Need a book? Engineering books recommendations...

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

Re: Wood beam splits

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Jim,
 
Is the beam split or checked? A split goes all the way through the thickness -- the 3-inch dimension. From your description, it sounds more like a seasoning check. If this is an older beam, there was a reduction in the allowable design value for shear based on possible checking.
 
Checking is natural and usually is not a problem, just excites owners when they see it.Your suggested fix might be a little much if the beam is only checked. Maybe one or two bolts to make the owner happy if he insists on some repair, but best not to do anything. 
 
Is the beam deflecting excessively? Unless the beam is split into two pieces and sagging, it is unlikely that you will have a failure. As for a repair, if the beam is split and sagging, then you might want to use stitch bolts or lag screws. Use a few bolts/lag screws to keep the beam from becoming two separate pieces. Install connectors generally at the ends of the beam and away from higher stressed areas of bending.
 
Bruce Pooley P.E.
Timber Design
3448 S. Newland Court
Lakewood, CO 80227
 
 
 
----- Original Message -----
From: Jim Wilson
Sent: Sunday, June 27, 2004 1:42 PM
Subject: Wood beam splits

SEAINT,
 
I am reviewing a 3"x12" doug fir beam with wood splits along the length of the member.  I've searched the archives and AWC and only come up with the elimination of the shear stress adjustment factor CH in the 2001 NDS.  NDS 1991 Appendix E which provided Kv as a shear coefficient for horizontal shear has also been removed in the current NDS.
 
What is the current recommended design approach if there are no prescribed adjustments for splits?
 
AITC Tech Note 18 has a somewhat elaborate procedure for splits in Glu-lam beams, but does the theory transfer over to regular cut wood?
 
To repair an in-service beam with a deep mid-height longitudinal crack at bearing, my thoughts are to drive lag bolts vertically from the bottom of the beam up through the crack and almost to the top of the beam.  I would start with say 4 bolts 3-6" inches on center, starting at the bearing point.  The bolts would then act as shear pins to transfer horizontal shear between the top and bottom of the beam.  Do wood beams perform in such a way that this would be a logical and appropriate fix?  The beam is exposed, so plating the outside is far less desirable.
 
TIA,
 
Jim Wilson, PE
Stroudsburg, PA


Do you Yahoo!?
Yahoo! Mail Address AutoComplete - You start. We finish.