Its OK if Transverse Force is standing alone. Support design can use absolute value.

But in the test, phase is 0, wave solution give acceleration vector downward. This means Inertia Foce is downward.

Fy = Inertia Force + Transverse Force.

The sign of Transverse Force will impact to Fy because of change in element direction. Its effect to support design and loading information issue to Structural Discipline.

Which line (1,2,3) should be chosen? Since I don't want to be restricted by element input sequence. By logic, user can build the model whatever he want but still satisfy boundary conditions.