Parametric analysis of steel catenary risers under extreme loads

Steel catenary risers seem to be an economical solution for deepwater applications. However that solution is not always feasible and its feasibility must be verified case by case, considering both extreme loads and fatigue. The feasibility analysis of a steel catenary riser begins with some parameters pre-established hut others can be varied to make that solution feasible. The top pre-tension mainly governs the mechanical behavior of a catenary riser. If it is low, there will be large curvatures at the touchdown point region, if it is high the riser will be submitted to high stresses in the top. A careful choice of the top pre-tension level can make the riser meet all the design criteria. This paper introduces a feasibility study of steel catenary risers focused on the extreme loads. This study is implemented by means of a parametric analysis where the parameter to be varied is the top pre-tension. The goal of that analysis is to obtain, in a short time, the pre-tension range for which the steel catenary riser solution is feasible. To achieve this goal simplified models, frequency domain solutions and asymptotic expressions were used. The paper presents the main hypotheses that were adopted, describes the methodology employed and presents some numerical results.