ANSYS Time History

[RN123]

Hi,
I am applying time history acceleration to my ANSYS model which contains gap elements.

The time history input starts with 0.0 acceleration for a while before an acceleration is applied to the structure.

For the loading: The initial condition is for the structure under gravity acceleration. The time history is then applied.
After running the analysis, I found out that I am getting noise at the begining of the transient (forces in the structure although the applied accelerarion is zero, i.e. structure is under gravity acceleration only).
Does anyone know how can i get rid off or minimize the noise in the structure at the beginning of the time history (other than increasing damping). Please keep in mind that the structure has gap elements.

 

[kan123]

Are there initial strains that might cause some gaps to change state? Start with a few time steps of no load at all (because transient solutions make use of results at t-i). Then apply the initial gravity load gradually as a ramped load from zero so that the gaps can find the proper equilibrium. Then give the structure enough time to calm down before applying your time history load.