Seismosoft | Earthquake Engineering Solutions

hi
i want to calculate a constant-ductility inelastic spectra with a negative post-yield stiffness ratio.

i use the seismosignal , it seems it can only deal with the postive post-yield stiffness ratio.

is there any solution to do a constant-ductility inelastic spectra with a negative post-yield stiffness ratio?

Thank you very much.

Hi 2015james.

This is a difficult problem to solve. As noted in the figures in the following paper, the situation is quite unstable and a very, very tiny increment in force (acceleration) can produce an enormous increase in displacement.

http://www.luxinzheng.net/publication3/ ... s_WCEE.pdf

However, it is possible to solve the equations of motion with such a system and I have done so with BiSpec, which is, unfortunately, not a free program. You can get a time-limited demonstration version which might suit your needs for a short time. And there may be other programs which could solve the problem as well.

Perhaps this is a feature which the programmers of SeismoSignal and SeismoSpect might wish to explore for future versions. Currently, however, the problem is primarily an academic research issue since a negative post-yield stiffness is typically considered an instability and not permitted in real structures.

Best of luck 2015james.

Thank you for your prompt reply. Your suggestion does help me a lot.