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RE: Existing Beam: Repair or O.K.?

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If the sketch is representative of the situation (i.e. a "crack" on one side
with the rotation) and it is a solid timber member, then it is most likely a
check due to tangential shrinkage of the wood (i.e. the rings of the tree
wanting to shrink in circumference due to loss of moisture/drying).  Such
things are VERY common in large timber members.  Large timber members will
almost definitely check due to loss of moisture.  Such timbers usually start
out with moisture contents well above 19% (typically in the high 20's to low
30's if not higher sometimes) and frequently are put into service with
moisture contents still well above 19%, unless they are kiln dried.  The
only difference between a kilned dried timber and a green timber with
regards to checking is when the checking occurs.  Generally speaking, such
checks are accounted for in the shear provisions of the NDS and thus are
generally NOT a concern.  Only where there is REALLY severe checking that
results in checks that pass through most or all of the cross section is
there generally concern (i.e. maybe two checks on opposite sides of the
member that then meet in the middle).  If the check only passes through less
then one half of the member, then it is generally not a concern.  It is just
part of dealing with wood.

But, if it gives you warm fuzzies to repair or replace, then who am I to
stop you?

Now, if this is a glulam or some other engineered wood member, then that is
a whole other ball of wax.

Regards,

Scott
Adrian, MI

-----Original Message-----
From: Abolhassan Astaneh-Asl [mailto:astaneh(--nospam--at)ce.berkeley.edu] 
Sent: Monday, April 14, 2008 10:22 AM
To: seaint(--nospam--at)seaint.org
Subject: Existing Beam: Repair or O.K.?



Dear Mr. Allen:  Of your three options below, I think the third option might
be the way to go which to repair the damaged beam. However, we may need to
find out first what caused this crack in the beam? Without knowing the cause
of damage, the repaired beam can also be cracked for the same reason the
original beam cracked. Option one "to do nothing" does not seem to me an
option at all. Pretty much you have two options either repair the damaged
beam and if that cannot be done in a reliable and economical way, then the
beam has to be replaced. 
Hope my 2-cents is helpful.
A. Astaneh-Asl, Ph.D., P.E.
Professor and Consultant on
Structural Engineering, Earthquake Engineering and Protection of 
Buildings and Bridges against Blast and Impact
==========

From: "Bill Allen" <T.W.Allen(--nospam--at)cox.net>
To: "Seaint" <seaint(--nospam--at)seaint.org>
Subject: Existing Beam: Repair or O.K.?

I'm working on a small commercial remodel in Southern California. The = part
of the work for which I'm responsible is nearly complete. However, when =
the inspector came out to finalize the framing, he noticed problems in an
existing beam which is not part of my original scope of work. The = building
is three stories and is rectangular. There is a beam line running down = the
middle of the long direction. For my work, I had to remove and replace = the
existing beam where the office is being remodeled. Beyond my work, the
existing beam is unmodified. What caught the inspector's eye are small =
holes drilled in the beam used to pass electrical conduit. I haven't run the
numbers yet, but I believe these holes are O.K. What is troubling is = that,
on one span, there is a long crack down the wide face of the beam for = most
of the length. Worse yet, it appears that the beam above the crack has
rotated slightly. Below is a sketch prepared by my original CAD program.
I've exaggerated the rotation, but it is obvious. The beam is huge. It's
18-3/4"x701/4". It spans about 12-1/2 feet and supports two floors and a
roof. I'm concerned about two things; the ability of the beam to = transfer
VQ/I stresses through the cracked region and the ability of the beam to
remain stable if the crack propagates. Maybe there are other things I =
should worry about. There are three methods of addressing this problem that
I = can think about off the top of my head and they are:

1.      Do nothing; the beam is still structurally viable.

2.      Add Simpson LTP4s at 12" o.c. or so which would stitch the crack =
in
the hopes that it will keep the crack from enlarging/propagating and = will
hopefully transfer the VQ/I stresses by an unknown load transfer path.

3.      Don't mess around with it and repair the beam by sandwiching two
PSLs, one on each side and designed to take 100% of the load. I would = have
the contractor jack the beam as far as he can (there are bearing walls
above) before he bolted these beams to the existing beam. If I could get
100% of the load off the existing beam, it would then act to only = transfer
the load to the PSLs.

What would you do and why?

TIA,

 T. William (Bill) Allen, S.E.

ALLEN DESIGNS <http://www.AllenDesigns.com>=20

Consulting Structural Engineers
 V (949) 248-8588 . F(949) 209-2509

=====================================


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