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

RE: Change in Dimension Lumber Design Values

[Subject Prev][Subject Next][Thread Prev][Thread Next]
I usually use the allowable design values for the timber at the time of
construction.  Typically the timber of past was sawn from older growth trees
and therefore stronger than the saplings we currently build with.

Sharon Robertson Bonds, PE
Salerno/Livingston Architects
363 Fifth Avenue, Third Floor
San Diego, California  92101
(619) 234-7471

	-----Original Message-----
	From:	Conrad Guymon [SMTP:conrad(--nospam--at)karren.com]
	Sent:	Wednesday, May 30, 2001 10:52 AM
	To:	seaint(--nospam--at)seaint.org
	Subject:	Change in Dimension Lumber Design Values

	I have been asked to evaluate a building constructed in 1963.
Design
	drawings indicate that Construction Grade D.F. 2x10's are to be used
with an
	allowable Fb of 1500 psi for the roof framing.  Current code
accepted values
	(1997 UBC) for Const. Grade D.F. 2x10's are Fb*Csubf=1000*1.2=1200
psi.

	The structure was designed for 30 psf snow,  and the current snow
load
	requirement is 50 psf, (which is reasonable for the area).  I can
show that
	the structure works using the original design values, but not the
current
	ones.  The building appears to be performing adequately, but I need
	something to justify the use of the higher original allowable
stresses.
	I've been through the changes to the 1991 NDS, but the literature I
can find
	isn't much help.

	Does anyone have an explanation (with documentation) for the change
in
	allowable stresses?

	Thanks

	Conrad Guymon, P.E.


	* 
	*   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 

* 
*   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