PART 4 SHEAR LOAD
Pryout Failure Mode ( Pryout Bond )
Equation V cp
Equation 318-14 Chapter 17 Provision Comments for PROFIS Engineering
V cp
= k cp
A Na ψed , Na ψ cp , Na
N ba
A Na0
17.5.3.1 The nominal pryout strength , V cp for a single anchor …….. shall not exceed :
( a ) For a single anchor
V cp
= k cp
N cp
( 17.5.3.1a )
For cast-in , expansion , and undercut anchors , N cp shall be taken as N cb determined from Eq .
( 17.4.2.1a ), and for adhesive anchors , N cp shall be the lesser of N a determined from Eq . ( 17.4.5.1a ) and N cb determined from Eq . ( 17.4.2.1a ) ………………………………………………………
17.4 . 2.1 The nominal concrete breakout strength in tension , N cb of a single anchor …….. shall not exceed : ( a ) For a single anchor
N cb
= A Nc ψ ed , N ψ c , N ψ cp , N
N b
( 17.4.2.1a )
A Nc0
17.4.5.1 The nominal bond strength in tension , N a of a single adhesive anchor …….. shall not exceed : ( a ) For a single adhesive anchor
Concrete pryout is a shear failure mode that is calculated for cast-in-place anchors and post-installed anchors . ACI 318-14 Section 17.5.3.1 defines the nominal pryout strength for a single adhesive anchor ( V cp
) as the product of k cp and the smaller of N cb calculated per Eq . ( 17.4.2.1a ) and N a calculated per Eq .
( 17.4.5.1a ). Nominal pryout strength ( N cp
) 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 , a single adhesive anchor is subjected to only a shear load . No tension load acts on the anchor ; therefore , neither nominal concrete breakout strength ( N cb
) nor nominal bond strength ( N a ) are considered as tension design parameters , but a pryout parameter “ N cp ” corresponding to the smaller of N cb calculated per Eq . ( 17.4.2.1a ) and N a calculated per Eq . ( 17.4.5.1a ) is considered . adhesive anchor systems No tension load applied : N cb and N a
= 0 . Shear load applied , so calculate concrete pryout ( k cp
N cp
). adhesive anchor system : V cp = k cp
MIN { N cb
; N a }.
N a
=
A Na ψed , Na ψ cp , Na
N ba
( 17.4.5.1a )
A Na0
Reference the Variables section of the PROFIS Engineering report for information on : k cp
: Coefficient for pryout strength
Reference the Calculations section of the PROFIS Engineering report for more information on the following parameters :
A Na
: Area of influence for anchors in tension
A Na0
: Area of influence for single anchor in tension
ψ ed , Na
: Tension modification factor for edge distance
ψ cp , Na
: Modification factor for splitting
N ba
: Basic bond strength in tension
206 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions