• Journal of Advanced Research in Ocean Engineering
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• v.1 no.1
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• pp.44-54
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• 2015

Breakwaters are the coastal structures constructed either perpendicular (shore connected) or parallel (detached) to the coast. The main function of breakwater is to create a tranquil medium on its leeside by reflecting the waves and also dissipating the wave energy arriving from seaside, resulting in ease of manoeuvrability to boats or ships to their berthing places. Different types of breakwaters are being used at present, such as rubble mound breakwater, vertical wall type breakwater and composite breakwater. The objective of this paper is to investigate reflection coefficients (Kr) and dissipation (loss) coefficients (Kl) for physical models of Quarter circle caisson breakwater of three different radii of 0.550 m, 0.575 m and 0.600 m with S/D ratio of 2.5 (S=spacing between perforations, D=diameter of perforations). The models were tested in the monochromatic wave flume of the department, for different incident wave heights (Hi), Wave periods (T) and water depths (d). It was observed that reflection coefficient increased with increase in the wave steepness (Hi/gT2) and decreased with increase in depth parameter (d/gT2) and hs/d (Height of structure including rubble base/depth of water). The loss coefficient decreased with increase in the wave steepness and increased with increase in depth parameter and hs/d.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.215-226
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• 2004

A dynamic reliability model which can take into account the time history of loading sequences may be applied to the analyses of the hydraulic stability of armor units on rubble-mound breakwaters. All the parameters related to the stability of structures have been considered to be constants in the deterministic model until now. Thus, it is impossible to study the effects of some uncertainties of the related random variables on the stability of structures. In this paper, the dynamic reliability model can be developed by POT(Peak Over Threshold) method in order to take into account the time history of loading sequences and to investigate the temporal behaviors of stability of structure with its loading history. Finally, it is confirmed that the results of dynamic reliability model agree with straight- forwardly those of AFDA(Approximate Full Distribution Approach) of the static reliability model for the same input conditions. In addition, the temporal behaviors of probability of failure can be studied by the dynamic reliability model developed to analyze the hydraulic stability of armor units on rubble-mound breakwaters. Therefore, the present results may be useful for the management of repair and maintenance over the whole life cycle of structure.

• Proceedings of the Korea Contents Association Conference
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• 2016.05a
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• pp.239-240
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• 2016

Traditional town with wooden houses like Japanese historic local town is vulnerable to disaster. Wooden houses crowed in this study area, there is no gap between buildings and buildings. When disaster occurs, they can not use evacuation routes based on the value of probability of rubble flow. Disaster prevention design of traditional town using spatial information for residents is a modern idea in the field of disaster prevention study. Therefore, it is basically important and effective to create information, especially on the current situation such as dangerousness of the area. Here, we report on a disaster prevention design regarding probability of street blockade and probability of rubble flow at a large earthquake directly under our study area. In this study, we explain about necessity of temporary evacuation areas like open space. As a result, we found some ideas to secure evacuation routes from traditional houses to designated refuge places using temporary evacuation areas.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.2
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• pp.128-135
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• 2002

An existing numerical model fo r determining the wave field and pore pressures inside rubble mound breakwater was reformulated here especially to enhance the predictability of interior pore pressures. The pore pressures strongly depend on the nonlinear wave field occurring along frontal slope which is very difficult to be numerically reproduced. In the present study, hence, the amplitude and phase informations of wave pressures along the frontal slope are obtained directly through a hydraulic model test and are incorporated into the numerical model. The interior wave field is analyzed by a boundary element method, and thereby the pore pressures are determined. It was found that the calculated pore pressures agreed quite well with experimental values.

• Journal of Korea Water Resources Association
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• v.38 no.11
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• pp.947-954
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• 2005

In this study, laboratory measurements are presented for run-up heights and overtopping of water waves on slopes of rubble-mound breakwaters armored with tetrapods. The effects of wave steepness, surf similarity and wave period on the run-up height and overtopping are investigated in detail. A measurements. A very reasonable agreement is observed. A slopes of breakwaters become milder, run-up heights become smaller. The overtopping rate also is considerably rate also is considerably affected by wave steepness and period.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.4
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• pp.246-257
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• 2015

The progressive degradation paths of structures have quantitatively been tracked by using stochastic processes, such as Wiener process, gamma process and compound Poisson process, in order to consider both the sampling uncertainty due to the usual lack of damage data and the temporal uncertainty associated with the deterioration evolution. Several important features of stochastic processes which should carefully be considered in application of the stochastic processes to practical problems have been figured out through assessing cumulative damage and lifetime distribution as a function of time. Especially, the Wiener process and the gamma process have straightforwardly been applied to armors of rubble-mound breakwaters by the aid of a sample path method based on Melby's formula which can estimate cumulative damage levels of armors over time. The sample path method have been developed to calibrate the related-parameters required in the stochastic modelling of armors of rubble-mound breakwaters. From the analyses, it is found that cumulative damage levels of armors have surely been saturated with time. Also, the exponent of power law in time, that plays a significant role in predicting the cumulative damage levels over time, can easily be determined, which makes the stochastic models possible to track the cumulative damage levels of armors of rubble-mound breakwaters over time. Finally, failure probabilities with respect to various critical limits have been analyzed throughout its anticipated service life.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.2
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• pp.37-45
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• 2022

A simplified model using the lifetime distribution has been presented to estimate the Mean Residual Life (MRL) of rubble-mound breakwaters, which is not like a stochastic process model based on time-dependent history data to the cumulative damage progress of rubble-mound breakwaters. The parameters involved in the lifetime distribution can be easily estimated by using the upper and lower limits of lifetime and their likelihood that made a judgement by several experts taking account of the initial design lifetime, the past sequences of loads, and others. The simplified model presented in this paper has been applied to the rubble-mound breakwater with TTP armor layer. Wiener Process (WP)-based stochastic model also has been applied together with Monte-Carlo Simulation (MCS) technique to the breakwater of the same condition having time-dependent cumulative damage to TTP armor layer. From the comparison of lifetime distribution obtained from each models including Mean Time To Failure (MTTF), it has found that the lifetime distributions of rubble-mound breakwater can be very satisfactorily fitted by log-normal distribution for all types of cumulative damage progresses, such as exponential, linear, and logarithmic deterioration which are feasible in the real situations. Finally, the MRL of rubble-mound breakwaters estimated by the simplified model presented in this paper have been compared with those by WP stochastic process. It can be shown that results of the presented simplified model have been identical with those of WP stochastic process until any ages in the range of MTT F regardless of the deterioration types. However, a little of differences have been seen at the ages in the neighborhood of MTTF, specially, for the linear and logarithmic deterioration of cumulative damages. For the accurate estimation of MRL of harbor structures, it may be desirable that the stochastic processes should be used to consider properly time-dependent uncertainties of damage deterioration. Nevertheless, the simplified model presented in this paper can be useful in the building of the MRL-based preventive maintenance planning for several kinds of harbor structures, because of which is not needed time-dependent history data about the damage deterioration of structures as mentioned above.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.4
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• pp.7-17
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• 1984

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.399-402
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• 2007

This project is the 1st. stage for the foreshore reclamation at Jang-Hang area and its scope is to construct a seawall as outer facilities, road adjacent to the seawall and drainage gate. for the safe protections of the facilities at the reclaimed land hereafter, we adopted the mild slope rubble mound type for the seawall structure which was excellent in interrupting the wave overtopping, as a result of numerical & hydraulic model test about alternative 4 sections. For the flooding prevention of the reclaimed land, we planned the drainage system that could make the flood water level lower than the reclaimed land level. Also, we planned the eco-friendly waterfront area with 8 nature themes through the whole seawall sections.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.777-782
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• 2001

Occurrence of crack in the Half-loc of rubble mound breakwater under T.T.P (Tetrapod) can cause serious problems in structural safety. There, probing of such cracks in marine structures is an important process in evaluating the overall integrity of structures. Ultrasonic, SASW(Spectral-Analysis-of-Surface-Waves)and Impect-Echo methods were used for the inspection of pilot concrete and SFC (Steel Fiber Concrete) block in this study. The advantage and limitations of these methods for non-destructive inspection in concrete blocks are investigated. As a result, it has been verified that these methods proved to present effective solution for detecting the crack of the pilot concrete block.