Dear Dave/Richard,

C-II software is considering stochastic approach for friction effect simulation.

Is this the right approach for friction effect simulation?

Requested to elaborate in details.

Regards

The CAESAR II approach to friction does not involve a random variable that can be anticipated/predicted by its probabilities (stochastic).
I would call it trial and error (but there is some randomness in the solution).
Initially, the program assumes the friction force will prevent the pipe from sliding so a pair of friction restraints, perpendicular to each other and the restraint defined with friction, are included in the model. If the load on these friction restraints is greater than mu*N, the pipe will slide and another iteration is required to evaluated that (i.e., the model was not correct at this point). On the next iteration, we know the normal load for the friction restraint and, from those friction restraints, we know the direction the pipe wanted to move. So, replace the friction restraints with a force vector of mu*N and apply it against the current slide direction. This next iteration, confirms that the friction load magnitude and direction are consistent with the current assumptions (within a specified tolerance); if not, another iteration is required. These iterations continue until all supports work together successfully.
CAESAR II does not necessarily calculate the "true" response of each nonlinear pipe position, but it does reach a possible solution for this family of nonlinear conditions. Maybe this is your stochastic reference point.
By the way, I will be presenting a webinar on nonlinear conditions in CAESAR II on 27 March (2018). You may want to attend. This is an updated re-do of a similar presentation from November 2014. Register here: Failure to Launch

Dear Dave/ Richard,

Thank you very much for quick response.

In continuation to the above subject matter, I have some query,

We know that Friction restraint stiffness affects the accuracy of the results.
The default value used by CAESAR-II for the friction restraint stiffness is 1.0E+06 lb/in.

By considering the above friction restraint stiffness & stochastic approach,
Will my stress analysis results are accurate or closed to reality?

Regards.

Dear Dave/ Richard,

I have same query as mentioned above.

With default value of friction stiffness and stochastic approach (trial and error) approach,

Will the stress analysis result will be accurate?

Requested to reply .

Regards,
Shamalia Bhavin

The CAESAR II solution in piping models with nonlinear conditions, satisfies the required equilibrium. But there is no guarantee that the CAESAR II solution is unique.

Continuing with what Dave posted, if you review the User's Manual on the subject of friction, you will see that the referenced paper states that there can be multiple equilibrium solutions.

Quoting from the User's Guide:


With regards to accuracy, how confident are you in your value for "mu"?