Dynamic analysis of fixed marine risers with 1st and 5th order Rogue waves

In offshore structures,risers are valuable constituents used in oil and gas industry. conventional steel risers affect the deck of an offshore platform considerably due to their weight under the influence of environmental loads,impacting the fatigue and serviceability life of the structure. the study of behavior of the risers in extra critical environmental conditions could be contributory to developing the effective economical alternatives to boost up the serviceability life of the structure. to this aim,in the current study,a traditional gas export riser,oil export riser and also a thermoplastic composite pipe as a new material in offshore applications are assumed for an offshore jacket located in the north sea. to simulate the extra critical condition,a rogue wave has been considered. the rogue wave with return period of 100 years has been exerted on the mentioned risers by dynamic analysis in the time domain with finite element method using ansys software. for an accurate analysis,two well-known wave theories including the 1st and 5th order wave theories are utilized. afterwards,the displacements and in particular reaction forces of the mentioned risers were compared. it is shown that for gas export riser and oil export riser,5th order wave places less force on the main deck of the offshore jacket in comparison to the 1st order wave. also,thermoplastic composite pipe response to rogue wave has a minimal effect on the deck structure as compared to the gas export riser and oil export riser.