Is this moment a bending or a torsion?

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    Bending Moment Torsion
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Discussion Overview

The discussion revolves around the classification of a moment acting on a beam, specifically whether it should be considered bending or torsion. Participants explore the implications of the moment's direction and the resulting shear forces on welds, examining the technical definitions and interpretations of torsion in this context.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that the moment causes the beam to rotate in the support plane, indicating a moment in the Z direction while the longitudinal axis is in the X direction, questioning the classification as torsion.
  • Another participant notes that the plate is attempting to rotate about an axis perpendicular to its face, leading to pure shear loads on the welds.
  • A participant expresses confusion about whether the moment can be classified as torsion, seeking clarification.
  • It is proposed that the situation can technically be considered torsion due to the dependence of shear load magnitude and direction on the distance from the center of the moment.
  • Another participant agrees with the assessment of shear loads and discusses the implications of weld strength and the skill of the welder on the overall strength of the connection.

Areas of Agreement / Disagreement

Participants express differing views on whether the moment should be classified as torsion. Some argue it can be considered torsion under certain conditions, while others maintain that it is not torsion. The discussion remains unresolved with multiple competing interpretations.

Contextual Notes

Participants reference specific technical definitions and conditions regarding torsion and shear loads, indicating that the classification may depend on the interpretation of these terms and the specific geometry involved.

Amaelle
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Homework Statement
look at the image
Relevant Equations
torsion vs bending
Greetings!
1650474068323.png


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!
 
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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.
 
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Amazing! clear now, but it´s not torsion right?
 
Amaelle said:
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.
 
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Lnewqban said:
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.
 
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Lnewqban said:
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!
 
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