Need a book? Engineering books recommendations...

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

RE: Field Grading of Existing Wood Framing

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Here are a couple of links that might help:

http://www.awc.org/HelpOutreach/faq/FAQfiles/Wood_Repair.html
http://www.awc.org/HelpOutreach/faq/FAQfiles/In-Grade_Testing.html

The second one addresses the in-grade testing program to which you
alluded below.

What we typically recommend for existing structures is to evaluate the
"old" lumber per the "old" code and "old" design values and "old" loads
to see if it was designed properly (or even designed at all) - that'll
give you a benchmark. Then evaluate per "current" code and "current"
design values and "current" loads to see the magnitude of difference.
Then use engineering judgement to repair or reinforce if there's a large
disparity.

Of course, if the local jurisdiction mandates a different approach,
you'll have to adhere to that.

HTH

Buddy

John "Buddy" Showalter, P.E. 
Director, Technical Media 
AF&PA/American Wood Council 
1111 19th Street, NW, Suite 800 
Washington, DC 20036 
P: 202-463-2769 
F: 202-463-2791 
http://www.awc.org 

The American Wood Council (AWC) is the wood products division of the
American Forest & Paper Association (AF&PA). AWC develops
internationally recognized standards for wood design and construction.
Its efforts with building codes and standards, engineering and research,
and technology transfer ensure proper application for engineered and
traditional wood products.

********************* 
The guidance provided herein is not a formal interpretation of any AF&PA
standard.  Interpretations of AF&PA standards are only available through
a formal process outlined in AF&PA's standards development procedures.

********************* 


From: "Jeff Smith" <jeffsmith7(--nospam--at)comcast.net>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: Field Grading of Existing Wood Framing
David,
Your reply is consistant with some other sources I have reviewed. I have
heard of engineers using the allowables from the code they were
approverd under if the lumber was stamped, but that was a while ago. Old
lumber is not necessarily stronger than new lumber of the same grade. As
I understand it, the old grading procedures did not take into account
the degree of imperfections in lumber used in real conditions, they
tested smaller less representative sticks. It makes me wonder how many
buildings there are out there that may be subjected to failed members. I
have been looking for a code section or document that states that
current NDS values need to be used for old lumber, do you know where
this is?
Thanks for your reply,
Jeff

-----Original Message-----
From: Gaines, David [mailto:David.Gaines(--nospam--at)hdrinc.com] 
Sent: Thursday, April 17, 2008 3:53 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Field Grading of Existing Wood Framing
Jeff,
If the joists have split at the knots, repair them by sistering on new
LVL or PSL beams on both sides. Shore up the damaged purlin before you
attach the new wood. If there are other purlins with weak points that
are susceptible to cracking or failure, recommend that they be repaired
by the same means as well. It's a lot cheaper to repair them before they
crack. The new lumber can be bolted on to the 4x112 purlins below the
2x4 or 2x6 subpurlins.
Recommend to inspect as much of the roof as you can get to and itemize
the areas you can not inspect. You only need to upgrade the purlins and
beams you are adding loads to or remodeling in. Write a careful Scope of
work outlining what you're offering to do and what you're not covering.
By re-grading the existing lumber you are not likely to improve on a
Select Structural grade (nothing better than SS) and the allowable
lumber stress values for any grade will be lower today than what they
were in 1977.
If they're adding TI loads to the original, 1977 beams you need to
evaluate them by the current code, not the 1977 code. Current lumber
grading values have been revised to lower values and so most of the
purlins you check will not work with the original loads, much less
additional loading. You'll need to reinforce the structure anywhere they
modify, remodel or add loads. Check your beams and girders in areas that
may be affected by added loads too.

Dave Gaines, P.E.
Structural Project Engineer
HDR ONE COMPANY | Many Solutions
251 S. Lake Ave, Suite 1000
Pasadena, CA 91101
T: 626.584.4960
F: 626.584.1750
email: david.gaines(--nospam--at)hdrinc.com 

-----Original Message-----
From: Jeff Smith [mailto:jeffsmith7(--nospam--at)comcast.net]
Sent: Thursday, April 17, 2008 3:10 PM
To: seaint(--nospam--at)seaint.org
Subject: Field Grading of Existing Wood Framing
I am looking at a 70's office building that has 2 cracked 4x roof
purlins out of maybe 300. There is a knot in the tension zone and
looking around the building there are several other beams that also have
knots in the tension zone. It is stamped Sel Str. The tenant
improvements will add some additional load to the beams. Based on an
analysis using allowables from the 1977 UBC these beams are adequate. Do
you think hiring a grader would be a good idea and once graded would it
be appropriate to use the design values from the 1977 UBC, can a grader
make that decision?
Thanks,
Jeff

******* ****** ******* ******** ******* ******* ******* ***
*   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 
******* ****** ****** ****** ******* ****** ****** ********