Forced Torsional Vibration of a Monopile for Its Extraction

The offshore monopile decommissioning demand will become definite in the coming years. Our responsibility is to ensure the rights and duties of other legitimate uses by completely removing the ageing monopile from the seabed to continuously redeveloping offshore wind farms within the same location. The growing number of past, present, and future...

Design of a suction pile multiline anchor system for floating offshore wind turbines

In this thesis I will show the realisation of a multiline anchor system using a suction pile anchor (SPA). From the literature research it can be concluded that the SPA is a suitable anchor for a multiline anchor system and that the most probable mooring configurations will be either the original single-line, the 3-line or the 6-line system....

Ice Loads: The effect of climate change on Arctic offshore structure design

For the development of Arctic offshore structures, design ice loads are required. These design loads represent the ice loads a structure may be exposed to for specified requirements. The design ice loads depend on magnitude of the ice loads and on the probability of exposure to the ice loads. Both are impacted by local sea ice conditions.<br/>...

Fiber optimization of a carbon windsurfing boom: FEM fiber optimization for mass and stiffness

The goal of this research is to optimize the fiber layup of a carbon windsurfing boom for weight and stiffness. A windsurfing boom should be stiff to provide an efficient basis for the energy transfer from the sail through the surfer to the board. The weight of the boom is important as the total weight of the rig influences the performance,...

Fatigue assessment of existing offshore wind turbine support structures for lifetime extension

Offshore wind turbines (OWTs), together with their support structures, are designed for an operational period of 20 years. The first generation of these offshore wind turbines has already reached or is approaching their designed lifetime of 20 years. Depending on the legislation and the governmental subsidies, a decision needs to be made about...

Vessel Motion Based Assessment of Pipeline Integrity During Installation

If weather conditions become rough, vessel motions with an increased amplitude are excited due to the presence of waves. The sagbend region of a suspended pipeline catenary may experience high loads due to these motions. When the loads become too high, the pipeline integrity cannot be guaranteed. In such case, the pipeline is lowered to the...

Conceptual Design of a Pile Installation Frame with Adjustable Footprint

An offshore wind turbine is placed on a so called “foundation” to gain height above the sea surface level. One of the used foundations is the jacket structure, which is kept in place by pre-piled supports. The piles are hammered into the seabed first, after which the jacket legs are stabbed into the piles. A template is used to guide the piles...

Floating installation of offshore wind turbines in a single lift

The wind energy industry is booming. In 2017 the installed wind capacity has overtaken coal as the second largest form of power generation in Europe. Costs of wind farms are driven down, and even the first offshore wind-farm contract without subsidies is a fact. Installing the Wind Turbine Generators (WTGs) more efficiently increases the profit...

Evaluation of transient lift loads during a decommissioning operation with a crane vessel

With the conversion of a heavy transport vessel into a crane vessel, Boskalis aims to strengthen its position in the offshore wind and decommissioning markets. The BOKALIFT 1, as the crane vessel will be named, is equipped with a 3,000 tonne crane and a class-2 Dynamic Positioning system. In order to utilise its exceptional large and strong deck...