PART 4 SHEAR LOAD
Pryout Failure Mode ( Pryout Bond )
Calculations A Na0
Calculations 318-14 Chapter 17 Provision Comments for PROFIS Engineering
A Na0
17.5.3.1 The nominal pryout strength , V cp for a single anchor or V cpg for a group of anchors , 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 c p shall be the lesser of N a determined from Eq . ( 17.4.5.1a ) and N cb determined from Eq . ( 17.4.2.1a ). ( 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 ) ……………………………………………………
17.4.5.1 The nominal bond strength in tension , N a of a single anchor or N ag of a group of anchors , shall not exceed : a ) For a single adhesive anchor
When calculating the nominal concrete pryout strength in shear ( V cp or V cpg
), the parameter A Na0 is a modification factor that accounts for the area of influence assumed to develop in concrete when a shear load applied to a single anchor without the influence of any fixed edges creates a prying ( i . e . tension ) action on the anchor . A Na0 is calculated per ACI 318-14 Eq . ( 17.4.5.1c ). The parameter “ c Na
” in this equation is calculated per Eq . ( 17.4.5.1d ), and corresponds to an assumed projected distance on either side of the anchor in the x and y directions .
The figure below illustrates how A Na0 is calculated . b ) For a group of adhesive anchors
N a
= A Na ψ ed , Na ψ cp , Na
N ba
( 17.4.5.1a )
A Na0
N ag
= A Na ψ ec , Na ψ ed , Na ψ cp , Na
N ba
( 17.4.5.1b )
A Na0
……………………………………………………….. A Na is the projected influence area of a single adhesive anchor or group of adhesive anchors that shall be approximated as a rectilinear area that projects outward a distance c Na from the centerline of the adhesive anchor , or in the case of a group of adhesive anchors , from a line through a row of adjacent adhesive anchors . A Na shall not exceed nA Na0
, where n is the number of adhesive anchors in the group that resist tension loads . A Na0 is the projected influence area of a single adhesive anchor with an edge distance equal to or greater than c Na
where
and constant 1100 carries the unit of lb / in 2 .
A Na0
= ( 2c Na ) 2 ( 17.4.5.1c ) c Na
= 10d a т uncr ( 17 . 4 . 5 . 1d ) 1100
A Na0
= ( c Na + c Na
) ( c Na + c Na
)
= ( 2.0c Na
) 2
Adhesive anchor systems can be shown compliance under the International Building Code ( IBC ) via testing per the ICC-ES acceptance criteria AC308 and the ACI standard ACI 355.4 . The parameter “ т uncr
” in Eq . ( 17.4.5.1d ) corresponds to the characteristic bond stress in uncracked concrete of the adhesive product selected for the PROFIS Engineering application being modeled . Values for т uncr are derived from AC308 / ACI 355.4 testing , and are shown as “ т k , uncr
” in the ICC-ESR for the adhesive anchor system . The PROFIS Engineering report designates this parameter “ т k , c , uncr
”.
Reference the Variables section of the PROFIS Engineering report for more information on the parameters т k , c , uncr and d a
.
Reference the Equations section of the PROFIS Engineering report for more information on A Na0 and c Na .
Example : Example of a bond strength table in an ICC-ESR showing characteristic bond stress values ( т k , uncr
).
235 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions