Structural response of offshore monopile foundations to ocean waves

Offshore monopile foundations are one of the most commonly used foundation concepts in offshore renewable energy, especially in areas with relatively shallow water. They are characterised by relatively large geometric dimensions compared with other offshore pile foundations and are distinguished from onshore piles by suffering from harsh ocean environments during their lifetime. One of the most significant aspects is associated with the wave effect on the behaviour of monopile foundations. To date, research has been conducted in the development of numerical models, which are capable of providing sophisticated and flexible representations of the monopile foundations. In this study, a three-dimensional scaled boundary finite element model (SBFEM) is proposed to investigate the structural response of the monopile foundations when exposed to ocean waves. Unlike other numerical techniques, SBFEM provides an analytical solution in the radial direction with numerical approximation along the circumferential and top faces of the monopile foundation, which considerably reduces the computational effort. The SBFEM model is validated by an equivalent finite element model, by which favourable computational efficiency and reliable accuracy are demonstrated. Subsequently, a parametric study is carried out in terms of various wave properties to gain an insight into the monopile behaviour. The purpose of this study is to make recommendations for improving the design of offshore monopile foundations, when wave load is a dominant factor.