Determining spliced (Dado and thru bolts) post load limitations

[4thorns]

Hi everyone. In the attached I've shown 3 details I'm using to try to determine the allowable wind loads for a wall stiffener in a log home. In this case the post isn't long enough to go from floor to roof. After studying it I feel that I should:

A: Consider the reduced section a cantilever, fixed where it meets the full section, to find it's max load based on max bending, shear and deflection.

B: Use single shear, in the reduced section, at the opposite end of the full section to determine the max load that the through bolts and lumber can withstand.

C: Use the smallest load of the two.

To me these seem to be the controlling factors. In this case I do not want to include the force resistance of the logs simply because I want to understand how the load is traveling through the splice in the post. I referenced the logs only to introduce a tributary load to the post.

I guess my question is, am I on the right track with my determinations?

Thanks,
Doug

 

[dhengr]

4thorns:
That’s a nasty detail, a poor moment splice, at the max. bending moment region of the member. There will be some rotation/curvature before your bolts really come into play, and then they load the thin pieces in the worst possible grain orientation, right near he end of that member. What size are the logs and the beam/col. and how long is the post? Why can’t you get a full length post in there? What’s forcing you to use that detail? That’s a half-lap joint, btw, not a dado. That would be an o.k. col. splice if fit-up well, but it is not a very good bending member joint at that location. I’d screw-n-glue that post to every log in the stack and try to figure out how to make that act as a bit of a composite section. Maybe rip a 3/8" + kerf the full length of the inside face of the post, 1" deep. Then put a 3/8" dia. post tensioning rod (mild steel) with 3"x3" t&b washer plates and nuts in that groove, and tighten the nuts. This would act as your tension element during wind induced bending.

 

[4thorns]

Thanks for the reply dhengr. yeah, I know it's an ugly solution from the past and I have other ways of handling this scenario now.

I just wanted to know if my thoughts in my op were correct in determining the connection's strength were correct.

 

[dhengr]

4thorns:
Where ever the two butt splice points are (looks like about L/3 & 2L/3), I would find the allowable bending moment at that point which could be carried by a half width post member, without over stressing that lesser width member. Now, I can extend that bending moment diag. to determine the center line moment, and W in lbs.ft. too. I would try to design the half lap joint for those moments and shears, with due consideration for bolt bearing, edge and end distances, etc, all per the NDS. Keep in mind that splitting (ripping) a timber can change its stress grade, and that you don’t want to leave any notches (stress raisers), right at the reentrant corner, when you cut the half lap. Maybe even drill these corners and saw to the drilled hole edge. And, you don’t want any knots or nasty grain slope at that location either. Posts and timber beams are graded slightly differently. Your cantilever concept probably comes into play as you design the lap joint and bolting. And..., what are your improved ways of handling this condition.

 

[4thorns]

Thanks for the info dhengr. The best fix I have for this situation is to run a timber beam from the gable, over the living area, back to the second floor system. (When that option is available) If I can't do that then I recommend an engineered post. Most of the time there are two such posts running from floor to roof.