Foundations for offshore renewable energy structures are subjected to a very large number of loading cycles of varying amplitude, frequencies and direction over their lifetime due to the combination of current, wind, wave and turbine’s operational loads. As a result, soil elements around offshore structures are also subjected to complex, cyclic and multiaxial stress states. Progressive accumulation of plastic strains under cyclic loading may leads to permanent, long-term deformations of the foundations which in turn may affect the serviceability of the offshore structure. Therefore, owing to the importance of accurately characterizing the long-term cyclic response of soils, this research presents new experiments which investigate the influence of simultaneous application of normal and shear stress cycles on granular soil samples. The applied stress conditions mimic those which may be experienced around an offshore monopile foundation. The Hollow Cylinder Torsional Apparatus (HCTA) has been employed to apply such multiaxial stress paths to investigate the evolution of accumulated plastic strain under the application of high number (up to about 3·10/sup 4/) of loading cycles.
Xiaoyang Cheng, Feng Yu, Maosong Huang, Erdin Ibraim and Andrea Diambra
Keywords: Cyclic loading; hollow cylinder torsional apparatus; strain accumulation; multiaxial stress; offshore
Publisher: DFI