Cyclic and post-cyclic response of shared pile anchors under isolated multidirectional load components

Shared anchors can reduce station-keeping costs for floating offshore wind farms, but they create complex multidirectional loads at the anchor head that are difficult to idealise in geotechnical design. Integrated aero-hydro-mooring analyses show that the resultant load on a shared anchor varies in magnitude, in-plane direction, and vertical inclination. This study examines the cyclic and post-cyclic behaviour of a shared pile anchor in drained sand by isolating these three load components and quantifying their effects on pile response. Three-dimensional finite element analyses were conducted in Abaqus using a calibrated hypoplastic sand model. Load components were varied independently across a range of mean inclinations to assess their influence on accumulated displacement, ratcheting rate, and post-cyclic resistance. Larger variations in load magnitude or direction increase cyclic displacement, while mean load inclination affects ratcheting direction and rate. A Directionality Index (DI) is proposed to compare different loading patterns and provides a first-order correlation with ratcheting rate across the isolated loading modes, although mean inclination remains an additional parameter. In-plane direction cycling produces the strongest circumferential redistribution of soil state and principal stress-axis rotation. Post-cyclic response depends strongly on loading direction: vertical resistance decreases, horizontal resistance increases, and inline resistance varies with mean inclination.