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Dear STKO members,

While modeling a slope subjected to seismic loading condition, I would like to apply acceleration time series to a node of the model bottom. In other words, I would like to simulate the "Prescribed Motion" boundary condition that is described in the FLAC dynamic manual on the page of 1-27.

In STKO, I can see the option to use NodeForce that is not what I want.

Also, I tried to use "Ground Motion" command of OpenSees. But, it did not output the acceleration time series at the model bottom same as the input motion that I entered.

The attached describe what I am trying to simulate in OpenSees. They contain the geometry of my model, STKO input file, and FLAC dynamic manual for your reference.

Thanks in advance!
Youngkyu

Before solving the problem with the ground-motion, may I ask you what you would like to achieve with the equalDOF in X along the vertical sides? It is not clear to me.
If you are trying to set the free-field columns this is not the correct way.
What you are imposing now is that all nodes of the vertical sides should move of the same amount in X.

Regarding the equal DOF at both lateral boundaries,
I would like to make the slope model existing in a rigid box which does not need the free-field columns.

In other words, the two lateral sides are assumed to move along with the prescribed motion specified at the model bottom.

Thanks.
Youngkyu

Ok so in this case you don't need EqualDOF at all.
You can simply fix in X all the nodes you want to apply the ground motion to.
It didn't work before because the nodes should be fixed (it's a prescribed motion)

Here's a working version of your model: Also I think you have a mistake (which I did not correct), please check it:
You input the gravity acceleration instead of the body force. This is fine for U-P elements, because they internally multiply it by the material mass density. But the standard quad element you are using requires the REAL body force: G*RHO

Thanks for your edit and checking my mistake.
Your edit is what I wanted to achieve.
You are right that I should put the body force for that element to give the gravitational loading.

Now, I can see how the prescribed motion works in OpenSees.

Best,
Youngkyu

You're welcome