• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.54-54
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• 2011

기존의 착저식 방파제를 보완하기 위하여 부유식 방파제가 개발되었고, 많은 연구가 선행되어 왔다. 부유식 방파제의 최대 장점은 경제성과 친환경성이다. 그러나 부유식 방파제는 소파성능이 떨어진다는 단점이 있으며, 이를 개선하기 위해 잠재와 혼용, 배열형에 관한 연구등이 선행되어왔다. 그러나 이것은 경제성이라는 강점을 고려하지 못하였다. 그래서 본 연구에서는 부유식 방파제의 중요한 장점중 하나인 경제성을 고려해, 단면현상 변화만을 이용하여 부유식 방파제의 소파성능 개선하고자 하였다. RANS(Reynolds averaged Navier-Stokes) 방정식에 기초하여 VOF법과 $k-{\varepsilon}$ 난류모델을 결합한 수치모델인 CADMAS-SURF를 이용하였으며, 구조물 단면형상 변화를 이용해 와의 상호 간섭을 유도하였고, 이에 따른 투과율 변화를 관찰 하였다. 결과를 살펴보면 요철1 단면에서는 구조물 전면 하단부분과 구조물 후면 하단부분에서 와의 간섭이 일어났으며 가장 아래 요철 부분에서 유속의 전달현상이 보인다. 투과계수는 일반적인 부유식 방파제와 마찬가지로 L/B가 1~4사이 값인, 비교적 단주기에서는 0.3~0.4의 투과율을 보였으나 L/B가 5를 넘어가면서 0.45~0.55의 투과율을 보였고, 요철2 단면에서는 전면과 후면에서 발달한 와가 전, 후면 돌출부에 의해 바닥까지 전파되지 못하는 양상을 보였으며, 돌출부 사이 중앙부분에서 가장 활발한 와의 간섭을 관찰 할 수 있었다. 돌출부 아래에서 역시 강력한 와의 간섭을 보이고 있다. 투과율 역시 가장 낮은 값을 보였으며 비교적 단주기 구간인 B/L 1~4 에서는 0.2~0.35 사이의 값을 가졌으며 5~10사이구간에서는 0.35~0.34의 값을 보이고 있다. 이 같은 결과는 와의 간섭이 가장 활발하게 나타난 결과로 보인다. 그리고 요철 3단면에서는 전면 돌출부 끝단에서의 활발한 와의 간섭을 관찰 할 수 있었다. 투과율은 세 단면 중 가장 높은 값의 투과율을 보이지만 B/L 3~4 구간에서 요철1 경우보다 낮은 값의 투과율을 보이고 있다. 결과에서 보듯이 도출부의 적절한 조합과 배치를 통해 언급한 연구목표(와의 생성과 간섭, 방파효율 개선)를 달성하였고 추후에 돌출부의 크기와 배치, 흘수의 영향, 수심의 영향 등을 고려한 연구가 진행된다면 더욱 우수한 단면형상을 개발 할 것이라 예상된다.

• Journal of Ocean Engineering and Technology
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• v.15 no.1
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• pp.7-11
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• 2001

In this paper, trapezoid sections and prominence sections were examined to improve the performance of floating breakwater in long waves. The linear potential theory is used and the boundary element method with a matching boundary is employed for numerical computation. The effects of the side slope of the trapezoid section and the geometry ratio of the prominence section on the floating breakwater were examined. It was found that trapezoid sections show lower transmission coefficients than the rectangular sections in the long wave range. In prominence sections the size of the sides are more important than the size of the top. Proper choices of the pontoon type geometry may move the local minimum point of the wave transmission coefficient toward the longer wave ranges and improve the performance of the floating breakwater in the long wave range for a given wave period.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.197-204
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• 2006

This experimental study of prominent section bending behavior beam without shear connector provides bond capacity between concrete profile and initial stiffness of SC beam by comparing the test result with a theological analysis result and an ANSYS(common structural analysis program) analysis result. The compared result provides a fundamental study for practical use of efficient SC beam. Test result indicates 88%-98% rate of theological result in moment capacity and composition ratio shows 30%-70%. In other words, the results are insufficient to make a complete composite action. Therefore, it is need to make pull shear connection of connection method.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2003.11a
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• pp.171-172
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• 2003

직물의 외관 품위는 직물의 촉각뿐만 아니라 시각적인 자극에 의해서 크게 결정된다. 견직물이나 양모직물의 광택 등 자연스러운 광학적 특성은 특히 구성 섬유의 특성이나 구성사의 구조, 직물 조직 등과 밀접한 관계가 있는데 그 중 섬유단면형태가 가장 중요한 인자라고 할 수 있다. 따라서 단면형상에 따른 직물의 외관 감성 특히 시각특성에 미치는 영향을 알아보기 위하여 직물의 광택도를 측정하였다. 그 결과 섬유 단면의 요철이 많으면 광택도가 감소하면 섬유단면이 매끈한 부분이 많은 섬유는 광택도가 증가하였다. 그러나 이섬도 혼섬단면사로 구성된 직물은 광택이 우수하면서 은은함을 부여해주었다.

• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.159-167
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• 2017

A precast concrete deck system is considered an effective alternative in terms of its rapid construction and quality assurance than cast-in-place concrete deck. In precast concrete deck system, structural performance and serviceability are mostly determined by the connection methods between the precast decks. This research proposes more improved precast deck system with asymmetric ribbed connection details improving the disadvantage of previous precast deck system such as difficulties in assembling precast decks. And in this precast deck system, a separate form is not required at the site because partition wall of the precast decks serves as a form when placing non-shrinkage mortar in the connection part of the precast decks. Therefore, rapid construction is possible. Flexural performance is verified through load tests considering main parameter such as rib length in the precast deck connection. From the test results, it can be inferred that the development of the rebar and prevention of adhesion failure in the partition wall of the precast deck system are important factors in securing the flexural performance. Although the structural performance of the precast deck system with asymmetric connection details is gradually reduced as the rib length in the precast deck connection increases, the proposed precast deck system shows sufficient flexural performance and can be applied to the connection part of precast decks effectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.1-9
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• 2015

Due to the increasing number of deteriorated bridges worldwide, the importance of maintenance and replacement of existing bridges are being emphasized. Cast-in-place concrete deck which is mainly applied to deck replacement of existing bridges have problems such as deterioration concerns by initial crack, labor cost increase, difficulties of maintenance and replacement, construction time increase, and indirect cost increase by traffic congestion. On the contrary, a precast concrete deck is considered as an effective alternative because of its quality assurance and accelerated construction. The connection method ensuring the required strength and durability is especially important, because the connection part of the precast concrete deck is vulnerable to cracks and leakage. Therefore, this study proposes precast bridge decks with ribbed connection which are more improved than existing bridge deck joints, and flexural performance is verified through various parameter tests.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1436-1441
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• 2004

The internal cooling passage of a gas turbine blade can be modeled as a ribbed channel. Most studies have considered square ribs. However, the ribs can be rounded due to improper manufacturing or wear during the operation. Hence, we have studied two different rib geometries in this study, i.e. square and semicircle ribs. We have performed large eddy simulations (LES) and experiments to validate the results from the simulations. LES predicts the detailed flow and thermal features, which have not been captured by simulations using turbulence models. By investigating the instantaneous flow and thermal fields, we propose the mechanisms for the local heat transfer distribution between ribs. For both the geometries, heat transfer is enhanced by the entrainment of the cold fluid by the vortical motions and impingement of the entrained cold fluid on the ribs.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.10a
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• pp.111-115
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• 1994

본 연구에서는 보강 되지 않은 사각단면 박스 구조물, 보강된 사각 단면 박스 구조물, 그리고 보강된 요철형 단면 박스 구좀ㄹ에 대하여 양단 고정(clamped-clamped)과 일단 고정 타단 자유(clamped-free)의 경계 조건에 대해 실험적 진동 해석을 수행 하였으며, 유한요소 code인 ANSYS를 이용하여 유한 요소 해석을 수행하였다. 또한 유한 요소 해석과 실험을 통하여 신뢰성이 검증된 요소를 각 박스 구조물에 적용하여 각 경우에 대한 응력해석을 유한요소법을 이용하여 수행하였다. 또한 각각의 경우에 보강재의 개수 및 단면 형상 변화, 그리고 두께 변화가 진동과 응력에 미치는 민감도를 연구하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.1
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• pp.85-94
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• 2016

In this study, a non-linear FEM model is presented to predict the static flexural performance of precast bridge decks with ribbed joint and is verified with previous experiment results through comparison. The several theory of material properties were applied to each mechanical properties in FEM model and FEM model's input variables were determined through experiment result and parametric study. The FEM results showed good accuracy in predicting the structural performance of the specimens and FEM model's average error rate was 5%. Also, each specimen's cracking aspect and failure mode can be predicted through FEM's plastic strain distribution. Thus, this FEM model can be used effectively for predicting the ultimate behavior and parametric study to development of design formula for joint.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.1
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• pp.149-157
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• 1999

Heat transfer in a duct is augmented remarkably by rib turbulators. However, increasing friction loss is accompanied due to ribs disturbing flows. Hence, pressure drops and heat transfer are considered simultaneously to decide heat/mass transfer performance in a rib-roughened duct. In the present study, the effects of rib cross section shape on pressure drop through a duct are investigated as well as those on heat transfer characteristics. The results show that the characteristics of heat/mass transfer and friction loss in the duct roughened with triangular ribs are similar to those with square ribs, while significantly different from those with semicircular ribs. The best performance in the duct is obtained by using semicircular shaped ribs among three types of ribs for the large rib angles of ${\alpha}{\geq}63^{\circ}$.