Torsional moment vs bending moment

• kitzlongg
In summary, the direction of the x, y, and z axes in a structural analysis can vary depending on the global and local coordinate systems used. In Staadpro, the global coordinate system is highlighted, while individual members have their own local coordinate system. The terms "bending" and "torsional" refer to transverse and axial moments, respectively, in the local coordinate system. However, in the global coordinate system, the Moment about x-axis is defined as torsional moment for the red circled beam, while Moment about z and y axes are bending moments. For the blue circled beam, the Moment about z axis is defined as torsional moment, while Moment about x and y axes are bending moments.
kitzlongg
Homework Statement
Anyone here familiar with StaadPro? In the software, Moment about x axis was defined as torsional moment.. While moment about z and y axes are bending moment... Why is it ?
Relevant Equations
Not applicable
The direction of x, y and a axes were shown in the highlighted part..

I think it is wrong. For red circled beam, i kinda agree that Moment about x-axis was defined as torsional moment.. While moment about z and y axes are bending moment...

But for blue circled beam, I think that Moment about z axis was defined as torsional moment.. While moment about x and y axes are bending moment...

Please correct me if I am wrong.

I have not used Staadpro, but I suspect that it uses both a global coordinate system (highlighted by you) and a local coordinate system for individual members of the frame, in which system the local x-axis is always along the axial length of the member. Thus , Mx moments are always torsional, regardless of the members location specified in the global coordinate system.

In structural analysis, the terms "bending" and "torsional" usually refer to transverse and axial moments respectively. These are essentially local definitions.

What is the difference between torsional moment and bending moment?

Torsional moment refers to the twisting force applied to an object, while bending moment refers to the bending force applied to an object. Torsional moment acts along the axis of an object, while bending moment acts perpendicular to the axis.

What causes torsional moment and bending moment?

Torsional moment is caused by a shear force applied to an object, while bending moment is caused by a bending force applied to an object.

How are torsional moment and bending moment calculated?

Torsional moment is calculated by multiplying the force applied by the distance from the axis of rotation, while bending moment is calculated by multiplying the force applied by the distance from the fixed end of the object.

What are the effects of torsional moment and bending moment on an object?

Torsional moment can cause an object to twist or rotate, while bending moment can cause an object to bend or deform. Both moments can lead to structural failure if they exceed the object's strength.

How are torsional moment and bending moment important in engineering and design?

Torsional moment and bending moment are important considerations in engineering and design as they affect the structural integrity and stability of an object. Properly accounting for these moments is crucial in ensuring the safety and functionality of structures and machines.

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