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RE: heavy timber frame

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Bruce,

Nels gives a viable option, but don't discount the mortise and tenon
option that the timber framer "wanted".  Mortise and tenon joints will
have some "moment capacity" (relative rigidity at the joint), and may have
more rigidity that the use of kerf/knife plate as the joint will likely be
tighter at the dowels (this assumes that you are talking "true" timber
framing which uses mortise and tenon joints with wood [typically oak]
pegs).  I would have to say that more than likely a mortise and tenon
joint with at least a couple of pegs and/or maybe a spline should more
than likely handle lateral loads that result from someone leaning or
pushing on the frame.  Resisting seismic is a potentially different
matter.

Quantifying capacity/rigidity of such connections will be a little
tougher.  You can try to make use of a moment on a bolt/dowel group type
calculations (i.e. figure J of the bolts/dowels and then figure
distribution of the moment to the various dowels as shear loads on each
dowel/bolt and then use NDS equations for the capacity of the
bolts/dowels...this will get a rough capacity, but there are "issues"
with this method).

As I do part-time work for a timber framer, I deal with mortise and tenon
as well as steel knife plate type connections on a regular basis.  We
typically do NOT really on the timber frame for lateral resistance
(usually use SIP shearwalls, stick-framed shearwalls, propertary
shearwalls, etc for that), but when we do rely on the timber frame, we
will do it with knee braces.  Generally speaking wood ain't so go for
moment connections.  This is not to say that wood cannot have moment
capacity/rigidity...just usually not too much.  But from your description,
you don't need a whole lot.

Free free to contact me "off list" if you want and I can give you a phone
number to call if you would like to discuss.

Regards,

Scott
Adrian, MI


On Thu, 15 Sep 2005, Nels Roselund wrote:

> Bruce,
>
>
>
> Ell-shaped plates installed into kerfs in the centers of the beams and
> columns would engage the wood each side of the plate in double shear; this
> seems like a reasonable way to stiffen the frame – the length of the plates
> and kerfs would be based on the moment and the perpendicular-to-grain
> capacity of the bolted connections.  The holes would need to be drilled with
> templates and drill press in order to avoid the need for oversized holes.
>
>
>
> Nels Roselund, SE
>
> South San Gabriel, CA
>
> njineer(--nospam--at)att.net
>
>   _____
>
> From: Bruce Holcomb [mailto:bholcomb(--nospam--at)brpae.com]
> Sent: Thursday, September 15, 2005 3:05 PM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: heavy timber frame
>
>
>
> Drew,
>
> We did discuss that just a little while ago.  That may be a good option as
> well, although I wonder about the potential movement in the bolted joint due
> to oversizing the hole.  I will probably need to look at this option a
> little but for now, I’ve been asked to not make any changes… the
> “higher-ups” are discussing…
>
>
>
> Thanks.
>
>
>
>
>
> BDH
>
>
>
> -----Original Message-----
> From: Drew Morris [mailto:dmorris(--nospam--at)bbfm.com]
> Sent: Thursday, September 15, 2005 4:47 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: heavy timber frame
>
>
>
> Could you add "L" shaped steel plates in the upper corners centered in the
> beams and columns with just bolts exposed?  I'm not sure if this would
> calculate out with the bolts bearing perpendicular to grain, but it would
> stiffen the joints.  Or hide the plates away from view?
>
> Bruce Holcomb wrote:
>
> I have been asked to review a heavy timber frame which will be located
> inside of a retail store and will serve as a canopy over a snack bar.  The
> drawings I received showed 8x8 posts, 8x12 beams and 4x10 purlins… all of
> Cedar.  I see nothing providing lateral stability for the structure.  Even
> though it is inside another building, I want to make sure it doesn’t fall
> over when the first tired customer leans against a post, so I added 6x6 knee
> braces, lag screwed into the beams and columns.  The knee braces extend
> 2’-0” from the inside of the beam / column joint each way.  The client had a
> fit… they don’t want any additional bracing.
>
>
>
> The beams and columns are typically connected with ¼” steel kerf plates.
> Has anyone built this kind of structure without additional bracing?
> Basically, the ¼” kerf plates create a moment joint?  The timber framer has
> said he wanted to change the kerf plates to mortise and tenon joints… will
> that create some lateral stability?
>
>
>
> I’m not too concerned about seismic… it’s in the Midwest, but I may have to
> produce calcs to provide to the city reviewer.  I want to make sure I can
> “prove” the structure is laterally stable.
>
>
>
>
>
> Bruce D. Holcomb
>
>
>
>

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