Crack in glulam?

[imported_Byggaren]

I find it very hard to believe that the beam would be overloaded without showing any deflection. Couldn't the dry season cause dry cracks in glulam? I will try to upload a picture of the crack shortly.
In my opinion, a beam loaded with a distributed load has the least stress in the middle of the beam.

On the contrary. A beam supported on two supports and subjected to load has its maximum field moment in the middle. Even with evenly distributed load. Half of the forces from half of the load go to the supports. Half the load goes directly to the middle, simply put. The shear forces are, however, greatest at the supports and zero in the middle.
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Byggaren

 

[anaitis]

On the contrary. A beam supported at two ends and subjected to a load has its maximum moment in the middle. Even with an evenly distributed load. Half of the forces from half the load go to the supports. Simply put, half of the load goes directly to the middle. The shear forces, however, are greatest at the supports and zero in the middle.
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Byggaren

I wonder if hebbe didn't mean exactly the same thing as you, i.e., the neutral layer? His expression "in the middle of the beam" was perhaps intended to describe in the middle of the beam vertically?

 

[imported_Byggaren]

I wonder if hebbe didn't mean exactly the same thing as you, i.e., the neutral axis?
His expression "in the middle of the beam" might have been intended to describe the middle of the beam in terms of height?

It is correct that half the height of the beam is referred to as the neutral axis in strength of materials. This is because the tensile and compressive stresses are zero along that entire line in a beam subject to bending moments. Or more precisely: the sign changes there.

"Middle of the beam," implying halfway up by height, can then only refer to the neutral line/layer.

If he means in the middle of the beam's width at the bottom, it's something else.

Addition: By "middle of the beam," he probably means halfway between the supports (as I read it).
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Byggaren

 

[sixten88]

The shear stress is calculated as follows: T = (S*V)/(I*b) where s = static moment, v = shear force, I = cross-section's moment of inertia, b = width of the cross-section. In this case, maximum shear stress is obtained at the support in the middle where s is largest, or Tmax = 1.5*v/a for this case. Maximum shear stress is always found in the neutral axis

 

[Abki]

In an experiment with gluing cracked glulam beams, they did not care about cracks that were less than 0.3 mm, cracks that were shallower than 5 mm or shorter than 100 mm did not need attention.
Sponsor was TräCentrum Norr.
More about the study can be read at
http://www.ltu.se/cms_fs/1.103935!/file/Slutrapport 8143 Spricklagning hållfasthet.pdf

Your question was registered in March, and if the timber/beam has been outdoors or in an unheated space, it might be the explanation for the crack. Timber in cold spaces should only be brought in during the summer.