About modelling a structure with bars interconnected by transversal and rotational springs

[asceduardo]

I am working on a finite-element model composed by rigid bars, which are interconnected by rotational and transversal springs. Since I was having trouble with the modelling, I have decided to start with a simpler model, whose analytical solution is well known. This simpler model is represented in the figure attached. The mesh is composed by four nodes:

Point A -> Node 1
Point B -> Nodes 2 and 3 (coincident)
Point C -> Node 4

Also, the motion in X-Translation and Y-Translation of nodes 2 and 3 are constrained for being the same. For the transversal spring, I have set a grounded spring on node 3 with stiffness "kt" in Y-Translation direction. For the rotational spring, I have set a two-coincident-node spring (from node 3 to node 2), with stiffness "kr" in Z-Rotation direction. Finally, the two beam elements are set from nodes 1 to 2 and from nodes 3 to 4, respectively.

The results given coincide with the analytical results for kr = 0, showing that for some reason the rotational spring is not being properly set. Does anyone know how to solve this problem? I am using ADINA software, but help from other softwares' users is also welcome.

Thanks in advance!

 

[e.kostson]

I am not familiar with the software, but since you mentioned that the rotational spring is not working as it should, it is very likely that this is because you are perhaps using truss elements that do not have rotational degrees of freedom (hence rotational spring is neglected). I would suggest to use beam elements that have both translational and rotational degrees of freedom, and see if that works.
Thank you and kind regards.

 

[asceduardo]

e.kostson,

Actually, I have set beam elements already. They are free to move in X-Translation, Y-Translation and Z-Rotation directions.