PART 4 SHEAR LOAD
Pryout Failure Mode ( Concrete Breakout )
Calculations A Nc0
Calculations 318-14 Chapter 17 Provision Comments for PROFIS Engineering
A Nc0
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 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 ). ( 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 cb of a single anchor or N cbg of a group of anchors , shall not exceed : a ) For a single anchor
When calculating the nominal concrete pryout strength in shear ( V cp or V cpg
), the parameter A Nc0 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 Nc0 is calculated with the effective embedment depth of the anchor
( h ef ) input into the PROFIS Engineering model . The geometry for A Nc0 is defined by a projected distance of 1.5h ef from the anchor in the x and y directions . The figure below illustrates how A Nc0 is calculated . a ) For a group of anchors
N cb
= A Nc ψ ed , Na ψ c , N ψ cp , N
N b
( 17.4.2.1a )
A Nc0
N cbg
= A Nc ψ ec , N ψ ed , N ψ c , N ψ cp , N
N b
( 17.4.2.1b )
A Nc0
……………………………………………………….. A Nc is the projected concrete failure area of a single anchor or group of anchors that shall be approximated as the base of the rectilinear geometrical figure that results from projecting the failure surface outward 1.5h ef from the centerlines of the anchor , or in the case of a group of anchors , from a line through a row of adjacent anchors . A Nc shall not exceed nA Nc0
, where n is the number of anchors in the group that resist tension . A Nc0 is the projected concrete failure area of a single anchor with an edge distance equal to or greater than 1.5h ef
A Nc0
= 9h ef
2
( 17.4.2.1c )
A Nc0
= ( 1.5h ef + 1.5h ef
) ( 1.5h ef + 1.5h ef
)
= ( 9.0h ef
) 2
For cast-in-place anchors , PROFIS Engineering permits users to input h ef values ranging between 4d anchor and 25 ”.
Cast-in anchors : 4d anchor ≤ h ef
≤ 25 ”.
For post-installed mechanical anchors , PROFIS Engineering permits users to input specific h ef values that are relative to a specific diameter as given in the ICC-ES evaluation report for the anchor .
Post-installed mechanical anchors : reference product approval .
For post-installed adhesive anchors , PROFIS Engineering permits users to input a range of h ef values that are relative to a specific diameter as given in the ICC-ES evaluation report for the anchor .
Post-installed adhesive anchors : h ef , min ≤ h ef
≤ h ef , max . Reference the product approval for h ef , min and h ef , max values .
Reference the Variables section of the PROFIS Engineering report for more information on h e f .
Reference the Equations section of the PROFIS Engineering report for more information on A Nc
.
277 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions