Initial displacements

[MDSmith526]

I am seeking a way to model initial imperfections beyond just creating a node in a displaced location in R^3 space. This only sets an initial offset for the three translational degrees-of-freedom. Is there a mechanism to set initial values for other degrees of freedom at a node? For instance, can the nodal rotation about x start at a non-zero value?

If not, would be best place to add this capability be in an addition to the node class? I have a pretty good idea about how to do this.

Thanks

[fmk]

yes the node class would need to be modified, and you could probably modify node command with the optional <-initialDIsp $ndf values> to get them input.

[MDSmith526]

We found that this is already in the tcl node command node x y <-disp xo yo rzo> or node x y z <-disp xo yo zo rxo ryo rzo>

After minor testing, these seem to work. However, looking at the node.cpp, revertToStart() will remove the initial displacements. Is this something that should be corrected in a future version?

[fmk]

it is a bug that i will need to fix. it will only effect those who bring the model back to initial stage and do another analysis. for now you can of course overcome the limitiation by rebuilding the model if you need to restart.

thanks for finding it and also that the command option already exists .. apologies for all the undocumented features in the code.

[MDSmith526]

No apologies necessary. I'm glad to help contribute any way I can. The node.cpp revertToStart() may not be a problem, depending on what classes use initial displacements. The 3d coordinate transformations all grab initial displacements and store them as variables. The transformation revertToStart() methods do not clear those initialdisplacement variables, so I think they are retained. However, it probably would be cleaner to make sure the node retains them as well.