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Ansys Learning Forum › Forums › Discuss Simulation › LS Dyna › Prescribed motion set_ displacement › Reply To: Prescribed motion set_ displacement

November 6, 2024 at 4:09 am
mostafam
Subscriber

Hi Pedram,

Thank you so much for your answer and help.

Let me upload the photo of my soil column model here:

As you can see, here is my soil column model.

I am using 67 hexahedral solid elements with element type 1 (no rotation get recorded) on top of each other. I am fixing base in z direction. 

I am constraining the nodes (CONSTRAINED_NODE_SET) at each elevation to have the same response in x, y, and z direction (except the nodes at the base which are constrained in x and y directions). I am doing so to have pure shear behavior (periodic boundary condition mentioned in the first reference you mentioned).

Then I apply PRESCRIBED_MOTION_SET as dispalcement to the nodes at the base.

When I check the acceleration response at the base nodes, I see considerable big numbers. And I am not getting what is wrong. The records at the other elevations look fine since I verified them using OpenSees.

Also, when I use velocity as my input motion, I do not see such problem. I am just looking for the reason that dispclement has such problem.

 

Thanks

Mostafa