When does a glulam beam break?

[Melkerman]

Now the glulam beams are in place for the roof over the patio. Looks very strong and nice.

But I'm curious, what load can a glulam beam actually handle?
When does it break (or bend beyond recognition)?

For example, a beam 115x225 with a span of 3m and a load in the middle?

Anyone know?

 

[saturnus]

1826 Kg
There is rarely any risk of glulam beams (with the right dimension) breaking; it's primarily the supports that take the strain when overloaded.

 

[Melkerman]

cross!
that was a quick response, did you calculate it or find it in a table, have another span of 4.5 m that would also be fun to find out.
Thanks!

 

[sdrlnd]

A beam with that dimension can support approximately 21.83 kN/m.
Check träguiden.se for more fun tables ;-)

 

[Melkerman]

21.83 kN/m.
I don't quite understand, does it mean that a glulam beam (115x225) that is one meter long can handle a load evenly distributed that corresponds to about 2100kg?
And one that is two meters, 4200kg?? But doesn't a longer beam hold less well?

Checked on träguiden.se, but didn't really find the right information.

 

[Mikael_L]

21.83 kN/m.
I don't quite understand, does this mean that a glulam beam (115x225) that is one meter long can withstand a load evenly distributed that corresponds to about 2100kg?
And one that is two meters can withstand 4200kg?? But doesn't a longer beam hold less?

Checked traguiden.se, but didn't quite find the right information.

http://www.traguiden.se/TGtemplates/popup1spalt.aspx?id=736&contextPage=1458
You are absolutely right, this value that sdrlnd provided is not an allowable load, but a design value.
(And it has the unit kNm, not kN/m)
I think it is the maximum bending moment. (someone with more knowledge, please correct me)

And then you calculate what load it corresponds to.
Or usually, you start from the loads and geometry, as that is known beforehand.
Then you calculate the required bending moment and support forces and so on, and finally choose a beam that meets all requirements.
see:
http://www.traguiden.se/TGtemplates/popup1spalt.aspx?id=816&contextPage=185

 

[Melkerman]

This is difficult. How did you come up with 1826kg saturnus?
And what is really the difference if you consider a load in the middle of a beam, or evenly distributed over the entire span?

 

[Nyfniken]

And what is the actual difference if you consider a load in the middle of a beam, or evenly distributed across the entire span?

A distributed load can be seen as a mass of point loads. Loads directly over the supports don't bend the beam at all. Then it gets worse the closer you get to the middle.

 

[Melkerman]

Yes, exactly, if the beam can withstand 1826kg at a single point in the middle, it can handle significantly more if the load is evenly distributed across the entire span?

 

[sdrlnd]

Hi! Just as you say, the value I provided is a design value and not an actual max load. I noticed that I wrote knm incorrectly, my bad! Regarding whether it's a point load or not, the beam has a maximum load regardless of the load type. By distributing the load over more points than one, the risk of buckling is less. Other factors such as lateral-torsional buckling, moment in connections, etc., also affect how the beam can be loaded. When calculating how much the beam can withstand, you place the load where it's most critical, i.e., in the middle of your beam (L/2).