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RE: porches in seismic areas

• To: <seaint(--nospam--at)seaint.org>
• Subject: RE: porches in seismic areas
• From: "Joseph R. Grill" <jrgrill(--nospam--at)cableone.net>
• Date: Thu, 15 May 2008 16:35:10 -0700

Yes, I was thinking lighter loads. Also, only "similar" to a Simpson base.
If the side plates are taller, say 12", then the bolts could have a 9"
spacing.  A 5/8" bolt in a 6x6 DF would give you 1420x1.6=2272 lbs per bolt.
At 9" couple that would give a 1704 ft-lb moment resistance.  At 7' you
could restrain a 240# lateral load. That would be for the bolts only.  At 90
degrees that same 240 lbs applied at the top (I'm being kind of general
here) of two 3" wide plates produces a moment at the bottom of the plates of
1440 in-lbs (if I'm correct). Looks like 2-3/8" plates might work at the 90
degree situation.  Depends on how big the porch and how many posts resisting
the seismic or wind. If deflections at the top of the post are agreeable, if
may be work.
Joe

-----Original Message-----
From: chris.slater(--nospam--at)gmail.com [mailto:chris.slater(--nospam--at)gmail.com] On Behalf Of
Chris Slater
Sent: Thursday, May 15, 2008 4:00 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: porches in seismic areas

I think the loads would have to be incredibly light.

Given a 7' column, with only 500# of lateral load, you get 3500 #-ft.
That's resisted by the couple in the bolts, at 3" apart.  So each bolt
winds up needing to be able to resist 14 kips.  Pretty sure NDS values
for through bolts in double shear are at the most in the 4 kip range.
Maybe less...

Am I missing something?

On Thu, May 15, 2008 at 3:14 PM, Joseph R. Grill <jrgrill(--nospam--at)cableone.net>
wrote:
> Another option?  But, probably for lighter laterally loaded columns.
Using
> a column base, shaped similarly to a Simpson CB or LCB but heavier plates
> and bolts.  For loads in one direction the side plates resist the column
> base moment by bending.  For loads in the perpendicular direction the
bolts
> resist the column base moment in bolt values perpendicular to grain.  Any
> thoughts?
>
> Joe Grill
>
>
>
> From: Jnapd(--nospam--at)aol.com [mailto:Jnapd(--nospam--at)aol.com]
> Sent: Wednesday, May 14, 2008 12:43 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: porches in seismic areas
>
>
>
> Andrew
>
>
>
> You are correct steel tubes are not that expensive and I use them all the
> time.  Contractors and home owners freak out when you mention steel. They
> don't understand where to buy, how to use and therefore it must cost way
to
> much is the normal response.
>
>
>
> I tell clients all the time you can use the City or County spec for knee
> braced patio supports; but if you go beyond the size they recommend I will
> not sign or approve any knee-braced wood post..no exceptions.
>
>
>
> Dennis and I do most of our work within 0-15 km of the San Andreas Fault.
> Our area has been expecting a 6.5 - 7.5 Quake for the last 20 years.
> Landers and Big Bear quakes were not on the main fault branch.
>
>
>
> What I do when requested is install a 6x6 post inside a HSS6x6x.25 column.
> The tube extends 2-3 ft above ground with the post embedded 12' into steel
> tube. Clients put stone or brick around the tube so you see just the wood.
> The height of the wood depends on how many post are available.
>
>
>
> I always consider a trellis roof as a solid roof..because within 5 years
it
> usually is.
>
>
>
> I sleep quite well at night.
>
>
>
> Joe Venuti
> Johnson & Nielsen Associates
> Palm Springs, CA
>
> ________________________________
>
> Wondering what's for Dinner Tonight? Get new twists on family favorites at
> AOL Food.

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