Generalized P-y curves for monopile design using the PISA methodology
Generalized P-y curves for monopile design using the PISA methodology
The PISA design model is rapidly becoming the standard methodology for the design of offshore monopile foundations supporting wind turbine structures. The PISA model allows designers to either derive from finite element models (FEM) or use rule-based equations, to obtain normalized parameters. Despite the clear benefits, due to the relatively high computational cost and specialist knowledge required to calibrate advanced constitutive models from specialized soil testing, FEM-based PISA calibrations are only adopted during detailed design stages. On the other hand, the rule-based approach has documented limitations namely in new provinces, for soils with distinct geological histories than those tested as well as in layered soil profiles. Since binding monopile geometry decisions are, however, made at earlier project phases, this presents a dilemma for practising engineers. This paper presents an alternative approach of the P-y curve components of the PISA method. It can used at both early stages of design, to derive the normalized parameters in layered profiles, and at detailed design stage to inform the best-fit procedure of the normalized curves. The input soil profiles may contain both coarse and fine-grained formations, either exhibiting drained or undrained behaviour. The new formulation takes into account physical principles of the soil resistance components, to define the PISA normalized parameters.