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ψ cp , N
= MAX
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c a , min , 1.5h ef ≤1 . 0
c ac
c ac
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17.4 . 2.7 The modification factor for post-installed anchors designed for uncracked concrete in accordance with 17.4 . 2.6 without supplementary reinforcement to control splitting , ψ cp , N
, shall be calculated as follows using the critical distance c ac as defined in 17.7.6
If c a , min ≥ 1.5c ac
, then ψ cp , N = 1.0 ( 17.4.2.7a )
If c a , min < c ac
, then ψ cp , N = c a , min
( 17.4.2.7b ) c ac
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ψ cp , N is a modification factor that considers splitting failure when calculating the nominal concrete breakout strength in tension ( N cb or N cbg
) for a post-installed anchor . Since ACI 318 anchoring-to-concrete provisions do not specifically consider concrete splitting as a failure mode , splitting is addressed through the
ψ cp , N modification factor . The parameter ψ cp , N is only considered when designing post-installed mechanical or adhesive anchors installed in uncracked concrete . Splitting failure will typically not occur for cast-in-place anchors ; therefore , the parameter ψ cp , N is not considered in PROFIS Engineering when modeling cast-inplace anchors .
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but ψ cp , N determined from Eq . ( 17.4.2.7b ) shall not be taken less than 1.5h ef
/ c ac , where the critical distance c ac is defined in 17.7.6 .
For all other cases , including cast-in anchors , ψ cp , N shall be taken as 1.0 .
17.4 . 2.6 For anchors located in a region of a concrete member where analysis indicates no cracking at service load levels ……………..
17.7.6 Unless determined from tension tests in accordance with ACI 355.2 or ACI 355.4 , the critical edge distance c ac shall not be taken less than :
Adhesive anchors ................................................ 2h ef
Undercut anchors ................................................ 2.5h ef
Torque-controlled expansion anchors ............................... 4h ef
Displacement-controlled expansion anchors .......................... 4h ef
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Splitting failure is influenced by the distance of an anchor from a fixed edge “ in a region of a concrete member where analysis indicates no cracking at service load levels ”. The parameter c ac that is used to calculate ψ cp , N is defined in ACI 318 as the “ critical edge distance required to develop the basic strength as controlled by concrete breakout or bond of a post-installed anchor in tension in uncracked concrete without supplementary reinforcement to control splitting .” ψ cp , N does not need to be calculated if the smallest fixed edge distance ( c a , min ) is greater than or equal to c ac
, or if cracked concrete conditions are assumed . Testing per the ICC-ES acceptance criteria AC193 and the ACI test standard ACI 355.2 is used to derive c ac values for mechanical anchors . Testing per the ICC-ES acceptance criteria AC308 and the ACI test standard ACI 355.4 is used to derive c ac values for adhesive anchor systems . cac values derived from this testing are provided in an ICC-ESR . ACI 318-14 Section 17.7.6 provides c ac
-values for post-installed anchors ; however , these values are only intended to be used as “ guide values ” in the absence of c ac values derived from product-specific testing . PROFIS Engineering uses the c ac
-value that is given in the ICC-ES evaluation report for an anchor to calculate ψ cp , N
.
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The value for ψ cp , N that PROFIS Engineering calculates will be limited to |
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MAXIMUM { c a , min
/ c ac : 1.5h ef
/ c ac }
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where c a , min is the smallest fixed edge distance being modeled in the application and h ef is the effective embedment depth that has been selected for the anchor being modeled . |
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Reference the Variables section of the PROFIS Engineering report for more information on the following parameters : |
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c a , min
: The smallest fixed edge distance being modeled
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c ac
:
Value derived from testing per AC193 / ACI 355.2 or AC308 / ACI 355.4 for the anchor being modeled
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h ef
:
Effective embedment depth that has been selected for the anchor being modeled
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Reference the Calculations section of the PROFIS Engineering report for more information on the parameter ψ cp , N
.
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