I have inherited an awesome project through the most unfortunate circumstances, the loss of a great engineer moving onto bigger and brighter pastures.

The project is going to be an ASCE 41 non-linear dynamic analysis and has had geotech engineers involved in picking out ground motion that represent similar ground motions that the faults near this building may produce.

Converting from time history to response spectrum can be done in ETABs, but post processing the data is kinda difficult, I can't seem to find a way to programmatically access the response spectrum curves that ETABs produces.

It's also never a bad day when you have to break out the Chopra Book, so I decided to try to code the process.

The Results

 

You can find the code to make plots like these  on my github:
The required data format is a .txt file that is separated with returns and tabs. I have heard not all geotechs provide their time history data in this manner, so if you want to use this, you may have to edit.

Starting into this, I thought this process involved using fourier transforms to transition from the time domain to the frequency domain, I clearly had forgotten my structural dynamics. Reading chapter 5 of Chopra and getting some guidance from fellow engineer Bryant, I was able to recreate the Newmark method outlined in the Chopra book. Adding a whole bunch of for loops later, some awesome plots popped out.

Comparing the BSE-2E plots (the big, rare earthquakes in ASCE 41) to the code generated response spectrum yielded a ~1.3 increase in peak accelerations at the typical plateau of the response spectrum (time histories were produced high accelerations). 

The BSE-1E time history plots were much closer to the code generated BSE-1E response spectrum.

ASCE 41 Python

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  • Latest Comments
  • retug on Diaphragm Slicer New and Improved -

    Thanks Trenno.

    I will work to get metric units incorporated, that's a great idea.

    On your second point, I think something like that could be done, it's just a bit awkward with how CSI currently has it setup. In order to make section cuts, I need to unlock the model, ...

  • Trenno on Diaphragm Slicer New and Improved -

    Awesome work S&T!

    Firstly, I'd recommend if you're going to feature the tool on CSI's website then maybe incorporate metric units (aka real units!) 

    Secondly, I'm wondering if there would be a way to set up the workflow using something akin to RAM Concept design strips. Perhaps the strip width ...

  • e95kwon on Transfer Diaphragm Design -

    My understanding is that for a 5-story building you would have:

    • (1) load case A (ELF)
    • (1) load case B for each level except the roof so total (4)
    • therefore (4) load combos for diaphragm design

    I believe the intent is to envelope higher mode actions as you mentioned ...