PART 3 TENSION LOAD
Side-Face Blowout Failure
Equation N sbg
Equation ACI 318-14 Chapter 17 Provision Comments for PROFIS Engineering
N sbg
= α group
N sb
17.4.4.1 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 f ́c ( 17.4.4.1 )
If c a2 for the single headed anchor is less than 3c a1
, the value of N sb shall be multiplied by the factor ( 1 + c a2
/ c a1 )/ 4 , where 1.0 ≤ c a2
/ c a1
≤ 3.0 . 17.4.4.2 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 not exceed
N sbg
= 1 + s
6c a1
N sb
( 17.4.4.2 )
where s is the distance between the outer anchors along the edge , and N sb is obtained from Eq .
( 17.4.4.1 ) without modification for a perpendicular edge distance .
For the illustration below : N sbg = [ 1 + ( s y1
+ s y2
)/ 6c a1 ] N sb
= α group
N sb
When modeling a group of anchors in tension , the side-face blowout strength for a single anchor ( N sb
) is calculated , and modified by the factor ( 1 + s / 6c a1 ). PROFIS
Engineering designates this group modification factor “ α group
”.
The parameter “ s ” corresponds to the distance between the outer anchors ( e . g . s y1
+ s y2 in the illustration to the left ) along the fixed edge being considered for side-face blowout . 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
Per Section 17.4.4.2 : “ N sb is obtained from Eq . ( 17.4.4.1 ) without modification for a perpendicular edge distance ”. The modification factor “ for a perpendicular edge distance ” is defined in 17.4.4.1 as ( 1 + c a2
/ c a1 )/ 4 , and is designated “ α corner
” in PROFIS Engineering . The PROFIS Engineering report will not include α corner when calculating side-face blowout for a group of anchors in tension . α corner is only considered when calculating side-face blowout for a single anchor in tension .
Reference the Variables section of the report for more information on the parameters c a1
, c a2 , A brg
, λ a
, f ́c and s .
Reference the Calculations section of the report for more information on the parameters αgroup and Nsb .
Reference the PROFIS Engineering report section for N sb ( single anchor ) for information on the parameter α corner .
107 NORTH AMERICAN PROFIS ENGINEERING ANCHORING TO CONCRETE DESIGN GUIDE — ACI 318-14 Provisions