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RE: Delaminating glulam valley beam

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Peter:

I agree with Bruce's comment.  Seasoning checks are usually observed near a
glueline, where the drying stresses are the highest.  Drying stresses are
induced because the beam typically starts at 12% moisture content (OD basis)
after manufacturing then drops to about 8% moisture content (OD basis) in
your "normal" residential application.  However, the beam is often exposed
to the weather during construction where it can pick up some more moisture.
The bottom line is that checks are a natural characteristic of wood products
and are not normally detrimental to strength.  Please see the following APA
publications for more information.  Their website is www.apawood.org

EWS R465 - Checking in Glued Laminated Timber
EWS R475 - Evaluation of Check Size in Glued Laminated Timber Beams

Scott M. Kent, P.E.
Quality Manager
Wood Science & Technology Institute
6300 SW Reservoir Avenue
Corvallis, OR  97333
T: (541) 929-9784
F: (541) 929-3694
email:  scottk(--nospam--at)woodcompositesengr.com


-----Original Message-----
From: seaint-return(--nospam--at)seaint.org [mailto:seaint-return(--nospam--at)seaint.org]On
Behalf Of Bruce Pooley
Sent: Thursday, November 30, 2000 8:11 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Delaminating glulam valley beam


Peter

Most of the reported delamination of glulam beams is really seasoning
checks. I have been out on several jobsites in the last few months and 99%
is checking.

I would be glad to assist you by reviewing the photos.

You can obtain additional information regarding checking from AITC and APA.
Both organizations have technical notes that address checking. APA's tech
note is available online for free.

You may contact me at
bdpooley(--nospam--at)home.com

Bruce Pooley
Timber Design
3448 South Newland Court
Lakewood, CO 80227
----- Original Message -----
From: "Peter McCormack" <PMac(--nospam--at)realloghomes.com>
To: <seaint(--nospam--at)seaint.org>
Cc: <aec-residential(--nospam--at)polhemus.cc>
Sent: Thursday, November 30, 2000 6:22 AM
Subject: Delaminating glulam valley beam


I have received a report of a valley beam delaminating at the
second lamination from the bottom. The beam is a 5 /18" x 12"
(24F-V4) and from my calcs is structurally adequate. The other
valley beam is fine.

I am trying to determine the cause of delamination. I have doubts
about it being poor manufacture.  I am still obtaining information
regarding storage prior to construction, if the beam was left
exposed to the elements for any length of time etc.

The building was constructed during the fall of last year and
complete this spring. The building is located in NY. I am relying on
2nd hand information in getting the facts i.e. I have not seen the
problem personally).

Any comments appreciated. I have some jpeg files showing the
problem if anyone is interested which I will post directly(the seaint
listserver will not accept a email if it is to large)