Changing parameter during earthquake

[jackjo]

Hi every body
I have a frame model (one span and one story). I want to analyze the model under earthquake motion excitation. The earthquake motion duration is 30 seconds. In the first 15s of duration, I want to analyze the model with column section A, and in the second 15s of duration with column section B. Namely,

0,.......................,15,......................,30
sectionA sectionB

How can I do this?, Please guide me with a simple example.

Thanks

[fmk]

you cannot switch the column section in the beam elements .. you can remove the beam and add a new one but the iniial condition when new one is added would put it in a state of 0 stress which is not probably what you want.

what exactly are you trying to do with the new section: addFibers, removeFibers or change material properties.
you may need to get your hands dirty and go in and modify the code to suit.