How to get the relative displacement in the animation

[DeelakaSathsara]

Hi STKO team,

I have performed a dynamic analysis of a building. When I animate the results in the post processor, the ground is moving and the results are not showing the displacement of the roof relative to the base. Is there a way to fix the ground and get the relative displacement of the building in the animation?

Thank you.

[STKO Team]

Since the ground moves as a rigid body, you can simply extract U at a top node and at a base node and substract.
otherwise don't use ground motion but use a uniform excitation: that will automatically give you the relative acceleration/displacement