|
α group
= 1 +
|
s
6c a1
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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
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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 the factor ( 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 Section 17.7.1 and the minimum edge distance requirements given in Section 17.7.2 for these anchors .
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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 .
17.7.1 Unless determined in accordance with 17.7.4 , minimum center-to-center spacing of anchors shall be 4d a for cast-in anchors that will not be torqued , and 6d a for torqued cast-in anchors and post-installed anchors .
17.7.2 Unless determined in accordance with 17.7.4 , minimum edge distances for cast-in anchors that will not be torqued shall be based on specified cover requirements for reinforcement in 20.6.1 . For cast-in anchors that will be torqued , the minimum edge distances shall be 6d a
.
Illustration 1
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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 . 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 . 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 equals ( s y1
+ s y2 )/ 6c a1
.
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 ”. When calculating α group
, PROFIS Engineering limits the value of the total spacing along the outer edge to 6c a1
; which means that PROFIS Engineering uses “ α group ” values in the range : α1.0 ≤ α group
≤ 2.0
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For the example shown in Illustration 2 , PROFIS Engineering would calculate
α group
= ( s y1 + s y2
)/ 6c a1 if ( s y1
+ s y2 ) < 6c a1
. PROFIS Engineering would calculate α group
= 2.0 if ( s y1 + s y2
) > 6c a1
.
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Reference the Variables section of the report for more information on the parameters c a1
, c a2
, and s .
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Reference the Equations section of the report for more information on the parameter α group
.
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Reference the Equations and Calculations section of the report for more information on the parameter N sb
.
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Illustration 2 |
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N sbg
= [ 1 + ( s y1 + s y2
)/ 6c a1 ] N sb
= α group
N sb
|