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RE: Washers for A490 Bolts

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Title: RE: Washers for A490 Bolts

>Over here on the dark side, the conventional wisdom (and my experience)
>is that any joint which is not tightly clamped eventually works loose
>because relative movment or vibration unscrews nuts. This may only be
>true of machinery which tends to cycle, but I get very nervous when bolts
>aren't preloaded.

I agree in principle, except I'm not nervous when snug-tight bolts are used in an appropriate application.

The RCSC Specification has very specific requirements that bolts be pretensioned when subject to fatigue, vibration and impact. Other cases too as outline in the specification. However, I believe these kinds of applications are the exception, not the rule, in the typical building design.

The acceptability of snug-tightened installation in appropriate applications is verified by testing as described in the RCSC Specification, it's Commentary and the Guide to Design Criteria for Bolted and Riveted Joints, as well as usage. Furthermore, the continued acceptable performance of thousands if not millions of old building structures with ASTM A307 (common) bolts -- snug-tightened bolts from a time when nobody ever knew we could pretension a joint -- seems to me to lend significant real-world verification.