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.

Hello Judi

there is two ways you can try from my opinion. define the PFAK under keyword LZPL, factor of the last; or you can try to define the mass or call the mass in module DYNA.

VG

Yuan