ́V ) can be calculated knowing the angle θ and the spacing ( s ) between anchors 3 and 4 .
V resultant
= [( V 2 , x + V 4 , x
) 2 + ( V 3 , y + V 4 , y
) 2 ] 0 . 5
= [( V x ) 2 + ( V y
) 2 ] 0 . 5 tan -1 θ = ( V x / V y
)
e ́V = ( s / 2 ) ( sin θ )
Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
e ́V : Parameter for shear eccentricity
c a1
: Parameter for edge distance in the direction of the applied shear load
Reference the Equations section of the PROFIS Engineering report for more information on ψ ec , V
.
191 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions