This paper presents a novel design method to predict fatigue of flood gates due to dynamic wave loading. The accumulation of fatigue damage is predicted probabilistically over the entire lifetime of the structure rather than with a set of normative events. Load events are defined using a joint probability distribution of historical wind and water level data. The random phase-amplitude model is employed to obtain realisations of the wave state for every combination of environmental conditions. Linear wave theory and pressure-impulse theory are used to predict both quasi-steady and highly dynamic wave pressures. The stress response of the structure is predicted with a hybrid semi-analytical and finite element model. By applying a mode matching technique the fluid-structure interaction is solved in a computationally efficient manner. This facilitates the large number of simulations required for a comprehensive fatigue analysis without making concessions in the physical modelling. The fatigue damage is then evaluated with the linear Palmgren-Miner method by applying a rainflow algorithm. A Monte Carlo analysis is performed to estimate the expected fatigue lifetime of the structure. The modular structure of the model routine allows for easy adaptation to other situations where fatigue due to hydrodynamic loading is of interest. The design method is applied to a case study of a flood gate with an overhang inspired by the situation at the Afsluitdijk. Non-fundamental modes are taken into account without simplification of the fluid-structure interaction process and found to be governing for the fatigue damage for the studied case. Moreover, the interference of vibrations due to consecutive wave impacts is shown to have a significant influence on the outcome of the fatigue assessment. For the case study, the design method leads to a 10-20% reduction of the governing fatigue damage compared to a method commonly used in practice. At specific locations on the flood gate fatigue damage is found to be underestimated by current design methods. The presented design method is therefore found to be a significant improvement.@en

Flood gates form an essential part of many flood defence systems in coastal areas. During storm events, these gates are subjected to extreme loads from various sources. This dissertation addresses the dynamic behaviour of flood gates induced by wave impacts. A semi-analytical fluid-structure interaction model is developed to predict vertical flood gate vibrations. This model aims to overcome both the lack of accuracy involved with existing engineering methods and the high computational costs of numerical finite element methods. Scale experiments have been performed of wave impacts on flexible gate structures with an overhang to validate this model. The resulting dataset is made available for further research on the involved physical phenomena. Methods are then presented to design and assess the safety of flood gates subjected to wave impacts. At the Afsluitdijk in the Netherlands, wave impacts on the flood gates have played a major role in the design. Several case studies are performed in this dissertation based on that situation.@en

This paper establishes a computationally efficient model to predict flood gate vibrations due to wave impacts including fluid–structure interaction. In contrast to earlier models, composite fluid domains are included to represent the situation of a flood gate in a dewatering sluice with the presence of an overhang that causes the confined-wave impacts. The dynamic response of the gate-fluid system is derived in the frequency domain using a substructuring mode matching technique, in which the gate vibrations are first expressed in terms of in-vacuo modes while the liquid motion is described as a superposition of linear potentials. Pressure impulse theory is employed to predict the impulsive wave impact loads, which are superposed on the quasi-steady wave loads. The computational efficiency of the developed model allows for a large number of simulations. This makes it possible for the first time to perform probabilistic evaluations for this type of problems without doing concessions on the accuracy of the physical modelling of the involved fluid–structure interaction processes. This is demonstrated by application of the developed models within a probabilistic framework resulting in the explicit quantification of the failure probability of flood gates subjected to wave impacts.@en

The hydrodynamic pressures for a vertical flood gate situated in a discharge sluice are investigated. Exact analytical solutions are presented for the hydrodynamic pressures acting on the gate. This solution is first employed to investigate the hydrodynamic pressures for a horizontally vibrating rigid gate. For this case, regimes of frequencies and water depths are identified for which fluid compressibility and surface waves play a significant role in the hydrodynamic response. Subsequently, the hydrodynamic pressure is analysed for the case of a flexible gate of various boundary conditions. It is concluded that the derived regimes are applicable to flexibles gates as well. Values for the added mass coefficient are presented for various types of gate supports.@en

A model is developed to predict bending vibrations of flood gates with fluid on both sides. The liquid flow is three-dimensional and the gate is represented as a thin plate. The fluid response is considered within the linear potential flow theory including the effect of compressibility and the generation of free surface waves. This way, the hydrodynamic fluid pressure exerted on the gate is predicted accurately in both low and high-frequency regimes. Both the structural and fluid responses are expressed in the modal domain as a superposition of modes. A semi-analytical solution of the fluid-interaction problem is obtained by describing the complete system in terms of in vacuo gate modes, which is computationally efficient compared to existing numerical methods. This allows for the accurate prediction of flood gate vibrations for a large number of simulations, making it possible to perform fatigue calculations and probabilistic evaluations. The case of a typical flat flood gate subjected to an impulsive wave impact is studied with the developed model. Results show the capability of the model to efficiently quantify flood gate vibrations considering the involved fluid-structure interaction, which can lead to more economical designs compared to common engineering practice.@en

This paper describes a first case study of the application of a newly developed fluid-structure interaction model to the design of flood gates. The gates in the Afsluitdijk, that will be replaced in the coming years, are considered. Due to the presence of a concrete beam in front of the gates breaking wave can occur, leading to high impact pressures acting on the gate. For this case both a quasi-static approach and a more detailed semi-analytical model representing the dynamic behaviour including fluid-structure interac-tion are applied to determine the maximum deflection of the gate. Results show the capability of the model to efficiently quantify flood gate vibrations while considering the involved fluid-structure interaction. For the Afsluitdijk case this leads to a slightly lower maximum deflection of the gate, and therefore potentially al-lows a more economical design.@en