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RE: How to calculate capacity of two Log beams, one on top of the other ?

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Assuming the beams are of equal length and the top one can't slip off, I
would assign half the load to each beam and calculate them separately,
assuming their deflections will be equal. Even if contact is not perfect, it
would seem like the deflections are going to have to be about the same.

I think the logs are normally hewn at the contact surface so there is
reasonable contact between them. If the logs are not planed so they have a
horizontal contact surface, it would seem to me you might be better off
assigning all the load to the top log, since it is the loaded element,
assuming it could slide sideways off the lower one. 


-----Original Message-----
From: Zhou, Helen [mailto:HZhou(--nospam--at)stlouisco.com]
Sent: Thursday, May 19, 2005 8:41 AM
To: seaint(--nospam--at)seaint.org
Subject: How to calculate capacity of two Log beams, one on top of the
other ?


When you have two beams with same sizes and simply supported, one on top
of the other with no connection between, I always think the bottom beam
shall be designed for almost 100% load, because load distribution is
unknown.

I am reviewing plans of the log home, have 23.5 ft span beam with 6000
lb concentrated load in the center and 240plf distributed load, M=51810
lb-ft. The engineer use two 14" dia Engelman Spruce, select structure
(fb=1100, Mu=24750 lb-ft, E=1,300,000), one beam sits on the other with
no any connection, the engineer calculation claimed total Mu=2x24750
lb-ft.

Please help me.


Thank you !


Helen Zhou
Saint Louis, MO

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