One more idea: you can use fixed supports at each end and have an acceleration load, which is the original data that was generated by matlab before I double integrated it to displacement.  I can provide an acceleration file or a displacement file with different settings if you want.

If you have no nonlinear materials, then you can put a Modal analysis first and feed that solution into the setup cell on the Transient Structural, then run the linear MSUP transient solution, which may run a bit faster. The Transient Structural will take an Acceleration load, but not a non-zero Displacement if it is using the MSUP solution.