Hello,

I am new to pipe stress analysis and have been thrown in at the deep end. The final part of the pipe stress analysis philosophy I need to assess is the modal analysis and ensuring the natural frequencies are not below 3Hz.

I know there is a way to do this in Caesar 2, however my questions is, is this an acceptable way of assessing the natural frequency in industry or is it best practice to use other software such as Ansys mechanical for such a task?

P.s. please don't be concerned, my work is being checked by a pipe stress engineer however I am having to pick up some of the work due to resourcing issues.

Assuming both analyses are utilizing beam elements, I would expect that there would be settings within ANSYS that would align with settings within CAESAR and come up with similar results.

However, CAESAR comes out of the box as keyed into the piping codes, and is going to make generalizations on behalf of the user to drive conservative results.

E.G. having 100 cm thick pipe with 12.5% MT means having pipe that weighs 100 cm thick but has the allowable stress of 87.5 cm. I suppose that would mean that for modal analysis, it should have the stiffness of 87.5 cm, too.

How far off from reality do these conservative assumptions make? I suppose you could remove variables to find out. What's the natural frequency of 100 cm pipe with 12.5% MT? What's the natural

Thus, the benefit of CAESAR is that two different users of the software should generally come to the same conclusion, whereas two different ANSYS users will invariably come to different conclusions, based on what they think should be safely conservative.

And, of course, there are things ANSYS does that CAESAR does not.