] [Thread] [Date] [Author]

[Roger Turk <73527.1356(--nospam--at)compuserve.com>]

Tom Skaggs wrote:

. > The NDS commentary covers the topic pretty well.  I'll paraphrase.... if 
. > the material is clear grain, check and shake free, "the tension perp 
. > design value may be considered as about one-third the shear design value
. > parallel to grain". As the NDS Commentary further says, "undetectable 
. > ring shake and checking and splitting that can occur as a result of 
. > drying in service, very low strength values for this property can be 
. > encountered in commercial grades of lumber".
 
. > Good luck....
 
. > Tom

This is the same requirement for radial tension stresses in GLBs, *except* 
for DF!  Curved GLBs in a roof over a gymnasium designed by the Structural 
Engineer to these requirements (as permitted in the 1967 UBC) started failing 
in the late 1960s.  GLB fabricators told the contractor that when *they* 
designed curved GLBs, they limited radial tension in DF to 15 psi.

A paper presented at an SEAOC convention in the early 70s discussed this and 
opined that the presenter considered even 15 psi too high.

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

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