Hi all,

Can someone explain why you have to define the direction of the load twice in Relief load analysis in Caesar II , first on Force Sets screen and the second time on Spectrum Load cases screen (Dynamic analysis). I feel the need to define the direction of the force on Force Sets screen is redundant.

Regards

Vish

Hi All,

I have a piping system that is subject to harmonic displacements at a node. Harmonic analysis provides only stresses due to harmonic forces/displacements. You can not combine harmonic forces/displacement with static cases.

Is it that the reason for this is that you can run static case with maximum harmonic forces/displacements and check whether the system meets code requirements?


Please comment.

Regards

Vish

Yes you're somewhat right. You have to define the direction on the "load case" dialog (again) because (a) you have to fill that field in, and (b) we use that as the label for the output report.

Hi Richard,

Thank you for quick response.
Any comments on my query regarding combining of dynamic harmonic forces with static load cases?

If I want to combine harmonic and static response, I would probably send the harmonic output to Word and then copy and paste the tables into Excel where these numbers can be combines with the static results.

Be sure to capture the frequency/phase pair that produces the greatest response. But that gets complicated since the phase angle that produces maximum response changes from point to point in the system.

And there's the + & - thing. You probably want to add and subtract the harmonic response (instead of evaluating a specific phase angle and also that phase angle + 180).

I wouldn't do combinations with stress. Harmonic stress amplitude is best addressed as a strict fatigue analyis or at least with a conservative endurance limit in mind (ala OM3 or API 618).

Clearly it's not push button. Nor should it be.

Yes, that is a good idea that will be considered for the future, but normally harmonic analyses is used to diagnose and eliminate problems -- either the cyclic stresses are found to be below the endurance limit (and therefore have minimal contribution to the static evaluation), or the problem is eliminated. It is unusual that a significant harmonic response is retained as part of the operating cycle.