We will be doing some large bore pipework soon.
By large bore i mean 18-42"

I am wondering what exactly, are the limitations Caesar has, and how to work round them.

I suspect that as the d/t ratio approaches 100 and the fixed beam theory breaks down, then some other form of analysis is required.
I would also suspect that FEA is nessesary for satisfactory support design, include pipe wall loadings.

anybody?

Saddle Supports may be designed by the Zwick formula, Trunnion/ Staunchions per N Cases as well as clips.....

The localized stresses at these supports/ restraints can be quite large.

The bigger question may be surronding the branch intersections these will Code SIFs & Flexibilties break down significantly at higher d/t ratios.... Rich Ay has an article in an old newsletter that is of some help in this regard.....

A copy of FEPIPE and Section VIII Div2 or Section III NB3200 would be of enormous value...


I have used a hybrid approach to this before using FEA as needed and the beam element model for gross loads / deflections.

Hi Tim,

I would use CAESAR II to model the system with a beam approach and then look at the local support stresses on the second pass. Look at AWWA manual M-11 for saddle designs. Also the Lincoln Arc Welding books by Blodgett also address saddle supports. there is also an AISC Nomograph that presents the design of horizontal vessel saddles that could be reviewed.

Perhaps an interesting discussion could be built around deciding upon at what pipe D/t you should go from single shoe supports to trunnions and similarly at what pipe D/t you should go from trunnion supports to saddles. Also, think about mid span (or less) stiffening rings to allow longer spans.

Regards, John.

Thanks gents
Great answers.

I was thinking i should know all that but hey, you can't be an expert at everything!

A caveat comes to mind.... negative pressure make sure that at no moment in time you will pull a negative collapsing pressure!

Yes indeed. Once you get above NPS 30, atmospheric pressure may cause damage to standard wall pipe. Perhaps another good reason for having a look at the guidance of AWWA M-11 (and I suppose ASME B&PV Code, UG-28). Good stuff in M-11, that can be applied to more than just water pipe.

Regards, John