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Re: Fixed or pinned support

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You could probably consider it to be partially fixed.  You will most
likely have to consider bending in the base plate, unless a bolt box is
welded to the column and the base plate to transfer the column moment
directly to the bolts.  There's a design example of fixed based plates in
the Structural Engineering Handbook, among other sources.  Bottom line
is, draw the loading conditions of the connection as a FBD and determine
what the moment capacity is (considering bolt pull-out, base plate
bending, bearing on the concrete, etc. to determine the weak link).  Use
that as an applied resistive moment (including an appropriate safety
factor) at the pinned connection and there's your partially fixed, albeit
simplified, connection.  Of course, other factors may come into play as
well (shear transfer, rotation at the support, the inelastic response
that I'm sure the engineers in high seismic areas are much more familiar
with than me, etc.), but it's certainly more realistic than assuming a
pinned connection.

Mark Nowmos

"R.P. Mehrotra/engg" wrote:

>
> If foundation bolts are spaced closest to the column web (as required
> for placing the nuts) these could be considered as HINGED, though not
> theoretcally. The farther the placing of foundation bolts, it shall be
> towards ideally fixed condition.
>
> RP Mehrotra
>
> -- Original Message -----
> From: Nacionales Alex <acnacionales(--nospam--at)yahoo.com>
> Date: Thursday, May 3, 2001 8:22 am
> Subject: Fixed or pinned support
>
> > Hello.
> >
> > I am checking  a structural computation for a four
> > storey steel framed building. The framing in the
> > calculation shows fixed supports but the detail in the
> > plan shows the supports are steel baseplates with 4
> > 25mm-anchor bolts. The columns are directly welded to
> > the baseplates. It is my opinion that this kind of
> > connection is a pinned type connection and should be
> > treated as such in the calcs.
> >
> > Thank you for your comments.
> >
> > Alex C. Nacionales, C.E.
> >
> >
> >
> >
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