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c Na
= 10d a
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т uncr
1100
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17.6.5.1.1 ……… A Na is the projected influence area of a single adhesive anchor or an adhesive anchor group that is approximated as a rectilinear area that projects outward a distance c Na from the centerline of the adhesive anchor , or in the case of an adhesive anchor group , from a line through a row of adjacent adhesive anchors ……..…….
17.6.5.1.2 A Na0 is the projected influence area of a single adhesive anchor with an edge distance of at least c Na .
where
A Na0
= ( 2c Na ) 2 ( 17.6.5.1.2a )
c Na
= 10d a т uncr ( 17 . 6 . 5 . 1 . 2b 1100
17.6.5.3.1 Modification factor for adhesive anchor groups loaded eccentrically in tension , ψ ec , Na shall be calculated by Eq . ( 17.6.5.3.1 ).
ψ ec , Na
=
1
1 + e ́N
c Na
( 17.6.5.3.1 )
17.6.5.4.1 Modification factor for edge effects for single adhesive anchors or adhesive anchor groups in tension , ψ ed , Na
, shall be determined by ( a ) or ( b ) using the critical distance c Na as defined in Eq . ( 17.6.5.1.2b )
( a ) If c a , min
> c Na , then ψ ed , Na
= 1.0 ( 17.6.5.4.1a )
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ACI 318-19 Chapter 17 bond strength calculations are predicated on the parameter “ c Na
”, which is defined in Chapter 2 as the “ projected distance from the center of an anchor shaft on one side of the anchor required to develop the full bond strength of a single adhesive anchor ”. c Na is calculated per Equation ( 17.6.5.1.2b ).
The parameter “ d a
” corresponds to the diameter of the anchor element selected for the PROFIS Engineering application being modeled . The parameter “ т uncr
” corresponds to the characteristic bond stress in uncracked concrete of the adhesive product selected for the PROFIS Engineering application being modeled .
The modification factor A Na accounts for the area of influence assumed to develop with respect to bond failure , for the edge conditions and anchor spacing that have been input into the PROFIS Engineering model . Per the provisions for A Na given in Section 17.6.5.1.1 , PROFIS Engineering limits the geometry used to define A Na to a maximum projected distance from an anchor of c Na .
c Na is also used to calculate the following bond strength parameters :
A Na0
: modification factor for the idealized area of influence assumed to develop in concrete , with respect to bond failure , for a single anchor without any edge influences . Reference Equation ( 17.6.5.1.2a ). ψ ec , Na
: modification factor for an eccentric tension load acting on a group of anchors . Reference Section 17.6.5.3.1 . ψ ed , Na
: modification factor for a fixed edge distance less than c Na . Reference
Section 17.6.5.4.1 . ψ cp , Na
: modification factor to consider splitting failure . Reference Section 17.6.5.5.1 .
Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
da : diameter of anchor element т uncr
: characteristic bond stress of an adhesive anchor in uncracked concrete
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( b ) If c a , min < c Na
, c a , min ( 17 . 6 . 5 . 4 . 1b )
then ψ ed , Na = 0.7 + 0.3
c Na
17.6.5.5.1 Modification factor for adhesive anchors designed for uncracked concrete in accordance with 17.6.5.1 without supplementary reinforcement to control splitting , т cp , Na
, shall be determined by ( a ) or ( b ) where cac is defined in 17.9.5 .
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Reference the Calculations section of the PROFIS Engineering report for more information on the following parameters :
A Na
: area of influence modification factor
A Na0
: idealized area of influence modification factor for a single anchor
ψ ec , Na
: modification factor for tension eccentricity
ψ ed , Na
: modification factor for edge distance
ψ ec , Na
: modification factor for splitting
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( a ) If c a , min ≥ c ac
, then ψ cp , Na = 1.0 ( 17.6.5.5.1a )
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( b ) If c a , min < c ac
, then ψ cp , Na =
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c a , min
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≥ |
c Na ( 17 . 6 . 5 . 5 . 1b ) |
c ac
|
c ac
|