Non-linear run Marc/Nastran Grid Force Equilibrium.

[franc11HD]

Hi,

I used the Grid Force Output from a Marc run. I am trying to rebuild the equilibrium between two adjacent nodes linked by Beam element.

When using a linear run, I easily, from the forces and moments on node A get the resulting forces and moments on node B by simpling using the forces times the lever arm from initial position of node A and Node B.

This works great.

When I used the non-linera run, I am absolutely not able to retrieve the moments at node B that the *.grd file gives me. I thought that for non-linear runs, the grid force balance actually gives the forces and moments at the displaced nodes, therefore, the lever arms might be different than when the nodes are in the initial position. But even considering the final location of the nodes, I can't calculated the right moments (forces are of course the same as node A.)

Is there something I am missing here? Is the rotation of the node A and B actually needs to be accounter for? If yes, how?

Thanks for any help you can provide.

 

[ESPcomposites]

Have you tried to use the freebody tool in Patran?

Brian

http://www.espcomposites.com

 

[franc11HD]

ESP,

No I haven't but I don't think it will solve my problem. The freebody tool in Patran uses the Grid force point balance *.grd output from Nastran/Marc.

So I don't think it will be much of a help for me. What I need to know is how to calculate the moments from one node to the other of a beam element when a non-linear run is performed.