How to define a timestep larger than the default in dynamic analysis

3DEC
1

Hi,
When performing dynamic analysis using 3DEC 7.0, I wanted to increase the timestep. After using the command ‘model dynamic timestep fix 0.001’, the timestep remained at 1.4327e-4 (which seems to be the default value) and displayed the message ‘timestep calculation deactivated’. However, when I tried setting a smaller timestep than the default using ‘model dynamic timestep fix’, it worked successfully. Why is this happening, and how can I define a timestep larger than the default?
Thank you in advance!
JLUJYP

2

Hi there.

3DEC numerical scheme is conditionally stable, which means that any timestep greater than a threshold one will lead to unstabilities, and thus to non-physical behaviors. I am pretty sure a timestep cap is hard-coded, hence your situation.

As I understand it, this condition exists whatever the module used (including dynamic). Dynamic analysis can add another condition on the timestep for damping concerns.

Cheers

Theophile