Check Anchor

PULL-OUT CHECKS ON ANCHOR BOLTS IN ANCHOR BOLT LAYOUTS

If a bolt layout is classed as an anchor, the pull-out checks are used to supplement the normal

strength checks made on the layout. In practice, the pull-out force N on each bolt is compared with a limit value Fd which depends on the standard being used (see the relevant dialog box), thus

generating a utilisation index, E. This utilisation index is associated with the bolt layout, not the

constraint block on which the bolt layout is presumably anchored. As in the other cases, this index

is compared with that obtained for the bolt layout after the other checks and, if larger, is stored

along with the cause which gave rise to it.

In detail the rule is the following:

where γ is a safety factor depending on the standard used, in this way:

1 for EC3, IS800LS, BS5950 and CNR limit states

1,333 for AISC-LRFD

1,5 for CNR allowable stress

1,666 for IS800WS

2 for AISC-ASD

This check is omitted if a compression is present, as it is assumed that there will be a

bearing surface to react it.

If a prying forces factor greater than 1 has been defined, the traction forces used for this

check are those of the analysis amplified by this factor.

The calculation of limit pull-out force FL depends on the kind of the anchor defined by the user

and on some parameters. It is possible to define 5 different kinds of anchor, that are checked in 5

different ways.

Kind 1

The bond stress between the bar and concrete is responsible for the resistance. The rule is:

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Page 1 of 3Pull-out checks on anchor bolts in anchor bolts layouts

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where: fbd is the design tangential bond stress between the bar and concrete;

ϕ it is the bar diameter

a it is the minimum distance between the bar and the free surface of the constraint block (end

of concrete)

ln it is the straight length of anchor

Kind 2

Similar to kind 1 but also a hook is resisting, which increases the pull-out force. The rule is:

where

fbd is the design tangential bond stress between the bar and concrete;



of concrete)


r is the hook radius

l2 is the length of the straight part of the bar, after the hook

Kind 3

Similar to kind 1, but also a washer circular plate is present. The rule is:

where: fbd is the design tangential bond stress between the bar and concrete;

fcd is the design compressive stress of concrete





of concrete)


r is the washer radius

Kind 4

Similar to kind 3, but the resisting mechanism use concrete cone detachment from constraint

block. Basically the formula provided in Eurocode 2, §6.2 is assumed, considering the maximum

force guaranteed by such mechanism and checking that specific limit between dimensions are

met. The rule is:

where: fcd is the design compressive stress of concrete


of concrete)


r is the washer radius

The program checks also that the dimensions meet the necessary inequalities, and thus also a, r and ln are used.

Kind 5

If the user wishes to directly input the limit pull-out force (unfactored) he/she may wish to input

directly the value of FL (that will be later divided by γ to get Fd).

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Check Anchor