Eigenvalue analysis of simple models

[user]

When I try to run an eigenvalue analysis of a very simple model (e.g. vertical cantilever with a lumped mass on top), the program does not converge.

[seismosoft]

This is a known problem, which we hope to address in the not-so-distant future. In the meantime, our advice is for you to add a very small amount of distributed mass (e.g. 0.0001) to your element, and this should make it run without major influence in the expected result.

SeismoSoft Support

[nikko]

Hello,seismosoft support!
I encounter the same problem and I have tried to add a very small amount of distributed mass to some elements(e.g. beam)in a multistorey RC structure,but the result is still disconverge. Could you give some advises?

At the same time, I use the same model which doesn't contain any distributed mass elements instead of defining"Addition Mass/Length" in the "Section module"to carry out dynamic analysis, but the programme shows "unable apply the entire pernament load".I have confirmed the model many times including check the elastic module,the section of element and so on. I sure that the structure members have enough bearing capacity to the loading I apply! I hope you can give some suggestion about this problem.

Thank you very much!

[seismosoft]

Dear Nikko,

We very much appreciate the mature way in which you approached these difficulties of yours, checking the models carefully and trying to find solutions in the Help System and older posts in the Forum before deciding to contact us.

The problems you described are known to us, and have been dealt with in the newer version of SeismoStruct that we are currently working on. Hopefully it will be released sooner, rather than later.

Kind regards,

Seismosoft Support