How should a stiffnessring be inputted in the model , without having problems concerning the diameter/wallthickness ratio?

I tried the following method without result:

- Use a element with a length equal to the width of the ring.

- Wallthickness (t) in this element is equal to body-radius of the ring.

- Diameter (D) is equal to the outer diameter of the ring.

This configuration give the folowing error: "diameter/wallthickness-ratio to large". This is an clear error, because a pipeline with these values will not behave like a thinwalled construction.

(24-11-2009, 10:05 AM)Richard Wrote: [ -> ]How should a stiffnessring be inputted in the model , without having problems concerning the diameter/wallthickness ratio?

I tried the following method without result:

- Use a element with a length equal to the width of the ring.

- Wallthickness (t) in this element is equal to body-radius of the ring.

- Diameter (D) is equal to the outer diameter of the ring.

This configuration give the folowing error: "diameter/wallthickness-ratio to large". This is an clear error, because a pipeline with these values will not behave like a thinwalled construction.

Richard,

It is surely possible to model the ring-stiffener in the way you descibe.

The exact expression of the error you encountered is probably:

E310/1: Dia / wall thickness ratio <= 2.

It is very unlikely that this ratio occurs at the location of the ring-stiffener. I suspect that the error has been caused by an input error.

The function of the ring is to prevent ovalisation of the cross-section due to top soil loads resulting in decrease of the wall bending stresses, not only at the ring location, but over a certain length at both sides of the ring as well. To achieve this the Ovalisation redistribution option in Ple4Win should be set to Allowed.

Rien Radder

The normal ratio is between 20 and 200. This ratio can be viewed in the PIPEDIM output table.

If the ratio exceeds 200 or is lower then 20 the program will give a warning W310/1.

If you are doing a NEN3650 calculation, there is also a minimum nominal wallthickness criteria (for transport). According to the NEN3650 a lower nominal wallthickness is not allowed, Ple4Win will give you a warning W310/4.