• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.141.1-141.1
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• 2007

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.5
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• pp.345-356
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• 2009

Tetrapod has been used as the armor blocks of most rubble mound breakwaters constructed in Korea. The Hudson formula has been widely used in the design of breakwater armor blocks in Korea. In the present study, we calculate the load and resistance partial safety factors of the Hudson formula for Tetrapod armors. The partial safety factors were calculated for the typical breakwater cross-sections of 12 trade harbors and 8 coastal harbors in Korea. The mean and standard deviation of them were also calculated. The mean values were compared with the partial safety factors of US Army (2006). The load and resistance factors are slightly smaller and larger, respectively, than the US Army values. However, the overall safety factors obtained by multiplying the load and resistance factors are close to the US Army values. The result of the present study could be used as the basic data to propose authorized partial safety factors in the future.

• 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 Korean Society of Coastal and Ocean Engineers
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• v.25 no.3
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• pp.138-146
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• 2013

Tetrapod, one of the famous armor blocks for rubble mound breakwaters, has been widely used in the world. In order to evaluate the required weight of Tetrapod, many researchers have proposed various stability formulas. Since the stability formulas were proposed by curve-fitting the experimental data, some uncertainties are included in the formulas. The main uncertainties are associated with experimental data, derivation of the formula, and variability of the design variables. In this study, a new stability formula is developed by using M5' model tree, which reduces the uncertainty in the derivation of the formula. The index of agreement is used to evaluate the performance of the developed formula. The index of agreement for the new formula is higher by about 0.1 than the previous formula. The performance of the previous formula was not good when the predicted stability number is greater than about 3.0. However. the new formula is accurate regardless of the magnitude of stability number. As a result, the new formula performs better than the previous formula, while expressed in the form of a tree but still in an explicit form.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.141-146
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• 2005

This paper an application example of PIV system for analyzing the flow of submerged structure. In this paper, we introduce an analysis method to predict the characteristics of flow around the neighboring fields of tetrapod and fishing reef in order to develop a high performance model. Flowing phenomenon according to velocity distribution and flow separation around the submersed body were obtained by PIV system. Flow visualization has conducted in a circulating water channel by a high speed camera and etc.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.109-117
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• 2011

It was calculated using empirical formulas for the weight of Tetrapod, which was a representative armor unit in the rubble mound breakwater in Korea. As the formulas were evaluated from a curve-fitting with the result of hydraulic test, the uncertainty of experimental error was included. Therefore, the neural network and M5' model tree were used to minimize the uncertainty and predicted the stability number of armor block. The index of agreement between the predicted and measured stability number was calculated to assess the degree of uncertainty for each model. While the neural network with the highest index of agreement have an excellent prediction capability, a significant disadvantage exists that general designers can not easily handle the method. However, although M5' model tree has a lower prediction capability than the neural network, the model tree is easily used by the designers because it has a good prediction capability compared with the existing empirical formula and can be used to propose the formulas like an empirical formula.

• Journal of the Korea Institute of Building Construction
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• v.6 no.2 s.20
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• pp.73-79
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• 2006

The purpose of this study is to enhance the development of construction waste-recycling technologies and its economical efficiency by developing environment-friendly tetrapod, precast concrete, where recycled aggregate is used in order to promote recycling of waste concrete. The results of concrete mechanic characteristics experiments by the circulation coarse aggregate-replacement ratio are as the following. The circulation aggregate is lower and higher than natural aggregate in specific gravity and absorption ratio, respectively so that in case of mix proportioning, unit volume increases, while unit aggregate amount decreases. From the result, sufficient experiments of physical characteristics of circulation aggregate are required to get proper mix proportioning. When circulation aggregate-replacement ratio increases, compressive strength tends to decrease comprehensively, but 50% of replacement ratio is good enough to use. When circulation coarse aggregate's replacement ratio is 0%, drying shrinkage, which causes cracks in concrete and deteriorates durability, shows the minimum length change and the higher the ratio, the larger the length change. Thus. when using circulation coarse aggregate, drying shrinkage should be fairly examined. In freezing-and-thawing resistance, weight loss tends to comprehensively increase its loss at the circulation aggregate-mixed site. And the examination of surface aggregate-omission ratio is further needed and dynamic elastic modulus and durability factor(DF) require more study as well. In order to use circulation aggregate to tetrapod, a clear standard for strength should be first prepared and at the same time, more study about durability is needed.

• 어항어장
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• s.89
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• pp.69-71
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• 2010

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.4
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• pp.249-258
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• 2003

In this study, the stability of armor blocks of rubble-mound breakwaters is investigated based on the 2-dimensional hydraulic model test with irregular waves. Amor blocks were used the three types; rock, cube and tetrapod. And Hudson formula and van der Meer formula which are used for calculating the weight of armor blocks are considered. Hudson formula was developed from regular wave tests, while van der Meer formula was developed from irregular wave tests. The purpose of this paper is to compare and test two selected stability formulas using the experimental data.

• 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.