Effective axial forces in offshore lined and clad pipes

• A general deduction of the effective axial force for pressurized cylinders is made.
• It is demonstrated that the effective axial force governs second order load effects.
• A closed analytical formula is developed for the effective axial force in two-layer cylinders.
• A simplified formula suitable for engineering practice is also developed.
• The effects of liners and cladding on the effective axial force are investigated.

To protect pipelines from corrosion attacks, some offshore pipelines have corrosion resistant liners or cladding made from stainless steel. Stainless steels have higher temperature expansion coefficients and lower Poisson’s ratios than ordinary high strength carbon manganese steels. Due to the differences in material properties, liners and cladding have a non-trivial influence on the critical design parameter called the effective axial force in offshore pipelines. Current offshore design codes do not contain guidance on how to include the effects of liners and cladding on the effective axial force. In this paper, an exact analytical formula for the effective axial force in lined and clad pipes is deduced. A simplified approximate formula, which is more suitable for use in engineering contexts, is developed and its validity verified by comparisons to results of the complex exact one.