Iv tried to search for this answer but couldnt find what i was looking for.

My company did a stress analysis on some piping lines to determine if slug flow was over stressing the system as a study. We ran both static and dynamic cases and presented our findings and that was it for the study. Now our client wants us to recommend changes but our stress guy who originally did the study is no longer with the company. Iv reviewed his work as i wanted to be sure what we were submitting would be correct. He calculated slug flow forces and inputed them into time history analysis correctly but i think he might of set up the non-linear restraints wrong in the dynamic case.

My question is, from the static case where we had guides and limit supports with various gaps, and places where there were just +Y supports, is it necessary to change the model so there are no non-linear supports? Such as, is it necessary to make all +Y supports into Y supports, and change all gaps on guides so there are no gaps so the pipe is held down?

The manual says Static Load Case for Nonlinear Restraint Status: Most often the user selects the operating case to set the nonlinear restraint configuration.

I tried both ways, and i was getting huge stress values when i have 0 gaps and the stress was many multiple times low when i left the gaps in there and selected the corresponding operating case.

Thanks
joe

That difference is because your operating case restraint status set by CAESAR II may not have all your supports active.Whereas when you manually change those non-linearities in your model, you make all those supports active.

Joe,

The operating temperature of the piping results in thermal expansion of the piping system. The gaps are required at guides and line stops to keep the expansion stresses to reasonable values by letting the piping to expand freely, until the restraint then becomes effective for restraining the dynamic loads. If you change all the gaps to zero, then it is likely to exceed the allowable expansion stress by over-constraining the piping, as well as having huge loads at some of the zero gap restraints.

The design of the restraints for dynamics is different than for the sustained or thermal expansion cases. I would call it 'boxing in' the piping. First, the piping is configured with enough flexibility for thermal expansion, with initial restraints selected and located to carry weight for the sustained stresses. Second, the pipe runs are evaluated for restraint of slug loads by including a line stop / guide in each change of direction. Some longer runs might need additional guides. Some short runs could have enough restraint from nearby line stop / guide. All line stops / guides could require some gap unless it is located a point of neutral thermal expansion. It would be a more complicated piping geometry to make it flexible enough for thermal expansion using all zero gap guides and line stops. The design for dynamics restraint involves a balance of flexibility for thermal expansion and of stiffness for avoiding vibration response to the dynamics loads.

No, CAESAR II will do this for you, that is the purpose of defining the "Static Load Case for Non-Linear Restraints". CAESAR II looks at the results from this load case and performs the linearization for you. So if a +Y lifted off in the case you select, CAESAR II will remove it from the model for the dynamic run. If a gap closes, CAESAR II will take the gap out completely for the dynamic run. If the gap didn't close, CAESAR II will take out the restraint for the dynamic run.

Is it possible that you can send me the ".C 2" file, the units file attached along with that(in the following ID: markme026@gmail.com)

I would like to involve with such a kind of troublesome cases.