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Quasi Static Cyclic Push-Over Analysis

Posted: Wed Jan 22, 2020 2:57 am
by maitreyakurumbhati

I am trying to use perform a simple load controlled Quasi Static Cyclic Push-Over Analysis of a simple portal frame.

The portal frame is supposed to be subjected to a nodal load vector.

Can anyone tell me how can I set up the analysis for the frame?

Also, if it set the "tsTag" in the loadpattern to "0" or "None" , will it be set by default to a "Plain" type time series?

Thank you,
Maitreya Manoj Kurumbhati

Re: Quasi Static Cyclic Push-Over Analysis

Posted: Wed Jan 22, 2020 9:51 am
by MassimoPetracca
If you want to do a cyclic push-over analysis with load-control and nodal loads, I assume that your model will never show a softening branch, otherwise you need to do a displacement-control or to apply an imposed displacement condition.

Assuming that you want to do a load-controlled cyclic analysis with nodal loads:
  1. create your model + define and assign physical properties and element properties
  2. define and assign conditions: 1) fixities, 2) verical loads, 3) horizontal loads
  3. define 2 time series, a linear one (for verical loads), and a Path one (for cyclic loading)
  4. in the analysis step: define
    • recorder
    • add constraint pattern
    • add load pattern -> vertical load with linear time series
    • analysis
    • add load pattern -> horizontal load with Path time series
    • analysis
Check out our e-learing web page, there are videos and materials from previous webinars, and a new webinar for next week, about micro-modeling of masonry structure. There we will show how to do a cyclic displacement-controlled analysis.

Re: Quasi Static Cyclic Push-Over Analysis

Posted: Mon Jan 27, 2020 4:41 pm
by maitreyakurumbhati
Thank you so much.

That perfectly answered my problem.

I just one more question, is there any way I can provide input of an adaptive analysis method like this? (other than sourcing the tcl file as a custom command in the analyses)

Herein I am asking the script to change the algorithm to say Newton if it hits convergence issues and then switch back to the original stated algorithm.
Capture.PNG (13.33 KiB) Viewed 1216 times
Thanks again!!

Re: Quasi Static Cyclic Push-Over Analysis

Posted: Tue Jan 28, 2020 8:55 am
by STKO Team
In the current version you can't. However right now we are implementing adaptive time step directly in the analysis command, where the user can choose:
  1. fixed number of increments (the default for OpenSEES)
  2. adaptive time step based on convergence properties (i.e. changing the time step size)
  3. adaptive algorithm
I will let you know when this new feature will be available.