Testing, simulation and design of offshore lined pipes under axial compression

As one of the means to inhibit offshore pipeline corrosion, lining a thin layer of stainless steel within the carbon steel pipeline provides an economical and durable design. Current design codes EN1993-1-1 and DNV-OS-F101 ignore the contribution of the liner pipes towards the crosssection capacity, which might lead to inefficient design. The focus of this study is to investigate the interaction of the two pipe layers arises during manufacture and the development of local buckling of the lined pipe under compression. Experiments to study the interaction behaviour of the liner pipe and the outer pipe, including saw tests and ring-split tests were performed. Then a series of short lined pipes were tested under axial compression, with a built-in camera to capture the development of liner wrinkling. After the tests, numerical models were developed and validated, and a series of parametric studies were conducted. The obtained test and FE results were used to assess the applicability of the codified provisions for the design of lined pipes under compression. Improved design method was developed considering the liner pipe contribution and material strain hardening. The proposed approach provides better prediction accuracies on the structural behaviours of lined pipes under axial compression.