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RE: plate washers on anchor bolts

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Do you have some examples of “harm”?  Large numbers of washer/plates?  I would have thought that closely spaced washers/plates would encourage a single plate type of embedded.  The analysis of anchors seems to suggest a “bearing” face so the washer/plate concept is a natural kneejerk good idea … ? 


I sometimes wonder if our anchoring bolts/rods should be a combination of rebar-type deformations plus a head … a kind of developed length plus mechanical anchorage.  Has anyone seen any published research with this idea?


Here, we no longer refer to the anchors as “anchor bolts”, simply as “anchors” or “anchor rods”.


Thor A. Tandy P.Eng, C.Eng, Struct.Eng, MIStructE, MSCSE
Victoria, BC




From: Tom.Hunt(--nospam--at) [mailto:Tom.Hunt(--nospam--at)]
Sent: Wednesday, November 17, 2010 6:54 AM
To: seaint(--nospam--at)
Subject: Re: plate washers on anchor bolts



This has been an issue for many years.  You are absolutely correct that the large plate washer at the bottom of a headed anchor bolt can actually cause more harm than good.  I think there are those who feel uncomfortable with relying on just the head of the bolt or tack welded nut and think the plate washer is just a good "belts and suspenders" approach.

Thomas Hunt, S.E.

From:        PFFEI(--nospam--at)
To:        seaint(--nospam--at)
Date:        11/17/2010 05:17 AM
Subject:        plate washers on anchor bolts

I am curious why some engineers install plate washers on the embedded ends of foundation anchor bolts.  The headed deformation of a heavy hex nut is enough to develop F1554 grade 36 rods in tension (per ACI Appendix D calculations) and AISC Column Base Plate Design Guide also shows nut sufficient to develop rod. It would seem that plate washers could be detrimental in closely spaced anchors - they could cause cracking through failure plane interconnecting plate washers.  Does anyone have any information on this practice?
Thanks- Paul Franceschi
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