The design of a riser system is a very time consuming process, with results that depend on the designer's experience. This motivates the study of tools to speed up the design process and help the designer achieving good results. Optimization is one such tool, which has been successfully used in several areas. In this work, the use of an optimization technique (Genetic Algorithms) for the design of a steel riser will be addressed, with the maximum dynamic stress amplitude along the riser span as objective function. The optimizer can vary the length for each segment as well as the floater diameter, inside user-defined ranges. Pipe inner and outer diameter and material for both pipe and floater are considered given. Restrictions such as minimum tension, minimum curvature radius and maximum stress are applied to verify each configuration's feasibility. A case study addressing the viability of installing a steel riser in an FPSO turret subject to a centenary wave environmental condition is performed and the results obtained are discussed.
Due to the tight requirements that must be met, the design of a marine riser system is both very time consuming and difficult. Several environmental load conditions must be taken into account, generating a large number of load cases, which must be all numerically simulated. As the riser system is highly non-linear, this analysis is computationally very expensive. As there are many candidate solutions, the best one is not straightforward for the designer, often requiring an experience-based exploration of the many possibilities until a satisfactory solution is found. However, as the solution space is very big, some automatic tool, like parametric analysis software, is necessary to perform a comprehensive exploration of this space, taking a long time to perform the huge number of simulations needed.
