Dimension glulam beam / light beam / plywood beam

[Albireo]

Hello!
I am in the process of modifying an existing deck (with a roof).
The floor joists are currently 45x200x4080mm with a support in the middle.
The support in the middle is to be "rationalized" away.

But first (before dimensioning for my deck)
Assume that the existing floor joist 45x200x4080 is to be directly replaced with the same load.
What dimensions would the following products get?
- Glulam beam (e.g., Martinsson or ... most suppliers seem to use spruce)
- Plywood beam (type Kerto beam)
- I-joist (type Masonite-Beams or Hunton)
- Box beam (masonite or plywood on the sides)

 

[justusandersson]

When comparing different beam types, it is sufficient to compare their respective modulus of elasticity and moment of inertia. Load and span are irrelevant in this case. 45x200 C 24 corresponds, for example, to glulam 56x180 and kerto 39x200. I can't find any relevant data quickly when it comes to masonite beams (although they do exist). Box beams can be made by oneself (if one has a good saw) with infinitely many size variations.

 

[Albireo]

Where can these relationships be found? (or better the modulus of elasticity and the moment of inertia for different products?)

 

[justusandersson]

The moment of inertia for beams with rectangular cross-sections is most easily calculated using the formula "b x h ^3 / 12". Compound structures can be a bit more complex to calculate depending on the geometry. Elasticity modules are detailed in the wood guide and manufacturers' websites. By multiplying the elasticity module and the moment of inertia, one can compare a glulam beam with a steel beam, etc. It is important to be consistent when it comes to the choice of units (types).