Time History Displacements Problem

[MARIOS75]

Hi

I have a simple structure and I'm applying  an harmonic excitation at it's base. It's duration is 2.5sec. After that the structure oscillates freely for another 2.5secs. Results for the first part seem ok but for the free oscillation part  after the first 2.5sec it seems that the structure oscillates about a new equilibrium position.

Thank you.

[Rafal.Gaweda]

Damping not set in THA case.
Define it

[MARIOS75]

Hi Rafal,

thanks for your reply.

I need zero damping.

So is there a restriction in analysis and I have always to set a value for damping.

Thank you.

Marios

[Rafal.Gaweda]

No restrictions, just be aware of results you get
No damping -> oscillation
Your choice

[Rafal.Gaweda · Accepted solution]

One more thing:
your functions should end at such time step where value = 0 to avoid unnecessary oscilaltion

[MARIOS75]

I'm not sure what do you mean.

The structure should oscillate with or without damping after the end of the harmonic load.

It's weird anyway.

Even with damping present the structure ends up again oscillating about an new equilibrium position towards the end of the response.

Thanks again.

[Rafal.Gaweda]

See below

[Rafal.Gaweda]

Because of diagrams scaling you can not see clearly oscilation diagram after 2.5s

You can export results from table to excell and generate diagram there

[MARIOS75]

Thanks Rafal.

Closing the expression with a zero value seems to solve the equilibrium position problem but  I still I haven't been able to verifry the results for the free oscillation part.