Periodic displacement loads

 I want to simulate a dynamic motion of a pipe under periodic displacement loads.

The whole periodic displacement loads was decomposed into 2 halves. The first half was from 0 at initial configuration to a middle configuration to final configuration, then the second half goes back from final configuration to middle configuration, to initial configuration (Fig.1). The displacement loads of these 4 configurations was given. Using Abaqus Explicit, the whole dynamic motion was simulated.

But, I find a problem as follow.