Seismosoft | Earthquake Engineering Solutions

Dear Seismosoft,
I have installed the new version (v6.5) of Seismostruct. I’m performing a dynamic time history analysis for a precast industrial building with considering the whole structure and the three components of ground motion. The DTHA is running fine when damping is not considered or mass proportional damping is considered for overall damping. However, the analysis stops at the beginning of the variable loading (“Unable to apply the next load step. Analysis terminated” warning appears at the analysis log and the analysis stops) when stiffness proportional damping or Rayleigh damping is considered.
Best regards.

Have you input the correct damping coefficients? If these are not calculated correctly, numerical instability is very common.
Refer to the help system at the Program_Settings>Damping, for further information and a better understanding of damping.

Dear Stelios,
The period of the model for the first mode and second mode (period of second mode is needed for Rayleigh damping) are inserted to damping properties with a damping ratio of 5% (which is a general acceptance for reinforced concrete buildings). By the way the models are working fine with the previous version (v5.2.2) of Seismostruct. Thank you for your attention.

Can you please send me the spf file, so that I can have a look? Thanks

Dear Soydan,

We have looked into your model and can confirm that there seems indeed to be a problem when end-releases are used together with stiffness-proportional damping.

We are now looking into this issue, and wonder if, for the time being at least, a workaround for your analyses could be to:
- use truss elements instead of frame elements with end-releases?
- use frame elements with links at the ends instead of frame elements with end-releases?
- use frame elements with end-releases without (stiffness-proportional) damping?

Thank you very much for signalling this problem to us; as soon as we manage to resolve it, we will release a new version. In the meantime, we do hope that at least one of the workarounds suggested above can be of some help.

Seismosoft Support