Journal of Waterway, Port, Coastal, and Ocean Engineering

This study focuses on the probability of structural member damage due to impulsive wave pressure, and consequently, a design method is proposed. The flowchart of the proposed design method could be divided into evaluation by the impact load or dynamic magnification, depending on the ratio of the duration of the wave pressure to the edge period of the member. Large-scale destructive experiments using regular waves were conducted to verify the validity of the proposed design flowchart. A risk factor was used to evaluate the design procedure and the probability of occurrence of residual strain. Furthermore, large-scale destructive experiments with solitary waves were conducted. Experimental results were applied to the design flowchart to determine the validity of the proposed design method.

Waterborne debris impacts during inundation events are a widely observed threat to structures in coastal communities. This study investigates the probability of impact and magnitude of wave–current (N = 1,170) and current-only (N = 156) debris events on exposed and sheltered buildings within a 10 × 10 building array, using laboratory measurements of structural loading response, flow hydrodynamics, and video recordings of flow transport and impact. A methodology based on a structural system with a single degree of freedom is implemented to estimate the applied debris impulse from collisions and to investigate the dynamic impact of waterborne debris on structures. Results show that the debris collision probability varies greatly, between 42% for unsheltered rows and 2% for nine rows of sheltering. Given a collision, the normalized debris impulse in sheltered buildings is at maximum 0.8 times the impulse for unsheltered conditions, and this reduction increases as the number of sheltering rows increases. Using empirical exceedance probabilities of the applied debris impulse, a framework is developed to estimate the maximum structural loading response within a building array, along with a comparison with data and existing standards. The effect of the impact duration on the relation between the applied debris impulse and the maximum structural response is also discussed.

Pile breakwaters have been adopted in coastal regions with soft seabeds, owing to their advantageous features. They are subjected to wave run-ups, which would increase the wave transmission and threaten the superstructures above the piles (e.g., wharves, bridges, and pipelines). However, there are still no systematic design codes for this kind of structure. In this paper, an accurate prediction of the wave run-up on a pile breakwater is proposed, using a combined experimental–numerical approach. An experimental campaign comprising the effects of wave steepness, relative wave height, relative pile diameter, and blockage ratio is carried out by recording the run-up of both regular and irregular waves. A computational fluid dynamics (CFD) model is validated by the experimental data and then utilized to examine the hydrodynamic process. Two distinct patterns are identified by the localized flow field, which depend on the relationship between the pile diameter and the incident wavelength and lead to significant differences in the run-up height. By analyzing the experimental data set, a semiempirical formula is developed in the framework of the velocity stagnation head method, which gives satisfactory predictions to the run-up of both regular and irregular waves. The research outcome can provide a guideline for the structural design of a pile breakwater.

A comprehensive experimental program was designed and conducted to investigate the effects of propagation of tsunami-like bores over a permeable surface, including the impacts on pore pressure variation around a square structure. A dam-break generation system was selected to model the tsunami-like bores and the effects of different impoundment depths were investigated to estimate pore pressure variations around a structural model. The latter was installed within a sand bed, and the hydraulic bores propagated over both horizontal and inclined surfaces as well as over dry and wet bed conditions. The latter involved the presence of a still-water layer over the sand bed. The transient variations of pore pressure distribution around the structure were measured, and their results were correlated with impoundment depth, still-water depth, and bed slope. A total of nine pore pressure tensiometers were installed on the front and side walls of the structure to record the time-history of pore pressure variation during bore propagation and subsequent impact onto the rigid structure for both sub- and supercritical bores. The magnitude of peak pore pressure and the time to reach peak pore pressure were found to be correlated with the still-to-impoundment depth ratio. It was found that effective peak pore pressure recorded on the side of the structural model was smaller and it occurred later in the supercritical bores compared with the subcritical bores. The contour plots of pore pressure in both front and side walls of the structural model were developed for a better understanding of the pore pressure distribution during the initial peak and the subsequent quasi-steady-state flow conditions. Experimental results indicate that the magnitude of pore pressure increased with increasing impoundment depth. Furthermore, pore pressure magnitude around the structure was considerably higher in the inclined bed tests, and they reached peak values faster than those observed for the horizontal bed tests. For both the horizontal and inclined bed tests, the front wall of the structural model exhibited larger pore pressure values than those observed on the side walls.

The effects of tsunami-like dam-break bores on the evolution of scour around a square structure were experimentally investigated for bores propagating over a saturated bed. The bores were generated using a rapid-release gate installed inside a hydraulic flume with a relatively wide range of still-to-impoundment depth ratios and two different bed slopes. The time history of the scour formation was recorded for the front and side walls of the structural model for both supercritical and subcritical hydraulic bores. The magnitude of the maximum scour for various test conditions was linked to the still-to-impoundment depth ratios and bed slopes. The time variations of scour rate and Shields parameter were generated from scour profiles and the results were then used to study the incipient motion of sand particles around the structural model concerning different tsunami-like bore heights and two bed slopes. The analysis of the presented experimental results revealed that the deepest scour hole and the greatest scour rate were observed for the case of the horizontal beds. On the other hand, the critical Shields number was smaller for the case of the inclined bed tests, causing the earlier erosion of bed materials in the inclined bed tests compared with the horizontal ones. These experimental results revealed that regardless of the bed slope, the front and side corners of the structural model had higher scour depths than the centers of the front and side walls. Furthermore, owing to subsequent deposition, the lowest ratio of the equilibrium scour depth to the maximum scour depth was observed in the side corner of the model, although this ratio was greater in the horizontal bed compared with the case of the inclined bed test. In addition, for both sub- and supercritical flows, the scour rate showed a directly linear correlation with an increasing still-to-impoundment depth ratio in the front and side corners.

Gathering data for cascading seismic and tsunami events is difficult due to space constraints in existing experimental facilities, the application of scaling laws for both the fluid and structure, and limitations of computational software in simulating multiple hazards within the same analysis. To overcome these limitations, this study demonstrates the feasibility of a real-time hybrid simulation testing method to enhance wave–structure interaction simulations. While real-time hybrid simulations have been utilized for structures subjected to seismic events for decades, considerations for hybrid testing make its application to hydrodynamic problems challenging, including testing in wet or submersible environments and satisfying similitude time constraints. A cylindrical bridge pier specimen connected to a three-dimensional numerical bridge model was subjected to cascading seismic and tsunami events deploying a three-loop hardware architecture for real-time hybrid simulation. The domain was partitioned such that the wave–structure interaction on the bridge pier was physically tested in a wave flume and coupled to a numerical model of the remaining bridge components. To simulate existing damage, seismic loading was numerically applied to the hybrid model prior to the physical wave loading. Results illustrate that this simulation approach is feasible for future investigations using real-time hybrid simulation.

The study establishes, with the aid of field measurements and numerical modeling, that the upper reach of the Hooghly estuary (India), though damped, registers an intense tidal bore. The lower estuary is amplified but does not show signs of bore formation. Limited quantitative studies are available on bores forming in damped estuaries. This study attempts to fill this gap using tidal gauge and velocity observations supplemented with simulation results obtained using the open-source numerical shallow-water solver TELEMAC 2D. New estimates of bore intensity in the Hooghly are presented confirming that the bore Froude number may reach 1.37 in the upper estuary for higher tidal ranges. The numerical model is used to gain further insights into the formation and evolution of the Hooghly bore. The model, despite using a vertically averaged velocity field, simulates tidal wave propagation and estimates of velocity magnitude during bore propagation with significant accuracy. The study demonstrates that the proposed model is an efficient and inexpensive tool for capturing the bore phenomenon and may be used to supplement field observations. Using the simulation results, key features of the Hooghly bore, such as the distance of the bore inception from the ocean mouth and the threshold tidal range for bore formation are investigated. The numerical simulations highlight the impact of riverbed asymmetry in bore appearances in natural estuaries. The analysis also reveals new information about bores in the Hooghly estuary, which may be useful for planning shipping and berthing operations in the port terminals along the river. A comparison with other estuaries witnessing tidal bores indicates that the Hooghly experiences a strong bore, despite the high dissipative forces owing to the rapid convergence of river width.