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Horizontal plate anchors are widely used to secure tension leg platforms via mooring lines. A thorough understanding of the monotonic, cyclic and post-cyclic behaviour of plate anchors is essential to accurately estimate plate anchors' capacity. This paper presents a systematic investigation of horizontal rectangular plate anchors subjected to vertical monotonic and cyclic loads in quartz sand under drained conditions using three-dimensional finite-element simulations. The upgraded SANISAND-MS model is employed to accurately capture sand's ratcheting behaviour. The monotonic uplift load is affected by the contact types used between the soil-anchor interface, and it increases with increasing embedded depth ratio, aspect ratio, and relative density. The results of cyclic tests reveal that in loose and dense sands, the cyclic amplitude ratio and cyclic asymmetric ratio affect the displacement accumulation at the cyclic stage. The cyclic loading leads to a higher post-cyclic uplift load than the monotonic tests. Moreover, the post-cyclic uplift load increases more in tests with a high cyclic amplitude ratio. Investigation on local soil responses shows that this can be attributed to sand's densification, which increases sand's strength and stiffness. The study also supports the development of long term analysis for anchoring systems subjected to cyclic loading in offshore applications. • The numerical result shows that when the soil-anchor interface does not allow for a gap, the uplift load is larger compared to the case where a gap is allowed, as the soil below the plate anchor contributes to shear resistance. • Parametric studies are conducted to explore the effects of soil relative density, cyclic amplitude ratio, cyclic asymmetric ratio, embedded depth, anchor geometry, and soil-anchor interface. The local soil response is investigated in detail to gain insights into the local anchor-soil interaction mechanisms. • The simulation results successfully captured the overshooting effect observed in the plate anchor's load-displacement response during the post-cyclic stage. This effect can be attributed to soil densification, which increases strength and stiffness, and creases a more stable sand micro-level configuration. [ABSTRACT FROM AUTHOR]

Accurate simulation of foundation response subjected to repeated loading require reliable sand constitutive models to reproduce realistic sand cyclic behaviour. Many elastoplastic constitutive models adopted the hypoelasticity law, which results in physically inaccurate strain accumulation prediction of soil when subjected to elastic cyclic loading. To address this issue, the existing elastoplastic bounding surface model SANISAND-MS has been upgraded with a hyperelastic formulation that is derived from the Helmholtz free energy function. The complete form of the derived nonlinear elasticity functions enhanced by stress induced anisotropy is presented in this work. The calibration of the upgraded SANISAND-MS is briefly discussed. It is demonstrated that the hyperelastic formulation with volumetric-deviatoric coupling: (1) guarantees no accumulation of elastic strain upon elastic cyclic loading, and (2) captures the stress-induced anisotropy of sand under reverse loading. This upgraded SANISAND-MS model with a physical adaptation and thermodynamically consistent elasticity law can predict strain accumulation accurately and is physically appropriate. Moreover, the upgraded SANISAND-MS is suitable for simulating problems with high-cyclic loads and is able to be used in boundary value problem simulations in areas including offshore engineering and railway engineering. [ABSTRACT FROM AUTHOR]