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During the past few decades, there have been many instances of significant damage to coastal infrastructure, especially bridges, due to ocean waves generated by hurricanes and tsunamis. Since ocean waves and currents co-exist and twist with each other in natural marine environments and their interaction may result in more severe damaging waves, taking both of them and their interaction into account is important in better understanding of damage processes of coastal bridges. This paper conducts a numerical investigation on hydrodynamic load on a bridge deck due to joint action of solitary waves and currents. Effects of prominent factors including current velocity, submersion depth, wave height, and water depth have been studied. Efficiency of air vents in reducing the hydrodynamic load has also been discussed. The numerical investigation indicates that, in a linearly pattern, a current in the wave direction leads to a higher maximum of the hydrodynamic force in the horizontal direction, and a current in the opposite direction results in a lower maximum. However, the behaviors of other characteristics of the force, including the maximum of its vertical component and the minimums of its horizontal and vertical components, become complicated and highly nonlinear because of water overtopping on the deck. In addition, a current can play a pronounced role, either positive or negative, in efficiency of air vents in reducing the hydrodynamic load. It is anticipated that the findings in this paper will enhance our understanding on mechanism of bridge damage by waves and may also be useful in design of future coastal bridges. [ABSTRACT FROM AUTHOR]

In recent years, excavating materials from the reef flat gradually becomes the main source of sand and aggregate for the coral-lined coasts in tropical and subtropical regions, especially the low-laying atoll islands. These artificial excavation pits are bound to have significant impacts on the wave hydrodynamics over the fringing reefs. However, effects of the excavation pit on the hydrodynamic characteristics of tsunami-like wave over the fringing reef are few studied. To fill the knowledge gap of previous research, effects of artificial excavation pit on the transformation and runup processes of tsunami-like wave over the fringing reef have been systematically investigated in this study based on a high-resolution two-phase flow model. Effects of several main factors are carefully discussed. Research results indicate that the presence of excavation pit can have noticeable influences on the wave transformation and runup processes of tsunami-like wave over the fringing reef. Complex interactions between the breaking surge bore and the water body in the excavation pit can be observed. The complicated flow field in the pit can dissipate more wave energy and result in a lower maximum wave runup height. However, the local wave height near the pit in most situations can be amplified. It is hoped that the research findings can broaden the understandings on the wave hydrodynamics over the fringing reef with the artificial excavation pit. • Effects of artificial excavation pit on the transformation and runup processes of tsunami-like wave over the fringing reef are investigated by applying a two-phase numerical model. • Influences of main factors, such as wave height, water depth, pit location, pit depth and width, forereef and backreef slopes, and reef-flat length are discussed in detail. • Results indicates that the presence of artificial excavation pit can significantly influences the hydrodynamic characteristics of tsunami-like wave over the fringing reef. [ABSTRACT FROM AUTHOR]

When hydrodynamic loads of the bridge deck exerted by extreme surges and waves exceed the restraining capacity of the superstructure and substructure, bridge deck will be pushed off from the substructure. However, before the final failure of coastal bridge deck, its dynamic behavior can be idealized as a mass-spring-damper system. In the harsh ocean environment, extreme surges and waves coexist. It is their joint impact that has finally caused the damages of the coastal bridges. In previous studies, only the damage effect of ocean surface waves on the movable bridge deck was considered, and the influence of background current was not considered. In this study, hydrodynamic characteristics of movable coastal bridge deck under joint impact of solitary wave and current have been well investigated. Effects of the wave height, water depth, submersion depth, background current speed, and lateral stiffness on the hydrodynamic characteristics of movable coastal bridge deck were systematically analyzed. The results indicate that the existence of background current can significantly influence the hydrodynamic characteristics and dynamic responses of movable bridge deck under the action of solitary wave. The effective wave celerity gradually increases with background current speed, which eventually enhances the horizontal load and lateral displacement of the movable bridge deck, and it finally increases the potential risk of bridge damage. • Hydrodynamic characteristics of movable bridge deck under the joint impact of solitary wave and current have been investigated considering the effects of wave height, water depth, submersion depth, background current speed, and lateral stiffness. • ▪Results indicate that the existence of background current can significantly influence the hydrodynamic characteristics of movable bridge deck under the impact of solitary wave, increasing the potential risk of bridge damage. • ▪Although the lateral stiffness of the bridge deck has significant impact on the lateral displacement, it has limited influences on the peak values of both horizontal and vertical loads of the movable bridge deck. [ABSTRACT FROM AUTHOR]

Coral reefs are abundant in tropical and subtropical coastal regions. Besides their important role to ecosystems, coral reefs also act as natural buffers that help protect coastal regions from impacts of extreme surge and waves, such as those generated during hurricanes and tsunamis. Recent studies revealed that the bottom of coral reef has very similar properties as porous media. This paper investigates the hydrodynamic characteristics of the transformation and runup processes of tsunami-like wave impinging on a permeable fringing reef by applying a nonhydrostatic numerical wave model (NHWAVE). Effects of prominent factors, such as wave height, water depth, and thickness, median diameter and porosity of the permeable layer of fringing reef, on the hydrodynamic characteristics of tsunami-like wave over permeable fringing reef are discussed in detail. Results show that when the friction effects of the bottom of fringing reef are modelled using the classical quadratic friction law, the protective function of fringing reefs can be grossly underestimated. Research findings drawn from this study can further broaden our understanding on the hydrodynamic characteristics of fringing reefs under the impact of extreme surges and waves. • Transformation and runup processes of solitary wave over the permeable fringing reef are numerically investigated by applying a nonhydrostatic wave model. • Effects of prominent factors, such as wave height, water depth, thickness, median diameter and porosity of the permeable layer of coral reef are discussed in details. • Results indicates that if the friction effects are modelled by applying the classical quadratic friction law, the protection function of coral reef to the coastal regions can be grossly underestimated. [ABSTRACT FROM AUTHOR]

Coastal bridges are vulnerable to extreme surges and waves generated during hurricanes and tsunamis. Over the past few decades, extensive research works were conducted to study the damage mechanisms of coastal bridges under the impact of extreme surges and waves. However, these research efforts mainly focused on the hydrodynamic characteristics involved in surge waves impinging bridges. However, there has been little research on mitigation measures to protect coastal bridges. This study examines the installation of a submerged porous breakwater to protect coastal bridge decks from the impacts of solitary waves. As an environmentally friendly wave-reduction device, submerged porous breakwater structures have been widely implemented in coastal regions due to their ease of installation and cost effectiveness. To investigate the performance of the submerged porous breakwater on the hydrodynamic loads of a coastal bridge deck under the impact of a solitary wave, a high-resolution numerical wave tank is established based on an open-source flow solver REEF3D, which numerically solves the governing equations of incompressible two-phase flow on a staggered mesh arrangement and captures the interface between air and water using a high-resolution level-set method. The hydrodynamic characteristics of coastal bridge decks with the installations of submerged porous breakwater are systematically investigated by considering the effects of six prominent factors, i.e. wave height, submersion depth, water depth, permeability, spacing distance between breakwater and bridge, and aspect ratios of breakwaters. Results show that the submerged porous breakwater is effective in reducing the hydrodynamic loads applied to the coastal bridge decks under most of the situations. Therefore, it is believed that the findings drawn from this paper can further enhance our understanding on the damage mechanism of coastal bridges under extreme waves and should be instructive for future bridge designs. • A high-resolution numerical wave tank is established by using the open-source flow solver REEF3D. • The numerical wave tank is well calibrated by simulating solitary waves impacting bridge deck model and over submerged porous breakwater. • Effects of the submerged porous breakwater on hydrodynamic load applied to the coastal bridge deck under impact of solitary wave have been systematically studied. • Results show that the submerged porous breakwater is effective in reducing the hydrodynamic loads applied to the coastal bridge decks. [ABSTRACT FROM AUTHOR]

The wave profile of solitary wave has been widely used as a tsunami paradigm for decades to capture the main features of actual tsunamis. Since most of the fatalities were attributed to overland flow of tsunamis, the runup and rundown processes of solitary waves have been extensively studied experimentally and numerically. Comparing to previous research, this paper systematically investigates the hydrodynamic characteristics of breaking solitary wave runup on a permeable sloped beach using a nonhydrostatic model. Firstly, the computational capabilities of present numerical model in predicting solitary wave runup process and flow field in permeable media are well validated with experimental data. Then, a series of computational runs have been performed to study the breaking solitary wave on permeable sloped beach. Effects of three prominent factors on the maximum runup height of breaking solitary wave are considered in detail: the thickness (B), median diameter ( d 50 ), and porosity (n) of the permeable layers. The porosity of the beach has a substantial impact on the flow field for breaking waves running up a sloped beach. The maximum wave runup height can be substantially reduced if the permeability of the beach is considered. It is also found that the maximum wave runup height decreases with permeable layer thickness. However, the reduction rate gradually decreases. The influences of median diameter are very limited and can be ignored. In addition, based on our results, we also proposed a new empirical formula to calculate the maximum wave runup height of breaking solitary wave on permeable sloped beach. The findings of this paper are expected to be useful for developing an improved understanding on the runup processes of breaking solitary wave on sloped beach with some permeability. • A non-hydrostatic numerical model was presented to simulate the breaking solitary wave runup on permeable sloped beach. • Effects of prominent factors on the hydrodynamic characteristics of breaking wave runup permeable sloped beach are investigated. • By analyzing the computational results, empirical formula for predicting the maximum wave runup height for impermeable beach has been adapted to account for the effects of permeability. [ABSTRACT FROM AUTHOR]

In this study, a tsunami wave profile observed during the 2011 Japan Tsunami has been parameterized and applied for predicting hydrodynamic characteristics of coastal highway bridges under the impact of tsunami surge waves. The propagation of tsunami waves from the open sea to the inshore bridge site and its final impact at coastal highway bridge are typical multiscale coastal flow phenomena, whose integral simulation is beyond the reach of most existing numerical models. To simulate such multiscale flow phenomena, a newly developed coupled modeling system named the SIFUM-FVCOM system has been applied to study the tsunami wave impact at a coastal highway bridge deck. The effects of three dominant factors, particularly distance to the shoreline, clearance height, and tsunami wave height, on the resultant hydrodynamic loads at the bridge deck have been numerically investigated. The findings of this paper are believed to be instructive to improve our understandings on the hydrodynamic characteristics of coastal highway bridge under the impct of real-world tsunami wave and their future design. • A hybrid modeling system is presented and applied to investigate the multiscale hydrodynamic characteristics of highway bridge deck under the impact of real-world tsunami. • Instead of using solitary wave profile as the typical tsunami wave model, tsunami wave profile observed during 2011 Great Japan Tsunami is parameterized and applied. • The effects of dominant factors, such as distance to the shoreline, clearance height, and tsunami wave height, on the resultant hydrodynamic loads at bridge deck have been numerically investigated. [ABSTRACT FROM AUTHOR]