2.0 SHEAR
2.2 Pryout Failure Mode
Calculations ψ ed , N
Calculations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
ψ ed , N
17.6 . 2.4.1 Modification factor for edge effects for single anchors or anchor groups loaded in tension , ψ ed , N
, shall be determined by ( a ) or ( b ).
( a ) If c a , min ≥ 1.5h ef
, then ψ ed , N = 1.0 ( 17.6.2.4.1a )
( b ) If c a , min < 1.5h ef
, then ψ ed , N = 0.7 + 0.3 c a , min ( 17 . 6 . 2 . 4 . 1b )
1.5h ef
When calculating the nominal concrete pryout strength in shear ( V cp or V cpg
), the parameter ψ ed , N is a modification factor that accounts for fixed edge distances less than 1.5h ef , where h ef corresponds to the effective embedment depth that has been selected for the anchor being modeled in PROFIS Engineering .
It is important to understand that “ ψ ed , N ” calculated for concrete breakout failure in tension is not necessarily the same as “ ψ ed , N
” calculated for concrete pryout failure in shear since the number of anchors in tension may not be the same as the number of anchors in shear . In the illustration below , a fixture is being attached with six anchors , which are numbered 1-6 . Anchors 2 , 3 , 5 and 6 are subjected to a tension load , but all six anchors are subjected to a shear load . The edge distance c a1 is less than the edge distance c a2 , and both edge distances are less than 1.5h ef
.
Since anchors 1 and 4 are in compression , the fixed edge distance in the -x direction from anchors 2 and 5 that is relevant to concrete breakout in tension calculations equals c a1
+ the spacing between anchors
1 and 2 ( s x12 ). Assuming c a1
+ s x12 is greater than 1.5h ef
, the only fixed edge distance that is considered for ψ ed , N when calculating concrete breakout in tension is the distance in the + y direction ( c a2 ).
ψ ed , N would be calculated for concrete breakout in tension as follows :
ψ ed , N
= 0.7 + 0.3 ( c a2 / 1.5h ef
)
All six anchors are in shear , so both c a1 and c a2
( which are less than 1.5h ef ) are considered for ψ ed , N when calculating concrete pryout in shear . Since c a1 is less than c a2
, ψ ed , N would be calculated for concrete pryout in shear using c a1 as follows :
ψ ed , N
= 0.7 + 0.3 ( c a1 / 1.5h ef
)
Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
c a , min
: parameter for the smallest fixed edge being modeled .
h ef
: parameter for anchor effective embedment depth .
Reference the Equations section of the PROFIS Engineering report for more information on ψ ed , N when calculating concrete pryout strength .
231 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions