PART 4 SHEAR LOAD
Pryout Failure Mode ( Pryout Bond )
Equation V cpg
Equation 318-14 Chapter 17 Provision Comments for PROFIS Engineering
V cpg
= k cp
A Na ψec1 , Na ψ ec2 , Na ψ ed , Na ψ cp , Na
N ba
A Na0
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
………………………………………….
Concrete pryout is a shear failure mode that is calculated for cast-in-place anchors and post-installed anchors . When designing post-installed adhesive anchors , ACI 318-14 Section 17.5.3.1 defines the nominal pryout strength for a group of anchors ( V cpg
) as the product of the coefficient for pryout strength ( k cp ) and the smaller of N cbg calculated per Eq . ( 17.4.2.1b ) and N ag calculated per Eq . ( 17.4.5.1b ). Nominal pryout strength for an anchor group ( N cpg
) is predicated on the number of anchors subjected to shear load , which may be different than the number of anchors subjected to tension load .
For the example illustrated below , four anchors are subjected to a tension load , but all six anchors are subjected to a shear load . Therefore , with respect to tension , concrete breakout ( N cbg
) and bond strength ( N ag
) are calculated for anchors 1,2,3 and 4 ; but with respect to shear , a pryout parameter “ N cpg
” corresponding to the lesser of N cbg and N ag is calculated for anchors 1,2,3,4,5 and
6 .
N cbg
= A Nc ψ ec , N ψ ed , N ψ cN ψ cp , Na
N ba
( 17.4.2.1b )
A Nc0
17.4.5.1 The nominal bond strength in tension ………… N ag of a group of adhesive anchors , shall not exceed
( b ) 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
Summary of ACI 318-14 adhesive anchor system pryout calculations :
V cpg
= k cp MIN { N cbg
; N ag }.
207 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions