Response of a stiff monopile in cohesionless soil to the offshore loading conditions
Author
Lada, Aleksandra Katarzyna
Term
4. term
Education
Publication year
2014
Pages
178
Abstract
Specialet undersøger, hvordan en stiv, stor-diameter monopile funderet i friktionsjord (kohæsionsløs jord) reagerer på offshore belastningsforhold, hvor cykliske, laterale laster dominerer. Baggrunden er, at gældende designstandarder baseret på p‑y kurver primært stammer fra fuldskalatests af slanke pæle og kun i begrænset omfang tager højde for cykliske belastninger, lastkarakteristika og antal belastningscykler, hvilket er problematisk for stive monopiles. Formålet er at evaluere langsigtede effekter af laterale laster på rotation, stivhed og den ultimative jordmodstand for sådanne fundamenter. Metodisk gennemføres småskalaforsøg i laboratoriet ved Aalborg Universitet med varierende laststørrelse og -retning, inklusive efter-cykliske tests, for at vurdere rotationsophobning og stivhedsændringer samt ændringer i den ultimative modstand. Derudover anvendes PLAXIS 3D til en række numeriske analyser, der sammenligner stive og fleksible pæles adfærd og undersøger, hvordan pælediameter, pælelængde og lastens excentricitet påvirker den ultimative kapacitet. Resultaterne skal bidrage til bedre forståelse og potentielle forbedringer af designpraksis for offshore monopilefundamenter; konkrete kvantitative fund fremgår ikke af uddraget.
This thesis examines how a stiff, large-diameter monopile embedded in cohesionless soil responds to offshore loading conditions dominated by cyclic lateral loads. The motivation is that current design standards based on p‑y curves rely on limited full-scale tests of slender piles and capture cyclic loading, load characteristics, and number of cycles only poorly, which is problematic for rigid monopiles used in offshore wind farms. The objective is to evaluate long-term lateral load effects on rotation, stiffness, and ultimate soil resistance. The study employs small-scale laboratory tests at Aalborg University with controlled load magnitude and direction, including post-cyclic tests, to assess accumulated rotation, changes in stiffness, and changes in ultimate resistance. In addition, PLAXIS 3D finite element analyses compare the behavior of stiff and flexible piles and explore how pile diameter, pile length, and load eccentricity influence ultimate capacity. The work aims to inform improved foundation design for offshore wind turbines; specific quantitative findings are not detailed in this excerpt.
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