|
α group
= 1 +
|
s
6c a1
|
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 )
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 .
|
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 ), per Eq .
( 17.4.4.2 ). PROFIS Engineering designates ( 1 + s / 6c a1 ) as “ α group
”.
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 . Illustration 1 to the left shows six anchors , all of which are in tension . The total factored tension load acting on these anchors is designated “ N ua
”. These anchors have been numbered 1 through 6 in Illustration 2 . 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 . PROFIS Engineering designates the portion of the factored tension load
N ua acting on anchors 4 , 5 and 6 as “ N ua , edge ”. The “ α group
” parameter “ s ” from Illustration 2 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 = ( s y1 + s y2
)/ 6c a1 .
|
||
Illustration 1 |
Section 17.4.4.2 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 Illustration 2 , 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
|
||||
|
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 α group and N sb . |
|||||
Illustration 2 |
|||||
|
N sbg
= [ 1 + ( s y1 + s y2
)/ 6c a1 ] N sb
= α group
N sb
|