Base Shear results - Time history vs Pushover analysis

04-Unexpected behaviour/errors
Post Reply
Ricardo Ferreira
Posts: 5
Joined: 04 Jul 2021, 20:33

Base Shear results - Time history vs Pushover analysis

Post by Ricardo Ferreira »

Hello.
I'm having some issues comparing results of a time history analaysis and a pushover analysis of the same building. The maximum base shear value obtained in the pushover analaysis is much lower than the maximum value of total shear at supports obtained in the time history analysis. In the pushover analysis i'm usig infrmFB for the columns and beams while for the time-history analysis i'm using infrmFD for the same structural elements.
Does this somehow affect the calculation of the non-linear of the elements, hence, the shear distribuition in the structure?
Is there any limitation regarding time-hystory analisys when using Academic licence?
Thanks in advance.
Ricardo.
huffte
Posts: 978
Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
Contact:

Re: Base Shear results - Time history vs Pushover analysis

Post by huffte »

When you run the pushover, do you get inelastic behavior? That is to say, does the solution converge in the post-yield region of response? If you have convergence issues, the solution may be terminating prior to any inelastic behavior. Examine hysteretic plots in the post-processor to assess inelastic behavior.

What do you mean by "infrmFD"? Do you mean "infrmDB"? If so, did you subdivide the elements in the time history analysis? This could be the problem since infrmDB elements need to be relatively short to produce accurate results. Refer to the "Element Class" section of the help system for further discussion. Generally speaking, infrmFB elements do not typically require subdivision into smaller element lengths. Perhaps a change to infrmFB elements in the time history analysis would provide a more reasonable basis for comaprisons.

Is there some particular reason you use different element types for the two analyses?
Tim Huff
Ricardo Ferreira
Posts: 5
Joined: 04 Jul 2021, 20:33

Re: Base Shear results - Time history vs Pushover analysis

Post by Ricardo Ferreira »

Hello Tim
When I run the pushover analysis I di get ineslatic behaviour and didn't had convergence issues. However, for the time history I did had some issues that were only overcome when using infrmFD instead of infrmDB elements. I didn't made any subdivision in the infrmDB elements. Maybe that is why I get different results, don't you think?
huffte
Posts: 978
Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
Contact:

Re: Base Shear results - Time history vs Pushover analysis

Post by huffte »

What version of SeismoStruct are you using? I don't seem to have an "infrmFD" element in the version I am using so I cannot say what the problem might be.
Tim Huff
Ricardo Ferreira
Posts: 5
Joined: 04 Jul 2021, 20:33

Re: Base Shear results - Time history vs Pushover analysis

Post by Ricardo Ferreira »

Hello again
I'm using seismostruct 2021.
huffte
Posts: 978
Joined: 22 Jul 2011, 10:19
Location: Cookeville, Tennessee, USA
Contact:

Re: Base Shear results - Time history vs Pushover analysis

Post by huffte »

I am running 2021 as well. I still cannot identify the "infrmFD" element class. Are you sure you do not mean "infrmFB". Maybe you have an update later than my installation with a new element class. If so, maybe the help section will assist you. If you do, in fact, mean "infrmFB", then discretizing the elements in your "infrmDB" model would certainly be worth investigating. Or, simply switching to "infrmFB" non-discretized elements.
Tim Huff
User avatar
z.gronti
Posts: 824
Joined: 16 Oct 2013, 08:14

Re: Base Shear results - Time history vs Pushover analysis

Post by z.gronti »

The element class name is "infrmFB", i.e. Inelastic force-based frame element type.

The only limitation of the Academic/Trial Version of SeismoStruct is that it supports code-based checks of up to twenty members and cannot send support email to Seismosoft within the program.
Zoi Gronti
Seismosoft Srl.
Post Reply

Return to “04-Unexpected behaviour/errors”