Modal Analysis with cables or tension only bars

[ben.hastings]

Hi,

I'm just wondering whether there are any special considerations to make when running a modal analysis with cables or tension only members modelled?

This is a feature stairs with hangers supporting the landings, and I'm going to model something simplistic with the hangers as either tension only members or cables.

I just want to get an idea of the natural frequency for various combinations of geometry.

Thanks.

Ben

[Artur.Kosakowski]

The calculations will be based on the stiffness matrix as obtained for the load case defined directly before the modal one. The vibrations are limited to 'small ones' around the equilibrium state of a cable/tension only bar so neither 'swinging' from side to side nor switching off tension only bars that would in such case be in compression and activating these that would be in tension (and were switched off for the preceding load case.

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[ben.hastings]

Thanks a lot for this Artur.

Ben.