Macro-element Models for Offshore Foundations

Macro-element modelling application in offshore foundation used by Martin (1994) as circular shallow footing resembles spudcan foundation (used in offshore industry). Later, jack-up spudcan foundations (considered as shallow foundation) were investigated widely by macro-element simulation. A limited range of macro-element models can be found for other types of offshore foundations, e.g., for suction caissons and piled foundations. In this study, the concept of macro-element was described by reviewing the most referenced models which have been developed over the past thirty years. Then, the application of macro-element in offshore industry was investigated to evaluate the effectiveness of this model in predicting the soil-foundation behavior under combined loading condition. Jack-up spudcan, suction caissons, and piled/monopile foundations are the types of foundations investigated in this research. Despite some discrepancies in the functionality of macro-element model, it can be claimed that the proposed macro-element models are reasonably reliable compared to (but less than) finite element modelling. Macro-element’s greatest strength lies in its simplicity. Its straightforward physical analogy makes it easy to comprehend, calibrate, and integrate into comprehensive analyses. However, macro-element foundation models are seldom utilized for offshore wind turbines design, and this can be attributed to several factors. The most important factor is that, despite the well-documented theoretical formulations of these models in research literature, there is a scarcity of guidance on their practical application to real-world case studies. It is recommended to combine 3D Finite Element Analysis (FEA) with constitutive models that can faithfully replicate soil behavior or alternatively, employ experimental results from model tests to calibrate the model.