FREE VIBRATION USING INITIAL CONDITION

[hibahashim]

Hello All,

I'm trying to analyse and get the curve of free vibration in a simple cantilever column fixed at the base. Is it possible?
I'm looking for ways to input initial conditions in order to cause the vibration, but all examples only show dynamic analysis when ground motion is provided.

Also in a model I made applying Earthquake data, the column moved with respect to ground motion but it moved like a rigid column instead of as a flexural column.

Please HELP!
Beginner at Opensees

[Jhno]

Apply a initial displacement of the top node.
Then wipeAnalysis and create a dynamic analysis.
Remove anyloading on the node. Analyze and record the displacement.

[hibahashim]

Dear Jhno,

Thank you, but that was were i had trouble.
I don't know the codes for providing initial conditions like displacement.

[Jhno]

TO impose the initial displacement use the integrator displacement
http://opensees.berkeley.edu/wiki/index ... nt_Control

You can provide a desired displacement. When it is done, you apply a wipeAnalysis command (be sure not to put space between wipe and analysis)
Then you construct a basic dynamic analysis system (see example in the wiki pages).
You put a recorder at the node you want to see, then you analyse and that's it.
You could also use a load pattern (http://opensees.berkeley.edu/wiki/index ... in_Pattern) but I guess that would complicate the process. The simplest way (in my opinion) is to use the displacement control integrator.

Maybe someone with better skills then me will have a diff. opinion?
Good luck !