Abstract
Amidst the backdrop of the European “Green Deal,” mandating climate neutrality by 2050, the expansion of offshore wind energy in the German North Sea gains increasing significance. The projected trend in offshore wind energy turbines (OWTs) towards exceeding 20 MW, with hub heights surpassing 240 m and rotor diameters over 300 m, demands a concomitant shift in substructure design. Jacket-type substructures, tailored for sites with larger water depths, are expected to increase individual pile diameters or overall structural density to bear the new, markedly increased top loads. These Offshore Megastructures present a new approach to traditional slender structures. This study investigates the impact of individual and combined wave and current conditions on a 3-legged jacket-type Offshore Megastructure in a 1/140 scale laboratory study. The structure, a simplified iteration designed to support a > 20 MW OWT, was mounted to a load cell for monitoring integral horizontal loads. Testing encompassed current-only, wave-only, and combined wave-current scenarios in both following and opposing configurations. Reference tests without structure, with a monopile, and tests with the jacket structure oriented at 0°, 15° and 30° were executed. Findings illustrate an influence of both wave steepness and jacket orientation on the integral horizontal forces. This relation changes in dependency of the presence and orientation of a superimposed current for values of wave steepness H/L > 0.01.
