1.0 TENSION
1.4 Side Face Blowout Failure Mode
Variables s
Variables ACI 318-19 Chapter 17 Provision Comments for PROFIS Engineering s
17.6.4.1 For a single headed anchor with deep embedment close to an edge ( h ef > 2.5c a1
), the nominal side-face blowout strength , N sb , shall not exceed
N sb
= 160c a1
A brg λ a ƒ ́c ( 17.6.4.1 )
17.6.4 . 2 For multiple headed anchors with deep embedment close to an edge ( h ef > 2.5c a1
) and anchor spacing less than 6c a1 , the nominal strength of those anchors susceptible to a side-face blowout failure , N sbg
, shall be calculated by :
N sbg
= 1 + s
6c a1
N sb
( 17.6.4 . 2 )
where s is the distance between the outer anchors along the edge , and N sb is obtained from Eq .
( 17.6.4.1 ) without modification for a perpendicular edge distance .
17.9.2 Unless determined in accordance with 17.9.3 , minimum spacing parameters shall conform to Table 19.9.2 ( a ).
Table 17.9.2 ( a ) — Minimum spacing and edge distance requirements
Spacing parameter
Minimum anchor spacing
Not torqued
Cast-in anchors Torqued
Anchor type
Post-installed expansion and undercut anchors
Post-installed screw anchors
4d a
6d a
6d a
Greater of 0.6h ef and 6d a
When modeling a group of anchors in tension , the side-face blowout strength for a single anchor ( N sb
) is calculated per Eq . ( 17.6.4.1 ) and modified by the factor
( 1 + s / 6c a1 ), per Eq . ( 17.6.4.2 ). PROFIS Engineering designates ( 1 + s / 6c a1
) as
“ α group
”.
PROFIS Engineering only performs side-face blowout calculations for the cast-in anchors in its portfolio . The software uses the minimum spacing requirements given in Table 17.9.2 ( a ) for these anchors .
N sbg calculations for a group of anchors in tension only consider the anchors nearest to the edge where side-face blowout is being considered . The illustration to the left shows six anchors , numbered 1 through 6 . Side-face blowout is being considered for the anchors highlighted in red , that are next to the x + edge , and numbered 4 , 5 and 6 . Assuming “ α group
” corresponds to the Eq . ( 17.6.4.2 ) parameter ( 1 + s / 6c a1 ), the value for “ s ” that is used to calculate α group corresponds to the distance between anchors 4 and 5 (= s y1 ) plus the distance between anchors 5 and 6 (= s y2 ). Therefore , “ α group
” for this application is defined using
“ s ” = ( s y1 + s y2
) such that α group = ( s y1
+ s y2 )/ 6c a1
.
Section 17.6.4.2 notes that “ α group ” is calculated when “ anchor spacing is less than
6c a1
”, “ where s is the distance between the outer anchors along the edge ”. For the example shown in the illustration , α group is calculated if ( s y1 + s y2
) < 6c a1 . PROFIS
Engineering limits the value of “ s ” to “ 6c a1 ”; which means that PROFIS Engineering permits “ α group
” values in the range : 1.0 ≤ α group
≤ 2.0
The PROFIS Engineering parameter “ α group
” corresponds to the parameter ( 1 + s / 6c a1 ) given in Eq .
( 17.6.4.2 ). For the application being illustrated below :
N sbg
= α group
N sb
= [ 1 + ( s y1 + s y2
)/ 6c a1 ] N sb
Reference the Variables section of the report for more information on the parameters c a1
, c a2 , A brg
, λ a
, and ƒ ́c .
Reference the Calculations section of the report for more information on the parameters α group and N sb
.
119 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-19 Provisions