PART 4 SHEAR LOAD
Pryout Failure Mode ( Pryout Bond )
Results V cpg
Results 318-14 Chapter 17 Provision Comments for PROFIS Engineering
V cpg
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 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 ) and the nominal bond strength for a group of anchors ( N ag
).
The bond strength parameter ( N ag
) for pryout failure in shear is calculated per ACI 318-14 Eq . ( 17.4.5.1b ), 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 ( 17.5.3.1b ) denotes the “ concrete pryout strength ” parameter “ N cpg
” to distinguish it from the bond strength parameter “ N ag
”.
For the example illustrated below , four anchors are subjected to a tension load , but all six anchors are subjected to a shear load . A nominal concrete breakout strength ( N cbg
) and a nominal bond strength ( N ag ) are calculated for anchors
1,2,3 and 4 ; but a pryout parameter “ N cpg ” corresponding to the smaller of N cbg calculated per Eq . ( 17.4.2.1b ), and N ag calculated per Eq . ( 17.4.5.1b ), is calculated for anchors 1,2,3,4,5 and 6 .
N cbg
= A Nc ψ ec , N ψ ed , N ψ c , N ψ cp , N
N b
( 17.4.2.1b )
A Nc0
17.4.5.1 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 pryout calculations for adhesive anchors .
adhesive anchor systems adhesive anchor system : V cpg
= k cp MIN { N cbg
; N ag }.
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 information on :
A Na
: Area of influence for anchors in tension
A Na0
: Area of influence for single anchor in tension
246 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions
ψ ec , Na
: Tension modification factor for eccentricity ψ ed , Na
: Tension modification factor for edge distance
ψ cp , Na
: Modification factor for splitting
N ba
: Basic concrete breakout strength in tension