Browsing by Subject "Offshore foundations"
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Item Laboratory model tests to assess the effects of scale and stress on the stiffness of laterally loaded foundations in sand(2018-05-04) Bauer, Jonas Fabian; Gilbert, Robert B. (Robert Bruce), 1965-Offshore wind farms have the ability to meet the energy demands of the USA four times over, and are located offshore where less turbulent, high-speed winds can generate electricity efficiently. The most popular option for offshore foundations are monopiles, which are characterized as large diameter steel pipe pile suited for relatively shallow depth (20 – 30m) so they have a large aspect ratio (length divided by diameter or L/D) of between 3 and 8. The most common design methods for laterally loaded monopiles rely on p-y curves, which were developed for relatively small-diameter and slender piles and might not be suited to predict the behavior of larger diameter and smaller L/D ratios. In order to evaluate the suitability of p-y curves to predict the load – displacement behavior of laterally loaded monopiles a consistent laboratory testing methodology to perform 1-g lateral load tests in sand was developed. The aim of this research is to compare the results from the 1- g lateral load tests to compared to the predictions of a newly developed 3D Finite Element Method (FEM) analysis as well predictions from the American Petroleum Institute (API), which utilizes the p-y method. A repeatable and consistent methodology to conduct a large number of 1-g lateral load tests in sand using spheres to model the state of stresses around a monopile for varying sphere diameters and embedment depths was developed. The sand was characterized by its dynamic properties, which were used as input parameters for the 3D FEM analysis. A total of 50 1-g model tests were conducted and analyzed. The results indicate that the 3D FEM is able the non-linearity in initial stiffness if accurate dynamic properties are used. Additionally, p-y were not able to capture the initial non-linearity in the load – displacement behavior and underestimated the initial stiffness for all tests.