one possible way (I've implemented that to a masonry-arched bridge) using remote forces (pressure .. etc) from the boundary conditions and change the coordinates as a parametric variable. Btw I've used ANSYS Workbench instead.

https://etd.ohiolink.edu/!etd.send_file?accession=osu1204131916&disposition=inline

See Chapter 3.

Dr. Claudio Pedrazzi is a set of single concentrated forces F(y) (N)... They will move, between a discretized distance, the time of the moving will influence the speed...

I need to study the dynamic behavior of the bridge swinging and so on, with its own mass, keeping into account the added mass of the train.

Thank you I will see that, my main problem is writing the code

Dr. Victor J. Adlucky,

this is a very good document!

Thank you!

the whole process has been already well explained by the previous answers, however , i wanna just attach to you my code ,which i used before, u can modify it according to your problem

!************************************************************

! Transient Analysis (MOVING LOAD)

!************************************************************

NDIV=10

PI=3.14

ALPHAD,4.886

BETAD,1.2433e-5

!

VELO=10

TIM=Lbr/NDIV/VELO

delta=1/100

!

*CREATE,FORCE

FDELE,ALL

DDELE,Up1,VOLT

TIME,ARG1

Force=node(ARG2,Wbr/2,Hbr)

amplitude=-10e2*cos(27*2*3.14*ARG1)

F,Force,FZ,amplitude

solve

*END

!

/SOLU

ANTYPE,4

TRNOPT,FULL,,DAMP

LUMPM,0

OUTRES,ALL,ALL

DELTIM,TIM ! Specifies the time step sizes

TINTP,,0.25,0.5,0.5

KBC,0 ! Ramped load step

*DO,K,1,100,1

*USE,FORCE,TIM*(K),(K)*delta

*ENDDO

Finish

regards

Thnak you Mr Claudio the PI=ACOS(-1) is a nice touch