2.0 SHEAR
2.1 Concrete Breakout Failure Mode
Calculations ψ ed , V
Calculations ACI 318-19 Chapter 17 Provision ents for PROFIS Engineering
ψ ed , V
17.7.2.4.1 Modification factor for edge effects for single anchors or anchor groups loaded in shear , ψed , V , shall be determined by ( a ) or ( b ) using the lesser value of c a2
.
( a ) If c a2 ≥ 1.5c a1
, then ψ ed , V = 1.0 ( 17.7.2.4.1a )
( b ) If c a2 < 1.5c a1
, then ψ ed , V = 0.7 + 0.3 c a2 ( 17 . 7 . 2 . 4 . 1b )
1.5c a1
17.7.2.1 Nominal concrete breakout strength in shear , Vcb of a single anchor or Vcbg 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 ψ ed , V is a modification factor that is used to account for fixed edge distances perpendicular to the direction of the applied shear load that are less than
1.5c a1
. Shear concrete breakout failure calculations are predicated on the fixed edge distance in the direction of the applied shear load ( c a1
). Edge distances perpendicular to the direction of the applied shear load are designated c a2
. If c a2 is less than 1.5c a1 , ψ ed , V is calculated per Eq . ( 17.7.2.4.1b ).
If more than one fixed edge perpendicular to the direction of the applied shear load exists , the smallest of these edge distances is used to calculate ψ ed , V
. For the application in the illustration below , if c a2 , x-
< c a2 , x + : ψ ed , V
= 0.7 + 0.3 ( c a2 , x-
/ 1.5c a1 )
Per Section 17.7.2.1.2 , when anchoring into a narrow section , the checks noted in ( a ) through ( c ) should also be made to determine if a modified c a1
-value should be used for the shear concrete breakout calculations . For the application below , h a is greater than 1.5c a1 , so no modified c a1
-value would be calculated .
( 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 Vcb or Vcbg 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 .
17.7.2.1.2 If anchors are located in narrow sections of limited thickness such that both edge distances c a2 and thickness ha are less than 1.5c a1 , the value of c a1 used to calculate A Vc in accordance with 17.7.2.1.1 as well as for the equations in 17.7.2.1 through 17.7.2.6 shall not exceed the greatest of ( a ) through ( c ).
( a ) c a2 / 1.5 , where c a2 is the greatest edge distance
( b ) h a
/ 1.5
( c ) s / 3 , where s is the maximum spacing perpendicular to direction of shear , between anchors within a group .
Per Section 17.7.2.1 ( c ), if shear force acts parallel to a fixed edge , ψ ed , V is taken equal to 1.0 . For the application illustrated below , shear load ( V ua ) acts parallel to the y- edge . the value for c a2 would be used to calculate A Vc
, but ψ ed , V would be taken equal to 1.0 .
Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
c a1
: fixed edge distance in the direction of the applied shear load
c a2
: fixed edge distance perpendicular to the direction of the applied shear load
h a
: concrete thickness
Reference the Calculations section of the PROFIS Engineering report for more information on ψ ed , V
.
195 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions