Log Shear Walls with Chink Joints
Log Shear Walls with Chink Joints
(OP)
I've read through some of the previous threads pertaining to log shear walls (thread726-101643 and thread337-25324) and have gained some good insight. However I would like to take this question one step farther. The log home client I deal with uses rectangular shaped logs (6x12) with a 4" chink joint between each log course. The chink joint consists of wood squash blocking at intervals no greater than 96" on-center with styrofoam block filling the remainder of the joint.
In regards to the horizontal shear capacity of the shear wall, we have been utilizing the steel pipe method of anchoring the logs together for horizontal shear while using all-thread rod at wall ends to combat uplift due to overturning.
A question has been posed by a contractor who has been building log homes on the west coast for years who has been utilizing another system that uses only 1/2" threaded rods for shear and uplift resistance. He had this system engineered several years ago by a Arizona PE.
My concern with this system is the ability of the threaded rods to resist bending that would be created at the chink joint. I understand that if the logs were on top of each other, the dowel-bearing yield states would govern. However with the chink joints, wouldn't the 4" gap create a moment arm on the threaded rod? I have used this reasoning with the pipe system I am currently using and it governs the allowable load versus the dowel-bearing check.
Are my concerns valid, or is my approach overly conservative? Any ideas or comments would be greatly appreciated.
In regards to the horizontal shear capacity of the shear wall, we have been utilizing the steel pipe method of anchoring the logs together for horizontal shear while using all-thread rod at wall ends to combat uplift due to overturning.
A question has been posed by a contractor who has been building log homes on the west coast for years who has been utilizing another system that uses only 1/2" threaded rods for shear and uplift resistance. He had this system engineered several years ago by a Arizona PE.
My concern with this system is the ability of the threaded rods to resist bending that would be created at the chink joint. I understand that if the logs were on top of each other, the dowel-bearing yield states would govern. However with the chink joints, wouldn't the 4" gap create a moment arm on the threaded rod? I have used this reasoning with the pipe system I am currently using and it governs the allowable load versus the dowel-bearing check.
Are my concerns valid, or is my approach overly conservative? Any ideas or comments would be greatly appreciated.






RE: Log Shear Walls with Chink Joints
DaveAtkins
RE: Log Shear Walls with Chink Joints
My biggest concern with this would be quantifying the amount of friction you could count on. With the clamping action, I would imagine you could count on a bolt pre-tensioning force along with the dead weight of the wall. However with wood shrinkage/settlement over time, the advantage created by the pre-tensioning would diminish.
Any ideas on a coefficient of friction?
I could see this idea working for a log system with a log to log connection with no chinking in a low shear application, but I'm still a little skeptical in using it with the chinked system I have. Especially in high wind regions where I'm getting of 400 plf of shear on my walls.
RE: Log Shear Walls with Chink Joints
RE: Log Shear Walls with Chink Joints
RE: Log Shear Walls with Chink Joints
The problem with assuming friction action, is the fact that wood shrinks as it dries out. I would think in most applications, wood shrinkage would relieve what ever friction that was intially present.
RE: Log Shear Walls with Chink Joints
Dik
RE: Log Shear Walls with Chink Joints
Actually utilizing friction maybe a common assumption. While looking for information on another topic I stumbled upon an article about log shear walls.
Still not sure that I would use friction. Then again I don't design any log structures.
If one does a Google search for Wood Design Focus, they can probably find several articles on log structures.