Wood Beam Extension
Wood Beam Extension
(OP)
I am working on a project (new construction) where I have 2 large Gluelam beams that run at 90 degrees to each other. One beam 'hangs' off the other. The beam end load is in the range of 13kips.
The problem I have is that the 'carrying' beam is not braced. It basically spans from support to support with a wood knee wall built on top of it, compliments of Mr. Architect.
I'm concerned about eccentricity rolling this beam. I don't want to try and "grab" it with my columns. Moment fixity in wood is something I don't really believe in, so I have scratched the idea of a monster moment connection that is basically a monkey holding its own tail.
As a solution, I thought about extending the incoming glue lam beam with a piece of steel that would rest on top of the 'carrying beam'. This would allow me to bear my load concentrically.
The attached sketch shows my concept.
My questions are as follows:
1. has anyone every done something like this with success or failure?
2. is there any concern about wood shrinkage v.s. the multiple rows of bolts?
3. is there any concern about cross grain tension? I tried to keep the bolts below the neutral axis.
The text book problem is pretty much this scenario but flipped 180 degrees....i.e. hanger rods on a wood beam, with the note to keep things above the neutral axis.
Prying action will be analyzed.
Thanks in advance.
The problem I have is that the 'carrying' beam is not braced. It basically spans from support to support with a wood knee wall built on top of it, compliments of Mr. Architect.
I'm concerned about eccentricity rolling this beam. I don't want to try and "grab" it with my columns. Moment fixity in wood is something I don't really believe in, so I have scratched the idea of a monster moment connection that is basically a monkey holding its own tail.
As a solution, I thought about extending the incoming glue lam beam with a piece of steel that would rest on top of the 'carrying beam'. This would allow me to bear my load concentrically.
The attached sketch shows my concept.
My questions are as follows:
1. has anyone every done something like this with success or failure?
2. is there any concern about wood shrinkage v.s. the multiple rows of bolts?
3. is there any concern about cross grain tension? I tried to keep the bolts below the neutral axis.
The text book problem is pretty much this scenario but flipped 180 degrees....i.e. hanger rods on a wood beam, with the note to keep things above the neutral axis.
Prying action will be analyzed.
Thanks in advance.






RE: Wood Beam Extension
RE: Wood Beam Extension
RE: Wood Beam Extension
How wide can you make the carrying beam? 8-3/4"?
RE: Wood Beam Extension
RE: Wood Beam Extension
RE: Wood Beam Extension
RE: Wood Beam Extension
Mike McCann
MMC Engineering
RE: Wood Beam Extension
RE: Wood Beam Extension
RE: Wood Beam Extension
Structural timber engineering
RE: Wood Beam Extension
RE: Wood Beam Extension
If I understood the item correctly, you still need to design for compression face buckling of your carrying beam. I am not exactly sure what you mean by "knee wall" on top of your carrying beam, but the image that comes to my mind would not provide compression face bracing for your carrying beam. It seams to me your carrying beam, as it is, may be braced at three locations, ie both ends and at the carried beam.
By the way, shrinkage and multiple bolt rows is an issue. So is cross grain tension although I don't see that yet in your original sketch.
In your original sketch, it's hard to tell what's going on with your carrying beam beyond the carried beam..... Is at a hinge connection or a column connection or.?
RE: Wood Beam Extension