Tsunamis, impulse-waves and dam-break waves have affected humanity in recent decades and the construction of vertical shelters can provide safety to people. However, for non-critical infrastructures, typically residential houses of lower height, overtopping is accepted during such events. This study experimentally quantifies the effect of building overtopping, i.e. water flowing over the roof, on the resulting loading process. Both surges and bores were investigated and the impact against buildings with two different heights was assessed. Detailed measurements of forces and moments allowed key differences to be captured between the scenarios with and without overtopping. Results showed that overtopping induced higher downstream water depths, leading to lower horizontal forces and a reduced resistance coefficient. Furthermore, cantilever arm, moment and impulse values were constantly lower in case of overtopping. Finally, this study presents an innovative methodology to assess the main loading features of buildings subject to overtopping, supporting engineers to design safer resilient structures.

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Tsunamis, impulse waves, and dam failures are disasters that challenge humanity, often leading to massive casualties and extreme economic losses. The highly unsteady flow conditions generated by such events are often in the form of turbulent bores. The purpose of this study was to investigate and validate a new generation system for bores propagating over dry and wet bed conditions. There are multiple techniques to generate such waves experimentally, and the study focused on the generation of tsunami-like inundation conditions through the vertical release of a water volume. A detailed methodology to characterize the generated waves hydraulically, in terms of their wave heights and flow velocities, is presented, and good agreement with the classical dam-break case for both dry bed surges and wet bed bores was demonstrated. Because of the importance of estimating the impact forces induced by such waves, particular attention was given to the wavefront celerity and the velocity profiles measured behind the wavefront; these were found in agreement with Prandtl's power law for open channel flows, and in-depth measurements allowed for the definition of an expression to estimate flow deceleration behind the wavefront. Along with considerations of the Froude number and momentum, this paper provides relevant information to assist engineers in designing safer infrastructures in areas prone to such extreme loading.

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Tsunamis, landslide-generated waves, and dam failures are rare, but highly destructive phenomena, associated with extreme loading on infrastructure. Recent events showed that specific measures must be taken to guarantee safety of both people and the built environment. This experimental study investigates the forces and moments exerted on free-standing buildings that are induced by both surges and bores. The hydrodynamic impact was characterized by high splash, subsequently followed by a quasi-steady flow around the structure. For dry bed surges, the time history of the horizontal force was proportional to the momentum flux per unit width. For wet bed bores, an attenuation of the peak force due to the presence of an aerated front was observed and the introduction of a reduction coefficient was necessary to achieve a realistic force estimation. Additional force analysis in terms of peak time, wave height at maximum force and impulse also pointed out some key differences between forces exerted by dry bed surges and wet bed bores. The occurrence of the maximum tilting moment on the building coincided with the maximum horizontal force and an evaluation of the cantilever arm was possible. These findings provide engineers with practical information for the design of safer coastal structures.

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Previous studies and field surveys showed that specific structural designs can decrease the load on free-standing buildings along the coast, providing safer vertical shelters. This experimental study investigated the effect of openings in buildings (windows, doors and foyers) on horizontal forces and tilting moments induced by both dry bed surges and wet bed bores. Four configurations with seven porosity values ranging from 0% (impervious) to 84% (highly permeable) were systematically tested. Due to the presence of openings, the flow through the building reduced the upstream water depths. The porosity resulting from the presence of openings was shown to produce a linear reduction of the maximum horizontal force, when compared to the corresponding impervious building. The configuration with an impervious back showed results similar to those measured for the fully impervious buildings. The occurrence of the maximum tilting moment was shown to coincide with the maximum horizontal force and an estimation of the cantilever arm was therefore possible. The latter was constant for all configurations, independent of the geometry of the openings. Finally, two equations to predict the maximum horizontal force and the tilting moment were proposed, taking into account the effect of building openings within the resistance coefficient. These showed good agreement with experimental data and previous studies. These findings provide engineers with practical information for the design of safer vertical shelters in tsunami-prone areas.

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In the aftermath of the 2011 Tohoku Earthquake and Tsunami Japanese tsunami protection philosophy now dictates that coastal defences should prevent the land that they protect from being flooded under a Level 1 event (with a return period in the order of about 100 years). To ascertain the overtopping mechanism and leeward inundation heights of tsunamis as they hit coastal structures, the authors conducted physical experiments using a dam-break mechanism, which could generate bores that overtopped different types of structures. Three different types of structures were considered, namely a wall of “infinite” height, a coastal dyke, and a vertical tsunami wall. The results show that the velocity of the tsunami bore is crucial in determining whether the structure will be overtopped or not, and thus it is imperative to move away from only considering the tsunami inundation height at the beach.@en

Following the 2011 Tohoku Earthquake and Tsunami, Japanese tsunami protection guidelines stipulate that coastal defences should ensure that settlements are shielded from the coastal inundation that would result from Level 1 tsunami events (with return periods in the order of about 100 years). However, the overtopping mechanism and leeward inundation heights of tsunami bores as they hit coastal structures has received little attention in the past. To ascertain this phenomenon, the authors conducted physical experiments using a dam-break mechanism, which could generate bores that overtopped different types of structures. The results indicate that it is necessary to move away from only considering the tsunami inundation height at the beach, and also consider the bore velocity as it approaches the onshore area. The authors also prepared a simple, conservative method of estimating the inundation height after a structure of a given height, provided that the incident bore velocity and height are known.

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In the context of a comprehensive research project investigating the hydrodynamic loading on structures with openings, this paper focuses on the wave generation techniques currently used and the test results associated with it, proposing a particular tsunami-like wave using a vertical water volume release mechanism. The latter allowed a certain volume of water to flow gravitationally from an upper reservoir into a lower basin through a set of pipes. The propagation of the resulting wave took place in a horizontal channel where wave height and velocities were measured. Both dry bed surges and wet bed bores were investigated, however the present paper mostly focuses on dry bed surges. The study indicated that the surges generated with this mechanism had similar behavior to those resulting from a dam-break technique and a good agreement between the experimental points and the theoretical solutions of Ritter (1892) and Whitham (1955) was found. Lastly some differences between wet bed bores and dry bed surges are presented and briefly discussed herein.@en