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RE: Fixed base timber column

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Trying to convince yourself that you can "fix" a wood member to develop
an end moment ( i.e. keeping the relative angle 90 degrees between the
cassion and the post) can get you into trouble. I had a similar design
problem with 12x12 posts that needed to cantilever up, and what I ended
up doing was using side plates with thru bolts an all four sides of the
post, making the side plates extend a decent distance up the post(more
than 6 or 12 inches), making the plates thick to keep that 90 degree
angle at the base, and adding a triangular stiffener plate, also to help
keep that angle at 90. Remember, the post loads the bolts  perpendicular
to the grain as the base of the post wants to rotate under load. But of
course, all the plates and bolts are exposed......Hope, this helps, but
I would say that if you need to crank a decent moment into the cassion,
I can't see how you could make it work with no visible connection

                 Monte Griffiths, S.E.

> ----------
> From: 	Thomas Long[SMTP:tomlong(--nospam--at)]
> Reply To: 	seaint(--nospam--at)
> Sent: 	Wednesday, January 20, 1999 7:59 AM
> To: 	SEAOC
> Subject: 	Fixed base timber column
> Importance: 	High
> I am designing a free standing trellis.  The footprint is about 100ft
> x
> 20ft.  The owner wants to use 10x10 timber columns, 10x12 beams with
> 4x8
> lattice at 36" o/c.  The columns are founded on 18" diameter caissons.
> The
> timber columns are spaced at 14'-0".
> The owner would not like to see the typical knee braces to support the
> timber frame from lateral movement, and no exposed connections.  I
> have been
> tossing ideas around in my head about how to approach this fixed base
> timber
> column condition.
> The ideas I have come up with are:
> 1. Use a vertical steel plate in the center of the column and bolt
> through
> and plug the holes.  I do not feel to good about this.
> 2. Embed threaded rods into the concrete either when they pour the
> caissons
> or then drill into the column and install with epoxy adhesive.  Not a
> bad
> solution, but how do I design it.
> 3. Embed a 2" +- pipe column into the concrete and drill the column
> and then
> bolt through and plug.  Hard to drill into the timber and to
> construct.
> Has any body designed a structure like this and if there is, how did
> you do
> it, what is the best solution.
> Thank you in advance.
> Thomas Long
> Thomas Long Engineering