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Re: Cross-grain Tension

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Thor,

Your response to Daryl indicates a different situation other than just 
cross-grain tension.  What you are describing is a notch, and the theoretical 
tension stress at a reentrant corner is *infinity*, (see any theory of 
elasticity text) which is why glass breaks so cleanly when it is scored.

While the codes do permit such notches and kerfs, I will not accept them 
without mechanical reinforcement.  I have seen splits start at these notches 
in lightly loaded residential rafters, and if the slope of the grain is 
upward, extend to the top of the rafter.

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

Daryl Richardson wrote:

. > Thor,

. >         I was referring to 1995 Wood Design Manual by Canadian Wood
. > Council, Table 11.15.

. >         I only looked up the topic in the index; I did not read the
. > applicable pages to confirm whether "specified" meant working or
. > factored.  I realize that 1 MPa = 145 psi, which makes the posted values
. > much higher than the 15 psi mentioned by others on the list.

. >         Hope this helps.

. > Regards,

. > H. Daryl Richardson

. > vicpeng wrote:

>  Hi Daryl. Which handbook is this?  Is it the Wood Design Manual
> 1995?  If so, I chucked mine a while back.  Also if so, can you give
> me the section reference?  I see our buddies over the fence are
> suggesting 15 psi allowable (?) for radial tensions, which
> approximates (?) 20 psi (0.14 MPa) for limit states (?).  That is well
> under the 0.83MPa you suggested (?). What I am looking at is,
> restraint against the possible splitting at a support notch on the
> tension side.  Since the split would be assumed to be initiated by
> deflection of the beam, it approximates radial tension (?)  This is an
> academic exercise on my part which probably has no bearing on "real"
> life.  I like the idea of side plates if tolerances allow, or I've
> found (in my workshop) that (gluing if there is a real split) lag
> screws, or similar, across the split will often work.  I'm trying to
> make my findings "calc".  Hence the liberties. BTW I have resurrected
> the Lorraine Bldg notes you sent me but found that the pps from Dennis
> doesn't work on my current system (it did before so I'm at a loss) so
> I am waiting for an update from him. Thanks
> Thor A Tandy  P.Eng
> Victoria BC

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