The ability to predict the fatigue of flood gates due to dynamic wave loading is becoming increasingly important as coasts and waterways worldwide are being reinforced to suit a changing climate. There are few comprehensive ways to do so however, which often leads to conservative estimates. This thesis presents an integral framework with which the fatigue of flood gates due to dynamic waveloading can be described in much more detail, while also being efficient and adaptable to different circumstances. First, the fatigue experienced by a single load event is evaluated based on readily available data. This was done by creating a phase-amplitude model from a wave spectrum based on the site properties and environmental conditions. These wave loads can then be transformed to pressure spectra with linear wave theory and pressure impulse theory, which will dynamically excite the fluid-structure system. The gate is then parametrically modelled in a FEM software package in order to export the in-vacuo response modes. These are combined with a fluid-structure interaction model to derive the response of the system to external pressures. The fatigue was evaluated with the standard Eurocode method to find a fatigue damage factor. Next, the load events imposed on the gate over its lifetime were probabilistically defined. This was done by fitting two independent probability distributions to historical wind- and water level data, the latter of which was also adjusted for climate change. These probability distributions are then split into segments which are integrated to obtain discrete load cases with representative values for the average wind velocity, water level, and probability of occurrence. Two filters were also applied to remove the load cases which cause a negligible amount of fatigue. Computing the fatigue damage caused by the average values of each of these load case bins then gives a set of fatigue damage factors with an associated probability of occurrence, which can be used to perform a Monte Carlo analysis. A case study for a hypothetical parametrically defined gate with an overhang located in the Afsluitdijk was performed, where the response for different gate configurations and environmental conditions was evaluated. The fatigue response was evaluated for fatigue across the gate, at the critical coordinate, and per mode. A ULS check was also done for the chosen design. Results following from the model were also compared to those of methods commonly used in practice.The method gives insight into the relative importance of different modes and load events, can compute fatigue for the entire gate or just a critical coordinate, and does so in a much more time-efficient manner than current numerical models. It gives a more comprehensive view of the fatigue over the lifetime of the gate by modelling its entire lifespan rather than a set of design load events. The modular structure of the integral framework allows for easy adaptation to other use cases in hydraulic engineering where fatigue due to hydrodynamic loading is of interest.

At this moment hydraulic structures are designed based on a simple method: the Dynamic Amplification Factor (DAF) method. This method does not consider the full dynamic interaction between the wave impacts, structure and water. The research project DynaHicS focusses on the dynamic behaviour of hydraulic structures, taking into account fluid-structure interaction (FSI). The main goal of the DynaHicS project is to develop new design guidelines to identify dynamic behaviour of hydraulic structures, so that more economical designs can be made in the future. The master thesis focusses on improving the current design method, which can contribute to the development of a new design method for hydraulic structures in the future. The present design method, the DAF method, is extended in time and space. This is done by developing a method to determine the force-time signal of multiple wave impacts, whereby the results from scale model tests are no longer required. In this method the spatial variation (height and width) of the wave impact force over the structure surface is taken into account.

A new semi-analytical model is developed to predict the dynamic response of slender gates in combination with an overhang, which are subjected to standing waves. Still little is known for these types of gates for this specific forcing type. The semi-analytical model is still in its development phase and must be validated on its performance. This thesis aims for validation of the modal calculations performed by the Semi-Analytical model for submerged gates, which include fluid structure interaction. Several experiments were executed in the wave flume at the faculty of Civil Engineering at the Technical University of Delft. Dry hammer tests, wet hammer tests and wave tests were executed for different water levels. Different plates were investigated in the experiments: Solid Plate and Reinforced Plate. A measurement plan was designed to obtain reliable results from the measurement devices (strain gauges and accelerometers). The experimental data was subjected to an Experimental Modal Analysis algorithm. The Frequency Domain Decomposition turned out to be most suitable for this situation. The mode shapes that were found were subjected to a Modal Assurance Criterion (MAC), in order to compare them with the semi-analytical prediction. The results from the wet modal analysis showed that the Solid Plate had good correspondence with the prediction of the semi-analytical model. The mode shapes turned out to have a high MAC values, while the natural frequencies showed small relative errors for the modes under consideration. The Reinforced Plate was less accurate. In the wave experiments the first three modes were found, which were also believed to have the highest energy input. Considerable high MAC values assured that the identified modes were indeed the same as the modes of the semi-analytical prediction. The natural frequencies showed larger errors for especially the first mode (approx. 30%). It was observed that several measurement errors might have influenced the results of the Reinforced Plate. After finalizing the experiments for this plate, I discovered that the stiffeners and front plates came loose from the U-frame. The dynamic quantities of the Reinforced Plate were therefore adjusted during the experiments. The datasets of the experiments that were most trustworthy were selected for the different analyses. The Regular Wave Impact experiments showed good correspondence and where therefore assumed to be correct. The Solid Plate was concluded to behave as predicted by the semi-analytical model. High correlation between the predicted and identified modes and small errors in the natural frequencies were observed. The data from the Reinforced Plate showed that the high energy modes were identified for the wave experiments. Modal shapes had high correlation between predicted and identified ones, while the natural frequencies had somewhat large errors. It was observed that small natural frequency errors for the input modes resulted in relatively small errors for the calculated modes. Further validation of the model should focus on the prediction of maxima and time series of the response. The step from modal analysis to a time series is a final step in the semi-analytical model.

Hydraulic structures that are surrounded by flowing water can experience undesirable Flow-Induced Vibrations. These vibrations have a record of negative consequences. The most important cause of vibrations is self-excitation. This is a mechanism in which the forces acting on the hydraulic gate are amplified by the movement of the hydraulic gate itself which then further increases the vibration intensity. This mechanism potentially results in structural failure of hydraulic gates. Therefore, prevention of this type of excitations should be priority number one in the design stage of hydraulic gates One of the vertical self-excitation mechanisms is the galloping-type vibration and is addressed in this thesis. In this research the possible occurrence of galloping-type vibrations of a dynamic one degree of freedom system is simulated. CFD computations were used to obtain a force matrix that served as an input for the simulation of vertical vibrations of the one degree of freedom system. This research has shown that the force matrix, obtained using CFD software, can used to derive the hydrodynamic damping coefficients due to flow and hydrodynamic stiffness coefficients due to flow and buoyancy for a range of combinations of opening heights and accompanying vertical velocities of the hydraulic gate. The damping coefficient that was required to obtain a fully stable situation for all initial opening heights complied with the results found by determining the negative hydrodynamic damping coefficients due to flow. Therefore, this research has shown that the stability to galloping-type vibrations and the required external damping coefficient can be derived from the force matrix obtained using CFD. The research performed has shown that the hydraulic gate, designed as an FRP laminate experienced roughly twice as high negative hydrodynamic damping values than a typical steel hydraulic gate consisting of a plate stiffened with ribs. This means that the FRP laminate requires twice as much external damping to neutralise the significantly higher negative hydrodynamic damping due to flow. The steel hydraulic gate experiences a larger range of negative hydrodynamic damping albeit with much lower negative hydrodynamic damping coefficients than the FRP laminate hydraulic gate. Concluding this research, results show that FRP hydraulic gates are more susceptible to galloping-type vibrations than traditional steel hydraulic gates, meaning that either the design of the hydraulic gate has to be altered or much more external damping, in this case twice as much, is required to compensate for the negative hydrodynamic damping due to flow, with respect to steel hydraulic gates.

Vertical sliding valves that are part of a filling and emptying system of a lock are often subjected to an underflow of water during emptying and filling. The flow induces time varying forces on the structure which leads to dynamic behaviour of the valve. Whether the structure is in the range of resonance and what the amplitude of the vibrations will be depends on the mass, damping, stiffness and forcing quantities of the system. This thesis focussed on gaining insight in the behaviour of such a cylinder and its various components in terms of stiffness and damping of the total system including the vertical sliding valve. The research questions focussed on whether it is possible to influence the dynamic characteristics of a system (natural frequency and dynamic amplification) by adjusting the geometry of the hydraulic cylinder. Furthermore it is investigated which components are influencing the dynamic characteristics of the system and which damping and stiffness components are found to be subordinate to the dominant sources. Results were based on a Python script that included all relevant sources of damping and stiffness of a hydraulic cylinder, as well as the fluid structure interaction components such as added mass, damping and stiffness. The added damping components included the self-excitation suction damping. The sensitivity of different components to the natural frequency and dynamic amplification was explored. This was done for different cases, where in each case one variable varied while the others were kept constant. The results from the sensitivity analysis were used to find an optimal parameter that would lead to an optimal design in terms of natural frequency increase or decrease, reduction of the dynamic amplification and a minimal influence on the mass of the system. Besides these two studies, a third study was adopted to find the relative influence of different damping and stiffness components of the hydraulic cylinder for varying boundary conditions such as water level difference and gate opening. The study showed four components of a hydraulic cylinder that influenced the dynamic characteristics the most when varying their dimensions in a realistic range. These where the diameter of the hydraulic cylinder, the cylinder length, the thickness of the rod and the length of the tube that transport fluid into the cylinder. From these, the tube length and the cylinder diameters turned out to be the most effective design variables for tuning the stiffness, damping and correspondingly the natural frequency and the dynamic amplification of the system. Furthermore it was found that under all conditions (varying water level, gate opening height, pressure and stiffness), the stiffness was mostly determined by the axial stiffness of the rod and piston as well as the stiffness due to compaction of the cylinder fluid. For damping it was found that the cylinder only had limited influence and that most damping resulted from friction between the valve and the guiding rails.