Time varying force input to multiple nodes

[suusie]

Hello sir/madam,

I would like to inquire regarding time varying (=time-history) force (kN, N, etc.) input on different nodes. Also, my preference is to input these force-history input on multiple nodes (not only ground level).

I know we can do this for acceleration, velocity and displacement inputs by using "timeSeries Path ~", "pattern MultiSupport ~", "groundMotion 1 Plain ~" and "imposedMotion ~". But we cannot do this for force loading, i.e., we don't have "groundMotion 1 Plain -force 1 ~". (<- if this is possible, it would be perfect!)

We can input static force on different multiple nodes by using "load~" command, but this is different thing, since I want to input "force time-history", which is dynamic.

If there is any way to input "force time history" on multiple nodes, I would like anyone to let me know.

Yours truly .

[fmk]

same as accelerations .. put how the load values in a Path time series, and create a load pattern with that load and a reference load equal to 1.0 in dof dirn. if all nodes have different histories (you can scale the ref loads if there is some constant relationship between mag at each node) you will need a load pattern for every load.

[suusie]

Thanks for your reply, fmk.

I want to clarify what you said above.

You mean, if we want to input force-history, we need to input both force-history & 1.0-force-history (=always 1.0 not 1g) at the same time to the same node and same DOF?

Below is the very short example .tcl for inputting force-history. I want you to check this script and tell me if this is o.k. If not o.k., can you tell me which sentence I should change? The script is aiming to input force-history input to node#1 and DOF#1.

# -------------------------------------------- example .tcl file --------
timeSeries Path 1 -dt $dt -filePath $fileForce -factor $fact; # The file contains force-history (kN, N etc.)
timeSeries Path 2 -dt $dt -filePath $fileAccel -factor 1.0; # The file contains 1.0-force-history (always 1.0 not 1g) = Reference load

pattern MultiSupport 1 {

groundMotion 1 Plain -accel 1;
imposedMotion 1 1 1; # Force-history is set to node #1 dof1

groundMotion 2 Plain -accel 2;
imposedMotion 1 1 2; # Constant-force-history (=Reference load, always 1.0 NOT 1g) is set to node #1 dof1

}

[fmk]

NO .. apply them as nodal loads not support displacemets!

timeSeries Path 1 -dt $dt -filePath $fileForce -factor $fact; # The file contains force-history (kN, N etc.)
pattern Plain 1 1 {
load $nodeTag1 1.0 0.0 0.0
load $nodeTag2 0.5 0 .0 0.0
}

would apply the loads in that file to node $nodeTag1 and half the forces ad node $nodeTag2

[suusie]

Oh, I got it, thanks!