PART 4 SHEAR LOAD
Pryout Failure Mode ( Concrete Breakout )
Calculations ψ ec2 , N
Calculations 318-14 Chapter 17 Provision Comments for PROFIS Engineering
ψ ec2 , N
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 . 2.1 The nominal concrete breakout strength in tension …….. N cbg of a group of anchors , shall not exceed :
( b ) For a group of anchors
………………………………………
N cbg
= A Nc ψ ec , N ψ ed , N ψ c , N ψ cp , N
N b
( 17.4.2.1b )
A Nc0
17.4.2.4 The modification factor for anchor groups loaded eccentrically in tension , ψ ec , N shall be calculated as
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 concrete breakout strength ( N cbg
), calculated per Eq . ( 17.4.2.1b ), but with respect to concrete pryout failure . The parameter “ ψ ec , N
” in Eq . ( 17.4.2.1b ) 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 , N 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 . ( 17.4.2.4 ) and designates this parameter “ ψ ec2 , N
”. PROFIS Engineering designates the eccentricity parameter e ́N in Eq . ( 17.4.2.4 ) “ 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 ”. ψ ec , N
=
1
1 + 2e ́N
3h ef
( 17.4.2.4 ) but ψ ec , N shall not be taken greater than 1.0 . If the loading on an anchor group is such that only some anchors are in tension , only those anchors that are in tension shall be considered when determining the eccentricity e ́N for use in Eq . ( 17.4.2.4 ) and for the calculation of N cbg according to
Eq . ( 17.4.2.1b ). In the case where eccentric loading exists about two axes , the modification factor , ψ ec , N
, shall be calculated for each axis individually and the product of these factors used as ψ ec , N in Eq .
( 17.4.2.1b ).
PROFIS Engineering calculates “ ψ ec , N ” for both directions .
|
ψ ec1 , N
=
|
1 |
ψ ec2 , N
=
|
1 |
|
1 + 2e c1 , N
3h ef
|
|
1 + 2e c2 , N
3h ef
|
For this example , the value for “ ψ ec , N ” used in Eq . ( 17.4.2.1b ) equals the product of ψ ec1 , N and ψ ec2 , N : ψ ec , N
= ( ψ ec1 , N )( ψ ec2 , N
).
280 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions