Inelastic Spectra

03-Unexpected behaviour/errors
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huffte
Posts: 889
Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
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Inelastic Spectra

Post by huffte »

It appears that there might be a problem with inelastic spectra in SeismoSpect when the SeismoSignal Method is selected in the options for generating inelastic spectra.

I get the same basic shape with SeismoSpect as I do with SeismoSignal, but the displacement spectra amplitudes are different - higher in SeismoSpect - by a factor of 981.

So I suspect that this is merely a units problem and a conversion has been omitted somewhere internally when "SeismoSignal Method" is set in the options for inelastic spectra.

I think this must be the culprit - as I look more closely I see that every point in the SeismoSpect run is exactly 981 times higher than the corresponding value in SeismoSignal.

I am generating inelastic spectra for a ductility of 6.0.
Tim Huff
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seismosoft
Posts: 860
Joined: 06 Jul 2007, 04:55

Re: Inelastic Spectra

Post by seismosoft »

Huffte, many thanks, as usual.

We will look into this matter and eventually correct things in the next release of the software.

Thanks again, appreciated.

Seismosoft Support
huffte
Posts: 889
Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
Contact:

Re: Inelastic Spectra

Post by huffte »

As it turns out, it also appears that there may be some misleading results in SeismoSpect when inelastic displacement spectra are generated using either the Krawinkler option or the Miranda-Bertero option. As noted in the excellent Help system of SeismoSpect, acceleration multiplied by (w)^2 produces displacement for elastic spectra (but not so for inelastic spectra).

It does appear to me, however, that the reported inelastic displacement spectrum is equal to the inelastic acceleration spectrum multiplied by (w)^2.

I suspect that the same is true for the SeismoSignal option for generating inelastic spectra as well, but it is more difficult to tell owing the apparent units conversion issue.

Thanks very much and keep up the excellent and appreciated work.
Tim Huff
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