• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.4
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• pp.383-389
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• 2006

In three dimensional wave field, a direct numerical simulation model, which is able to handle free-fall and slope-fall of a waterdrop due to overtopping, is proposed to evaluate the overtopping rate on the coastal structures like an absorbing revetment. A comparison between the numerical model and existing experimental results for overtopping rate was made to validate the proposed numerical model's accuracy, and showed fairly good agreement between them. It is confirmed in numerical and hydraulic(existing) model test that the overtopping quantity on a absorbing revetment becomes larger with an increase in Ursell number. Also, the overtopping rate estimated by 3-D numerical model is compared with it obtained by 2-D numerical model.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.3
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• pp.49-56
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• 2023

The allowable mean overtopping discharge is used as a design parameter for coastal structures. The crest elevation of coastal structures should ensure the wave overtopping discharge within acceptable limits for structural safety and the safety of pedestrians, vehicles, operations, and so on. In this study, two-dimensional physical model tests on typical rubble-mound structure geometries were performed and the the mean wave overtopping discharges under various water depth and wave conditions were measrued. The various test conditions were applied to the tests with the change of the wave steepness, relative freeboard and relative wave height. An empirical formula from the experimental data was proposed to predict the mean wave overtopping volumes.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.315-325
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• 2017

This study aims to provide information for the design and use of structural lightweight concrete (SLWC) for floating concrete structures in a marine environment. An experimental program was set up and comprehensive experimental campaign were carried out to determine SLWC mix proportions that can satisfy specified concrete strength, density, and slump values all of them were determined from previous research. Comparisons with previous SLWC mix designs that have been utilized for actual floating concrete structures were made. Key aspects needed to be considered regarding to the use of SLWC for floating marine concrete structures were discussed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.36 no.3
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• pp.105-115
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• 2024

In coastal structure design incorporating revetments, the assessment of wave overtopping discharge relies on hydraulic model experiments. Numerous empirical formulas have been developed to predict overtopping discharge based on quantitative data from these experiments. Typically, for revetment structures aimed at mitigating wave overtopping, crest height is determined by considering the maximum amplitude of the design wave, resulting in a relatively high freeboard compared to wave heights. However, achieving complete prevention of all wave overtopping would require the crown wall to have substantial crest heights, rendering it economically impractical. Therefore, the concept of limiting discharge has been introduced in the design of revetment structures, aiming to restrict wave overtopping discharge to an acceptable level. Consequently, many coastal structures in real-world settings feature relatively lower freeboard heights than incident wave heights. This study investigated wave overtopping discharge on rubble-mound breakwaters with relatively low freeboard heights through hydraulic model experiments. Furthermore, it conducted a comparative analysis of the predictive capabilities of existing empirical formulas for estimating overtopping discharge using experimental data.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.20 no.6
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• pp.35-50
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• 2017

This study is to see the recovery effect of the Deltacon method by investigating the amount of sand deposition, the topographical cross section and the vegetation structure; and to derive the effective recovery method of coastal erosion area. The target areas of this study include Jinri coastal dune, Bajireum coastal dune and Seopori coastal dune in Deokjeok-do Island, Ongjin-gun, Incheon. In order to assess the current status of the coastal erosion area recovery, the soil profile structure map was prepared on the site and then the amount of sand deposition within 1m was calculated indoors. The vegetation recovery status of the costal erosion area was assessed via the analyses of the topographical profile structure and the plant community structure, and we aim to derive the effective recovery plan of the Deltacon method with the results. With the Deltacon method, structures with ductile material, special non-woven fabric bags filled with soil and vegetation can be performed therefore the structuralstability and prevention of sand erosion can be achieved. The amounts of sand deposition of Bajireum coastal dune, Seopori costal dune and Jinri costal dune were calculated $0.98{\sim}2.54m^3$, $1.02{\sim}2.96m^3$, and $0.27{\sim}0.75m^3$, respectively, and it is considered that the costal erosion recovery is actively performed for Bajireum costal dune and Seopori costal dune. The analysis results of vegetation structures by topography show that the installation of the send collecting net in steep areas has been highly effective and the Deltacon-constructed target areas have been restored to vegetation and the costal dune, which is similar to the natural dune. The investigation of the plant community structure in Deokjeok-do Island costal dune, Incheon displayed similar research results of the existing costal dune flora and confirmed the emergence of Lathyrus japonicus, Carex kobomugi, Elymus mollis, Vitex rotundifolia, and Calystegia soldanella and others. In order to carry out further effective recovery with the Deltacon method, improvements to rootage of herbaceous vegetation are needed in areas without foredune herbaceous vegetation, and continuos maintenance & management monitoring of connected windbreak forest to costal dunes are also necessary.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.315-323
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• 2015

Damage level of coastal structures has been scaled up according to increase of wave height and duration of the storm due to the abnormal global climate change. So, the design criteria for new breakwaters is being intensified and structural strengthening is also conducted for the existing breakwaters. Recently, interlocking concept has been much attention to enhance the structural stability of the conventional caisson structure designed individually to resist waves. The interlocking caisson breakwater may be survival even if unusual high wave occurs because the maximum wave force may be reduced by phase lags among the wave forces acting on each caisson. In this study, the dispersion characteristics of wave forces using interlocking system that connect the upper part of caisson with cable in the normal direction of breakwater was investigated. A simplified linear model was developed for computational efficiency, in which the foundation and connection cables were modelled as linear springs, and caisson structures were assumed to be rigid. From numerical experiments, it can be found that the higher wave forces are transmitted through the cable as the angle of incident wave is larger, and the larger the stiffness of the interlocking cable makes larger wave dispersion effect.

• Wind and Structures
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• v.8 no.3
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• pp.179-196
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• 2005

This paper describes the application of a wireless data acquisition system to monitor wind pressures and velocities with absolute pressure sensors and an anemometer. The system was developed for future deployment, as part of a research effort currently underway to instrument coastal homes in Florida to monitor roof wind pressures during hurricanes. The proposed wireless system will replace the current system that involves a large amount of hardwired connections from the sensors to the data processing unit that requires labor intensive wiring and preparation of the home. The paper describes comparison studies and field tests to assess the performance of the system. The new system offers the advantages of light hardware, ease of installation, capacity for 48 hours of continuous data acquisition, good frequency and amplitude responses, and a relatively simple maintenance. However, the tests also show that the shape of the shell that has been previously used to protect the sensors might interfere with the proper measurement of the pressures.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.263-268
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• 1997

One of the principal causes of the deterioation of coastal concrete structures is the corrosion of reinforcing steel induced by the attack of chloride ions. An experimental study was performed to investigate the distribution of concentration of chloride ions in a coastal concrete structure and to measure the half-cell potential of embedded steel by using the copper-copper sulfate reference electrode. Quantitative analysis showed that the concentration of chloride ion in the aqueous phase near the surface of embedded steel exceeded a threshold value for corrosion, 0.05% by weight in concrete. The absolute value of half-cell potential at some members of embedded steel was measured to be higher than 350mV, indicating that the probability of corrosion is more than 90%. The prediction on corrosion based on the experimental measurements was confirmed by the observation of corrosion on the surface of steel bars in the concrete core taken out of the concrete structure.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.2
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• pp.84-90
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• 1993

Iterative solution procedure (Conjugate Gradient Method, Panchang et al., 1991) is implemented for solving the complete mild slope equation for the spherical shoal and the coast with detached breakwater. The numerical results agreed well with the experimental data. The disadvantage that mild slope eguation could be solved only for small domains is now overcome by using this solution procedure. Moreover it can be easily applied to the coastal regions with complex geometry and structures, and needs not so much computer time as the conventional models.

• Journal of Ocean Engineering and Technology
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• v.7 no.1
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• pp.156-161
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• 1993

Structures built in the coastal area often cause unexpectedly severe shoreline change on the adjacent beaches. Therefore, beach evolution is one of the most important problem in the coastal engineering. Beach evolution in the coastal area consisted of wave transform model and sediment transport model. Ebersoale's elliptic mild slope equation which considered the effect of combind wave refraction and perline and Dean's one line theory for the sediment transport model were used in this study. Kwangan beach was selected as study area and field observations were done. Numerical simulation for beach evolution in the Kwangan beach was performed and shoreline change predictions were suggested as results.