Marine structures

Research front Svein Sævik is a professor in marine structures with the main field of interest related to structural mechanics in general, however, specializing on the development of methods for global and local response analysis of slender marine structures such as flexible pipes, marine cables, umbilicals and pipelines. Since 1992 research work has been carried out at NTNU/Marintek releated to development of mathematical models describing the mechanical behaviour of flexible pipes, umbilicals and power cables. The main motivation for the work has been to increase the understanding of how such structures behave and to allow combining mathematical models and small scale testing to predict the lifetime in a reliable way, hence avoiding expensive and time consuming full scale tests for each new application. The work has been supported by world wide oil companies and manufacturers during more than a decade. The knowledge gained is now used in research related to ensuring reliable design of offshore dynamic copper cables used in floating offshore windmills. The following research topics are currently ongoing: Small scale fatigue testing of flexible pipe tensile armour in sweet and sour conditions. Further development of numerical methods for stress analysis of umbilicals, power cables and flexible pipes. Development of methods for online monitoring of stresses in complex slender structures including full scale testing. Development of fatigue design methods for power cables focusing on dynamic load conditions (wind mills, environmental friendly offshore power supply). Development of methods for simulating trawl gear/ pipeline interaction with structures in arctic areas. Development of methods for describing local buckling of deep water risers. Applicability The results from the research work is and has been used to provide more reliable design of pipelines, dynamic cables, flexible pipes and umbilicals. This specially relates to predicting realistic lifetime estimates for flexible risers and umbilicals which provides important input to the decision-making during operation. Can the riser be operated 3 more months? For an oil riser in the North Sea there will typically be a loss in cash flow of several million NOK per day if the answer to this question is "no". Further if the umbilical is not working, the valve control at the production template is lost and the whole system may have to be closed down potentially having dramatic economical consequences. For dynamic power cables hanging from future offshore floating wind mills installation, reliable long term behavior is essential. What would happen if each individual cable failed from 500 windmills?