A simple rotational spring model for laterally loaded rigid piles in sand

Monopiles are the most popular foundation for offshore wind turbines. These foundations typically have a low length to diameter ratio and undergo rigid body rotation when subjected lateral load. This paper presents results from an extensive numerical investigation involving 3D finite element analyses demonstrate that moment-rotation response of monopile in sand can be represented using single non-linear rotational spring located at depth about 0.75 times pile embedment. Expressions elastic stiffness under very rotations developed these combined with observations measured variations stiffness, supported by analyses, used develop simple approximate expression determine monotonic load sand.