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Lag screws in withdrawal from end grain

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The 1994 Edition of the UBC says "lag screws should not be loaded in
withdrawal from end grain.  When this condition cannot be avoided, the
tabulated nominal withdrawal value, W shall be multiplied by the end grain
factor, Ceg=0.75."

The 1991 edition has a similar statement.  I don't find the 'should not'
statement in the 1991 NDS.  Neither Standard allows wood screws to be used in
end-grain withdrawal.

"Should not" seems to be advisory, not mandatory.  How serious is the
advisory?  The required modification factor does not seem a very restrictive
way of dealing with a bad idea; is Ceg=0.75 a realistic adjustment?  

I have a retrofit condition in which use of lag screws inserted into the end
of an existing 10x10 will make a difference between a quick and simple hidden
installation and a costly, complicated, and possibly unsightly installation;
does this qualify as "Cannot be avoided"?  A Ceg=0.3, or even less, is
workable for the purposes of this particular Detail.

Does anyone have any background on the intent behind the uncharacteristicly
advisory wording of these Code provisions, or insights on how to handle an
allowable factor for something that should not be done?

Nels Roselund
Structural Engineer