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RE: washers

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Title: RE: washers

>what are the requirements for installing washers on bolted steel to steel
>connections?  I have always understood washers to be a standard part of a
>connection, but have a contractor who wants to charge an extra.  Is it
>required on only high strength bolts and therefore installed without having
>to specify?  Are they required on A307 bolted connection and base plate
>connections if standard holes are used?   What code section specifies washer

Washer requirements for joints with ASTM A325 or A490 bolts can be found in Section 7(c) of the 1994 RCSC Specification for Structural Joints Using ASTM A325 or A490 Bolts, which is on-line here:

Those links are the specification, commentary and appendix, respectively. RCSC is now finalizing a new version of this Specification (the 2000 version). I'll post a link to this when it is available.

Another source for simplified information on washer requirements based upon the RCSC requirements is a paper in the 2nd Quarter 1996 AISC Engineering Journal "Specifying Bolt Length for High-Strength Bolts" by, well, me. Here is a slightly editted version of what it says:

RCSC Specification Section 7(c) indicates the cases in which 5/32-in.-thick ASTM F436 washers must be used with ASTM A325 and A490 bolts. Such washers are not required for these high-strength bolts in standard,

oversized, and short-slotted holes except:

1. under the turned element when the bolt is pretensioned by the calibrated wrench method.

2. under the head and nut when ASTM A490 bolts are used in combination with material with a specified
yield point below 40 ksi.

3. to cover an oversized or short-slotted hole in an outer ply. For ASTM A490 bolts over 1 inch in diameter through an oversized or short-slotted hole in an outer ply, the washer must be 5/16-in.-thick; two 5/32-in.-thick washers do not meet this requirement.

Some alternative design fasteners provide a bearing circle on the bolt head and/or nut of diameter equal to or greater than the diameter of an ASTM F436 washer. When such fasteners are used, the need for washers in cases 1 and 2 above is eliminated.

When high-strength bolts are used through long-slotted holes in an outer ply, <there are more detailed requirements; see the RCSC Specification>


Hope this helps.