Constructing box beams

[SebastianP]

I am planning an extension of approximately 7.5x12m, with a shed roof.
I would like to design with a beam instead of a shed roof truss, mainly for ceiling height and sloping interior ceiling.

Glued laminated timber seems to be both heavy and expensive; I calculated 90x360 as a suitable dimension.

My question is whether it would be possible to construct box beams using the following method:
finger-jointed C24 45x145x8,5M, with 500mm P30 construction plywood glued and screwed on the outside. I have a mechanical workshop and would, in that case, build a press jig with hydraulic cylinders for gluing.

If this is feasible, how is such a beam calculated?

 

[Gabbe1]

Interesting thought, in general, I like to solve things on my own. But you mention the price as a reason, is it really cheaper to build a press jig than to buy a glulam beam?

 

[SebastianP]

Interesting thought, generally I like to solve things on my own.
But you mention the price as a reason, is it really cheaper to build a press jig than to buy a laminated beam?

I avoid the cost of the press jig, as I already have all the necessary materials. Otherwise, the calculations might get a bit tricky...

 

[Hiltimannen]

I have personally done it this way but with 2 pieces of 45x220 (K 24) glued edge to edge. Then I screw-glued K-plyfa on both sides with staggered joints. Then I cut the beam to the slope I wanted. Worked perfectly fine on a 4 m span and heavy snow loads.

 

[SebastianP]

Attaching a small image of my intended construction. In this case, 400mm plywood and 120x45 regel.

 

[anaitis]

Have you double-checked to ensure that your box beam has the same stiffness as the glulam beam?