buried pipe restraint stiffness

In Caesar buried model, it takes up & down stiffness the same value as transversal stiffness, but it's really different, particularly up stiffness depends on depth of earth and normally is much smaller than transversal stiffness, is the way used by Caesar too conservative or not?

How can we take consideration of earth weight above the pipe buried in order to get vertical loads on sleepers or foundation under pipes since earth weight is not included in the calculation of buried pipes.


than you

Dear All,

According to the question posted above by Zhiyuan Xu on Modelling Buried Pipe with Caesar II, one find out that there was no consideration given for the following:

1. Earth Load (When Pipe is buried above Water Table, below Water Table and Undisturbed or Unsaturated Soil)

2. Surface Live Load (which always depends on the height of cover)

3. Ovality of Pipe due to the effect of Earth and Live Load and the Through-Wall Bending associated with it.

4. Buoyancy Force craeted by Pipe below water table and the associated Bending Stress.

Will someone shed more light on all the aforementioned please?

Thanks
Soj

Read Pressure Vessel & Piping (PVP) Paper 1271 (2002) on modeling buried piping with Pipe Stress Programs.

The methodology empolyed by CAESAR II is according to the papers published by L. C. Peng in Hydrocarbon Processing, in 1978.

Thanks for the reference given.

Is there anyone that can send me a scanned copy of the above mentioned paper?

Thanks.
AAO

This should get you to the Peng technical papers, not sure about the others.

Peng Engineering


KLee777

Mr. XU has a valid point.

Peng's 1978 paper provides formulations to calculate the soil spring function for the longitudinal-axial direction and tranverse-lateral directions only. In addition, Peng's formalations are outdated, and more recent and comprehensive formulations for soil restraint springs appear in the technical literiture regarding the soil-buried pipeline interaction.

The formulations for the vertical uplift and vertical bearing soil springs are not covered in Peng's 1978 paper. The reader will need to refer to subsequent more updated publications for these soil restraint functions (i.e. Nyman, Trautman, Luscher). The American Pipeline Alliance (ASCE) has a good paper summarizing this information.

Since CAESAR II does not have the capability to generate these vertical uplift and vertical bearing soil spring funtions properly, these need to be User specified in accordance with the criteria provided by the referenced authors.

CAESAR II does need to be upgraded with respect to this information.