The effect of fictional and thermal forces upon sea bed pipeline buckling behaviour.

The objective of the research programme has been to develop design parameters applicable to in-service submarine pipeline buckling behaviour. The programme has involved experimental and theoretical studies and computer graphics are widely employed throughout. Initially, as detailed in Chapter 1, the necessary buckling mechanisms in. pipelines subjected to axial compression have been identified and analysed in the form of relatively basic fully mobilised studies. In addition, errors and limitations contained within these studies have been determined and delineated. Consequently, geotechnical experimentation as reported in Chapter 2 was deemed necessary particularly given the dearth of information available relating to the nature of the friction resistance force between the pipeline and its supporting medium. Full scale values for the axial and lateral friction coefficients together with their respective fully mobilised displacements have been deduced upon the basis of model tests. A semi-empirical formula has thereby been produced for use in design practice. Further, a novel interpretation of sea bed recovery, or the pipeline's submerged self-weight inertial characteristics associated with vertical buckling, has also been determined. Following on from the above geotechnical study,more refined quasi-idealised analyses,dealt with in Chapter 3, have been undertaken incorporating the appropriate full scale deformation-dependent axial and lateral friction-response loci together with the respective sea bed recovery characteristics. These analyses enable, for the first time, definition of the appropriate critical temperature rise at which axial-flexural bifurcation occurs. Finally, noting that previous buckling analyses have been based on quasi-idealised buckling phenomena, attempts have also been made to incorporate practical submarine pipeline imperfections. Pipelines are not perfectly straight in field conditions and, consequently, the imperfection studies denoted in Chapter 4 have attempted to model the appropriate behaviour. Design charts have been produced accordingly and suggestions made regarding further studies.