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V b
= 7
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l e
0.2
d a
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d a λ a ƒ ́c
c a1
1.5
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17.7.2 . 2.1 Basic concrete breakout strength of a single anchor in shear in cracked concrete , V b , shall not exceed the lesser of ( a ) and ( b ):
( a ) V b
= 7
l e
0.2
d a
d λ a
( c a1 ) 1 . 5 ( 17.7.2.2.1a ) a ƒ ́c
where l e is the load-bearing length of the anchor for shear : l e
= h ef for anchors with a constant stiffness over the full length of embedded section , such as headed studs and post-installed anchors with one tubular shell over the full length of the embedment depth ; l e
= 2 da for torque-controlled expansion anchors with a distance sleeve separated from expansion sleeve ; l e
≤ 8d a in all cases .
( b ) V b = 9λ a ƒ ́c ( c a1 ) 1 . 5 ( 17.7.2.2.1b )
V b corresponds to concrete breakout in shear for a single anchor without any geometry influences .
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ACI 318-19 Chapter 2 defines the parameter V b as the “ basic concrete breakout strength in shear of a single anchor in cracked concrete ”. V b calculated using Eq . ( 17.7.2.2.1a ) can be considered relevant for anchors that are not rigidly attached to the fixture , i . e . an annular space exists between the anchor element and the hole in the fixture through which the anchors are located . V b calculated using Eq . ( 17.7.2.2.1b ) is a limiting value . PROFIS Engineering calculates V b using both equations , and shows the controlling equation in the Equations section of the report , and the V b
-value calculated using the controlling equation in the
Calculations section .
Consider a single anchor installed near a fixed edge with a shear load acting on the anchor towards that edge . Assuming there are no fixed edges perpendicular to the direction of the applied shear load , and the concrete has an “ infinite ” thickness ; if concrete breakout occurs , it could be defined by the calculated capacity V b using either Eq . ( 17.7.2.2.1a ) or Eq . ( 17.7.2.2.1b ). V b is calculated using both equations and the smaller calculated value is used to calculate the nominal concrete breakout strength in shear ( V cb or V cbg ). Geometry influences are considered via the parameters A vc , ψ ed , V and ψ h , V
. Reference the Design Guide sections for these parameters for more information .
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ACI 318 anchoring-to-concrete provisions define the parameter l e as the “ load bearing length of anchor for shear ”. This “ length ” corresponds to the embedded portion of an anchor element that is effective in transferring shear load into a concrete member . For anchor elements that have a constant stiffness over their embedded depth , l e equals the smaller of the anchor element effective embedment depth ( h ef ) and eight times the nominal diameter of the anchor element ( d a
). For anchor elements that do not have a constant stiffness over their embedded depth ( i . e . “ anchors with a distance sleeve separated from expansion sleeve ”), the l e value equals 2d a
.
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Reference the Variables section of the PROFIS Engineering report for more information on the following parameters : |
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l e
: load bearing length of anchor in shear
d a
: anchor element diameter
λ a
: lightweight concrete modification factor ƒ ́c : concrete compressive strength
c a1
: edge distance in the direction of the shear load
h a
: concrete thickness .
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Reference the Calculations section of the PROFIS Engineering report for more information on the following parameters :
V b calculated per Eq . ( 17.7.2.2.1a )
V b calculated per Eq . ( 17.7.2.2.1b ).
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