free vibration

[toy0410]

Hello,

I want to let a 2dof model free vibration from second mode situation, but meet few questions.

How can i set the initial displacement like second mode? Is it used node x y <-disp x0 y0>?

If yes, how to release the initial condition that made the model free vibration?

Thanks.

[fmk]

if elastic you could simply add the correct loads that followed the shape you want, analyze and then remove the load pattern.
if nonlinear, the task is harder ... you could impose the displacements at all dof using imposed motions .. this would require a load pattern for every dof .. use penalty to analyze and then again remove all the load patterns.

[toy0410]

Dear fmk,
I use rectangular time series command to control and release the initial condition.
Finally, it's working now. Very appreciate for your reply.

[hibahashim]

Hello All,

I have been trying to design a cantilever column model with a certain mass to represent free vibration. But all the examples and discussions I've seen are either of Dynamic analysis where there is ground acceleration or Static Pushover analysis with a static load.
I need to provide initial conditions to cause the free vibration. Please help as I am a beginner.