Is this moment a bending or a torsion?

[Amaelle]

Homework Statement

look at the image

Relevant Equations

torsion vs bending

Greetings!

As you could see the moment try to make beam to rotate in the support plane with the wall which mean for me this moment is on the Z direction but the longitudinal axis is the X direction and I know that for a moment to be torsion it needs to be in a longitudinal direction, but the solution says it´s a torsion! any help would be highly appreciated thanks!

 

[Lnewqban]

It seems that the 100x12 plate is trying to rotate about an axis that is perpendicular to the 100x12 face.
That makes both welds resist pure shear loads.

 

[Amaelle]

Amazing! clear now, but it´s not torsion right?

 

[Lnewqban]

Amazing! clear now, but it´s not torsion right?

Technically, it can be considered torsion, because the magnitude and direction of the shearing load for each section of the welds (along L) depend on the radius or distance between it and the center of the moment M.

 

[Baluncore]

That makes both welds resist pure shear loads.

I agree.
It is a couple.
The shear is in the contact zones of the welds which have an area of contact with the plate. But the mid-plane of the flat surface weld has an area of only 1/√2 = 70%.
So the strength will come down to the strength of the weld metal, and the skill of the weldor.

 

[Amaelle]

Technically, it can be considered torsion, because the magnitude and direction of the shearing load for each section of the welds (along L) depend on the radius or distance between it and the center of the moment M.

I was thinking the same thing after you pointed out to the shear forces! thanks a million!