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ψ ec , Na
=
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1
1 + e ́N
c Na
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≤ 1.0 |
17.7.3.1 Nominal pryout strength , ………………… Vcpg of an anchor group ……….. shall not exceed …..( b )………..
( b ) For an anchor group
V cpg
= k cp
N cpg
( 17.7.3.1b )
17.7.3.1.2 ………………. for adhesive anchors , N cpg shall be the lesser of N ag calculated by
Eq . ( 17.6.5.1b ) and Ncbg calculated by Eq . ( 17.6.2.1b ).
17.6.5.1 Nominal bond strength in tension ………… N ag of an adhesive anchor group
……………. shall be calculated by ……( b )………….
( b ) For an adhesive anchor group :
N ag
= A Na ψ ec , Na ψ ed , Na ψ cp , Na
N ba
( 17.6.5.1b )
A Na0
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Concrete pryout strength for a group of anchors in shear ( V cpg ) is calculated per Eq .
( 17.7.3.1b ). The parameter “ N cpg ” in this equation corresponds to the nominal bond strength
( N ag
), calculated per Eq . ( 17.6.5.1b ), but with respect to concrete pryout failure . It is important to understand that “ N ag
” calculated for bond failure in tension is not necessarily the same as “ N ag ” calculated for concrete pryout failure in shear . Reasons for this can include :
• the number of anchors in tension is not the same as the number of anchors in shear .
• the tension load may be eccentric with the anchors in tension but the shear load may not be eccentric with the anchors in shear .
• the shear load may be eccentric with the anchors in shear but the tension load may not be eccentric with the anchors in tension .
• tension and shear eccentricities are not necessarily equal .
When considering concrete pryout failure , the parameter “ ψ ec , Na
” in Eq . ( 17.6.5.3.1 ) is a modification factor that accounts for shear load eccentricity . Therefore , when calculating the nominal concrete pryout strength in shear using Eq . ( 17.7.3.1b ), the parameter ψ ec , Na 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 the nominal concrete pryout strength ( V cpg
).
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17.6.5.3.1 Modification factor for adhesive anchor groups loaded eccentrically in tension ,
ψ ec , Na shall be calculated by Eq . ( 17.6.5.3.1 ).
ψ ec , Na
=
1
1 + e ́N
c Na
( 17.6.5.3.1 )
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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 ”.
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17.6.5.3.2 If the loading on an adhesive anchor group is such that only some of the adhesive anchors are in tension , only those adhesive anchors that are in tension shall be considered for determining the eccentricity e ́N in Eq . ( 17.6.5.3.1 ) and for the calculation of N ag according to Eq . ( 17.6.5.1b ). |
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17.6.5.3.3 If a load is eccentric about two orthogonal axes , ψ ec , Na shall be calculated for each axis individually , and the product of these factors shall be used as ψ ec , Na in Eq .
( 17.6.5.1b ).
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If shear eccentricity exists in more than one direction , PROFIS Engineering calculates a ψ-modification factor for each direction using Eq . ( 17.6.5.3.1 ). PROFIS Engineering designates the ψ-modification factor for eccentricity in the x-direction “ ψ ec1 , Na
”, and the ψ-modification factor for eccentricity in the y-direction “ ψ ec2 , Na
”. Per Section 17.6.5.3.3 , PROFIS Engineering uses the product of these modification factors in Eq . ( 17.6.5.1b ) to calculate the pryout parameter ( N cpg
) per Eq . ( 17.7.3.1b ) when shear eccentricity exists in both the x and y directions .
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Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
e c1 , N
: parameter for shear eccentricity with respect to the x direction
e c2 , N
: parameter for shear eccentricity with respect to the y direction
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Reference the Calculations section of the PROFIS Engineering report for more information on the following parameters :
c Na
: edge distance parameter for adhesive anchors
ψ ec1 , Na
: modification factor for shear eccentricity with respect to the x direction
ψ ec2 , Na
: modification factor for shear eccentricity with respect to the y direction .
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