Dear Dave/Richard

I'm doing a dynamic analysis for occasional earthquake case on a flow line. I noticed that for some supports with guides, if during static analysis the guides didn't close , then the guides will not work during occasional dynamic analysis unless you closed them. Why in dynamic analysis Caesar doesn't see that there's a restraint with gaps in the calculation?

The dynamic solutions in CAESAR II are linear, because the Eigen solution is linear. Read the help text on the first option on the Control Parameters dialog (Static Load Case for non-Linear Supports).

Thanks Richards. So in other words, if in static analysis there are inactive gaps, we need manually alter them so they are active during dynamic analysis?

No, CAESAR II will do that for you in the Dynamic Solution. All you have to do is reference the proper static load case.

What do you mean by the proper static load case?
If none of the static load case is linear, the inactive gaps in the static case will not work in dyanmic analysis, unless,as my understanding from the help text, you manually alter them i.e close the gaps. Is it a normal practice to close all gaps on the CII model for dynamic run?

Select the dominate OPE load case, the one that will probably be active when the dynamic event occurs. CAESAR II will take the results from this load case and linearize your system.

Linearize the System:
- Inactive gaps will be removed, active gaps will be closed.
- Inactive uni-directional restraints will be removed, active uni-directional restrains will be made bi-directional.

Linearize the System:
- Inactive gaps will be removed, active gaps will be closed.

We are back to my first question. So the inactive gaps in the static load cases were removed in dynamic analysis. So that's why Caesar didn't see the gaps there. But then, we are unrealistically model the dynamic analysis. The purpose of the guides with gaps are to control the seismic movement without putting too much stress during static loads. If Caesar remove them for dynamic run, what should we do to make caesar see that they are there?

Take Snubbers in dyn input.