Fatigue Analysis Of Flare Boom During Jacket Transportation

With the development of fatigue life assessment technology of offshore platforms,fatigue analysis of appurtenant structures has become a hot research topic.Nowadays,most research work focused on the main structural components,but some slender truss-type structures such as the torch arm also requires fatigue analysis.As offshore installations in the deeper waters,the harsher ocean environmental conditions should be considered.Moreover,the towing of topside structure integrated with torch arm has been applied frequently in recent years.Therefore,towing fatigue of torch arm inevitably becomes a challenge problem,but few research has been carried out in this area at present.In this study,a torch arm of jacket platform was taken as an example,and the fatigue characteristics of the torch arm under overall towing procedure were analyzed emphatically.In this paper,a finite element model of a torch arm of jacket platform was established.The structure of the torch arm was a traditional three-point connection type,and the fatigue of in-place and overall towing were analyzed respectively.First of all,the hydrodynamic characteristics of the tow barge were derived,and then the fatigue damage of the torch arm under the overall towing condition was calculated.Secondly,based on the different environmental conditions,the fatigue damage under the in-place condition induced by wave and wind were both analyzed.Finally,the towing fatigue damage ratios of the torch arm were calculated.It shows that towing fatigue damage of fatigue hot points didn't meet the design requirements and the towing fatigue damage ratios are also very high.It indicates that it is necessary to take towing fatigue into consideration for the fatigue design of torch arm structure.As a result,a design and optimizing method for torch arm structure in whole life cycle was proposed.In order to better adapt to overall towing of torch arm and meet the requirements of fatigue design,this study further improved the traditional three-point torch arm and proposed a new type of torch arm structure.Also,the fatigue damage of the improved design in its whole cycle life was analyzed.Based on the maximum towing fatigue damage value and the maximum damage distribution,the connection locations between the torch arm structure and the topside structure were optimized,and the optimal design scheme based on fatigue analysis was introduced.The research achievements of this paper provide theoretical and methodological guidance for the design and improvement of torch arm of jacket platforms.