PART 4 SHEAR LOAD
Pryout Failure Mode ( Concrete Breakout )
Calculations ψ ed , N
Calculations 318-14 Chapter 17 Provision Comments for PROFIS Engineering
ψ ed , N
17.4 . 2 . 5 The modification factor for edge effects for single anchors or anchor groups loaded in tension , ψ ed , N
, shall be calculated as If c a , min
≥ 1.5h ef , then ψ ed , Na
= 1.0 ( 17.4.2.5a )
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 hef corresponds to the effective embedment depth that has been selected for the anchor being modeled in PROFIS Engineering .
If c a , min < 1.5h ef
, then ψ ed , Na = 0.7 + 0.3 c a , min ( 17 . 4 . 2 . 5b )
1.5h ef
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
= 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 .
282 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions