How to calculate the moving loads on a bridge in Code_Aster?

jingjing

How to calculate the moving loads in Code_Aster? Mainly refers to vehicle load ？

ArchibaldArchambaud

Hi first,

What do you mean by *the* moving load?

You can define a pressure load for instance as a function of time and space using the FORMULE command and apply it using AFFE_CHAR_MECA_F (which means APPLY_MECHANICAL_LOAD, the trailing _F meaning the argument of the command is a Function).

You can have a look at the test case "ssnl130a.comm" in $ASTER_ROOT/STA9.4/astest.

jingjing

Thank you very much!

My major is bridge engineering,and what i should do most is designing and analyzing the bridge.So here "the moving loads" mainly refers to vehicle load on bridges.

May I give you a clear explanation? and I hope that you can help me with this question.

ArchibaldArchambaud

Hi Jingjing,

In order to calculate a moving load, say of a train, on a bridge, here is what I do :

==================================================================================================

V=0.1; # Speed of the train

L_TRAIN=1.; # Length of the train

P=1000.; # Weight of the train

FONC_T = FORMULE(NOM_PARA=('INST','V','P','L_TRAIN','X'),VALE="""P*(((V*INST-X)>0)-((V*INST-L_TRAIN-X)>0))*(V*INST-X)*(V*INST-L_TRAIN-X)""");

FORCE_T=AFFE_CHAR_MECA_F(MODELE=MODELE,

FORCE_NODALE=_F(GROUP_NO='BRIDGE',

FY=FONC_T)

);

==================================================================================================

This results in a parabolic load in the Y direction moving at a speed V on the bridge in the X direction. All you have to do is to apply this load on the bridge and run a dynamic calculation.

I think it should help you.

jingjing

Thank you!

I will have a try!

nihilsson

Hello,

Apparently one needs to provide the values of V, P and L_TRAIN explicitly to the function FONC_T when it is called within AFFE_CHAR_MECA_F, because if I use the for it is suggested above by Archibald I get:

!------------------------------------------------------------------------------------

! Erreur lors de l'interprétation de la formule 'FONC_T'.

! Les paramètres de la formule n'ont pas été fournis.

! Paramètres manquants : 'L_TRAIN', 'P', 'V'

! Conseils :

! Si le problème reporté ci-dessus ressemble à 'NameError: 'XXX'...',

! vérifiez que le paramètre 'XXX' fait bien partie des paramètres de définition de

! la formule (mot clé FORMULE / NOM_PARA).

! Ceci est une alarme. Si vous ne comprenez pas le sens de cette

! alarme, vous pouvez obtenir des résultats inattendus !

!------------------------------------------------------------------------------------

RichardS

Hello nihilsson,

just delete 'L_TRAIN', 'P' and 'V' from NOM_PARA.

Regards,

Richard