The ever-increasing size of offshore wind turbines, combined with the development of wind farms at more remote sites with deeper waters and more extreme weather conditions, presents significant logistical challenges. Furthermore, the offshore wind sector faces reduced government subsidies, narrow profit margins, and a lack of industry guidelines, all while striving to lower the levelised cost of energy in order to remain competitive in the market. Developers must navigate complex decisions regarding foundation selection and installation strategies. However, existing research lacks systematic approaches to optimise these decisions, with particular gaps in studies addressing multi-vessel operations, vessel compatibility with component size, alternative transport vessels, and the specific challenges of substructure installation. This lack of structured frameworks hinders evidence-based decision-making in foundation selection and installation planning. This research develops a framework to address the question: How can a multi-vessel optimisation framework integrating alternative transport vessels and accounting for weather uncertainty improve foundation selection and installation scheduling to minimise costs?  The first phase of this study develops a deterministic decision tree model that evaluates foundation selection based on environmental parameters and identifies cost-optimal Transport and Installation (T&I) strategies. Analysis of 23 previous installation projects highlights water depth as the primary decision factor, with a 50-metre threshold distinguishing between monopile foundations for shallower waters and suction bucket jackets for deeper waters. A 127-nautical-mile threshold marks the transition from shuttling to feeder strategies. Cost sensitivity analysis reveals that water depth significantly impacts cost, while seabed conditions show minimal influence. The decision tree model’s foundation type prediction accuracy is 43.5%, reflecting the complexity of real-world decision-making. This phase provides a visualisation of pathways for early-stage project decision-making, emphasising the importance of more detailed installation schedule optimisation using Mixed Integer Linear Programming (MILP) and stochastic approaches.  The second phase employs MILP to optimise installation scheduling for a case study and assess the installation performance of monopiles versus pin-pile jackets using the assembly-line installation strategy. The deterministic model incorporates constraints (e.g., task precedence, operational, deck capacity) and weather limitations using historical site weather data, while a stochastic extension models weather uncertainty using Weibull distributions. The performance of monopile-transition piece (MP-TP) strategies is compared with pin-pile jacket (PP-JK) strategies, focusing on weather sensitivity, costs, and computational performance. In addition, logistic setups are evaluated by varying the number and type of vessels used, from three to five. The results show that MP-TP strategies outperform PP-JK strategies, with MP-TP installations preferring shuttling over feeding when a 2.5-metre wave height limit is applied. For PP-JK installations, Heavy Transport Vessels (HTVs) are preferred over barges due to their higher deck capacity, despite the lower installation rate of the associated installation vessel. The use of a single installation vessel capable of installing all component sizes is found to be more cost-effective than using smaller and cheaper additional vessels. Weather uncertainty significantly influences installation scheduling, as shown by both deterministic and stochastic models.  The developed decision support tool provides a basis for further research in offshore wind logistics and other industries. Although the findings are applicable within the scope of this study, future research should explore additional factors such as stochastic risk assessments for pile refusal and assess the impact of larger wind farm sizes and dynamic port-to-farm distances.

The Netherlands faces a significant challenge in maintaining its estimated 85,000 bridges, most of which were constructed between the 1950s and 1970s. Addressing this "Replacement and Repair Challenge" requires prioritizing bridges at high risk of deterioration to optimize maintenance efforts. Internationally, predictive maintenance studies have successfully utilized Bridge Deterioration Models (BDMs) that leverage inspection and supplementary data to train machine learning models for predicting bridge deterioration. This study investigates whether Dutch bridge inspection data, collected under the NEN 2767 standard, could similarly support BDMs for predictive maintenance. The aim is to evaluate the suitability of NEN 2767 data for this purpose and identify necessary modifications to enhance its predictive capabilities. Data from five provinces and seven municipalities were analyzed using the "4 Vs" framework: Volume, Variety, Velocity, and Veracity. Results indicate that, due to data inconsistencies, limited feature diversity, and insufficient volume, the Netherlands is not yet prepared to apply machine learning to NEN 2767 data. To explore these challenges further, semi-structured interviews were conducted with five government agencies and four inspectors. Findings suggest that while there is confidence in the NEN 2767 standard, significant variation exists in data collection and storage methods. Furthermore, maintenance decisions rely on additional information that is not consistently recorded in government databases alongside NEN 2767 data. A literature review on BDMs identified 25 critical features that could improve the predictive accuracy of NEN 2767 data for Dutch bridge deterioration. Based on these insights, four key recommendations are proposed. Firstly, preliminary recommendations were presented to stakeholders, after which some adaptations were maded to improve their quality. These for recommendations are as follows: (1) Extend the CUR 117 standard to enhance data collection, storage, and sharing protocols; (2) Develop a standardized Inspection Procedure, which would involve certification through the CUR 117 commitee; (3) Incorporate the 25 additional features identified as relevant for predictive maintenance; and (4) Utilize the Schouw, an annual inspection process, as a means to capture more maintenance data on bridges. These steps would collectively strengthen the predictive capabilities of NEN 2767 for proactive bridge maintenance in the Netherlands.

This research addresses the challenges of installing floating wind turbines on semi-submersible platforms, with a focus on managing relative motions during offshore integration. Traditional methods, which rely on large onshore marshaling yards, are constrained by the limited space available at ports to meet the increasing demands of the offshore wind industry.

In response, the study proposes a shift to floating-to-floating installation, where turbine integration takes place on a moored floater directly at the wind farm. A major challenge in this approach is controlling the relative motions between the two floating bodies. To address this, a multibody model is developed in OrcaFlex, simulating the interaction between a heavy lift vessel and the VolturnUS-S platform. This model highlights the complexity of relative displacements, providing the foundation for introducing concepts aimed at minimizing these horizontal motions.

The chosen concept features a donut-shaped external platform equipped with winches for horizontal motion compensation. In the proposed 10-step installation process, the turbine tower is suspended from a crane while a gripper restricts pendulum motions, and an Active Heave Compensation system manages the relative heave motions. The external platform, suspended below the tower as it is attached to the gripper, is first lowered and secured onto the floater. Once in place, the tower is lowered, with the winches providing the necessary stiffness to control relative horizontal displacements during this phase.

The winch wires are modeled as springs with equal stiffness applied in both horizontal directions. Time-domain simulations in OrcaFlex, validated by an analytical model in MATLAB, reveal that a stiffness of 8887 kN/m is required to effectively limit horizontal displacements to 0.2 m for significant wave heights up to 2.5 m. This design choice ensures 92% workability for this installation step, considering a maximum crane angle of 2 deg and a maximum horizontal relative displacement of 0.2 m. Ensuring functionality under the simulated sea states reveals a design requirement of 1823 kN for the compensation system in the horizontal direction for Hs = 2.5 m and a Tp ranging from 6 to 11 s. While this force exceeds the capacity of a simple winch, it remains within a feasible range for a dedicated compensation system.

Hyperloop is a high-speed transportation mode that operates through magnetic levitation of so-called pods which are then transported through a tunnel in which a low-pressure environment is created. Due to reduced air resistance and friction, high velocities are achievable. This thesis addresses the behaviour of such a system operating at high velocities, focusing mainly on dynamic stability. The novelty of this study lies hereby in the implementation of a more realistic guideway model in the analysis. This was achieved by modelling the Hyperloop tube as an infinitely long cylindrical shell on a viscoelastic foundation from which the vehicle is suspended through an electromagnetic force, including an active control system.

This study aims to evaluate the system’s stability and its sensitivity to changes in the model by using mainly analytical methods which are supplemented by numerical computations where needed. There are two fundamentally different instability mechanisms studied, namely the electromagnetic instability caused by the inherent unstable nature of the suspension system and the wave-induced instability which originates from the energy feedback of radiated anomalous Doppler waves excited by the vehicle moving at large velocities. The research is motivated by two central questions: (1) What is the influence on the steady-state response when employing the more realistic guideway model? (2) What is the influence on the stability when employing such a model?

To address the first research question, only the steady-state of the guideway is analysed. Hereby, the electromagnetic force as well as the vehicle are disregarded and replaced by a constant moving load. To solve the system, the governing equations are projected on circumferential modes and transformed from space-time to the Laplace-wavenumber domain. This study analyses various scenarios based on their dispersion curves and/or steady-state response compared to a reference case.

For the second research question, the study analyses stability phenomena whereby the response of the guideway is expressed using a convolution of its Green’s function and the unknown electromagnetic force. Linearising the system around its steady-state equilibrium allows a computation and analysis of its eigenvalues which describe its stability. To complement and verify the analysis of the linearised system, a non-linear transient model is solved by using a numerical time-stepping algorithm.


The study highlights that the cylindrical shell model significantly affects the critical velocity, compared to an Euler Bernoulli beam model. Analysing the vehicle-structure interaction through the linearised stability analysis reveals stability concerns primarily driven by wave-induced instability when operating at supercritical velocities. In the subcritical regime, instability is only caused by the electromagnetic suspension, which can be overcome when choosing the right control parameters. To reduce the risk of instability it is advisable to choose the structural dimension such that the system operates at subcritical velocities to avoid the interaction between the two instability mechanisms.

This research advances the understanding of Hyperloop dynamics and its stability, providing a foundation for future studies and practical implementations aimed at developing the novel transportation mode.

This thesis is a about a novel float-over concept for the installation of offshore substations in the Dutch North Sea. This new technology is a topside jacking system integrated into the H-851 float-over barge which should be able to jack the topside to a higher elevation before a float-over installation.

First, a high-level concept design of the novel float-over technology is presented. Thereafter, the stability for the jacking stage is investigated via hand calculations. Analytical models are developed to model the jacking system during select stages of the float-over and jacking of the topside. These models are used to verify the assumed design loads on the jacking system and other components required to install the offshore substation. As of now, the design loads are based on guideline for a different type of float over making the design loads a guestimate.

The float-over barge H-851 proved to be very stable without ballasting during the jacking of the topside. Initial ballast errors did not affect the barges stability significantly, the effect was only a 30% increase in heeling angle for the worst case. The effect for wind loading was more profound as the heeling angle increased with 100%. Due to the large initial stability of the barge, the heeling angle after jacking is still of no concern. For the investigated cases, however, care should be taken to ballasting the barge before jacking as initial errors become larger after jacking.

It was found that the driving systems for the jackings system can be designed in the global horizontal direction using less than 5% of the topside weight, given the sea states in this thesis. A lower stiffness jacking system resulted in lower horizontal loads on the driving system. The jacking system showed a difference in local horizontal loads over the jacks from stern to bow as great as 150%. This is due to the position of the topside with respect to the centre of the barge and in combination with the roll, pitch and heave behaviour of the barge and topside.

The mating analysis had multiple findings. It was found that the impact loads on the LMU’s were significantly lower by using the jacking system compared to the DSF for North Sea waves. However, the effect of the horizontal load (compression force) was less significant which resulted in lower or equal loads on the LMU’s. The horizontal loads at the interface between topside and barge were larger for a jacking system compared to a DSF.

Increasing the stiffness of the jacking system resulted in an increase of loads on the jacks and LMU’s. This was found due to the lower eigen period in the dominant motion for stiffer jacks. An interesting finding is a torsion moment with its centre at the interface between barge and topsides. This point was found to be dependent on the stiffness of the interface.

The projected rise in monopile installations for offshore wind turbines has spurred interest in innovative installation methods to install larger monopiles using floating vessels while simultaneously enhancing workability and efficiency. One such innovation is the motion-compensated gripper frame (MCPG), which stabilizes the monopile by compensating for environment induced motions affecting both the monopile and the floating vessel. The MCPG is capable of compensating for the wave-frequent motions during lowering of the monopile as well as during the hammering phase of the monopile.
This thesis aims to create a frequency domain model to assess the performance of a motion-compensated pile gripper (MCPG) system for offshore monopile installation using a floating installation vessel. Simulating in the frequency domain offers the advantage of minimum computational time, enabling a large number of scenarios to be simulated in a shorter amount of time compared to time-domain simulations. To assess the installation up until the piling phase, two dynamic models have been created, each based on a particular installation. The first steps of the installation process are divided into three phases: upending, lowering, and pre-piling. Two dynamic models were created, focusing on the second and third phases. The phase 2 model accounts for the lowering of the monopile, while the phase 3 model concerns the situation where the pile has reached its self-penetration depth.
The equations of motion were derived for each system and transformed to a state-space model to implement the controller for the motion-compensated gripper. The state-space models were converted into transfer functions in the frequency domain and subjected to first-order wave forces calculated by the diffraction analysis software WAMIT. The method of obtaining the frequency response was validated using data provided by GustoMSC while the motions of the monopile were validated by comparison to an analytical compound double pendulum model.
This research proposes a response-based approach tune the controller proportional and derivative gains. The gains were determined based on the response characteristics of the phase 3 system. These gains were subsequently applied to the phase 2 system across all drafts. The system’s performance and tuning method were assessed using stability analysis, frequency response, spectral analysis and modal analysis. The models and tuning approach were tested using 6, 12 and 15 meter diameter monopiles, which for the phase 2 system were suspended at drafts of 5, 25 and 45 meters. Simulations were conducted for various sea states, comparing open-loop (without controller) and closed-loop (with controller) scenarios. The systems are analyzed based on the following parameters: the monopile roll angle, crane cable offlead angle, gripper force, gripper stroke and gripper stroke rate.
Results indicated that the MCPG effectively eliminated monopile roll motion in both phases. In the closed-loop phase 3 system, gripper stroke and stroke rate were dominated by vessel sway motion, while phase 2 did not show much reduction in gripper stroke and stroke rate. The operability analysis identified the critical operability limits: in the open-loop phase 3 system, the monopile roll angle was the primary limit, followed by gripper stroke. In the closed-loop system, gripper stroke rate and force became the primary limits. For phase 2, gripper stroke was the main limit in both open and closed-loop systems, with stroke rate becoming more significant in the closed-loop system. The MCPG shifted the limiting criteria from monopile roll angle to gripper stroke rate in phase 3. The combined operability of the phase 3 system including the MCPG was found to be 25%.
Finally, the research recommends the addition of time-domain simulations to capture non-linear effects. It is also recommended to extend the models to three dimensions in order to simulate non-beam or bow waves. The phase 3 model can also substantially benefit from the addition of soil loads.

The field of wind energy has experienced significant expansion and development driven by the need to reduce reliance on fossil fuels. Offshore wind turbines have become increasingly popular leading to larger turbines with greater energy output to match the growing demand. The most common foundation type of offshore wind turbines is the monopile foundation, consisting of two large diameter steel tubulars, the monopile (MP) and the transition piece (TP).
As wind turbine generators (WTGs) increase in size, the transportation and installation of MP foundations becomes more complex and expensive, requiring specialized vessels with adequate lifting capacity. This research investigates a new connection – the underwater wedge connection – as a method of connecting an MP to a TP underwater. By having an underwater connection, the size of the MP can be reduced as it no longer has to exceed the waterline.
The wedge connection consists of a dowel with an inclined plane and two flanges. A number of dowels will be placed around the circumference of the connection, fitted onto flanges on both the MP and TP. As the dowels are pushed into position, the inclined plane creates a vertical preload between the two flanges. This allows a tensile load on a segment of the connection (caused by the bending moment in the foundation) to be transferred to the foundation via two load paths: reduction of the preload, and by loading the dowel itself in shear.
First an analysis on the current state of art and relevant design codes was carried out. This analysis highlighted the requirements the connection needed to satisfy, in order to serve as starting points to make decisions regarding the design. The preliminary design of the connection is made using analytical calculations. The structural integrity of the flanges and the dowel at the Ultimate Limit State (ULS) was verified. A 3D model of the connection was then created to perform numerical analyses using ANSYS Static Structural. The behaviour of the connection under ULS and Fatigue Limit State (FLS) loading is studied. The opening and failure point of the connection along with the sensitivity of various parameters are also investigated.
The results show that connection was able to effectively transfer both tension and compression loads. The connection has a mechanical advantage of 1.95, meaning that it achieves the same preload as the ULS load by applying only 51.3% of the ULS segment load during installation. The connection opens gradually and only opens at a load higher than the ULS load. Even after opening, it continues to transmit loads effectively, with ultimate failure governed by the yielding of the lower flange. Additionally, the connection exhibits good fatigue resistance, with a low fatigue damage level of 3.8%.
It is recommended to conduct experiments to validate the numerical model employed in this study. Further studies should also be carried out to investigate the impact of structural imperfections on the behaviour of the connection.

This study examines the effect of adding helical piles to the foundation mechanism of monopile installation templates. A monopile installation template is a gravity-based structure, which is placed on the seabed. The installation template is utilised for the installation of monopiles, and to ensure its verticality during this installation. At this time, challenges arise for the stability and operability of the installation templates due to the increased dimensions and mass of these structures. The increased demand for green energy leads to the growth of monopiles, in both number and size. The growth in monopile size leads to the increasing required dimensions of the installation templates. The installation templates are, however, often restricted in size and mass by the capabilities of the installation vessel.
The installation templates generally use mud-mats as foundation system to ensure stability and prevent the template from excessive settling. The mud-mats cause significant dynamic effects, especially when taken through the water line. Moreover, the sliding capacity of mud-mats is often insufficient, leading to potential sliding failure of the template. A literature review is conducted using different sources, such as reviews, offshore guidelines, research papers, and expert interviews, to investigate installation templates and different foundation mechanisms. The investigated foundation mechanisms are suction buckets, mud-mats, and (helical) piles. The literature review demonstrates that helical piles show greatest potential of being added to the mud-mat foundation. Therefore, solely helical piles are considered in the current study, and the following research question is answered: How, and to what extent, does adding helical piles affect the footprint of the monopile installation template designed for the benchmark project? The current study uses a project carried out by Heerema Marine Contractors as benchmark. All parameters of this project are used as input for the study. Findings of analytical analyses on the (environmental) loading and mud-mat capacity are validated with the benchmark project results. Subsequently, the helical pile geometry is optimised for maximum uplift capacity, using the methodology shown in the figure below. The capacity is optimised for uplift capacity, as it is assumed that the mud-mats can bear the compressive loading. Additionally, the lateral capacity would significantly increase by utilising piles, and therefore optimising for lateral capacity is not recommended. The obtained geometry, optimised for maximum uplift capacity, is then assumed to be constant and used to determine the uplift, compressive, and lateral capacity. The analysis shows a positive correlation between embedment depth and capacity (uplift, compressive, and lateral). The helical pile capacity is added to the mud-mat capacity. Consequently, effects on design variations are examined, such as reduction in template's mass and size, mud-mat size, and variations in helical pile geometry and soil parameters. The analysis shows a significant improvement in capacity of the foundation, in both compressive and lateral capacity. The uplift capacity of the helical piles ensure no uplift of mud-mats occurs. This leads to a more evenly load distribution among the mud-mats, lowering the maximum factored load on the legs. Consequently, the mud-mat size and the template's mass and dimensions could be reduced. It can be concluded that a reduction in mud-mat size directly results in the potential of reducing the template dimensions. The reduction in both template and mud-mat size would automatically lead to a decrease in mass. However, the reduction in template mass could lead to a decrease in structural performance. This should be investigated in further studies. Variations in soil characteristics show that the performance is even more enhanced in denser sands. Concluding, the helical piles have a positive influence on the template's overall capacity. The findings show that a reduction in the footprint of the template is possible, of maximum 13.6%.

Due to the increasing size of offshore wind turbines, the jack-up vessels and cranes installing them need to increase in size. The increase in length of the crane boom results in an increase of the dynamic response of the crane. This increase in response results in higher loads in the crane. The magnitude of the higher loads are unknown and not yet accounted for in crane design. To get a better insight in the dynamic response of the crane and higher loads, a probabilistic model is developed to quantify the annual probability of the crane.
To define the different crane operations, a measurement data set of crane operations is made available. From this data set, the different lifts types, exposure times and occurrences are identified. Multiple jack-up configurations are chosen with different water depth and wave heading. Next to the crane and jack-up configuration, long-term wave statistics are used for the environmental conditions, as input for the probabilistic model.
Time-domain simulations are performed in a rigid multi-body analysis software, to simulate the dynamic response of the crane, due to wave induced excitations. Due to the random nature of waves, convergence of the results is researched. For this, numerous time-domain simulations with different sea-states have to be performed, this is unwanted.
A methodology is developed, using the frequency domain, to limit the number of required time-domain simulations. Using the devised methodology, configurations with similar statistical description can be identified and grouped.
The annual probability of failure can be calculated using the devised methodology and probabilistic model. The resulting annual probability of failure is small, much smaller than required. A sensitivity analysis is performed, it is found that the annual probability of failure depends greatly on the input of the probabilistic model.
From the results and sensitivity analysis, multiple recommendations are given to decrease the sensitivity of the result. It can be said that from the devised methodology, a basis has been laid to quantify the annual probability of failure of the crane in normal operations.

Suction caisson jacket (SCJ) is one of the most promising substructures, under certain conditions, for offshore wind turbines. Their unique characteristic of large diameter (D) compared to their small wall thickness (t) conducts them an object of study, concerning their transportation to the offshore location, as their structural stability should be ensured. Their large D/t ratio leads the caisson into being a flexible structure, which should be stabilized in an already moving barge (due to wave motions and accelerations). The caisson is partially supported in the base perimeter, in order to leave enough space for both loadout equipment and the barge to coexist. The main objective of this thesis is to apply the most optimal configuration to sufficiently support the caisson on barge. Prerequisite of that is to examine the behavior of the caisson, when interacting with the barge during transportation. A parametric study is performed where the stresses and deformations of the caisson are retrieved and the buckling behavior is examined. The boundary conditions are applied in the bottom perimeter of the caisson and they are designed, so as the stiffness of the barge is taken into consideration. The parametric study considers changing the boundary conditions (supports) in the perimeter of the caisson. In total 6 cases were examined, in which the supports vary with respect to their length, their location in the base of the caisson and finally the value of their stiffness.
A finite element analysis is performed and the results were derived for every case of the parametric study. The equivalent von Mises stress is examined in the full length of the caisson and in the supported perimeter, as well as its most important components. For the supported perimeter, directional deformations are derived in radial, tangential and vertical direction. The results showed that the stresses developed very large peaks above yield limit at the edges of the supports, for each case, and the most influential component causing these peaks turned out to be bending stress in tangential direction. The bending stresses are caused by radial deformations, thus in order to reduce this stress component, radial deformations should be reduced. The comparison of the cases showed that the trend of the stresses remain the same for every case. It is also realized that the peaks in stresses and deformations in radial and tangential direction show the most reduction when the distance between the supported segments is reduced. A non-linear analysis performed indicates that the high stresses in every case (above yielding) are acceptable and this will lead to a redistribution of stresses in the caisson. The buckling behavior of the caisson is examined and in every case buckling failure does not have a high possibility to occur for the applied load combination. As a result of this study it is concluded that the most optimal grillage configuration has to do with reducing the unsupported area between the supported segments.

The current research stems from the motivation of controlling the phenomenon of traffic congestion in urban areas that can be deteriorated due to the implementation of a construction project. Nowadays, it is frequently observed that construction activities in complex urban environments appear undesirable effects on the communities surrounding the location of the construction project having as a focal point the “construction traffic”. Nonetheless, existing studies indicate traffic congestion is a significant contributor to the inefficient management of construction logistics. Unsuccessfully managing a project’s construction logistics is strongly correlated with the unsatisfactory performance of the construction process mostly due to the occurrence of delays in the implementation of the construction activities related to incorrect delivery of building materials and construction equipment. Likewise, inefficient management of construction logistics can lead to unmanageable traffic levels derived from additional transportation volumes related to the construction process. Since the multi-faced issue of traffic congestion can cause both a negative “domino effect” on the construction activities towards the realization of a construction project as well as unfavorable effects on urban city’s living conditions, positively impactful ways ought to be researched for reducing the adverse consequences of uncontrollable traffic. This thesis works for designing and developing a transportation prognosis model that can predict the extra transportation volumes on the location of the construction project due to the transportation activity of the needed vehicles along the construction process, offering an insight into traffic conditions of the examined relevant road. In this way, the designed prognosis model can be used as a proactive tool since it indicates if and when uncontrollable traffic levels can occur.

This paper investigates the technical, life cycle, and economic feasibility of a 30 MW upscaled downwind turbine, comparing it to a 15 MW X1 Wind PivotBuoy downwind turbine and a benchmark 15 MW IEA Umaine VolturnUS-S upwind turbine in the 450 MW Sud de la Bretagne I wind farm site. The study is significant due to the rising energy demand, the potential for decreasing the levelized cost of energy with increased turbine size, and the optimized use of space. The size limit of current upwind turbine designs could be addressed using a downwind turbine solution.

The research is conducted by modelling the global dynamic response of the structure using OpenFAST and computing the natural frequencies and stresses using a finite element model. A lifecycle analysis is performed to identify potential pitfalls and bottlenecks by analysing the individual lifecycle phases. The economic feasibility is assessed by simulating the annual energy production using TOPFARM and utilizing structural analysis and lifecycle assessment to quantify capital, operational, and abandonment expenditures. Based on the annual energy production and the performance indicators the levelized cost of energy is calculated.

The findings indicate that while the global stability is within boundaries, the stress in members is too high with a simple scale-up of the proposed design. Bottlenecks are found in lifting operations and supply chain readiness. The levelized cost of energy and capital expenditure increased due to substructure self-weight, rendering the proposed 30 MW scale-up currently unfeasible when compared to the other two wind farms.
These findings are important as they demonstrate that the 15 MW X1 Wind PivotBuoy is not scalable without design changes. The levelized cost of energy does not decrease with an increased floater solution. The 15 MW X1 Wind PivotBuoy downwind turbine seems more economically viable, making it a more interesting option for future development.

In the Netherlands, there is an increasing need to create residential spaces in its already crowded cities to accommodate the growing population. Constructing high-rise buildings is one way to try to solve the issue. However, high-rise buildings are sensitive to wind-induced vibrations. The accurate prediction of the dynamic response is important in high-rise building design. In building design practice, calculating the dynamic response of high-rise buildings under wind loading typically involves simplifying the structure as a single degree of freedom system, characterised by the first eigenmode properties and subjected to a white noise spectrum. The damping and natural frequency of the building substantially impact its dynamic response. These parameters are challenging to predict with accuracy. Additionally, in the presence of soft soils, soil-structure interaction can play an important role in energy dissipation and influence the structure's natural frequency. In practice, soil-structure interaction is either disregarded or simplified.
In order to assess the effect of soil-structure interaction on the dynamic response of the building, this study models in a robust manner: the foundation, the tower structure, and the wind load. This newly developed model is addressed as the HF model. The investigation consists of a case study and a parametric study. Additionally, this study compares the predictions by the newly developed model with those obtained with a model as specified in the Eurocode. The case study provides a comparison between the models and the measured dynamic response of the New Orleans Tower. The parametric study looks into the influence of soil stiffness and material damping on the dynamic response of high-rise buildings. Furthermore, it investigates how these parameters affect the dynamic response of structures with various slenderness ratios.
The case study was used to demonstrate that the developed model accurately predicts the measured dynamic response of the New Orleans Tower in the along-wind direction. For all the examined dynamic properties, the error compared with the measurements was lower than 7%. In the case of the Eurocode model, the results demonstrate that, when using the natural frequency estimation recommended by the Eurocode, it provides a 30%–35% underestimation of the peak acceleration compared to measurements. This Eurocode model overestimates the natural frequency and overall damping, which causes it to underestimate peak acceleration. However, the natural frequency determined in the design phase of the New Orleans Tower was significantly lower than the value obtained with the recommended estimation method in the Eurocode. With this lower natural frequency, the peak acceleration is overestimated by around 50%. This underestimation of the natural frequency and overestimation of the damping provided acceptable conservative results. Although this showcases the importance of accurate predictions of both natural frequency and damping, having poor predictions that cancel out each other’s effects is not desirable.
The results from the parametric study support the findings from the case study. This shows that the case study’s findings apply to the more extensive range of building configurations investigated in the parametric study. In general, the Eurocode model, for slender structures on soft soil, overestimates the natural frequency and overall damping, which causes it to underestimate peak acceleration.
The parametric study revealed that the building's first natural frequency and global damping ratio are significantly influenced by the soil stiffness and soil material damping, which can result in various effects on the peak acceleration. In the case of soil material damping, not considering it at all or considering a higher value could lead to 20% overestimation and 40% underestimation of peak acceleration, respectively. Soil stiffness had more intricate effects since it affected the natural frequency and the amount of energy dissipated by the soil radiation damping, the soil material damping and the structure material damping. For particular combinations of parameters, soil stiffness had up to a 40% increase in the peak accelerations compared to the fixed foundation.
The results of this research show that the soil stiffness and soil material damping, for the ranges of properties relevant to the Netherlands, significantly influence the accurate predictions of the wind-induced dynamic response of high-rise buildings. Especially, there was found a higher influence on the dynamic response for the extreme cases of high slenderness ratio structures on very soft soils.

The Arctic is warming more rapidly than other latitudes, which can result in the release of additional greenhouse gasses, global sea level rise and increase in extreme weather events. Additionally, this causes the rapid decline of sea ice and an ice free Arctic might occur during the summer in the 2040s. The decreasing sea ice cover accelerates the warming of the Arctic, which is known as the albedo feedback system. Solar radiation management (SRM) can be a solution to diminish or possibly stop sea ice decline. Within SRM a proposed technology, known as Arctic Ice Management (AIM), is distributing water on top of existing sea ice to increase the ice thickness enough to survive the summer melt. This raises the question: What water volume should AIM distribute on top of existing sea ice to counteract the annual Arctic sea ice volume loss? Based on data obtained during the period 1979-2020, the September trends for ice extent, ice area and ice volume are -83 400 km2yr-1, -49 200 km2yr-1 and -322 km3yr-1 respectively. The ice volume is considered as target parameter, as it accounts for both absolute areal ice loss and overall decreasing ice thickness. There are two main ice drift patterns in the Arctic: The Beaufort Gyre in the Beaufort Sea and the Transpolar Drift, of which the latter exports ice through Fram Strait into the Greenland Sea. Literature shows the ice remains within the Arctic for about five years when located in the Beaufort Sea and one to two years when located in the Transpolar Drift. For both locations, the ice decay is determined using an analytical approach first. This approach shows resemblance for ice located in the Beaufort Sea, but generally overestimates the ice decay in the Transpolar Drift. For this reason, an empirical approach is developed to determine the survival ice thickness. This results in accurate trends for ice decay of -2.1 to -2.7 cm day-1 in the Beaufort Sea and -0.8 to -1.4 cm day-1 in the Transpolar Drift. Considering 91 melting days results in an average survival thickness of 2.18 and 1 m respectively. AIM can be used to increase the ice thickness beyond this survival thickness and an AIM model is developed to show ice growth including AIM. The model concludes the AIM thickness, initial ice thickness prior to flooding and freezing duration after AIM define the effective ice thickness increase. The model is validated with small scale experiments, which indicate a delay between the flooding phase and continued natural ice growth. This delay can be the effect of the duration required to restore the temperature profile in the ice after flooding as shown by COMSOL Multiphysics simulations. Considering the AIM model, it is discouraged to implement AIM on ice thicknesses below 0.6 m and suggested for ice thicknesses approaching 1 m or higher to optimize the effective increase. The required water volume to compensate the annual sea ice volume loss highly depends on the location, initial ice thickness and target ice thickness and varies between 707 to 1095 km3 in the Beaufort Sea and between 386 to 464 km3 in the Transpolar Drift for the methods discussed in this research. To pump up this water volume, the expected power requirements are 4.5 to 7.0 GW and 2.5 to 3.0 GW respectively.

The offshore wind market is developing fast due to climate change. To ful fil in the growing demand for offshore wind market, one has to look for floating offshore wind solutions as nearshore shallow waters are depleting. Several types of floating wind structures can be distinguished in the following categories; Spar, semi-submersible and Tension Leg Platform (TLP) structures. Blue water developed a floating wind TLP, the BLUE-STAR, which is still under development and has not yet been applied in offshore wind projects.At the moment there are many factors unknown about the concept. This in comparison to semi-submersible structures of which more knowledge is available. The aim of the thesis is to describe if the TLP concept has an advantage over the semi-submersible structure and if the newly developed TLP concept can be a viable solution. For this, a simulation model to simulate the logistics of both structures, is developed. First, different types of offshore wind turbines are classified, including TLP and semi-submersible structures. This is followed by challenges the logistics of offshore wind farms are currently confronted with. This points out that the most important challenges are due to substructures, environmental conditions and T&I. Next, the logistic process of both the TLP and SSB structure are described. This is followed by a literature study which is divided into literature on weather conditions and literature on operations and logistics, in which the analytical approach and simulation-based methods are described.Discrete Event Simulation is used for the simulation model in Matlab. This is followed by an extensive description of the logistic process in general. The second part of the chapter elaborates on implementation of both structures into the described model. The fourth part of this thesis, elaborates on implementation of the simulation model by explaining the decisions and assumptions made for the simulation model. Furthermore, this part also discusses the inputs of the logistic process simulation.  The weather data provided by Blue water for the use of the simulation model is presented and this part of the thesis gives an evaluation of the simulation model. Based on this evaluation, is it concluded the simulation model functions correctly. In the final part of this thesis, the results of the logistic simulations of both structures are compared and a  sensitivity analysis is performed. For the sensitivity analysis, 4 cases are studied, these are: varying wind speed and wave height, variation of transport duration, seasonality and varying team performance. The aim of this sensitivity analysis is to study the influences of different input conditions.  Finally, results of the simulations and performed sensitivity analysis indicate that the newly developed TLP concept is not a realistic alternative compared to the SSB structure.    

One of the ways that Transmission System Operators (TSOs) can become more sustainable is by integrating sustainable goals in their projects using the associated procurement and tender processes. However, there are several limitations related to this integration. This research aims to identify these challenges by looking at the Dutch TSO, TenneT and its specific context. Furthermore, the research aims to provide a decision-support framework through which these limitations can be countered and the integration of sustainable goals in projects can be achieved.
First, a literature study was conducted to define sustainability and the concepts associated with it. To properly understand the context of TenneT and identify the limitations associated with sustainability, company professionals were interviewed. This pointed to the need for prioritisation and gradual integration of sustainability measures. A desktop study was also conducted to identify the company’s sustainable goals, their associated measures, and their real-life applications. A decision-support framework for integrating sustainable goals in projects, based on Multi-Criteria Decision-Analysis (MCDA) was proposed. Using the Best-Worst Method (BWM), as the selected MCDA method, developed by Rezaei (2015), a sustainability workshop was organised where decision-makers from TenneT were asked to select relevant sustainability goals for TenneT, and the ones selected by three or more decision-makers were then used for performing the BWM. To avoid focusing on already well-performing sustainability goals, the performance of their associated measures was studied, using a Maturity Model based on the work of Silvius and Schipper (2015). Finally, an Importance-Performance Analysis (Martilla and James 1977) was performed, to assess future actions for each sustainable goal. The BWM showed that the Planet aspect was selected as the most important one for stimulating sustainability in projects. Additionally, Reducing Emissions was selected as the most important sub-aspect while in the People aspect, Health and Safety ranked first. The Maturity Model showed that the least integrated goals in projects are Human Rights, Labour Conditions and Decent Work, Energy Consumption, Materials and Natural Resources and Circularity and Waste. The BWM and Maturity Model also produced interesting results regarding the awareness of decision-makers and how they perceive sustainable goals and the performance of their associated measures in projects.
Based on the Importance-Performance analysis, the research suggests integrating the sustainable goal of Circularity and Waste in the company’s following projects. This can be achieved by using existing sustainable measures, such as the Raw Material Passport (RMP), in the tender process. Using measures such as the RMP in the pre-qualification phases or selection phase, as entry requirements with specific targets to be met, or as an award criterion, aiming to create added value for the project, can stimulate the contractors and suppliers to act more sustainably. This will in turn increase TenneT’s sustainable performance and will help the company meet its own sustainable targets.

Projects in the Complex Engineer-to-order (ETO) sector are subjected to frequent schedule delays caused by engineering changes, supply chain delays and fabrication delays. Project organizations are faced with the challenge of realigning the project duration within the pre-determined time. Schedule delays often lead to 3-5% rise in project cost. This requires an efficient on-the-go reactive approach. At present, the development of strategy to realign the project is extensively manual in nature. This makes the exploration of alternative realigning strategies cumbersome. Lean Project Planning (LPP) and advances in Building Information Modelling (BIM) has enriched on-the-go planning. However, no existing tool equips the project organization to generate, visualize and evaluate possible set of alternative strategies in the event of a triggered change. No attention has been provided to integrate strategy generation algorithms like Evolutionary Algorithm with the LPP and BIM approaches. In this research, a tool was developed to enable the project organizations to generate and visualize strategies integrating Modified Evolutionary Algorithm (MEA) with LPP and BIM from a metaheuristic approach. Furthermore, by undertaking a case study on strategies adopted in real-life change events in a representative Complex ETO project, the reliability of the generated strategies was investigated. The application of the proposed tool in the real-life test case showed the advantages of having multiple alternative realignment strategies.

With increasing diameters of offshore monopile foundations, impact hammers require more energy per blow in order to drive them into the seabed. This does not only increase the fatigue loading on the monopile, but it also increases underwater noise that affects marine life. The increase in installation costs due to additional material on the monopile, noise mitigation and longer installation times drives contractors to look for alternative installation methods.
GBM’s Vibro-drill strives to install monopile foundations through a combination of jetting, liquefaction and fluidization to reduce the soil resistance to such low levels that the monopile will penetrate the soil under its own weight and thereby significantly reducing underwater noise. Although the working principles are still being tested, the Vibro-drill design needs to be improved for commercial application. The design must include the three operational functionalities stated above, but to make the Vibro-drill re-usable for consequential monopile installations, additionally retrieval and structural rigidity are required.
For this thesis, the Vibro-drill is re-designed to include these functionalities. Starting from a process description, all load cases and additional design requirements were found. Based on a first global load case, a first selection was made for the connection mechanism. Subsequently, a Multi-Criteria Analysis was performed yielding two suitable concepts: the Vibro-Boxer and the Vibro-Polyp.
The Vibro-Boxer relies on three extending arms that connect with a specially designed pile shoe using twelve hydraulic grippers. To feed the system with hydraulic fluid, water and air, an umbilical connects the installation vessel with the central hub of the Vibro-drill. At the end of each arm, eccentric weights are used to vibrate the pile tip. The Vibro-Polyp has a similar lay-out except for the arms and connection mechanism. Nine hinged arms form three sets of folding parallelograms to expand or contract the Vibro-drill. The connection is made through a set of pins on each arm that slide into holes in the pile shoe.
Due to unknown soil properties and effectiveness of jetting, liquefaction and fluidization, the loads on the structure cannot be determined deterministically. Therefore, a Monte Carlo simulation is used to perform the structural analysis based on a best guesstimate for the distribution of these unknown parameters. Based on this approach, a tool is created that aims at performing the structural analysis while iteratively improving the design. As test results will become available after finalizing this thesis, input for the unknown parameters can be updated to improve the results of the structural analysis.
Subsequently, based on this progressive insight, the design of the Vibro-drill can be optimized further. Note here that for the structural analysis, the system is assumed to be quasi-static which is a gross simplification of reality. Although this imposes limitations to the reliability of the results, this assumption is allowable for the preliminary re-design phase considered in this thesis. The structural analysis described here has been applied to both suitable concepts. For each concept, the external loads were identified and the internal loads
were calculated. A series of structural checks in the Monte Carlo simulation provided a probability of failure. For both concepts the probability of failure was initially too high and therefore improvements to the structural components were made. Based on the design criteria, the two optimized design concepts were compared. Due to the smaller frontal area of the Vibro-Polyp its soil resistance on the tip of the monopile and the Vibro-drill is the smallest and therefore requires the least eccentric force. Nevertheless, the structural analysis shows that its hinged arms are fatigue sensitive yielding a higher probability of failure. Therefore, despite its larger frontal area, the Vibro-Boxer has a higher reliability and is the most suitable concept for the Vibro-drill. Finally, a more detailed design of the Vibro-Boxer concept is delivered that complies with all design requirements. For this design, recommendations are given on how to update the design based on the dynamic analysis and future test results.

It is expected by the EWEA that in the North Sea only the wind energy capacity will increase to 45 GW. In 2015 the capacity was only 5.2 GW. Offshore contractors should be capable of installing lots of turbines and just that is a problem. As turbines increase in size installation vessels need significant upgrades. Therefore, most contractors look for cheaper and better solution for installing these large offshore wind turbines. The Sitting Up System or SUS is a new concept designed by Marine Innovators B.V. and installs fully assembled wind turbines with their foundation. It decreases offshore installation time and decreases operational cost significantly.
The SUS is designed to transport and upend wind turbines to a vertical position while anchored to the seabed. For now, the SUS is a concept and has multiple design possibilities, using either a hydraulic or a buoyant lifting system. Analysis on these lifting methods and their operational functionality resulted in a buoyant type lifting system. The SUS 3: 'Buoyant upend 2' concept consists of latticed structure and two buoyant modules. The large module is sunk to anchor the SUS and the small buoyancy module is pulled along the lattice to create an upending moment.
Using the software Matlab the upending motion of SUS 3 is modelled as a rigid body to find limiting wave conditions. The model uses second order stokes theorem and Jonswap to simulate waves on the structure. Loads on the structure are calculated using the Morison equation. Two DOFs are considered as the SUS can rotate around a hinge at the seabed and move the buoyancy module.
In the simulation a wind turbine of 200 meters height is upended in 30 minutes, while operating at 40 meters water depth. The first phase of the upending wave loads is most critical. The criteria for the SUS to operate depends on the acceleration of the top tower assemble of the wind turbine, these cannot exceed 0.1 g. In this case the limiting sea state is a Hs of 1 m with a Tp of 4.5 s, leading to a workability of about 16 percent. During the beginning stages of upending the natural frequency of the system operates around 10 seconds. This is critical as waves oscillate near this frequency. Though the simulation does not account for radiation or diffraction, the performance in later stages of upending gives a better result. Here, it can operate with a Hs of 2.5 meters resulting in a workability of 75 percent.
The SUS 3 is anchored with spudcans during upending and shear loads are most significant. These spudcans can experience a shear load of 24 MN, when considering a Hs of 3.5 with a Tp of 8.5. Therefore, anchoring method should be designed such that it can comprehend these shear loads more efficiently.
The work done by the winches pulling the buoyancy module is 13 percent more than the potential energy gained after upending with no waves. When waves are applied, energy is gained due to the uplifting force of waves. As the structure is lifted, resistance of pulling the buoyancy module decreases and can move more efficiently. Considering a Hs of 1.5 m and a Tp of 5.5 s will results in an energy gain of 5 percent. Therefore, this method is quite efficient in upending wind turbines offshore.

'Construction Knowledge' is the requisite knowledge for effective and efficient construction and its use in project processes across project lifecycle for better constructability is 'Construction Knowledge Integration (CKI)'. Past researches show that there is limited integration of construction knowledge in preparation stages of the project since these are carried out by different project teams. Hence, limited integration of construction knowledge in the realm of 'Offshore Wind' projects is the main problem being addressed in this research and optimizing it is the primary objective. The scope of this research is limited to optimizing CKI in the engineering & management processes of foundations in OW projects as these remain a major 'Balance of Plant' component executed by the primary contractor. This research gathered its data through desk research (literature study) and case studies of three ongoing OW projects. The former was aimed at finding the key concepts related to CKI which support its optimization. Literature study confirmed the importance of CKI in early stages, integrating construction knowledge from a mix of relevant sources and practices. The case study was aimed at finding the existing regime of CKI in OW projects and the key issues which hinder CKI. Case data was mainly gathered through 12 semi structured interviews of project staff. It revealed that the current regime was highly informal, with high reliance on use of lessons learned data and limited integration of knowledge from fabrication, installation and past/ongoing projects. The key issues hindering CKI were found to be lack of standard protocol for knowledge integration activities and lack of integrated knowledge database which hindered knowledge retrieval, sharing and creation. The recommendations were devised for all issues that had a causal or correlational linkage with the two key issues, where the main outline was to formalize knowledge integration efforts and recommend an essential setting for an integrated knowledge database. These recommendations also address the missing link to essential knowledge sources in the current regime. Complementing the detailed recommendations to each specific issue, this research recommends the offshore wind sector to formalize CKI efforts using a mix of tools and practices, focus on integrating relevant sources of knowledge, specially fabrication knowledge and realize and share the importance of construction knowledge integration in projects.