Rigid constraint of nodes

[john.kapogiannis]

Hello,

I wonder if there is a command in order to constraint specific nodes and make them move as a rigid body performing static analysis. For example, let the nodes ranging from 10 to 20 which are located in xz-plane and y=100

Thanks in advance
J. Kapogiannis

[Prof. R.L. Taylor]

Look in the User Manual for the LINK and ELINK command use.  If you link the nodes 10 to 20 together they all respond with the same displacement.  You can link all the dof's or just some to control how you want the behavior.

[firat_dal]

Look in the User Manual for the LINK and ELINK command use.  If you link the nodes 10 to 20 together they all respond with the same displacement.  You can link all the dof's or just some to control how you want the behavior.

Dear Prof. Taylor and FEAP community,

Is it possible to apply essential boundary condition (DISP, EDISp, etc.) on the edge that is previously LINKed in order that the nodes on the corresponding edge respond with the same displacement. For example, we have 2D rectangular element and we apply compression in the x-direction. Moreover, we LINK the nodes on the upper edge to make them have same displacement and lower edge is fully restrained using EBOUn. At the end of the compression in the x-direction, can we apply DISP,EDISp boundary conditions on the upper edge by deactivating LINK. I know that it is not possible to restrain the DOFs which are LINKed. By the way, I am using ver8.5 .

Thanks in advance.
Fırat Dal

[Prof. R.L. Taylor]

LINK connects active equations only, those which are part of the linear equation solve.

You can change a dof from active to deactive duriing the analysis. This may require unlinking.  Once you change from active to fixed you can specify a  DISPlaced value.

Possibly you can use LOAD groups to perform what you want to do.  With this option you can specify fixed degree of freedoms (those which have nonzero BOUN values) which can move with specified values.

Another option is to use a line element (truss) which can be in a REGIon that you ACTIvate or DEACtivate.  One end of the truss is connected to the linked dof and the other is fixed with a specified value.  You start the analysis with the element DEACtivated and the later ACTIvate and move with specified value.


All is delicate as you need to account for values from previous parts of the analysis.

[firat_dal]

Dear Prof. Taylor,

Thank you for your quick response and detailed explanations.

I would like to apply REGIon with ACTI/DEAC commands using line elements together with surface elements. However, I could not understand how to apply in the mesh command. I looked at user manual, example manual, as well as FEAP Forum comments. However, I could not understand how I should apply. Do you suggest me to look at any other material or could you please give me any simple example related with REGIon and ACTI/DEAC commands ?

Again, thank you very much for your instructions. Sincerely yours.
Fırat Dal