All,

I having significant troubles dealing with this error. I have quite a large piping model (several hundred nodes), complete with structural steel and some buried sections.

I can run my static analysis okay, but I just can't get the dynamic module to work to do a modal analysis. There error I get is as follows.

"Mode is dynamically unstable. (Rigid body modes) Need some extra restraint to prevent infinite sliding and/or rotation."

There are plenty of restraints within the model, including several anchors. I have done plenty of searching through the forum and can't find an answer to the problem. Can anyone help here?

Thanks

put a line stop on the longest spool of pipe in the system and check.

If doesn't work, put line stops in between and check.

Still doesn't work, remove gaps at one or two supports and check.

...still not, post the status here again.

Regards

Hi ,

check the c node anchors.. some node number missing while connecting the nodes....

Regards,

akula