![]() The design model is intended to be calibrated using bespoke 3D finite-element calibration analyses for specific site conditions, rather than relying on general purpose calibration charts and correlations. The PISA design model employs the same basic Winkler modelling concept that forms the basis of the p–y method, but extensions and enhancements are incorporated to improve the model's performance, notably by incorporating additional soil reaction components (distributed moment, base horizontal force and base moment). ![]() This model, also referred to below as the ‘one-dimensional (1D) model’, was an outcome of a project – known as PISA – that incorporated ground characterisation ( Zdravković et al., 2020a), field testing ( Burd et al., 2020b Byrne et al., 2020b McAdam et al., 2020), three-dimensional (3D) finite-element analysis ( Taborda et al., 2020 Zdravković et al., 2020b) and design model development ( Burd et al., 2020a Byrne et al., 2020a). In response to perceived shortcomings of standard forms of the p–y method for monopile design applications, a new design approach, termed the ‘PISA design model’ has recently been developed ( Burd et al., 2020a Byrne et al., 2020a). A summary of issues relating to the limitations of the p–y method for monopile design is given in Doherty & Gavin (2011). These concerns are informed by observations that the fundamental natural frequencies of wind turbine support structures – measured by way of supervisory control and data acquisition (Scada) instrumentation – are often systematically higher than those implied by the analysis models employed in the design process. API, 2010 DNV, 2016).Īlthough the p–y method is widely used for offshore monopile design, there is awareness that standard forms of the method may not provide realistic representations of behaviour for the relatively large-diameter monopiles that are now employed for offshore wind turbine applications. Functional forms of the p–y curves, and calibration parameters for sand and clay soil types, are specified in design guidance documents (e.g. Non-linear functions ( p–y curves) are specified to relate the pile displacement, y, to the local distributed lateral load, p, acting on the embedded pile. ![]() A widely used simplified procedure, known as the p–y method, employs a beam model for the monopile and a Winkler representation of the pile–soil interaction. This comparative study demonstrates that the PISA design model can be applied successfully to layered soil configurations, except in certain cases involving combinations of very soft clay and very dense sand.ĭesign procedures for monopile foundations for offshore wind turbine applications typically employ simplified models to facilitate the development of practical designs. The fidelity of the PISA design model is assessed by comparisons with data obtained from equivalent 3D finite-element analyses, demonstrating a good agreement in most cases. Results from the 3D analyses are used to explore the various influences that soil layering has on the performance of the monopile. The study comprises ( a) analyses of monopile behaviour using detailed three-dimensional (3D) finite-element analysis, and ( b) calculations employing the PISA design model. The paper describes a computational study on monopiles embedded in layered soil configurations comprising selected combinations of soft and stiff clay and sand at a range of relative densities. This design model has been previously calibrated for homogeneous soils this paper extends the modelling approach to the analysis of monopiles installed at sites where the soil profile is layered. However, if a beam has more than two reaction loads, as in the case of a beam fixed at one end and either pinned or fixed at the other end, it is statically indeterminate and beam deflection equations must be applied in addition to the equations of statics to determine the reaction loads.The PISA design model is a procedure for the analysis of monopile foundations for offshore wind turbine applications. ![]() If a beam has two reaction loads supplied by the supports, as in the case of a cantilever beam or a beam simply supported at two points, the reaction loads may be found by the equilibrium equations and the beam is statically determinate. These consist of a summation of forces in the vertical direction and a summation of moments. Two equations of equilibrium may be applied to find the reaction loads applied to such a beam by the supports. 1.3.4 Introduction to Reaction Forces and Moments on Beams Under Transverse Loadingįigure 1-30 shows a beam under transverse loading.
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