Structural design of pressure pipes

There exist various methods for structural design of buried pressure pipes. However, it must be remembered that sophisticated design methods needs a significant supervision of the construction work to be reliable. The need for detailed calculations varies for different materials. Ductile iron (DCI) pipes have high strength properties and for most DCI pipe installations a design check against EN 545 is fully sufficient as regards the structural design. Glass fibre reinforced polyester (GRP) pipes have a limited strainability and are thus highly dependent on the quality of the installation work. It is recommendable to check that the combined strain of the load cases which the pipe shall be designed for does not exceed the allowable strain for the pipe material. Polyethylene (PE) and Polyvinylchloride (PVC) pipes are flexible pipes with a high strainability. The allowable working pressure for these pipes will normally be determined by the PN class and the operating temperature and the need for structural design calculations is limited. It is interesting to note that PE pipes which have the lowest strength properties of all of the above mentioned materials have the lowest failure rate. The latter shows that it is not just the tensile strength, but other factors such as strainability and corrosion resistance which affect the structural performance of buried pipelines.