Rotation in the deformation of tall building

Is it normal to have rotation in the deformation as well as displacement? The plan is symmetrical, the supports at the base are not joints but supports, and wind loads and gravitational loads are applied. (189.7 KB)

Hello @Giovanni4,
I am not sure whether I understand your question correctly.

Opening your definition with version of K3D gives me a number of rigid body modes. This indicates that some parts of the model can move without deformation. Plugging the Eigenmodes results into the ModelView-component shows that some of the beams can rotate about their longitudinal axis (see attached (194.5 KB)).

Your model is quite large. In order to check where the problem lies please reduce it to the utmost minimum.

I have seen that you apply spring elements. Please keep in mind that these define only a stiffness relation between two nodes and no kinematic relation (see here). Maybe that’s part of the problem.

– Clemens

what is Eigenmodes for? You understood the problem, unfortunately I am not familiar with the programme and structural theory, I did not understand how I could solve this problem to have yes a displacement along the x-axis but not have the plane rotations.

  • Giovanni

Dear @Giovanni4, the Eigenmodes in Karamba3D are the Eigenvectors of the stiffness-matrix of the structural system (see here). You can solve the problem by removing the joints which cause the kinematic modes. Alternatively you can give the joints a small stiffness (see here).
– Clemens