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RE: A325 Bolts

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There was a study performed by Bethlehem many years ago regarding pretensioning bolts.  They put strain gauges on the bolts and loaded the assemblage in cyclic loads.  The strains oscillated with the applied load.  Then the applied the pretension and then repeated the loading. 
 
The bolt strain remained the same.  I may be able to dig up that research, but the point is that if a bolt is designed to basically have a static load from the pretensioning, there should be no change in the strain.  That is the issue when it comes to bolts in cold temperatures for this range. 


Regards,
Harold Sprague

> Date: Sat, 3 May 2008 07:12:11 -0700
> From: astaneh(--nospam--at)ce.berkeley.edu
> To: seaint(--nospam--at)seaint.org
> Subject: A325 Bolts
>
> Dear Mr. Sprague:
> With regard to behavior of bolts in cold temperatures, you have stated below that "If you are tensioning the bolts, the brittleness of the steel should not be an issue." Would you please elaborate further on this? Why is it so? Are there any references or tests done to demonstrate this? Also, I am interested in knowing if you have any information on behavior of pretension force in the bolt as the temperature changes. Let us say that the bolt is tightened when the temperature was 40 degrees, then the temperature drops to -60 deg-F during winter, what is the pretensioning in the bolt at this temperature?
>
> Sincerely,
> Abolhassan Astaneh-Asl, Ph.D., P.E.
> Professor and Consultant on Structural Engineering, Earthquake
> Engineering and Protection of Buildings and Bridges against Blast and Impact.
>
> From: Harold Sprague <spraguehope(--nospam--at)hotmail.com>
> To: <seaint(--nospam--at)seaint.org>
> Subject: RE: A325 Bolts
>
> I guess, I would have to ask for definition sub zero. Minus 10 degrees F is sub zero, but so is minus 270 degrees F. A 325 bolts are commonly used in bridges in very cold climates where the temperature gets down to minus 20=
> degrees and even colder.
>
> The A320 does not get excited until you are below 100 degrees F. The record low in Fairbanks, AK is minus 66 degrees F.
>
> The issue with cold temperatures and steel is how brittle the steel becomes. If you are tensioning the bolts, the brittleness of the steel should not be an issue. Regards,Harold Sprague
>
>
> Date: Fri, 2 May 2008 09:55:11 -0700
> From: asqengg2(--nospam--at)yahoo.com
> Subject: A325 Bolts
> To: seaint(--nospam--at)seaint.org
>
> We are working in subzero temp and instead of A320 bolts for exterior application, we are planning to use A325 instead. How much capacity reduction we are going to use for using A325 in such an environment?
>
> Thanks in advance.
>
> Cairo
>
>
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