You are certainly free to assume a fully fixed end condition or whatever assumption you want to make in order to satisfy yourself that you have provided a conservative design. However, I do not believe that adding a few extra bolts in the beam web near the neutral axis with a fairly small moment arm will be enough to provide full end fixity. There's too much flexibility due to bolt slip, deformation of the connection material, and the flanges of beam not being connected at all. Furthermore, in many cases the drag forces (multiplied by Omega) are much larger than the gravity forces so that the resultant force is nearly horizontal and the moment in the connection due to the double line of bolts is minimal. Of course, you must exercise some engineering judgment if you find this approach is not applicable to your particular connection configuration and loading.
>>> Mark Pemberton <Markp(--nospam--at)lbdg.com> 04/27/01 07:39AM >>>
I also agree that it would not be a conservative method
by only taking the eccentricity and not the moment resistance
into account. I've checked a few and the induced shear
stress is much higher when checking the bolt group for
the fixed (or even partially fixed) end moment.
Mark Pemberton, P.E.
From: Mark Gilligan [mailto:MarkKGilligan(--nospam--at)compuserve.com]
Sent: Friday, April 27, 2001 7:26 AM
Subject: Re: double bolt rows
With regards to the use of a double row of bolts you stated that " A
rational and conservative design method would be to design the bolt group
for the full eccentricity between the centroid of bolts and the support."
I would appreciate if you could explain the assumptions and explain why
this method is conservative for the case where the connection is used as a
I would expect that an appropriate approach would be to assume that the
connection was fully fixed for design and calculate the resulting moment at
the center of the bolt group.
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