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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 )
If c a , min < c ac
, then ψ cp , Na = c a , min
( 17.4.5.5b ) c ac
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When calculating the nominal concrete pryout strength in shear ( V cp or V cpg
), the parameter ψ cp , Na is a modification factor that considers splitting failure for an adhesive 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 , 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 cast-in-place anchors , and is not considered in PROFIS Engineering when these anchors are being modeled .
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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 .
17.4.5.1 ……………………………………………………………
and the constant 1100 carries the unit of lb / in 2 .
c Na
= 10d a т uncr 17 . 4 . 5 . 1d 1100
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 cac shall not be taken less than :
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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 , 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 cac , 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 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 adhesive anchor to calculate ψ cp , Na
.
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Adhesive anchors ............................................... 2h ef
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The value for ψ cp , Na that PROFIS Engineering calculates will be limited to |
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Undercut anchors ............................................... 2.5h ef
Torque-controlled expansion anchors ............................... 4h ef
Displacement-controlled expansion anchor .......................... 4h ef
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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 is the adhesive anchor edge distance parameter calculated per Eq . ( 17.4.5.1d ) for the adhesive anchor being modeled .
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It is important to understand that “ ψ cp , Na ” calculated for bond failure in tension is not necessarily the same as “ ψ cp , Na
” calculated for concrete pryout failure in shear since the number of anchors in tension may not be the same as the number of anchors in shear .
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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 AC308 / ACI 355.4 for the adhesive anchor being modeled
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Reference the Calculations section of the PROFIS Engineering report for more information on the following parameters : |
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c Na
: Edge distance parameter for adhesive anchors
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ψ cp , Na
: Modification factor for uncracked concrete
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