Base Motion

[Alejandre]

Hello everybody:

I have been develop a program to understand the base motion in mechanical elements,but i have some questions about my program, i'm not sure about it, because i don't know if there is a correct for 1 DOF and MDOF, i'm not sure about the result and if are correct or if i should make some changes. Here is all my code. I know that the results could be in time or frequency domain, and it depends of the kind of analysis.

*HEADING
prueba
*NODE, NSET=GLOBAL
1, 0., 0.
2, 0.333, 0.
3, 0.666, 0.
4, 0.999, 0.
*ELEMENT, TYPE=MASS, ELSET=P1
1, 2
2, 3
3, 4
*ELEMENT, TYPE=SPRING2, ELSET=P2
11, 1,2
22, 2,3
33, 3,4
*MASS, ELSET=P1
**Masa concentrada
1
*SPRING, ELSET=P2
1, 1
**Rigidez del resorte
1
*NSET, NSET=FIX
1
****************************************************
*AMPLITUDE, DEFINITION=PERIODIC, NAME=fn_senoidal
1, 6.2831, 0, 0.
0, 0.005
****************************************************
*STEP
*FREQUENCY, eigensolver=Lanczos
10, ,
*BOUNDARY, TYPE=DISPLACEMENT
FIX,ENCASTRE
*BOUNDARY
GLOBAL, 2
*EL PRINT, SUMMARY=NO, MODE=1, LAST MODE=10
*NODE PRINT, SUMMARY=NO, MODE=1, LAST MODE=10
U, RF
*OUTPUT, FIELD, MODE LIST
1, 2, 3, 4, 5, 6, 7, 8, 9, 10
*NODE OUTPUT
U
*END STEP
****************************************************
*STEP,NAME=RESPUESTA ESTABLE
*STEADY STATE DYNAMICS, FREQUENCY SCALE=LINEAR, INTERVAL=EIGENFREQUENCY
0.0,0.5,1,3
*MODAL DAMPING,MODAL=DIRECT
1,5,0.002
*SELECT EIGENMODES,GENERATE
1,5,1
*BASE MOTION, DOF=1, LOAD CASE=1, AMPLITUDE=fn_senoidal
*NODE PRINT,FREQUENCY=1
U,TU,TV
V,A
*NODE FILE,NSET=GLOBAL
U,V,A,TU,TV
*MODAL FILE
GU,GV,GA
*OUTPUT,FIELD, OP=NEW, FREQUENCY=1
*NODE OUTPUT,NSET=GLOBAL
U,V,A,TU,TV
*OUTPUT,HISTORY,OP=NEW, FREQUENCY=1
*NODE OUTPUT,NSET=GLOBAL
U,V,A,TU,TV
*MODAL OUTPUT
GU,GV,GA
*END STEP
*****************************************************

Does anybody have experience with a base motion?
Thank you!