Interpret table regarding glulam

[Dann3]

Hi!

Anyone willing to explain the practical impact of the values found again in this table: https://www.traguiden.se/konstrukti...onerande-barformaga-b42-78/?previousState=100

What do the V kN and M kNm values mean in practice

Thanks in advance /Daniel

 

[justusandersson]

V stands for the maximum allowable shear force and M for the maximum allowable bending moment. After calculating the current values of shear forces and bending moments, you enter the table and look for the glulam beam that meets the requirements. It is advisable to start by looking for the narrowest dimension first.

 

[Dann3]

V stands for maximum allowable shear force and M for maximum allowable bending moment. After calculating the current values of shear forces and bending moments, you refer to the table to find the glulam beam that meets the requirements. It is advisable to start looking for the narrowest dimension first.

Okay, but can you say that V then means compression in kN at a point along the fibers?
And the M force in kN per meter required to bend it when it is on its edge, or is that completely wrong? I'm just trying to understand what it means practically, an example would be nice

/Daniel

 

[Dann3]

okay I didn't read properly, I see now, you have to calculate the values for a given construction first and then use the table to find suitable dimensions

But how much can a glulam beam 225x42 gl28cs on edge withstand before it breaks, so to speak, the point load? And how much can it withstand over a span of 6 meters, weight along the entire beam, before it bends dangerously?

/Daniel

 

[justusandersson]

you must first calculate the values for a given construction and then use the table to find appropriate dimensions

Correct!

Your glulam beam can handle a point load in the middle of around 500 kg. (This does not mean it will collapse at 501 kg) For the beam's deflection to remain under 1/300 of the span, i.e., 20 mm, it should not have a larger distributed load than about 60 kg per meter. Note that the deflection requirement is much stricter than the requirement concerning the breaking limit.

 

[Dann3]

Thank you! Without being too troublesome, how is it that the requirement for deflection is so much stricter?

I’ve posted a thread in the garage section here on the forum as I’ve put up the glulam beam I mentioned and plastered the ceiling inside, but I’m wondering if the beam is sufficient. The free span is 5400mm, feel free to take a look if you like, there’s a drawing there too. The thread is called garage conversion... something and was posted here the other day.

Here is a direct link:
https://www.byggahus.se/forum/threa...sning-av-innertak-garage.301067/#post-2778290

Thanks for the explanation /Daniel

 

[Daniel 109]

If you're going to have a residence on the surface, you don't want any bounce in the floors. If it's a loft in a workshop, the requirements are a bit different.

 

[justusandersson]

A beam that is loaded bends down quite a bit before it breaks. This doesn't matter much in a roof structure. In a floor structure that you walk on, however, the deflection is usually limited (according to standards and construction rules) to 1/300 of the span. Larger deflections are perceived as uncomfortable. Additionally, there is a deflection requirement.

 

[Dann3]

So the limitation 1/300 is mostly about ensuring that you can walk on a floor, for example, without it sagging, rather than if the deflection requirement is exceeded the beam will fail?

Thanks again for the useful info for a relatively new homeowner /Daniel

 

[justusandersson]

Rather, it should not tilt too much. There is also a deflection requirement: a person weighing 100 kg should not cause a greater deflection than 1.5 mm when they stand on the most sensitive spot, regardless of the span.

 

[Dann3]

Okay, I understand, but it's also about it being a comfortable feeling for the person walking on the beam rather than the risk of it breaking?

/Daniel

 

[justusandersson]

Absolutely. Therefore, one should have some margins. Just replied to your other thread.