Various design types and dynamic modeling of marine pipelines

In this study, the maximum displacements of suspended, free standing and buried submarine pipelines obtained from dynamic analyses are compared. In this analysis, it is aimed to determine the most appropriate design options in the context of external factors. Submarine pipelines can be suspended designed in the case of the sea bedwhich is fractured or wavy and in the deep water. Suspended pipelines are supported to the sea bed at certain spans to transfer the loads. These pipelines can be analysed by the logic of the pipe resting on elastic foundations.Another method of constructing the pipelines is to bury the pipeline in to the seabed. This method is utilized to avoid the damage of external factors to the pipeline or instability of the pipeline.This study consists of six chapters. The first chapter is the introduction part of the study and the general idea of the study is given. The types of constructing the pipelines are discussed. In the second chapter, the calculation of the wave forces acting on the pipelines are discussed. The equations of shallow, medium and deep water wave velocities and accelerations using in calculating the wave forces are explained. The generalized single degree of freedom system that is used in this study are explained in details in third chapter. The forces utilized in calculation of stability of the pipeline, equations of those forces and the calculation of the maximum or minimum threshold values of those forces are explained in fourth chapter. In the fifth chapter, in order to consolidate the statements referred to the previous sections, three different types of pipelines are designed. The compability of the solutions obtained from generalized single degree of freedom system (GSDOF) and structural analyses program are presented. By the compability of the solutions, displacement-time values are utilized to find time and location depended equation of displacement by curve fitting method. In the last chapter,different designed pipelines are compared in terms of to maximum displacements. Brief observations are made releated to problem types in desing phase.It is seen that while buried pipelines have minimum displacement values, suspended ones have maximum displacements. Free standing pipelines have less displacement than suspended ones due to elastic sea bed. Suspended pipelines have maximum lateral displacement values. Since external forces are not taken into consideration, there aren't any displacement values occured in buried pipelines.Key words; Submarine pipelines, Wave Loads, Single Degree Of Freedom System, Stability Analyses, Sea-Pipeline-Soil Interaction