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Re: Bolt question

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> From: "Chan, David" <DCHAN(--nospam--at)>

> Here's a question for you bolt experts out there.  I'm reviewing

BOLT expert is better than NUT expert, I suppose! ;)

> drawings for a crane supported on a steel structure.  Drawings show 2"
> diameter A325SC anchor bolts.  Looking in the steel manual, A325's only
> come in a size up to 1-1/2 inches.  Would it be appropriate to use a 2"
> diameter A449 bolt for this application?

Identify it to the designer. The person who wrote the note is unaware of
the real A325 specifications. They are the ones to determine a

> One of my concerns is the vibration associated with the crane.  I'm
> guessing the engineer wanted a slip critical bolt for the pretensioning.

Guessing: slip critical would be due to potential load reversal, brittle
fracture and fatigue. Whether slip critical or not, A325 connections
should be pre-tensioned for dynamic conditions. I'm not sure that the
RCSC envisaged anchors to concrete in this category.

> Are all A449 bolts pretensioned?  If not, do you just indicate them on
> drawings with "pretensioned A449 bolt"?  Is the pretensioning of an A449
> similar to A325's and A490's at 70% of min tensile strength?

A325 is a headed bolt, so longer lengths, as might be required for a 2"
diameter anchor, will probably not be readily available, even if you
could get 2" dia A325. The A325 spec, in a footnote referenced from the
title,  specifically redirects to A449 for studs (threaded rod). Unlike
A307 threaded rod, A325 does not suggest that A449 is a direct

Pretensioning requirements for A449 would (probably) follow the same
guide lines as A325. Designer's decision.

Pretension in embedded anchors is a crap-shoot. Here today, gone
tomorrow. Let the designer spec tightening methods and maintenance
torquing as they see fit.

On the reality side; this type of anchor is probably mis-specified
regularly, substituted and installed adequately, on a daily basis, all
over the place. The scary part is an unqualified substitution. Any long
term performance issues will probably be seen as maintenance issues.

Paul Ransom, P. Eng.
Burlington, Ontario, Canada
<mailto:ad026(--nospam--at)> <>

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