wood to wood moment connection
wood to wood moment connection
(OP)
can anyone guide me on how to design wood to wood moment connection without steel plate? I have this weird residential roof lookout structure where I have to splice the 2x12 roof rafters.
so its like 2x12 sloping 4/12, spliced with flat 2x12. I want to put nails in the area where the 2 rafter overlaps (diamond shape). I have never taken timber design class so... Thanks!
so its like 2x12 sloping 4/12, spliced with flat 2x12. I want to put nails in the area where the 2 rafter overlaps (diamond shape). I have never taken timber design class so... Thanks!






RE: wood to wood moment connection
Even if you get the connection to take the moment, you probably won't be able to get it fixed, or to allow no rotation. Keep that in mind when you're checking deflection or any moment in your members that gets reduced by the connection you're looking at.
RE: wood to wood moment connection
RE: wood to wood moment connection
RE: wood to wood moment connection
RE: wood to wood moment connection
1. The direct force = total shear divided by number of fasteners, plus
2. The eccentricity force = moment times distance from centroid of fastener group divided by polar moment of inertia of the fastener group.
RE: wood to wood moment connection
RE: wood to wood moment connection
Now consider the direct shear. Each nail will experience an equal vertical force.
Add the two effects together. The outermost nail feels the highest load because the moment effect and the shear effect are acting in nearly the same direction.
Look up elastic analysis of eccentrically-loaded bolt groups in any steel textbook. The principles are the same for the nail connection.
RE: wood to wood moment connection
Don't use the instaneous center of rotation method, if you come across in the steel book. You need empirical values for that, which you won't have.
When you have the nail shear from eccentric loading, you can check the deformation of the nail-wood system and figure your deflection and see if it's acceptable. That information is in the NDS, where you would need nail slip for calculate diaphragm or shear wall deflection.
RE: wood to wood moment connection
RE: wood to wood moment connection
But I wouldn't have a problem with using a moment connection to support a very short eave rafter like COEngineer is doing. As long as it is properly designed, that is.
RE: wood to wood moment connection
Yet enough timber portal framed buildings have been built to show that it is a viable construction method (in Australia anyway).
RE: wood to wood moment connection
Anyway, my point is I believe you can design a connection to transfer moment from one wooden piece to another. However, I would not use nails for it. I recommend either lag bolts, lag screws or wooden dowels. And make sure you check all the eccentricities in the problem.
RE: wood to wood moment connection
I agree with UcfSE
RE: wood to wood moment connection
I think your case would be better analyzed by using the nails you have shown as a pin connection, say at the center of the group. Add a metal strap, 2x4 or sheathing on top of the two chunks that were nailed to the flat rafter. If you connect the chunks together with this member, it will act as a tension member (at least for gravity loads). This will create a couple and thus work as a moment connection, at least for the small moment I would expect from your picture.
The best way to make a moment connection in wood is to figure out how not to make a moment connectin in wood.
RE: wood to wood moment connection