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RE: Solutions for Wrong Grade Glue-lam?

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Hi Thor,

Are you 100% sure that the beam was placed right side up?

If not, the beam would be fine as-is.

Many times glu lam beams are placed upside down by mistake with a similar problem as you already described.

Can you live with the decreased stiffness if the beam were made into 2 simple span beams?
Would the increased deflection be noticeable?

Would you rather have the beam monitored on a yearly basis for cracks and then cut it over the column only if it starts to show some distress?

Good Luck

Dave Nuttall, P.E.
Green Bay, WI


-----Original Message-----
From: Thor Matteson, SE [mailto:matteson(--nospam--at)yosemite.net]
Sent: Tuesday, January 14, 2003 9:50 AM
To: SEAINT
Subject: Solutions for Wrong Grade Glue-lam?


I just got word that two glue-lam roof beams in a 3-year-old house I
designed
are not the specified grade.  The design is a two-span
condition--one span is about 18 feet
and the other is 22 feet.  For one of the beams, the 22-foot span has a
ridge and other strange
framing coming into it.  Governing shear and bending stresses occur over the
center support.

The beam was very clearly noted on the plan as 24F-V8 grade.   Any grade
markings on the installed beam were covered up by finish ceiling and
insulation, so I could not
verify the grade.  The owner assured me that they ordered what was specified
on the plans, but the only written information available was their invoice
from the lumber company and the beam manufacturer's shipping sticker from
the beam wrapper, which had some numeric codes on it along with beam size
and date of birth.   The beam mfr's representative recently called to
tell me that the numeric codes matched a 24F-V4 beam.

If this is so, the beam is over-stressed by almost double (what kind of
engineer would I be if I put an additional safety factor of two into
everything I design?  Unemployed....).

My initial thought is to turn the continuous beam into two simply supported
beams by cutting through it directly over the center post.  This would cause
the point of maximum bending stress to move from over the post (negative
moment) to somewhere close to mid-span (positive moment).  Since the beam is
fabricated for positive moment, everything should now be fine, assuming that
the beam can carry the positive moment.  Only difference is
that now the beams could sag more than twice what a continuous beam would
have, but for a roof without plaster ceiling it is still code-compliant.

Any thoughts?  Have any of you done this before?   What if the owners do
nothing?
(This seems scary to me, as the beam could fail in bending over the center
support;  this would not be a clean failure like a saw-cut, and
could
lead to shear failure, collapse, death, dismemberment, not to mention water
damage....)

Thor




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