Ok. However, I maintain dimensions as previously mentioned.
Yes, that seems reasonable to me as an amateur as well. It then means that the PDF file I found at svenskt trä does NOT match (which I think feels reasonable).
I have looked in the wood guide and apparently the span has been reduced, but I have designed and delivered wooden houses for 10 years with dim 45x220 c 600 and cross bracing 2-story compartment (or nogging, which is easier). There have been no problems. http://www.traguiden.se/TGtemplates/popup1spalt.aspx?id=679&contextPage=1465
A small question regarding cross-bracing in intermediate floors. If the top side is covered with floor particleboard that is screwed/glued, and the underside is provided with furring for ceiling gypsum, why use cross-bracing?|
I'm just surprised that the difference would be so significant in a floor structure. That there's a big difference for a beam is obvious; worst case, knots in the middle of the beam are of course very crucial for a single beam, but here it's about deflection in an entire floor structure with several interacting beams.
A small question regarding cross bridging in floor joists. If the top side is covered with chipboard that is screwed/glued and the underside is equipped with furring strips for drywall, why use cross bridging:|
Just wondering!
If you screw-glue chipboard on both the top and underside (we consider this scenario just to make it easier to visualize), the main strength contribution comes from the joist's height effectively increasing by the thickness of the chipboard (screw-glued acts almost the same as a homogeneous construction), and the chipboard provides more area for tensile and compressive forces that are greatest at the outermost part of the joist and null in the middle. (Compare with HEA-beam).
Moreover, the screw-glued chipboard on top indeed gives a slight contribution by connecting with the joist nearby, i.e., distributing a bit of force there, so the deflection on the loaded joist decreases slightly.
But this contribution is quite small, as the chipboard/chipboards simply bend rather easily.
However, if you use cross bridging/blocking, you actually transfer much force to the adjacent joist, and even to joists further away.
The cross bridging forces the joist to try to twist in order to bow down, and the joists on each side resist this force with relatively significant strength.
So, screw-glued chipboard adds strength to the joist itself, and cross bridging distributes the forces to adjacent joists, in brief and somewhat simplified terms.
The best approach is to do both if you want the most stable floor joists possible.
The greatest shear is at the supports. That's where the timber should be best.
I agree that the greatest shear is at the supports, but aren't the tensile and compressive stresses in the middle of the beam/rule/rafter significantly worse?
For example, you can see beams in various constructions that are several times thicker in the middle than at the supports.
I assert that it's in the middle of the span (and at the top and bottom of the beam) where it's most important for the timber to be fine.
There is a big difference in perceived deflection between 45x220 or laminated beams/kertubalkar. Unfortunately, it is significantly more expensive, so one must ask themselves if they want to spend the money on "comfort".
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