Making waves in offshore structure design
Floating production, storage and offloading (FPSO) vessels are under development for processing and storing oil and gas from offshore platforms. The Rebasdo project provided advanced designs for safe and efficient FPSO structures, including hulls, moorings and riser systems. The major source of uncertainty when designing the new vessels comes from the environmental conditions they must face. Floating structures employed in offshore production are at the mercy of the weather and are most vulnerable when they must remain in the same position and cannot be moved to avoid a storm. New probability models were developed by scientists and engineers to study the effect of waves, currents and wind on the FPSO units. Researchers were particularly interested in predicting the effects of wave crests and their impact on the floater and mooring systems. A statistical analysis of random waves was carried out by incorporating a second-order wave model wave-model into a spectral response surface method. The new approach enables statistical data concerning wave crests to be calculated rapidly and accurately under realistic sea conditions. However, the technique does not cover all aspects of a wave's movement and underestimates the height of wave crests for unidirectional seas. These findings are based on short-term data and can be combined with long-term statistical information concerning storms and the number of extreme wave crests predicted. Improved models can help predict extreme environmental effects that can lead to structural damage and serious economic consequences due to an interruption in production. Accurate simulations can be used to develop safety factors that can be applied to each stage of the design process of floating structures. Successful wave research can benefit shipyards and their engineers and designers as they adopt new safety rules and codes.
