|
V b
= 8
|
l e
0.2
d a
|
d a λ a f ́c
|
c a1
1.5
|
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
where l e is defined in 17.7.2.2.1 .
l e
0.2
d a
d λ a
( c a1 ) 1 . 5 ( 17.7.2.2.2 ) a ƒ ́c
( a ) Steel attachment thickness is the greater of 0.5d a and 3 / 8 in .
|
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 . ( 17.7.2.2.2 ) is only relevant for anchors that are rigidly attached to the fixture , e . g . a welded head stud . V b calculated using Eq . ( 17.7.2.2.1b ) is a limiting value .
V b calculated using Eq . ( 17.7.2.2.1a ) is not relevant to anchors rigidly attached to a fixture . PROFIS Engineering only calculates V b using Eq . ( 17.7.2.2.2 ) for the AWS D1.1 headed studs in its anchor portfolio . The V b
-value calculated using Eq .
( 17.7.2.2.2 ) is checked against the V b
-value calculated using Eq . ( 17.7.2.2.1b ) and the smaller value is used to calculate the nominal concrete breakout strength in shear ( V cb or V cbg ). The controlling V b
-equation is shown in the Equations section of the report , and the V b
-value calculated using the controlling equation is shown in the Calculations section .
|
|
( b ) Anchor spacing s is at least 2.5 in .
( c ) Reinforcement is provided at the corners if c a2
≤ 1.5h ef
.
( d ) For anchor groups , the strength is calculated based on the strength of the row of anchors farthest from the edge
17.5.2.2 The basic concrete breakout strength in shear of a single anchor in cracked concrete , V b , shall be the smaller of ( a ) and ( b ):
|
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 . ( 17.7.2.2.2 ) 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 . |
||||
|
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 , and l e
< 8d a in all cases .
( b ) V b = 9λ a ƒ ́c ( c a1 ) 1 . 5 ( 17.5.2.2b )
|
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 . The cast-in anchor elements in the PROFIS Engineering portfolio have a constant stiffness over their embedded depth ; therefore , the
l e
-value calculated by PROFIS Engineering for these anchors equals the smaller of the effective embedment depth ( h ef
) and eight times the nominal diameter of the anchor element ( d a ).
|
||||
V b corresponds to concrete breakout in shear for a single anchor without any geometry influences . |
Reference the Variables section of the PROFIS Engineering report for more information on the following parameters :
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 .
|
||||
|
Reference the Calculations section of the PROFIS Engineering report for more information on the following parameters :
V b calculated per Eq . ( 17.7.2.2.1b )
V b calculated per Eq . ( 17.7.2.2.2 ).
|