Need a book? Engineering books recommendations...

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

RE: Hold Downs With No Plywood Ductility

[Subject Prev][Subject Next][Thread Prev][Thread Next]
It's almost impossible to comment without knowing a LOT more details about the testing. Really, one can't comment without reading a full report.

Buddy Showalter, Tom Skaggs, and I could likely fill your e-mail inboxes to overflowing with a discussion of boundary conditions, wall/panel configurations, and their effects on test results. 8-)

Gary

Gary J. Ehrlich, PE 
Program Manager, Structural Codes & Standards 
National Association of Home Builders (NAHB) 
1201 15th Street, NW, Washington, DC 20005 
ph: 202-266-8545  or 800-368-5242 x8545 
fax: 202-266-8369 
gehrlich(--nospam--at)nahb.com 

-----Original Message-----
From: Jordan Truesdell, PE [mailto:seaint2(--nospam--at)truesdellengineering.com] 
Sent: Friday, May 09, 2008 3:12 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Hold Downs With No Plywood Ductility

How long had the assembly been in place before the testing was done. 2 
weeks or 20 years?  Not that this is definitely the case, but it would 
seem that the frictional interface between the plywood and the studs 
would add significantly to the stiffness of the assembly until the studs 
and sheathing reduced in size due to moisture-loss related shrinkage. 
Maybe they should test some assemblies after running them a few months 
in a kiln?

Of course, that would require a 2-5 year waiting period from the time of 
construction to time of safe occupancy. That might not sit well with the 
NAHB. ;-)

Jordan



David Merrick, SE wrote:
> Just heard a rumor out of San Jose State University.
>
> The ASD Hold Down capacity was 30% higher than the Plywood shear wall 
> and yet the Hold Down failed by ripping the screws out of the stud. 
> The plywood showed no obvious signs of distortion relative to the 
> studs. So the wall must have lifted off the base still square in shape.
>
> Ultimate load was 4.7 times the sheathing design capacity and 3.5 
> times the holdown capacity.
>
> Something is seriously wrong. This is the second event I have heard of 
> where the HD failed before the plywood.
>
> Ultimate strength of plywood needs to be reconsidered to not first 
> fail the HD, Resulting in little plywood ductility. You know, the 
> stuff that allows the very high rho of 6.5
>
> David Merrick, SE
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   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 
******* ****** ****** ****** ******* ****** ****** ********