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ψ cp , Na
= MAX
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c a , min , c Na ≤1 . 0
c ac
c ac
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17.4.5.5 The modification factor for adhesive anchors designed for uncracked concrete in accordance with 17.4.5 . 2 without supplementary reinforcement to control splitting , ψ cp , Na
, shall be calculated as :
If c a , min
≥ c ac , then ψ cp , Na
= 1.0 ( 17.4.5.5a )
but ψ cp , Na determined from Eq . ( 17.4.5.5b ) shall not be taken less than c Na
/ c ac , where the critical distance c ac is defined in 17.7.6 . For all other cases , ψ cp , Na shall be taken as 1.0 .
17.4.5 . 2 ……… For adhesive 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 cac 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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ψ cp , Na is a modification factor that considers splitting failure when calculating the nominal bond strength in tension ( N a or N ag
) for an adhesive anchor system . Since ACI 318 anchoring-to-concrete provisions do not specifically consider concrete splitting as a failure mode , splitting is addressed through the ψ cp , Na modification factor . The parameter ψ cp , Na is only considered when designing adhesive anchors installed in uncracked concrete . Splitting failure will typically not occur for castin-place anchors ; therefore , a splitting modification factor is not calculated in PROFIS Engineering when modeling cast-in-place anchors .
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 , Na 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 , Na 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 AC308 and the ACI test standard ACI 355.4 is used to derive c ac values for adhesive anchor systems . c ac values derived from this testing are provided in an ICC-ESR ACI 318-14 Section 17.7.6 provides c ac values for postinstalled 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 adhesive anchor system to calculate ψ cp , Na
.
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The value for ψ cp , Na that PROFIS Engineering calculates will be limited to : MAXIMUM { c a , min
/ c ac : c Na
/ c ac } where c a , min is the smallest fixed edge distance being modeled in the application and c Na corresponds to an assumed projected distance from the center of the adhesive anchor element calculated per Equation ( 17.4.5.1d ).
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Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
c a , min
: The smallest fixed edge distance being modeled
c ac
: Value derived from testing per AC308 / ACI 355.4 for the adhesive anchor system being modeled
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Reference the Calculations section of the PROFIS Engineering report for more information on the parameter c Na
.
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