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Rotational spring
Posted: Thu May 26, 2022 8:21 am
by gabrifio
Dear STKO team, I have modelled this beam in a 2d solid continuous. It has a nodal force at the top.
How can I add an elastic simple rotational spring at the top of the beam? I have tried with a zero-length element and material but it doesn’t seem to work.
Please find attached the model.
Thank you
Re: Rotational spring
Posted: Fri May 27, 2022 9:03 am
by STKO Team
From the model, I don't fully understand what you are trying to model.
Could you please post a sketch of what you want to represent?
Re: Rotational spring
Posted: Mon May 30, 2022 2:52 pm
by gabrifio
Hi, thank you for the response. Here is a sketch. It is a simple 2D model of a pile in an elastic medium. The only force is the horizontal force at the top node. The top node of the pile can be either free to rotate or fixed against the rotation if I add the fixed constraint, but I would like to insert a rotational spring to determine the degree of fixity of the top of the pile.
Please let me know if you need more details.

- Pile spring.png (53.4 KiB) Viewed 3330 times
Re: Rotational spring
Posted: Tue May 31, 2022 9:50 am
by STKO Team
Ok so in this case what you have to do is:
- Create an auxiliary node, coinciding with the Pile Head.
- Fix it in all DOFs
- Create an interaction (node-to-node, master = Auxiliary node, slave = Pile head)
- Add the zero-length with rotational spring to the interaction

- fix pile rot.png (92.6 KiB) Viewed 3318 times
Here's what you get with K=1 (Left) and K = 1.0e8 (Right)

- fix pile rot 2.png (62.67 KiB) Viewed 3318 times
Here's the modified file:
Re: Rotational spring
Posted: Tue May 31, 2022 2:05 pm
by gabrifio
Hi STKO Team, thank you very much!
Re: Rotational spring
Posted: Tue May 31, 2022 4:02 pm
by STKO Team
You're welcome