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Re: Lag screws in withdrawal from end grain

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>From: NRoselund(--nospam--at)
>Date: Mon, 7 Sep 1998 12:17:57 EDT
>To: seaint(--nospam--at)
>Subject: Lag screws in withdrawal from end grain
>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 
>factor, Ceg=0.75."

AITC handbook has the same wording (nearly same).  I use it if needed. I 
do not have earthquakes anyway!  Wind uplift... Not much in the NE 

>The 1991 edition has a similar statement.  I don't find the 'should 
>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 
>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 
>installation and a costly, complicated, and possibly unsightly 
>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 
>advisory wording of these Code provisions, or insights on how to handle 
>allowable factor for something that should not be done?
>Nels Roselund
>Structural Engineer

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