Hello there,

I have a question about support type X and type Y with gaps. All is ok in static calculations, but when I run dynamic in results I saw that the Displacements are how there is no any support (not counted gaps).
Can anybody explain me how to solve the problem?

Hi,

Dynamic Analysis is based on LINEAR approach. This means that ALL nonlinear (e.g. gapped or uni-directional) restraints' status is maintained unchanged, as was settled by the reference "Static Load Case for Nonlinear Restraint Status" previously specified in "Control Parameter" dynamic input menu. Such reference case (we'll name it LXX) is usually taken an OPE (operating, design etc.) Load Case from Static Analysis run.

Let's assume you have an X bi-directional guiding restraint with 3 mm gap.
If for LXX Case, the gap is "closed" and the pipe experiences +3 mm movement along +X direction, being stopped by the "gapped" X restraint, the Dynamic Analysis will FREEZE that X guide as it would be non-gapped,

If for reference LXX Case, the X-Guide remains "open" (let's say -2.2 mm movement along -X direction), Dynamic Analysis will IGNORE that X restraint, as it would not exist any more.

If the Dynamic Analysis found big movements in the "ignored" restraints' nodes, my advice is to modify the "gapped" restraints into "non-gapped" ones.
An alternative is to define "infinite" rigidity (e.g. 10^12) snubbers along the desired directions, in the "Snubbers" menu of Dynamic Analysis spreadsheet.

Good luck.

Thanks for your answer.