Mohamed Latheef

Pipeline damage due to internal flow induced vibration is known to pose challenging problems in oil and gas industry. To reduce these problems, it is necessary to understand the vibration characteristics of the pipeline conveying fluid. The Winkler foundation is reported to have a stabilising effect to the pipeline structure in the literature. Therefore, in this study, dynamic analysis of pipeline conveying fluid mounted on the Winkler foundation is performed to obtain the force response of the pipeline. The partial differential equation of the pipeline conveying fluid subjected to several boundary conditions is solved numerically and analytically by using the finite element and Green's function method. The results of both methods are compared and validated against other numerical schemes and existing reported analytical data. The results indicate that Green's function is more accurate than finite element method in determining the forced response of the pipeline at a higher fluid velocity for simply supported and fixed supported pipeline. The findings in the present study provide the physical insight of the Coriolis force and Winkler foundation stiffness effect to the pipeline conveying fluid.

For offshore structures, especially jacket supported structure such as fixed platform and offshore wind turbine, the underwater area provides an ideal site for corrosion formation and marine fouling. In this marine environment, the structures are exposed to particularly aggressive corrosion and colonized by marine organisms involving a diversity of species. In this paper, a number of cases are conducted where an existing fixed platform is subjected to uniform corrosion. Furthermore, the platform is also subjected to marine fouling. The platform is assessed to investigate the effects of corrosion and marine fouling on its structural strength by determining the Reserve Strength Ratio (RSR) value. It is found the platform is limited to at least 50 years of service life when subjected to average corrosion. However, the platform is no longer considered as safe after 37 years when subjected to severe corrosion. Moreover, there is an RSR loss of 38% when marine fouling is introduced at the first 5 years which is detrimental to the overall safety of the platform. On the other hand, there is minimum RSR loss of only 5% for most cases when marine fouling is introduced but still detrimental to the overall safety of the platform. The obtained outcomes were documented and will be useful information to conduct condition assessment (or structural health monitoring) of aged fixed jacket structures.

MetOcean conditions in the South China Sea (SCS) indicates that unlike other locations such as the North Sea, the magnitude of the currents can be relatively large. In addition, these currents are strongly sheared. The present study focused on the typical design problem of calculating the ultimate base shear and overturning moments for slender fixed structures with the inclusion of the interaction between the currents and the wave field. It has been found that the loads on average can be around 15% larger when this interaction is accounted for in the calculation of the loads, highlighting the importance. In addition, the level of these amplifications were found to be dependent on the sea state steepness and the relative water depth. While no clear trend was found (changed case by case) in the present work, incorporating the vertical structure of the current was found to change the pattern of the amplification of the loads.