Cantilever beam constraints

[tharun160190]

I know that fixed end of Cantilever beam is fully constrained, but I see in an Autodesk tutorial, only middle row nodes at the fixed end are fully constrained and the remaining nodes at fixed end are constrained only for translation in X direction. Can any one please help me with this?

Thanks

[S.LI · Accepted solution]

I assume you use solid brick elements here, instead of beam elements.

The constraints setting in the manual is actually all right.

Constraints on the middle row means to fix translation along X, Y, Z and rotation along X at the end.

The additional X constraints on other nodes at the end mean fixing rotations along Y and Z.

So finally, all 6 rigid body DOFs get fixed at the end.

Usually, this is good enough for simulating a cantilever beam, though there must be some difference between this setting and full constraints.

You can decide if this difference matters to you model or not.

[AstroJohnPE]

Hi tharun160190,

Can you be more specific? Which tutorial are you referring to? What direction is X compared to the length of the beam?

My guess is that they want to compare the stress at the fixed end with the "theoretical" value of M*c/I = F*L*(h/2)/I for a force at the end of the beam. This formula does not take Poisson's ratio effect into account. If the model is made of brick (or 2D) elements, and if all of the nodes at the wall are fully fixed, you will get a much different stress.

[tharun160190]

I t makes sense. I will try doing in both the ways.

Thank you very much for the help.

[tharun160190]

Hi John Holtz

    I was reffering to Finite Element Analysis in Practice Instructor Manual. Length of the beam is in X direction and I think the first reply to my post answers my question. Thank you very much for trying to help me 🙂