2.0 SHEAR
2.2 Pryout Failure Mode
Equations N b = k c λ a
Equations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
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N b
= k c λ a
|
1.5 h f ́c ef
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17.7.3.1 Nominal pryout strength , V cp for a single anchor or V cpg of an anchor group satisfying |
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17.5.1.3.1 , shall not exceed ( a ) or ( b ), respectively . |
( a ) For a single anchor
( b ) For an anchor group
where
k cp
= 1.0 for h ef < 2.5 in . k cp
= 2.0 for h ef ≥ 2.5 in .
V cp
= k cp
N cp
( 17.7.3.1a )
V cpg
= k cp
N cpg
( 17.7.3.1b )
17.7.3.1.1 For cast-in anchors and post-installed expansion , screw , and undercut anchors , N cp shall be taken as N cb calculated by Eq . ( 17.6 . 2.1a ) …………………..
17.7.3.1.2 For cast-in anchors and post-installed expansion , screw , and undercut anchors , N cpg shall be taken as N cbg calculated by Eq . ( 17.6 . 2.1b ) …………………… 17.6 . 2.1 Nominal concrete breakout strength in tension , N cb of a single anchor or N cbg of an anchor group satisfying 17.5.1.3.1 , shall be calculated by ( a ) or ( b ), respectively : ( a ) For a single anchor
( b ) For an anchor group
N cb
= A Nc ψ ed , N ψ c , N ψ cp , N
N b
( 17.6.2.1a )
A Nc0
N cbg
= A Nc ψ ec , N ψ ed , N ψ c , N ψ cp , N
N b
( 17.6.2.1b )
A Nc0
………………………………………….
17.6.2.2.1 Basic concrete breakout strength of a single anchor in tension in cracked concrete , N b , shall be calculated by Eq . ( 17.6.2.2.1 ) except as permitted in 17.6.2.2.3
N b
= k c λ a ƒ ́c h ef
1.5
( 17.6.2.2.1 )
When calculating the nominal concrete pryout strength in shear ( V cp or V cpg
), the parameter “ N b
” corresponds to the “ basic concrete breakout strength in tension ” that is used to calculate a concrete breakout strength ( N cb or N cbg ).
The parameter N b corresponds to a calculated concrete breakout strength for a single anchor without any fixed edge or spacing influences . The parameter “ coefficient for the basic concrete breakout strength in tension ” ( k c
) defaults to a value of 24 for cast-in-place anchors , corresponding to cracked concrete conditions . PROFIS Engineering always uses a k c
-value of 24 for cast-in-place anchors installed at an effective embedment depth ( h ef
) less than 11 in , for both cracked and uncracked concrete conditions . When designing cast-in-place anchors in uncracked concrete , the modification factor ψ c , n can be increased from a value of 1.0 ( cracked concrete conditions ) to a value of 1.25 ( uncracked concrete conditions ).
The default k c
-value noted for post-installed mechanical anchors and adhesive anchor systems in ACI 318-19 Section 17.6.2.2.1 equals 17 . Section 17.6.2.2.2 notes that testing per the ACI test standards ACI 355.2 and ACI 355.4 can be used to derive k c values for these anchors . k c values for mechanical anchors can be derived from testing per the ICC-ES acceptance criteria AC193 in conjunction with the ACI standard ACI 355.2 . k c values for adhesive anchor systems can be derived from testing per the ICC-ES acceptance criteria AC308 in conjunction with the ACI standard ACI 355.4 . These k c values are specific to either cracked or uncracked concrete conditions ; are relevant to the effective embedment depth range for the anchor ; and are provided in an ICC-ES evaluation report ( ESR ). PROFIS Engineering uses the k c
-value that is given in the ICC-ES evaluation report for a post-installed anchor to calculate N b
.
Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
k c
: coefficient for basic concrete breakout strength in tension .
λ a
: lightweight concrete modification factor . ƒ ́c : concrete compressive strength .
h ef
: effective embedment depth that has been selected for the anchor being modeled . ψ c , N
: modification factor for cracked or uncracked concrete conditions .
Reference the Calculations section of the PROFIS Engineering report for more information on the parameter N b
. where k c
= 24 for cast-in anchors and 17 for post-installed anchors . 17.6.2.2.2 k c for post-installed anchors shall be permitted to be increased based on ACI 355.2 or ACI 355.4 product-specific tests , but shall not exceed 24 .
17.6.2.2.3 For single cast-in headed studs and headed bolts with 11 in . ≤ h ef ≤ 25 in ., N b
, shall be calculated by :
N b
= 16λ a ƒ ́c h ef
5 / 3
( 17.6.2.2.3 )
214 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions