I have created a mass-spring-damper system in SOFIMSHA that runs over a bridge. However, I now notice that the mass is not observed in the dynamic calculation with STEP in DYNA.

Alternatively, I would now like to implement the mass in DYNA with MASS, but again no changes seem to be visible (despite a very large chosen mass). What can be the reason for this?

Now I have created an example wich is similar to my model but much easier and shorter.

I used the example dyna9 and changed it a bit:

```
PROG AQUA urs:1
KOPF EINFELDTRAEGER UNTER WANDERNDEN LASTEN
NORM DIN 1045-1 ; SEIT UNIE 0
BETO 1 C 20 ; QUER 1 1 A 1.38 IY 0.1412
ENDE
PROG SOFIMSHA urs:2
KOPF EINFELDTRAEGER UNTER WANDERNDEN LASTEN
SYST RAHM GDIV 1000 GDIR POSY
KNOT 1,26 0.0,20.0 FIX PP ; KNOT IMSH 1 26 TEIL 25
STAB FIT 1 26 QNR 1 ; EDGE 10 FIT 13 26
STO#V 2.0 $ SPEED in m/sec
STO#P 5 $ AXLE LOAD [kN]
LET#C #P/0.2 $ 25 mm spring displacement
LET#W SQR(10.*#C/#P) $ FREQUENCY
LET#D 2.*0.03*#W*0.1*#P $ damping
GRUP 1
KNOT 101 X 9.6 Y -2.0 FIX YPMM ; FEDE 1101 13 101 CP #C DP #D
MASS 101 MX 0 MY 1 MZ 0
ENDE
PROG SOFILOAD urs:4
KOPF LASTEN
LF 20
$LZUG USER ; LZPL P #P CONT 100,101; FUNK MULT; FUNK T 1./2 S -0.4
KNOT NR 13 TYP PYY P1 #P
FUNK T 1./2 S -0.4
ENDE
+PROG DYNA urs:9
KOPF Fussgänger mit manueller Schrittfunktion
STEU ELF W2 +1+2+4+8 WERT 10000
GRUP 0,1 ; STEU MCON 2
ECHO LAST
LET#DX 0.80 $ PACING WIDTH = DISTANCE OF NODES
LET#F1 2.10 $ PACING RATE in HERTZ
LET#V #DX*#F1 $ SPEED
LET#DT 0.05 $ TIMESTEP
LET#N DIV(30/#v/#dt)
$
STEP #n #dt
LF 20
$CONT NR 10 V #V
HIST U-Y 2 24 LFSP 90
HIST A-Y 2 24 LFSP 91
AUSW U,A,MY MAX 21
ENDE
PROG DYNR urs:11
KOPF Fussgänger mit einer Schrittfunktion
HIST 90 U-Y 7 2002 13 4001 19 3002
HIST 91 A-Y 13 1001
ENDE
```

In the middle of the bridge is a single degree of freedom system and a load that makes the bridge vibrate. If you have a look on the output (uy and ay) there is no change, no matter if the mass is 1t or 100t. So I guess the mass is not implemented correctly.

These are the results of the node displacement of another system:

Node 7 and 8 are the contact points of the moving spring. The following nodes are the contact points, LF 10000, 10001… are the loadcases of `DYNA STEP`

with the contact condition to an edge element consisting of the contact nodes.

I am wondering, why the displacement of node 7, which should have contact to the edge, has different values than the nodes 30712 and following.

I hope I have expressed this understandably and thank you for all your support.