2.0 SHEAR
2.1 Concrete Breakout Failure Mode
Variables l e
Variables ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
l e
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
= 2d a 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 )
17.7.2.2.2 For cast-in headed studs , headed bolts , or hooked bolts that are continuously welded to steel attachments basic concrete breakout strength in shear of a single anchor in cracked concrete , V b
, shall be the lesser of Eq . ( 17.7.2.2.1b ) and Eq . ( 17.7.2.2.2 ) provided that ( a ) through ( d ) are satisfied .
V b
= 8 l e
0.2 where l e is defined in 17.7.2.2.1 .……………………………… Examples of how l e is determined . d a
d λ a
( c a1 ) 1 . 5 ( 17.7.2.2.2 ) a ƒ ́c
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d a
= 0.875 ” h ef = 12.0 ”
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d a
= 0.625 ” h ef = 4.0 ”
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l e
= MIN { h ef ; 8da } = 7.0 ”
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l e
= MIN { h ef
; 8d a } = 4.0 ”
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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 .
Per ACI 318-19 Section 17.7.2.2.1 , the l e value for anchor elements that have a constant stiffness over their embedded depth equals the smaller of the anchor element effective embedment depth ( h ef
), and eight times the nominal diameter of the anchor element ( d a
). The cast-in anchors in the PROFIS Engineering portfolio and all post-installed anchors except the HSL-3 expansion anchor have a constant stiffness over their embedded depth .
Per ACI 318-19 Section 17.7.2.2.1 , the l e value for anchor elements that do not have a constant stiffness over their embedded depth equals 2d a
. HSL-3 expansion anchors have a “ distance sleeve ” that is separated from the expansion wedges ; therefore , l e
= 2d a these anchors . PROFIS Engineering uses the pre-calculated l e values given in Table 3 of ESR-1545 when HSL-3 anchors are being modeled . These l e values correspond to two times the anchor external diameter ( d a ). Values for d a are also given in Table 3 of ESR-1545 .
Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
d a
: anchor element diameter
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 )
V b calculated per Eq . ( 17.7.2.2.2 ). adhesive anchor element mechanical anchor ( constant stiffness )
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d a
= 0.71 ” h ef = 3.15 ”
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d a
= 0.75 ” h ef = 10.0 ”
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l e
= 2d a = 1.42 ”
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l e
= MIN { h ef
; 8d a } = 6.0 ”
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HSL-3 mechanical anchor ( with distance sleeve ) cast-in headed bolt
184 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions