How to impose a initial displacement/velocity??

[qindan_h]

I modeled a simply supported beam with lumped masses at 50 nodes and the nodes were connected using elasticBeamColumn elements. I want to vibrate the structure to get the vibration responses. Instead of applying a node force, I need to impose a initial displacement or velocity to one node. I don't know which command I should use.

Thank you very much!

[fmk]

the best you can do is to use a MultiSupport exciatation. do one step to move the node to given displacement, then remove the load pattern and let it vibrate.