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tony.ridley
Posts: 652
Registered: ‎09-07-2011
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Seismic versus Spectral

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06-25-2012 04:47 PM

Hi,

 

Now that Robot 2013 has AS1170.4 Earthquake analysis built in I have started using it. 

I was previously using modal + spectral and defining the response spectrum. 

I am aware from previous questions that for spectral you need to define spectra, run the model check base shear then re-run with scaled base shear.  The AS1170 automatic seismic should be doing these things for me. 

 

From the previous post

http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Barre-de-treillis-traction-compression-vs-s%... it seems that the "seismic" analysis is linear analysis, while "spectral" is linear dynamic. 

 

Question;

Please explain the difference between using "seismic" and "spectral" in terms of the analysis method that Robot employs.  Is one more accurate than the other or are they both the same.  Is one non linear and one linear?

 

Thanks,

Tony

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Artur.Kosakowski
Posts: 4,544
Registered: ‎12-17-2010

Re: Seismic versus Spectral

06-26-2012 12:06 AM in reply to: tony.ridley

These are the same (linear) types of response spectra dynamic analysis. The difference is that in the spectral analysis you define a spectrum yourself whereas in the seismic one it is given by the selected seismic code.

 

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Artur Kosakowski
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Valued Mentor
tony.ridley
Posts: 652
Registered: ‎09-07-2011

Re: Seismic versus Spectral

06-26-2012 12:29 AM in reply to: Artur.Kosakowski

Thanks,

 

In Rafals post (link in original post) he mentions to use modal +spectral as an alternative to seismic when encountering problems with non linear member types. 

 

So why does he mention this, if it is actually just the same anyway?

Tony

 

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Artur.Kosakowski
Posts: 4,544
Registered: ‎12-17-2010

Re: Seismic versus Spectral

06-26-2012 12:45 AM in reply to: tony.ridley

Tony,

 

I think he meant (non-linear) THA analysis. Starting from v.2013 for non-linear models you can also use the static force procedure.

 

 



Artur Kosakowski
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