Document Type

Thesis - Open Access

Award Date

2017

Degree Name

Master of Science (MS)

Department

Civil and Environmental Engineering

First Advisor

Junwon Seo

Keywords

computational fluid dynamic, monopile, multi-hazard, offshore wind turbine, retrofit

Abstract

Offshore wind turbines (OWT) provide a renewable source of energy with great proximity to many large cities. This has caused a major increase in OWT development and implementation, primarily in Europe, but spreading throughout the world. There are a multitude of different foundation options, each with their own benefits. The most common types are: monopile, jacket, TLP, Semi-Submersible, and SPAR. The monopile foundation OWT has been proven to be the most economic selection for water depths up to approximately 25m. This thesis has analyzed strictly monopile foundations due to their previous success and popularity. Three different chapters have been created to cover the two different research papers contained in this thesis. Chapter one utilizes the software ANSYS to complete a multi-hazard computational fluid dynamic (CFD) analysis of a monopile foundation OWT. A dynamic analysis was performed on the structure, with a p-y curve soil-structure interaction implemented. Chapter two aims to verify the plausibility of a retrofit solution to a significant problem certain previously installed monopiles have developed. The annulus grout of the transition zone of the structure has been determined to be under-designed, and thus has experienced crushing. This allows the tower to slightly slide down the monopile, increasing the chances of total structural failure. A retrofit bolted connected has been implemented, and proven to significantly increase the limiting shear capacity of the structure. The research paper in chapter three is focused on developing the retrofit solution into a more applicable design. Using a response surface methodology (RSM) an optimized design criteria has been generated based on six geometric/material parameters of the bolted connection: horizontal spacing, vertical spacing, bolt diameter, number of bolts in vertical columns, pre-tensioning load on bolt, and modulus of elasticity.

Library of Congress Subject Headings

Wind turbines -- Computer simulation.
Wind turbines -- Design and construction.
Offshore wind power plants.
Computational fluid dynamics.

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

99

Publisher

South Dakota STate University

Rights

Copyright © 2017 William A. Schaffer