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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 )
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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
). Since ACI 318 anchoring-to-concrete provisions do not specifically consider concrete splitting as a failure mode , splitting is addressed through a modification factor . The parameter ψ cp , Na is only considered when designing adhesive anchors installed in uncracked concrete .
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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 ……… where
and the constant 1100 carries the unit of lb / in 2 .
c Na
= 10d a т uncr ( 17 . 4 . 5 . 1d ) 1100
17.4.5.2 ……… For adhesive anchors located in a region of a concrete member where analysis indicates no cracking at service load levels ……………..
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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 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 is not 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 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 provisions given in the adhesive anchor ICC-ESR to calculate a c ac
-value .
This value is used to calculate ψ cp , Na for the anchor element being modeled .
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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
ICC-ESR-3187 4.1.10.2 Threaded Rod , Steel Reinforcing Bars , and Hilti HIS-N and HIS-RN Inserts : The modification factor ψ cp , Na must be determined in accordance with ACI 318-14 17.4.5.5 or ACI 318-11 D . 5.5 as applicable , except as noted below .
For all cases where c Na / c ac
< 1.0 , ψ cp , Na determined from ACI 318-14 Eq . 17.4.5.5b or ACI 318-11 Eq . D-27 , as applicable , need not be taken less than c Na
/ c ac . For all other cases ψ cp , Na shall be taken as 1.0 .
The critical edge distance cac must be calculated according to Eq . 17.4.5.5c for ACI 318-14 or Eq . D-27a for ACI 318-11 , in lieu of ACI 318-14 17.7.6 or ACI 318-11 D . 8.6 as applicable .
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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 being modeled . When design per ACI 318-14 has been selected , PROFIS Engineering calculates c Na per Equation ( 17.4.5.1d ).
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 т k , c , uncr
: Characteristic bond stress for uncracked concrete conditions
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c ac
= h ef
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т k , uncr
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0.4 |
⁎ 3.1 – 0.7 h 1160 h ef
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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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( Eq . 17.4.5.5c for ACI 318-14 or Eq . D-27a for ACI 318-11 )
where
h
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Reference the Variables section of the PROFIS Engineering report for Concrete Breakout in Tension for more information on the parameters k uncr
, h ef
, and f ́c . These parameters are used to calculate the limiting value for the characteristic bond stress in uncracked concrete , which is shown as “ т k , uncr
” in the ICC-ESR-3187
Eq . ( 4-1 ) to the left .
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h ef need not be taken as larger than 2.4 ; and т k , uncr is the characteristic bond strength in uncracked concrete , h is the member thickness , and h ef is the embedment depth . |