ABSTRACT
Offshore Wind Turbines (OWT) are a successful renewable energy solution; however, emerging turbine sizes require pile geometries beyond the calibration range of existing design standards. This necessitates soil sampling and rigorous finite element modelling, which is problematic for quick design estimates. Cone Penetration Test (CPT)-based p-y methods can provide preliminary deflection estimates, although their applicability becomes increasingly uncertain as pile slenderness ratios, length normalized by diameter (L/D), reduce. This is due to the increase in diameter incurring additional resistances that p-y models alone cannot account for. To incorporate the additional resistance, this paper defines a CPT-based moment-rotation (m-θ) model by rescaling empirically derived axial capacity functions (known as τ-w curves). Various monopile dimensions are simulated and pile-head displacements are compared for CPT-based p-y models with and without m-θ springs. The net effect of incorporating m-θ springs increases as monopile diameters (and rigidity) increase and diminishes as piles increase in slenderness.
