Need a book? Engineering books recommendations...

# Re: porches in seismic areas

• To: seaint(--nospam--at)seaint.org
• Subject: Re: porches in seismic areas
• From: "Chris Slater" <chris(--nospam--at)jdwylieengineering.com>
• Date: Thu, 15 May 2008 16:47:56 -0700

```That makes sense.  One more option to put in the holster.

Thanks!

On Thu, May 15, 2008 at 4:35 PM, Joseph R. Grill <jrgrill(--nospam--at)cableone.net> wrote:
> 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.
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> *   This email was sent to you via Structural Engineers
> *   Association of Southern California (SEAOSC) server. To
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> *   send to the list is public domain and may be re-posted
> *   site at: http://www.seaint.org
> ******* ****** ****** ****** ******* ****** ****** ********
>
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> *   This email was sent to you via Structural Engineers
> *   Association of Southern California (SEAOSC) server. To
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> *   send to the list is public domain and may be re-posted
> *   site at: http://www.seaint.org
> ******* ****** ****** ****** ******* ****** ****** ********
>

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted