• Journal of the Korean Society of Safety
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• v.24 no.5
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• pp.43-47
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• 2009

Armor block is used to reduce wave energy. To do this, the stability of coastal structure is enhanced. It is very expensive to develop a new type armor block. So, the research of new type armor block is very short. We develope truncated tetrahedron type armor block(new type block) which have a hole in center part. In this study, the stability of new type armor block is investigated by hydraulic model test. In the result, the stability coefficient($K_D$) of new type armor block is 11.8. this value is more superior than value of tetrapod.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.3
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• pp.131-138
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• 2021

The armor blocks are used to protect the body of the structure and dissipate wave energies, so it is crucial to evaluate the stability of the armor unit. The stability of armor blocks has been mainly evaluated through empirical coefficients called the stability coefficient obtained from hydraulic model experiments. In this study, a new type of single-layered armor block called K-Block was proposed, and a new experimental method based on the pull-out force was proposed to evaluate the stability of the armor unit, including the interlocking effects. The pull-out force test proposed in this study directly measures the force required to separate the armor unit from the armored layer on the slope by applying a tensile force in the vertical and horizontal directions to the installed armor unit. The proposed experimental method confirmed that the interlocking effects of the armor block could be quantitatively evaluated, and the high stability of the K-Block was verified.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.163-174
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• 2001

A dynamic reliability model for analyzing the stability of armor units on rubble-mound breakwater is mathematically developed by using Hudson's formula and definition of single-failure mode. The probability density functions of resistance and loading functions are defined properly, the related parameters to those probability density functions are also estimated straightforwardly by the first-order analysis. It is found that probabilities of failure for the stability of armor units on rubble-mound breakwater are continuously increased as the service periods are elapsed, because of the occurrence of repeated loading of random magnitude by which the resistance may be deteriorated. In particular, the factor of safety is incorporated into the dynamic reliability model in order to evaluate the probability of failure as a function of factor of safety. It may thus be possible to take some informations for optimal design as well as managements and repairs of armor units on rubble-mound breakwater from the dynamic reliability analyses.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.516-523
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• 2020

Since the aging of coastal structures have been increased, the researches about the reinforcements of the existing aged structures are needed. Especially, the existing armor units placed on rubble mound structures should satisfy the stability against the increased design wave conditions. However the researches about these design problems have not been performed. In this study, the hydraulic model tests to investigate the stability number about the additionally placed armor unit were conducted. The main armor unit is a Tetrapod. The test results showed that the stability number (Kd) for additionally placed armor units(Tetrapod) increased up to maximum 10% comparing with that for 2 layers tetrapod (Kd = 8) within these test conditions with the pattern placing for existing armor layers and the stable armor layer slope for the non overtopping condition.

• 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.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.2
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• pp.86-96
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• 2003

A fracture or breakage of the concrete armor units in the primary cover layer of breakwaters is studied by using the reliability analysis which may be defined as the structural stability. The reliability function can be derived as a function of the angle of rotation that represents the rocking of armor units quantitatively. The relative influences of all of random variables related to the material and geometric properties on the fracture of armor units is analyzed in detail. In addition, the probability of failure for the fracture of individual armor unit can be evaluated as a function of the incident wave height. Finally, Bernoulli random process and the allowable fracture ratio may be introduced together in this paper, by which the probability of failure of a breakwater due to the fracture of armer units can be obtained straightforwardly. It is found that the probability of failure of a breakwater due to the fracture of armor units may be varied with the several allowable fracture ratios. Therefore, it should be necessary to consider the structural stability as well as the hydraulic stability for the design of breakwaters with multi-leg slender concrete armor units of large size under wave action in deep water.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.205-214
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• 2004

Static reliability models are introduced to analyze the armor stability of rubble-mound breakwaters. Contrasted to the deterministic model, reliability models can estimate the probability of failure directly and calculate the influence of each design variables quantitatively. Thus, it can be possible to design armor units of the rubble-mound breakwaters rationally. In this study FMA(First-order Mean-value Approach), FDA(First-order Design-value Approach) and AFDA(Approximate Full Distribution Approach) of Level II approach of static reliability methods are used to analyze the armor stability of rubble mound breakwaters. The limitations and applications of each approach are studied straight-forwardly.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.4
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• pp.47-55
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• 2016

This study is on the stability re-evaluation of armor stones in saemangum seadike according to recently increased sea-level and frequent high wave incoming and the results are in the following. The field inspection of armor stones in the seadike revealed that damages of armor stones have been caused by higher waves than designed waves and that the reconstruction of armor stones and concrete grouting method have been used as the reinforcement work. The result of numerical simulation of wave channel conducted to estimate the safety weight of armor stones influenced by flows revealed that the safety weight of armor stones in the seadike No.4 was estimated as 5.47 tons by using the Isbash method, which is about 122 % more than 4.49 tons estimated by using Van der Meer method. Therefore, in designing armor stones which can be influenced by high waves such as the case of Saemangum seadike, it is necessary to apply the safety weight method of armor stones, based on the Isbash method, which produced the significant figures among the safety weight methods using flows as well as the safety weight method using high waves based on the Hudson method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.3
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• pp.142-151
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• 2004

A method for the determination of concrete armor unit weights with hydraulic stability and structural stability may be formulated in this paper. The hydraulic stability is analyzed by using Hudson's formula, the structural stability is also studied by evaluation of maximum flexural tensile stresses in armor unit induced by the impact loads and by comparison of those with the tensile resistance strength directly. The applicable criteria for concrete armor units can be represented as a function of design wave heights with return period, armor weights, and tensile strengths for the practical uses. In addition, reliability analyses for two failure modes are carried out to take into account some uncertainties. Finally, a series system for two-failure mode analysis can be made up straightforwardly, by which the optimal weights of armor units can be estimated with the various relative breakages, given the specific target probability of failure under the concepts of reliability-based design method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.5
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• pp.102-108
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• 2023

In this study, hydraulic model tests were performed to investigate the stability of armor units at harbor side slope for rubble mound structures. The armor units on the rear slope were rocks. The Korean design standard for harbor and fishery port suggested the design figures that showed the ratio of the armor weight for each location of rubble mound structures and it could be known that the same weight ratio was needed to the sea side and rear side slope of rubble mound structures. The crest elements were commonly applied to the design process of rubble mound structures in Korea and the investigation of the effects of super structures would be needed. The damage rate (S =2) was applied and the stable wave height was measured for each test condition. The results were suggested as the armor weight ratio of the rear side slope(armor rock) to the sea side slope (tetrapod) in relation to the relative crest height.