I believe that eastern white pine only shrinks 1/8" in 12". So I don't think that a 10 x 10 is going to shrink 1/2" especially in an un-heated environment of a horse barn.
Also, as wood only drys, on average of 1" per year letting a 10x10 sit for 2 years isn't going to do much.
Pegs are going to bend a lot before they break.
The engineering council has been doing tests of joints at each conference. At one conference I brought two "tie beam to post" joint connection. Both were made from one timber. All the same age and moisture content. I made all four pegs from one 1x1x4' oak stick. All the same age and moisture content. The only difference in the two joints was where the pegs were placed in the post. One set was traditional like the old fashion way of doing it. One was the modern way an engineer told me to place the pegs. I felt that the modern way was too close to the end of the tenon.
Both joints took over 6,000 lbs of force to get them to fail. Both failed within 200 lbs of each other. Basically almost the same.
Both joints failed by the pegs bending over from straight to a "U" shape. And there were two pegs in each joint.
I was expecting the "too close to the end of the tenon" peg holes to blow out the relish on the end of the tenon. Which neither did blow out.
My advice to you is to have each joint you question properly engineered by an experienced timber frame engineer for the size and location of the pegs.
In order for one joint to fail, others in the line will have to fail as well, at the same time. Unless the structure is exposed to external wind forces or seismic conditions, like earth quakes, the chances of more that one joint failing at the same time in the same way that would cause a catastrophic failure is very small. In my opinion.
Shrinkage failure can be preplanned by making the housing deeper so that there is more "shelf" for a beam is sit on should the post shrink some.
Draw boring the peg holes, which will cause the peg to act like a spring and which could help pull the joint together is a fairly common method to keep joints tight.
Just my ideas on the subject.
Jim Rogers
