Yes it happens because we did that model with an old version of STKO.
In the old version, we did not have the
wipeAnalysis command automatically set to True at the end of the Analysis command.
Also, we did not have the concept of
Fixed time-step and Adaptive time-step built-in into the Analysis command.
Therefore, what we used to do before (with the old version) was to use a "
fake" Analysis command with 0 steps, just used to set up the analysis components. After that, we used a custom command (Tcl) to implement our own fixed/adaptive time stepping.
In this new version, we implemented the Fixed and Adaptive time step directly in the Analysis command, and we also introduced the automatic wipeAnalysis at the end of the analysis command. The wipeAnalysis command makes the "fake" analysis settings useless, as it resets them!
So you can convert this file to the new version by simply:
- remove the last analysis step "[21] RUN - misc_commands.customCommand" where we just did 2000 steps for a duration of 1 second.
- in the analysis step "[20] analysis - transient" set: a) numIncr = 2000, and duration = 1.0. Optionally you can the Time Step Type to adaptive if you plan to insert non-linearities that can make the convergence harder to achieve.
- keep the wipeAnalysis ON
This file is useful to understand all the components you need to implement the FreeField + Absorbing Boundaries in OpenSees manually with the building-blocks OpenSees had before:
- apply fixities in stage 0
- remove fixities in stage 1
- replace reactions with equivalent forces
- create free-field and dashpots
However, this method was good but not completely correct:
It was missing a very important component that we could not find in OpenSees at that time. Transfer the Free field stresses at the soil domain as equivalent external boundary tractions. This was necessary to impose the free-field response to the sides of the main soil model.
Now, in OpenSees version 3.3.0 we added the new ASDAbsorbingBoundary2D/3D element which does all those steps automatically, and it includes also the above-mentioned component.
In the latest webinar we gave a preview of that:
Implicit-Explicit Contact Element Applied Examples: soil-foundation interaction and RC structures. If you download the files you will see a folder with some 2D/3D examples.
Finally, in the
next webinar (November 4th) we will talk about that element in more detail, and we will show how to create a Soil-Foundation-Structure interaction model from zero, using also this boundary condition to run a dynamic analysis.
Don't miss it!