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Re: Lag screws in withdrawal from end gr

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Ernie,

The reference that I have (Modern Timber Design by Howard J. Hansen) 
references:  "Lag Screw Joints:  Their Behavior and Design," by J. A. Newlin 
and J. M. Gahagan, Tech Bull. 597, U. S. Department of Agriculture, 1938.

The formula in the book for safe withdrawal loads from seasoned lumber with 
a factor of safety of about 5, presumably in side grain, is given as:

P = 1800 * (G^1.5) * (D^0.75)

where G = specific gravity of oven dry wood
      D = diameter of shank in inches

For joints alternately wet and dry, use 3/4 of the formula value.

For joints that will be damp or wet, use 2/3 of the formula value.

For lag screw inserted into the end of a piece, use 3/4 of the formula value 
(presumably adjusted for seasoning condition also).

Hope this helps to answer your question.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Ernie Natividad wrote:

. > Anybody out there knows the history of this code provision or is familiar 
. > with how allowable lag screw withdrawal values were obtained?
. >