PART 4 SHEAR LOAD
Pryout Failure Mode ( Pryout Bond )
Calculations ψ ed , Na
Calculations 318-14 Chapter 17 Provision Comments for PROFIS Engineering
ψ ed , Na
17.4.5.4 The modification factor for edge effects for single adhesive anchors or adhesive anchor groups loaded in tension , ψ ed , Na
, shall be calculated as
If c a , min ≥ c Na
, then ψ ed , Na = 1.0 ( 17.4.5.4a )
If c a , min < c Na
, then ψ ed , Na
= 0.7 + 0.3
17.4.5.1 …………………………………………………. where c a , min ( 17 . 4 . 5 . 4b )
c Na
When calculating the nominal concrete pryout strength in shear ( V cp or V cpg
), the parameter ψ ed , Na is a modification factor that accounts for fixed edge distances less than “ c Na ”, where c Na is the edge distance parameter calculated per Eq . ( 17.4.5.1d ) for the adhesive anchor being modeled in PROFIS Engineering .
It is important to understand that “ ψ ed , Na ” calculated for bond failure in tension is not necessarily the same as “ ψ ed , Na
” 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 3 , 4 , 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 c Na
. c Na
= 10d a т uncr 17 . 4 . 5 . 1d 1100
and the constant 1100 carries the unit of lb / in 2 .
Since anchors 1 and 2 are in compression , the fixed edge distance in the -x direction from anchors 3 and 4 that is relevant to the bond strength tension calculations equals c a1
+ the spacing between anchors 1 and 3 ( s x13 ). Assuming c a1
+ s x13 is greater than c Na
, the only fixed edge distance that is considered for ψ ed , Na when calculating bond strength in tension is the distance in the + y direction ( c a2
). ψ ed , Na would be calculated for bond strength in tension as follows :
ψ ed , Na
= 0.7 + 0.3 ( c a2 / c Na
)
237 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions