|
α group
= 1 +
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s
6c a1
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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 .
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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 .
( 17.6.4.2 ). 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 and edge distance 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 . Illustration 1 on the following page 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
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17.9.2 Unless determined in accordance with 17.9.3 , minimum spacing parameters shall conform to Table 19.9.2 ( a ). |
( s y1 + s y2
)/ 6c a1 .
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Table 17.9.2 ( a ) — Minimum spacing and edge distance requirements
Spacing parameter
Not torqued
Anchor type
Cast-in anchors
Torqued
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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 ”. 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 : 1.0 ≤ α group
≤ 2.0
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Minimum anchor spacing 4d a
6d a
Minimum edge distance
Specified cover requirements for reinforcement according to 20.5.1.3
6d a
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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
.
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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