I am trying to apply a horizontal (x-direction) acceleration force to the bottom surface of a column via a explicit dynamic analysis. Every time I try to run the program, I get an error what states that wave-speed deformation exceeds 1.0 in some of the elements. Since I’m not interested in the stress at the bottom of the column, rather the response of the column due to the g-load, should I make the bottom surface a rigid body (or surface if I can)? The DOF in the x direction is free to translate. Any tips on how to go about this problem would be appreciated.