Maritime structures operating out at sea experience large changes in wetted area because of free surface waves. Although these conditions are typical for maritime applications, a fundamental experiment that includes a structure in the air–water interface undergoing transitions from dry to wet and back does not appear to exist. This paper aims to fill that knowledge gap. We present an experiment in which a pendulum is suspended just above the still water level and then exposed to monochromatic free surface waves with different wave lengths. Additionally a reduced-order model is derived to compute the response of the pendulum and help interpret the experimental results. The motion response of the pendulum is demonstrated to depend highly on whether the wave period is much lower or higher than the dry natural period of the pendulum. Additionally, a sensitivity study with the wave amplitude in the model and a quantification of the variability in the experiment both indicate that the variability in the motion response of the pendulum is increased with respect to the variability of the incoming wave. We believe this experiment and the results make for an interesting benchmark of fluid–structure interaction in free surface waves. The properties of the pendulum and the experiment are available as open data at doi:10.4121/13187594 (Wellens and Bos, 2020).

To study how an extreme wave load on a maritime structure causes structural deformation, an experiment is conducted to measure the response of a one degree-of-freedom pendulum in a focused, breaking wave. The tube that makes up the base of the pendulum covers almost the entire width of the tank so that three-dimensional effects can be considered small. The experiment varies the focus location with respect to the position of the pendulum as well as the vertical clearance between pendulum and mean free surface. Although the energy of the wave input was the same for all experiments, the response of the pendulum varied greatly with small variations of initial vertical clearance and wave focus location, with the wave breaking farthest away from the pendulum causing the largest response. A reduced-order model for the response of the pendulum shows the same behavior when initial clearance and focus location are varied. Even when initial clearance and focus location were kept the same between tests, large variability of the pendulum response was observed, meaning that the impulse exerted by the wave must have been different. This is different from the literature on breaking waves against rigid walls that found that local pressures show variability between experiments but that the impulse typically is the same. The experimental data and a description have been made available.

Highly varying sloshing loads are a superposition of load components resulting from a sequence of different physical phenomena. However, not all features of spatial and temporal variations of sloshing loads and associated phenomena are equally important when failure of structure is considered. Therefore, the prediction of sloshing loads should be focused on those load components which lead to failure. These components can be found by employing a structural model, which should be fast computationally considering the huge number of possible sloshing loads. This paper presents a reduced order model based on the beam-foundation model which is derived for the Mark-III cargo containment system. The model is validated against a detailed finite element model and it conservatively predicts the stresses at failure locations. The calculation time using the model is approximately two orders smaller in comparison to a finite element model computation, which allows the model to be applied for finding governing load components and associated physical phenomena.