RE: Washers for A490 Bolts[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
- Subject: RE: Washers for A490 Bolts
- From: Charlie Carter <carter(--nospam--at)aiscmail.com>
- Date: Mon, 16 Apr 2001 07:37:33 -0500
>On one of our projects, 1-1/2" dia. A490N bolts were specified for shear
>tab beam connection. Because of fit-up, the contractor made the connection
>using short slotted holes in the beam web. However, the requirements for
>minimum 5/16" thick washers were overlooked. The beam is in place now and
>because of the existing conditions, the connection can not be accessed to
>replace the bolts and the washers. What is the reason for requiring 5/16 inch
Thicker washers are required for pretensioned applications with A490s of diameter greater than 1 in.because of the tendency of standard F436 washers to dish into the hole, thereby reducing the clamping force induced using an otherwise acceptable installation procedure.
>Can one use some reduced capacity when standard thickness washers are used
>instead of 5/16 inch washers?
One possible solution is to consider whether pretension is actually required in the first place. If the bolts are in shear, snug-tightened installation of A490s is often acceptable (pretension is often not required). And per RCSC Specification Section 6.1.2, for snug-tightened bolts in slotted holes in exterior plies, a standard ASTM F436 washer is suitable.
Hope this helps.
P.S. If you don;t already have it, you can get the 2000 RCSC Specification as a free download from http://www.boltcouncil.org.
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