Structural Steel Bolted Connections - in place acceptance criteria?

[woody1235]

Good Morning!
I am working on an existing structural steel framed building that has been is service for about 25 years. Since the owners are adding some heavier roof mounted AHUs, I asked that the affected existing girder to column connections (welded to column, bolted to beam web) be exposed and inspected to verify condition and bolt configuration versus the original design drawings.
These bolted connections were originally designed as A325 bearing, snug tight.
At 2 locations, the inspector found 1/8" to 3/16" gaps between the connection angle and the bolted girder web, with loose washers. (at one location the nuts had been tack welded). It appears they were never brought up tight during erection.
I don't believe trying to re-tighten them is an option; the girder is under heavy load, and I don't think you can re-tighten A325s.

Does anybody know of an acceptance criteria for this kind of condition, or how to determine if the capcity is actually decreased?

Thanks!

 

[canwesteng]

Why couldn't you re tighten the bolts? Unless they were pretensioned it should be ok.

 

[MotorCity]

If the connection is heavily loaded it would be very difficult, if not impossible, to tighten the bolts such that you would bring the plies into firm contact. The bolts will bind on the bearing surface and you may do more harm than good. If the connection is ok by calculation, the most I would do is insert shims into the gap. Otherwise I would leave it alone.

 

[woody1235]

Thanks!
canwesteng, I think you are correct that if the bolt is in good condition it can be re-used once.

Motorcity, the connection is OK by my load calc. I doubt it could be brought snug due to loading.

I'm inclined to leave it; I don't know that adding shims would actually do anything since already under load.
Asking in case there is some criteria that I'm not finding about this.

 

[JAE]

In addition to the answers above - I would be motivated to contact AISC in their Steel Solutions Center...found here:

https://www.aisc.org/steel-solutions-center/

and see what they might have to say.


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[jayrod12]

Even if you can't tighten them to snug-tight (all plies in contact) I would recommend trying to tighten them as much as possible, and then deforming the threads to prevent the nuts from backing off. It's one of those "I've seen it, I should make an effort" type scenarios.