PART 4 SHEAR LOAD
Pryout Failure Mode ( Pryout Bond )
Calculations ψ ec2 , Na
Calculations 318-14 Chapter 17 Provision Comments for PROFIS Engineering
ψ ec2 , Na
17.5.3.1 The nominal pryout strength , ………………… V cpg for a group of anchors , shall not exceed :
( b ) For a group of anchors
V cpg
= k cp
N cpg
( 17.5.3.1b )
For cast-in , expansion , and undercut anchors , N cpg shall be taken as N cbg determined from Eq .
( 17.4.2.1b ), and for adhesive anchors , N cpg shall be the lesser of N ag determined from Eq . ( 17.4.5.1b ) and N cbg determined from Eq . ( 17.4.2.1b ) ……………………………………………………
17.4.5.1 The nominal bond strength in tension ……………………… N ag of a group of anchors , shall not exceed :
a ) For a group of adhesive anchors
……………………………………………………
N ag
= A Na ψ ec , Na ψ ed , Na ψ cp , Na
N ba
( 17.4.5.1b )
A Na0
…………………………………………………. where
c Na
= 10d a т uncr 17 . 4 . 5 . 1d 1100
Concrete pryout strength for a group of anchors in shear ( V cpg ) is calculated per
Eq . ( 17.5.3.1b ). The parameter “ N cpg ” in this equation corresponds to the nominal bond strength ( N ag
), calculated per Eq . ( 17.4.5.1b ), but with respect to concrete pryout failure . The parameter “ ψ ec , Na
” in Eq . ( 17.4.5.1b ) is a modification factor that accounts for a resultant shear load that is eccentric with respect to the centroid of the anchors that are loaded in shear . ψ ec , Na is only considered for an anchor group loaded in shear when calculating V cpg
.
When shear load acting on a group of anchors is eccentric with respect to the y direction , PROFIS Engineering calculates “ ψ ec , N
” per Eq . ( 17.4.5.3 ) and designates this parameter “ ψ ec2 , Na
”. PROFIS Engineering designates the eccentricity parameter e ́N in Eq . ( 17.4.5.3 ) “ e c2 , N
” to likewise indicate that the software is considering eccentricity with respect to the y direction . If the resultant shear load acting on the anchorage is eccentric with respect to both the x and y directions ; PROFIS Engineering calculates “ ψ ec , N
” for both directions .
The illustration below shows how PROFIS Engineering considers shear eccentricity when calculating V cpg
. The resultant shear load ( V res
) is eccentric in both the x direction and y direction with respect to the centroid of the anchors that are in shear . PROFIS Engineering defines the eccentricity of the shear load in the x-direction as the parameter “ e c1 , N
” and eccentricity in the y-direction as the parameter “ e c2 , N ”. and the constant 1100 carries the unit of lb / in 2 .
17.4.5.3 The modification factor for adhesive anchor groups loaded eccentrically in tension , ψ ec , Na shall be calculated as ψ ec , Na
=
1
1 + e ́N c Na
( 17.4.5.3 ) but ψ ec , Na shall not be taken greater than 1.0 .
If the loading on an adhesive anchor group is such that only some adhesive anchors are in tension , only those adhesive anchors that are in tension shall be considered when determining the eccentricity e ́N for use in Eq . ( 17.4.5.3 ) and for the calculation of N ag according to Eq . ( 17.4.5.1b ). In the case where eccentric loading exists about two orthogonal axes , the modification factor ,
ψ ec , Na
, shall be calculated for each axis individually and the product of these factors used as ψ ec , Na in Eq . ( 17.4.5.1b ).
PROFIS Engineering calculates “ ψ ec , Na ” for both directions . ψ ec1 , Na
=
1
1 + e c1 , N c Na ψ ec2 , Na
=
1
1 + e c2 , N c Na
For this example , the value for “ ψ ec , Na ” used in Eq . ( 17.4.5.1b ) equals the product of ψ ec1 , Na and ψ ec2 , Na : ψ ec , Na
= ( ψ ec1 , Na )( ψ ec2 , Na
).
241 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions