Return to index: [Subject] [Thread] [Date] [Author]

Re: Wood Shearwall Deflection Calcs

[Subject Prev][Subject Next][Thread Prev][Thread Next]
The procedure for that calculation is WAG.
In point of fact, Simpson has never tested their straps in wood. So, not only is
there no load/deflection data, the capacity is probably very much less than
Simpson's catalog value.
Chuck Utzman,P.E.

Gerard Madden wrote:

> Paul,
>
> The value I am looking for is for the "Tiedown Elongation" which is:
>
> (demand force (LRFD level)/ ASD Rated Capacity of Hold Down) * Tie
> Deflection @ Allowable load from ICBO Report
>
> Then you also check for nail slip, shrinkage and crushing in the tie-down
> assembly and add them together to get total tie down device deflection.
>
> When the contractor forgets to edge nail the hold-down studs, multiply by
> (2/1.4) if you are using ASD :)
>
> -gerard
> SJ, CA
>
> -----Original Message-----
> From: Paul Crocker [mailto:paulc(--nospam--at)ckcps.com]
> Sent: Thursday, January 03, 2002 2:50 PM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: RE: Wood Shearwall Deflection Calcs
>
> I am not familiar with the manual you are referring to, but I have estimated
> deflection using one of the supplements to the '97 NDS manual a few times.
> For that method, my understanding is that for a rod the deflection is
> basically PL/AE plus any additional deflections that may occur due to
> slippage in the connections.  I have been told by an engineer working for
> one of the self-compensating hold-down products companies that the
> additional slippage number is nearly 0 for their products and so PL/AE is
> accurate enough.  For a strap, though, I imagine that there would be
> additional deflection due to nail slip and due to small kinks and bows in
> the strap between adjacent nails straightening out under tension.  Any
> shrinkage in the wood would only make such a condition worse, as 1/4" of
> shrinkage would leave 1/4" of slack in the strap that would have to be taken
> up before it would be fully activated.  Whatever you come up with, keep in
> mind that straps will be pretty unpredictable in that regard and probably
> don't lend themselves to being calculated to the hundredth of an inch.  I
> would not be surprised if that is why tables for straps are harder to find
> than for other hold-down systems.  Perhaps someone else out there can point
> you to some papers on it.
>
> Paul Crocker, P.E.
>
> -----Original Message-----
> From: Gerard Madden [mailto:gmadden(--nospam--at)duquette-eng.com]
> Sent: Thursday, January 03, 2002 10:46 AM
> To: SEAINT LISTSERVER (E-mail)
> Subject: Wood Shearwall Deflection Calcs
>
> Question,
>
> I am writing a spreadsheet to calculate drift for a wood shearwall. I have a
> question regarding the Tie-Down Elongation for premanufactured hardware. The
> Seismic Design Manual Volume ii, page 47, footnote 3 explains how to
> calculate it. The question I have is regarding straps. My Simpson catalog
> doesn't give the elongation value for straps, only for obvious hold-downs
> like HD's & PHD's. Yet the example in the SDM shows values for .05 and .03
> for walls 3 & 5 in the table respectively.
>
> How are they getting that value? Are the just doing Delta = PL/AE or is it
> something else.?
>
> thanks,
> -gerard
>
> Gerard Madden, PE
> Design Group Manager
>
> Duquette Engineering
> 10 South Third Street
> San Jose, CA 95113
> T: 408.494.0944 - ext 102
> F: 408.494.0940
> E: gmadden(--nospam--at)duquette-eng.com
> w: www.duquette-eng.com
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   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
> *   without your permission. Make sure you visit our web
> *   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
> *   without your permission. Make sure you visit our web
> *   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
> *   without your permission. Make sure you visit our web
> *   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
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********