The current demands of the Offshore and Maritime industry have lead to the design and
production of larger vessels of complex geometries. These vessels are subjected to unique
loading conditions that have not been investigated extensively. Such a case is presented
in wet deck slamming of large catamaran vessels. These vessels have been designed and
produced to conduct offshore platform installation operations and are expected to operate
in severe conditions where wet deck submergence becomes a threat.
Wet deck slamming is a water entry impact phenomenon that can induce extreme loads
when a part of the floating structure pierces the water surface during severe waves. This
event can trigger a transient dynamic response at both local and global levels. The event has
multiple influencing factors that can contribute to the severity and probability of occurrence.
Although the examination of slamming started over a century ago, the criteria concerning
the incident definition, identification and prediction are applied from different perspectives.
Modern methods identify slamming events based on the structural responses, while the sta-
tistical analysis considers correlation between the events, as opposed to older approaches
treating the incidents as independent.
Progress in understanding slamming is achieved through full-scale measurements, exper-
imental tests, and numerical simulations. Each method presents unique advantages and
drawbacks,and all three are used for knowledge development but also verification and vali-
dation. As numerical capabilities increase, it is also important for the experimental method
to evolve and explore new ways of representation of the complex events.
This project aims to investigate wet deck slamming using a rarely used form of model
that could closely mimic real life responses. This research can enhance the experimental
method capabilities and serve as stepping stone for further evolution of similar research.
The experimental test runs for the needs of the project were conducted in the Ship and
Hydromechanics laboratory facilities of TU Delft.

This master’s thesis investigates the fatigue resistance similarity between small-scale test specimens and large-scale structures, specifically focusing on steel welded joints. The primary goal is to improve the understanding of how fatigue data from small-scale tests can be reliably applied to predict the performance of full-scale maritime structures, thereby reducing conservatism in design and optimizing material usage without compromising safety. Fatigue resistance is a critical factor in the design and maintenance of maritime structures. Traditional design methods often use S-N curves derived from small-scale specimen tests, which can be overly conservative when applied to full-scale structures. This conservatism, while ensuring safety, leads to increased material use and associated costs. The aim is to identify and quantify the scaling phenomena that influence the transfer of fatigue data from small-scale specimens to full-scale structures. By proving fatigue resistance similarity and understanding these scaling effects, the research seeks to refine the fatigue design process, thereby enhancing efficiency and reducing environmental impact. The research utilizes various fatigue assessment concepts, including the Nominal Stress Concept (NSC), Hot Spot Structural Stress Concept (HSSSC), and the Effective Notch Stress Concept (ENSC). Finite Element (FE) models of large-scale specimens, created using Abaqus, are used to test these concepts. The study also explores the application of mean stress correction models to improve the fit of large-scale data within small-scale data scatter bands. The methods are evaluated based on their ability to incorporate local geometry information and their effectiveness in reducing scatter in fatigue data. The study demonstrates that incorporating local geometry information is crucial for achieving fatigue resistance similarity between small-scale and large-scale specimens. The HSSSC and ENSC, which account for local geometrical variations, provide better fits for large-scale data within the small-scale data scatter bands compared to the NSC. This confirms the hypothesis that local weld geometry plays a significant role in fatigue resistance similarity. Furthermore, applying a mean stress correction improves the alignment of large-scale data with small-scale data, highlighting the importance of considering residual stresses and load ratios in fatigue assessments.
The findings can have practical implications for the design and maintenance of maritime structures. By improving the accuracy of fatigue life predictions, the research supports the development of more efficient and cost-effective designs. The insights gained from this research help address uncertainties and improve design assumptions for vessel fatigue performance. By incorporating local geometry information and applying mean stress corrections, the research provides a more accurate and less conservative approach to fatigue life prediction. These advancements have the potential to reduce material usage and costs in maritime structure design, while maintaining high safety standards.

Governments are looking more and more to invest in renewable energy sources due to the energy transition that is currently taking place. One of the many renewable energy sources is wind energy which is increasingly positioned at sea. Wind turbines in deep parts of the ocean can be placed on floating structures which are often moored to the sea bottom by mooring ropes. For deep sea, the only viable option is a synthetic mooring line due to its almost neutral buoyancy.
Mooring ropes have a vital role in the offshore floating structure as it is keeping the structure in place. When a mooring line breaks, the consequences may be big, leading to serious damage or dangerous situations. Therefore, the structural integrity of mooring ropes should be evaluated regularly. For synthetic mooring ropes, the only method at this point in time is visual inspection. This can be done by divers or by Remotely Operated Vehicles (ROVs). This method is expensive, time consuming and in case it is done by divers, it is potentially dangerous. Furthermore, synthetic mooring ropes are susceptible to external damage which means inspection would have to be executed without direct contact with the mooring ropes. Therefore, it is necessary to assess the feasibility of a non-contact, non-destructive testing method in order to assess the structural integrity of a synthetic mooring line. The combination of non-destructive material property assessment and tension assessment is believed to produce a structural health monitoring instrument for synthetic mooring ropes.
In this thesis, a methodology is proposed which uses two independent non-contact, non-destructive measurements to assess the structural integrity of a high modulus polyethylene (HMPE) rope specimen. The measurements involved are ultrasonic guided wave (UGW) measurements and vibration measurements. The UGW measurements are performed to assess the stiffness of the test specimen according to the principle of attenuation of ultrasonic waves propagating through a specimen. The vibration measurements are performed to assess the natural frequencies of a manually excited test specimen. The assessed natural frequencies and the determined stiffness of the test specimen can be used to calculate the load acting on the test specimen.
The methodology is tested by conducting experiments in a laboratory environment where in-situ conditions are recreated by performing the tests underwater. It was concluded that the loads can be recalculated with varying accuracy of approximately 10% with respect to the actual values, with increasing accuracy for higher load values. It is concluded that the proposed methodology has the potential to determine load on a synthetic mooring line in a non-contact, non-destructive manner.

Ship-to-Ship (STS) cargo transfers can significantly improve the efficiency of offshore installations while reducing their associated costs. However, the added complexity of cargo transfers involving ship-mounted cranes at sea poses significant challenges. To address this, crane manufacturers have introduced Relative Heave Compensation (RHC) systems to assist crane operators. Nevertheless, concerns have emerged among installation vessel companies regarding the relative heave measurement systems, which rely on Motion Reference Unit (MRU) sensors placed on both ships. Given that many supplier vessels lack the required sensors and the communication protocols pose bureaucratic hurdles, this research focuses on proposing novel, feeder-independent relative heave measuring solutions. This work introduces two unexplored sensor units, namely the LiDAR-MRU and RADAR-MRU. In the absence of actual sensor data, a simulation workflow using Simulink and Unreal Engine (UE) is presented to generate synthetic data. After, four distinct measurement solutions are developed, implemented, and evaluated using the simulated data in MATLAB. The implemented solutions estimate relative heave distance and speed with a Mean Absolute Error (MAE) ranging from 0.3-5.2% and 0.8-4.3% of the reference's maximum amplitude, and processing times from 1.8-91.4 [ms]. The results underscore their potential for field implementation. However, future validation is needed with actual sensor data.

The Netherlands has agreed, by signing the Paris Agreement, to be climate-neural by 2050. To reach this goal, many large-scale renewable energy projects need to be developed in the coming years using for example wind, geothermal or solar energy. The problem with these projects is that they require large amounts of land and are especially needed in densely populated areas where the energy demand is high. For solar energy, a solution is to move it to bodies of water, creating a floating photovoltaic (FPV) system. Besides not requiring valuable land, FPV offers other benefits; The water has a cooling effect on the panels, increasing the efficiency of the solar panels. There is less water evaporation, which is desired in for example drink water basins. FPV systems have a high potential for system integration with nearshore and offshore wind turbines, optimizing space utilization and making cable pooling possible.

Multiple companies have already developed an FPV system, each designed for specific water categories and having its own (dis-)advantages. This thesis analyses different types of FPV systems and offers a tool for project developers to help decide what kind of system to select in a preliminary phase of project development.

As input to this decision tool, the environmental loads acting on FPV systems are calculated. The forces due to the wind, current and waves are found for three different types of systems. These systems are Floating Solar, Zimfloat and OceanSun. The forces are first found on a small section of the structures and then scaled up to a size of one hectare including sheltering factors. The results show that the membrane-type structure of OceanSun has significantly lower environmental forces than the Floating Solar and Zimfloat systems. These two are both built up of high-density polyethylene floaters and a metal frame holding the PV panels. The wind force is the highest on the Floating solar structure due to the larger tilt angle. The wave forces are found to be the highest for the Zimfloat structure which can be explained by the floaters. These are square blocks instead of circular tubes, making them less aerodynamic and having a larger volume which increases the inertia forces.

The decision tool uses a multi-criteria analysis that takes twelve important aspects of an FPV system
into account including the environmental loads. Examples of these criteria are energy production, costs, energy density and also less quantifiable criteria such as ecological impact, safety and the technical readiness level of the systems. The tool compares six different types of systems and can easily be adjusted to a specific location by changing the weight factors. With these weight factors, the tool provides a clear overview of the most important aspects of an FPV system and helps to decide in an early phase of project development whether a system is suitable for the desired location or not.

The decision tool is used for the case study ’Haringvliet’. Haringvliet is a former estuary in the Netherlands and is chosen as a potential location for an FPV park. The calculations mentioned above are performed using the site conditions found at Haringvliet. The conclusion of the decision tool is that the structure of Floating Solar is the most suitable for the Haringvliet. This is partly because Haringvliet is an ecologically protected area and the floating solar structure is very open, letting sunlight pass through the system into the water.

Fiber-reinforced composite (FRC) marine propellers potentially outperform metallic propellers in terms of efficiency and underwater radiated noise (URN) by hydro-elastic tailoring of the blades. Several methods can assess the extent of these potentials. Research shows that embedded sensing methods can be used in dynamic measurements of composites. This thesis studies a full-scale application of a network of embedded piezoelectric sensors in an FRC marine propeller blade. The study prefers using piezoelectric sensors because of their ability to operate in a relatively wide frequency range. The focus of the thesis starts with designing the full-scale network of embedded piezoelectric sensors. Since no literature includes this application on FRC blades, this study holds a pioneering role in embedding piezoelectric sensors in an FRC marine propeller blade. Detailed analysis of material dimensions - including sensors, wiring, and fiber plies - leads to a successful sensor network design. Considerations regarding the location of 24 sensors included both the in-plane and the in-depth position within the FRC laminate. Fabrication of an FRC blade has been done using a resin transfer moulding (RTM) process. For the first time, an FRC marine propeller blade is embedded with piezoelectric sensors. Demoulding of the blade caused damage to some of the sensor wires. An amount of 54% of the embedded sensors survived the process with full connectivity. The performance of the intact sensors after fabrication is assessed. These sensors are exposed to free vibration tests of the FRC blade. An excitation is imposed on the blade with an impact hammer. A data acquisition (DAQ) system is used to capture the responses of the embedded piezo-sensors. The frequency response functions (FRFs) of multiple locations on the blade are computed. These FRFs provide more insight into the dynamic behavior of the blade. A frequency range of 1-1000Hz is used in the modal analysis. The first five natural frequencies are found between 240Hz and 840Hz. Natural frequencies measured by the embedded piezo-sensors and surface-mounted strain gauges differ up until 25% from natural frequencies computed by a finite element model (FEM) of the blade. The mode shape of the blade at the natural frequencies is computed for by the FEM and embedded piezo-sensors. Some difference in mode shapes is demonstrated between measurements computed by FEM and those measured by the embedded piezo-sensors and surface-mounted strain gauges. The piezo-sensors and strain gauges are in agreement regarding the measured natural frequencies. Therefore, it is expected that discrepancies exist between the physical blade and FEM. Several points for improvement of the results have been found. The study provides the first-time feasibility of dynamic measurements from embedded piezo-sensors in an FRC marine propeller blade. Additionally, a framework for reconstructing the full-field vibration response is provided, which can provide more accurate results when the agreement between piezo-sensor and FEM measurements has improved.

For floating photovoltaic systems, an uncommon type of offshore structure is considered, which is very flexible and deforms with the motion of the waves. In this research, the bending characteristics of a drop-stitch floater is analysed, which is an inflatable panel. By inflating the drop-stitch floater to a low air pressure, it obtains a flattened shape and the ability to support the flexible solar panels, while still retaining flexibility to deform with the motion of the waves. The bending characteristics of a drop-stitch floater are more complex than common offshore structures due to different non-linearities: wrinkling, hyperelastic material behaviour and internal pressure-volume work. Getting a better understanding in the bending response is important to eventually determine the response and limit states in offshore conditions. A finite element and experimental analysis has been performed of the response in a three point bending load case. Also, an experimental uniaxial tensile test has been performed to evaluate the hyperelastic anisotropic material behaviour. Different yarns spacings, internal air pressures and face sheet thicknesses are evaluated. This showed that there are two types of failure modes with distinct behaviour for an uniaxial pure bending load case: a global wrinkling and folding failure mode.

Over the last two decades, the size and capacity of (container) vessels calling port at the Port of Rotterdam have increased considerably. To moor these huge and heavy ships safely at the quay, fenders are frequently installed. The present guidelines for the “Design of Fender Systems”, which were established in 2002, are due to be updated in 2023. Part of the update of these new guidelines for the design of fenders by working group 211 of the Permanent International Commission for Navigation congresses (PIANC) consists of the verification and validation of the hull pressure criterion, taking into account the recent growth of (container) vessels. Obtaining a generic criterion is challenging due to the enormous diversity in vessel sizes and structural layouts. In addition, fender dimensions and types may also have a significant influence on the fender-induced load. This leads to the following research question: “How can critical fender-induced loads acting on the parallel side hull be quantified, accounting for the diversity of vessels and fenders?”

In this research, parallel hull sections are used in numerical simulations to investigate the allowable load of fenders and to derive the influence of panel size and dimensions (tall or wide). Including detailed parallel hull sections for a representative group of vessels, makes it possible to look beyond simplified geometries, such as stiffened panels, and specific case studies. First, the structural response and corresponding governing failure modes were studied. In addition to existing failure modes described in fender-induced loads, tripping of stiffeners as a possible governing failure mode was included. A modification to available analytical formulations was made to describe the critical tripping pressure of stiffeners with a flange under patch loads more accurately. The proposed critical tripping pressure induced by a fender is underestimated by the analytical model in comparison to the numerical simulations of the parallel sections. When the rotational restraint of the web frame attached to the tripping stiffener is considered, a closer correlation between the analytical results and the numerical simulations of the parallel hull is foreseen. For the numerical simulations, a parametric approach was adopted, where different impact locations and contact areas were applied for several vessel types and sizes. The lowest steel grade of vessels currently applied in shipbuilding was implemented to obtain the lower limit of allowable fender-induced loads.

The key finding of this study is that allowable fender-induced loads are largely influenced by the vessel's structural dimensions, such as web frame spacing, and the size of the fender panel with respect to the ship's geometry. The constant hull pressure criterion currently used by PIANC can be maintained but should be limited to a total allowable reaction force, because, for large panels, it overestimates the capacity. Furthermore, it has been shown that for large ships, wide panels outperform tall panels because they activate web frame(s). Making panels much wider does not necessarily yield more capacity because the stress concentration remains in the web frames. For small vessels, the trend is less clear, as the web frame is activated at an earlier stage (less far apart) and the capacity does not increase exponentially with the width. In addition, high panels on small vessels sometimes lead to the activation of a deck and thus increase the allowable load. The overall conclusion of this research is that the PIANC criterion should be limited to a total reaction force. Furthermore, by correctly sizing fender panels, more efficient use of the vessel's capacity can be ensured, as web frames provide more capacity. The findings of this research can be used to allow small and large vessels to safely berth onto existing facilities.