2.0 SHEAR
2.1 Concrete Breakout Failure Mode
Calculations V b
Calculations ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering
V b
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
……………………………………………. ( b ) V b
= 9λ a f ́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 ) ……………………………………..
V b
= 8 l e
0.2 d a
Reference ACI 318-19 Fig . R17.7.2.1b . d λ a
( c a1 ) 1 . 5 ( 17.7.2.2.2 ) a ƒ ́c
Case 1 : One assumption of the distribution of forces indicates that half of the shear force would be critical on the front anchor and the projected area . For the calculation of concrete breakout , c a1 is taken as c a1 , 1 .
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 . When calculating V b with this equation , the value for c a1 can be determined from the near-edge anchors per Case 1 or Case 3 in the ACI 318-19 commentary Fig . R17.7.2.1b . V b calculated using Eq . ( 17.7.2.2.1b ) is a limiting value . If calculating V b with Eq . ( 17.7.2.2.1a ), the value for ca1 used in that equation would also be used to calculate V b with Eq . ( 17.7.2.2.1b ). For all of the post-installed anchors in the PROFIS Engineering portfolio , and all of the cast-in anchors except AWS D1.1 headed studs ; PROFIS Engineering calculates V b using Eq . ( 17.7.2.2.1a ) and Eq . ( 17.7.2.2.1b ), and shows the lesser V b -value in the Calculations section of the report .
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 . When calculating V b with this equation , the value for ca1 can be determined from the far-edge anchors per Case 2 in the ACI 318-19 commentary Fig . R17.7.2.1b . If calculating V b with Eq .
( 17.7.2.2.2 ), the value for c a1 used in that equation would also be used to calculate
V b with Eq . ( 17.7.2.2.1b ). PROFIS Engineering only calculates V b using Eq . ( 17.7.2.2.2 ) for the AWS D1.1 headed studs in its anchor portfolio , and checks this value against V b calculated per Eq . ( 17.7.2.2.1b ). The lesser V b
-value is shown in the Calculations section of the report .
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 .
Reference the Equations 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 )
197 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions