built up wood beam

[rittz]

Our design called for a 3-ply 2 x 12 built-up beam. The builder put a joint in the
end span (see attached sketch). This is not allowed by the NBCCanada. He has suggested a 4th ply be laminated in the end span. Essentially it seems he still
has a 3-ply beam as far as bending moment is concerned and should be OK for moment resistance He can’t get any end bearing without a lot of work. Are we
entitled to assume that the beam as now constructed will resist the horizontal
shear adequately. The span is 11 ft and the loads are just typical residential loads

 

[Lion06]

I'm really being picky here, but for flexure the 4th ply is acting simple, not continuous. It probably isn't a problem, it's quite possible that it was designed simple, just be aware of the difference.

Regarding shear - as long as you design and detail the connection from the 4th ply to dump its reaction back into the plies that actually bear on the wall, it's not a problem. It's unlikely that shear controlled anyway. I'm not saying it never happens, but I have never run across a wood beam that was controlled by shear (that didn't have a notch in it).

 

[msquared48]

If bending controls and three plies were needed, the splice does negate one of the plies for bending.

An additional full length ply needs to be added with support under it at the 6X6 column (add a 2X6 to the 6X6 column for full support).

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[ToadJones]

Mike-

Is the extra 2x6 post absolutely necessary?

 

[msquared48]

Probably not, but then 2/3 of the load from bending will be going to 1/3 the column bearing section without it. Just check the bearing if you don't want to put it in. I would add it myself, but that's just me.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[ToadJones]

I agree, I was just curious if you thought it was a necessity