• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1994.07a
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• pp.127-134
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• 1994

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.286-304
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• 2017

In this study, we proposed a new-type of circular perforated caisson breakwater consisting of a bundle of latticed blocks that can be applied to a small port such as a fishing port, and numerically investigated the hydraulic characteristics of the breakwater. The numerical method used in this study is OLAFOAM which newly added wave generation module, porous media analysis module and reflected wave control module based on OpenFOAM that is open source CFD software published under the GPL license. To investigate the applicability of OLAFOAM, the variations of wave pressure acting on the three-dimensional slit caisson were compared to the previous experimental results under the regular wave conditions, and then the performance for irregular waves was examined from the reproducibility of the target irregular waves and frequency spectrum analysis. As a result, a series of numerical simulations for the new-type of circular perforated caisson breakwaters, which is similar to slit caisson breakwater, was carried out under the irregular wave actions. The hydraulic characteristics of the breakwater such as wave overtopping, reflection, and wave pressure distribution were carefully investigated respect to the significant wave height and period, the wave chamber width, and the interconnectivity between them. The numerical results revealed that the wave pressure acting on the new-type of circular perforated caisson breakwaters was considerably smaller than the result of the impermeable vertical wall computed by the Goda equation. Also, the reflection of the new-type caisson breakwater was similar to the variation range of the reflection coefficient of the existing slit caisson breakwater.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.2
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• pp.137-146
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• 2006

This is the second of a two-part paper which describes comparison of reliability design methods by application to Donghae Harbor Breakwaters. In this paper, Part 2, we deal with sliding of caissons. The failure modes of a vertical breakwater, which consists of a caisson mounted on a rubble mound, include the sliding and overturning of the caisson and the failure of the rubble mound or subsoil, among which most frequently occurs the sliding of the caisson. The traditional deterministic design method for sliding failure of a caisson uses the concept of a safety factor that the resistance should be greater than the load by a certain factor (e.g. 1.2). However, the safety of a structure cannot be quantitatively evaluated by the concept of a safety factor. On the other hand, the reliability design method, for which active research is being performed recently, enables one to quantitatively evaluate the safety of a structure by calculating the probability of failure of the structure. The reliability design method is classified into three categories depending on the level of probabilistic concepts being employed, i.e., Level 1, 2, and 3. In this study, we apply the reliability design methods to the sliding of the caisson of the breakwaters of Donghae Harbor, which was constructed by traditional deterministic design methods to be damaged in 1987. Analyses are made for the breakwaters before the damage and after reinforcement. The probability of failure before the damage is much higher than the allowable value, indicating that the breakwater was under-designed. The probability of failure after reinforcement, however, is close to the allowable value, indicating that the breakwater is no longer in danger. On the other hand, the results of the different reliability design methods are in fairly good agreement, confirming that there is not much difference among different methods.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2006.09a
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• pp.161-164
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• 2006

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2001.08a
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• pp.84-93
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• 2001

• Journal of Korea Water Resources Association
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• v.51 no.9
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• pp.827-837
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• 2018

The stabilities of sliding and overturning of caisson and bearing capacity of mound against eccentric and inclined loads, which possibly happen to a composite caisson breakwaters, have been analyzed by using the technique of multiple failure modes. In deterministic approach, mathematical functions have been first derived from the ultimate limit state equations. Using those functions, the minimum cross section of caisson can straightforwardly be evaluated. By taking a look into some various deterministic analyses, it has been found that the conflict between failure modes can be occurred, such that the stability of bearing capacity of mound decreased as the stability of sliding increased. Therefore, the multiple failure modes for the composite caisson breakwaters should be taken into account simultaneously even in the process of deterministically evaluating the design cross section of caisson. Meanwhile, the reliability analyses on multiple failure modes have been implemented to the cross section determined by the sliding failure mode. It has been shown that the system failure probabilities of the composite breakwater are very behaved differently according to the variation of incident waves. The failure probabilities of system tend also to increase as the crest freeboards of caisson are heightening. The similar behaviors are taken place in cases that the water depths above mound are deepening. Finally, the results of the first-order modal are quite coincided with those of the second-order modal in all conditions of numerical tests performed in this paper. However, the second-order modal have had higher accuracy than the first-order modal. This is mainly due to that some correlations between failure modes can be properly incorporated in the second-order modal. Nevertheless, the first-order modal can also be easily used only when one of failure probabilities among multiple failure modes is extremely larger than others.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.5
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• pp.156-168
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• 2022

The design and construction are carried out to improve the structural stability of caisson breakwaters by installing new caissons on the front or rear of old caissons. The wave forces acting on caisson are excessively calculated by the resonance of fluid existing between the old caisson and the new caisson in the numerical analysis using potential flow. In this study, we used the damping zone option in ANSYS AQWA program to analyze the wave forces acting on individual caissons according to the interaction effects between the incident wave and the caisson. By applying the damping zone option to the fluid in which resonance occurs, the wave forces acting on individual caissons were calculated by the change of damping factor. In addition, the wave force characteristics acting on individual caissons were analyzed for the different distances between caissons in the frequency domain analysis.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.1
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• pp.11-20
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• 2003

In this paper we examine several methods tor calculating the reflection of irregular waves from a perforated-wall caisson breakwater using a regular wave model. The first method is to approximate the irregular waves as a regular wave whose height and period are the same as the root-mean-squared wave height and significant wave period, respectively, of the irregular waves. The second is to use the regular wave model, repeatedly, for each frequency component of the irregular wave spectrum. The wave period is determined according to the frequency of the component wave, and the root-mean-squared wave height is used for all the frequencies. The third method is the same as the second one except that the wave height corresponding to the energy of each component wave is used. Comparison with experimental data from previous authors shows the second method is the most adequate, giving reasonable agreement in both frequency-averaged reflection coefficients and reflected wave spectra.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.195-201
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• 2019

Long caisson breakwaters can improve the structural safety of a caisson due to the wave dispersion effect which reduces the average wave force acting on one caisson. However, in order to make long caissons, there are many manufacturing and construction limitations. Recently, interlocking caisson systems, which are to form a long caisson by interlocking individual caissons with adjacent caissons, have been much attention. In the present study, a interlocking caisson system with shear-keys was proposed and the wave dispersion effect according to the shear-key was evaluated analytically. As a result, (1) Because of the asymmetric shape of the interlocking caisson, the structure behavior and the wave dispersion effect of one are also asymmetric. (2) The wave dispersion effect is more influenced by the distribution and characteristics of wave acting on each caisson rather than the shape of the shear-key such as shear angle, height, shear length ratio. (3) The interlocking caisson breakwater is almost the same behavior and wave dispersion effect as a fully integrated breakwater.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.287-292
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• 2021

Load and resistance factor design is an efficient design approach that provides a system of consistent design solutions. This study aims to determine the load and resistance factors needed for the design of breakwater foundations within a probabilistic framework. In the study, four typical types of Korean breakwaters, namely, rubble mound breakwaters, vertical composite caisson breakwaters, perforated caisson breakwaters, and horizontal composite breakwaters, are investigated. The bearing capacity of breakwater foundations under wave loading conditions is thoroughly examined. Two levels of the target reliability index (RI) of 2.5 and 3.0 are selected to implement the load and resistance factors calibration using Monte Carlo simulations with 100,000 cycles. The normalized resistance factors are found to be lower for the higher target RI as expected. Their ranges are from 0.668 to 0.687 for the target RI of 2.5 and from 0.576 to 0.634 for the target RI of 3.0.