PROFIS Design Guide: US-EN Summer 2021 | Page 252

PART 4 SHEAR LOAD

Pryout Failure Mode ( Concrete Breakout )
Equation V cp
Equation 318-14 Chapter 17 Provision Comments for PROFIS Engineering
V cp
= k cp
A Na ψed , N ψ c , N ψ cp , N
N b
A Nc0
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 , Na 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
N a
= A Na ψ ed , Na ψ cp , Na
N ba
( 17.4.5.1a )
A Na0
Concrete pryout is a shear failure mode that is calculated for cast-in-place anchors and post-installed anchors . When designing cast-in-place anchors and post-installed mechanical anchors , ACI 318-14 Section 17.5.3.1 defines the nominal pryout strength for a single anchor ( V cp
) as the product of the coefficient for pryout strength ( k cp
) and the nominal concrete breakout strength in tension for a single anchor ( N cb
). 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 ) and the nominal bond strength for a single anchor ( N a
).
The concrete breakout strength parameter ( N cb
) for pryout failure in shear is calculated per ACI 318-14 Eq . ( 17.4.2.1a ), but predicated on the number of anchors subjected to shear load , which may be different than the number of anchors subjected to tension load . Note that ( 17.5.3.1a ) denotes the “ concrete pryout strength ” parameter “ N cp
” to distinguish it from the tension concrete breakout strength parameter “ N cb
”.
For the example illustrated below , a single anchor is subjected to only a shear load . No tension load acts on the anchor ; therefore , nominal concrete breakout in tension ( N cb
) is not calculated , but a pryout parameter “ N cp
” corresponding to N cb calculated per Eq . ( 17.4.2.1a ) is calculated .
cast-in anchors and mechanical anchors No tension load applied : N cb
= 0 . Shear load applied , so calculate concrete pryout ( k cp
N cp
). cast in anchor : V cp = k cp
N cb mechanical anchor : V cp = k c p N cb
252 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions