You say "I am facing the problem of rigid body motion". Do you mean a warning was issued? If the model seems to run properly, you can ignore this warning. I often get a warning when I know the model is properly constrained and it runs properly. I don't know why ANSYS generates this warning when the model is properly constrained.
Does your model run as expected or does your model not run properly?
Why did you break the solution into 41 steps?
How was the gravity load introduced? The proper way to do that is in Step 1, with Time Integration turned off, and with zero displacement in the Displacement load. Then in Step 2, turn on Time Integration and begin the Displacement load that is providing the ground motion. If you don't turn off Time Integration in step 1 to allow gravity to come to static equilibrium, time integration will compute the vertical motion of the structure as gravity is suddenly turned on or ramped on depending on the load setting. You don't want that.
What is the sample rate of the earthquake data (time increment between values in the data)?