This paper addresses unique design considerations for the support structure of an offshore wind turbine in US waters and how the Working Stress Design (WSD) approach can be applied. The Load and Resistance Factor Design (LRFD) criteria specified in IEC 61400-3 are primarily developed based on the experience from offshore wind turbines installed in European coastal areas. Due to the higher variability of the wind and wave climate in hurricane-prone areas, offshore wind turbines in US waters would not achieve the same level of safety as those in European waters if the existing IEC design criteria were applied. To address this, a set of acceptance criteria, accounting for the unique design consideration related to tropical storms, has been developed and are published in the ABS Guide for Building and Classing Offshore Wind Turbine Installations. Extensive calibrations have been carried out to verify the adequacy of design load conditions and structural design requirements of the ABS WSD-based design criteria. Metocean conditions in the US Gulf of Mexico (GoM) and East Coast were used in the calibrations to calculate the aerodynamic and hydrodynamic loads as well as the structural responses of the typical designs of offshore wind turbines.

The goal is to define conditions under which a GustoMSC CJ46-X100-D jackup rig designed for unrestricted service can be rated for full operational drilling capabilities in areas with a relatively weak soil top layer and a more benign environment. The GustoMSC CJ46-X100-D jackup rig is designed with environmental criteria derived from the southern North Sea and a bearing pressure of 53.5 MT/m2 (10.96 ksf); however, the maximum soil bearing pressure in some areas of the Arabian Gulf and elsewhere cannot exceed 41.5 MT/m2 (8.5 ksf).