• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.4
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• pp.293-300
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• 2013

In this study we proposed a simplified finite element model of anchor bolt system inserted through concrete structures considering clamping forces. The three different finite element types using LS-DYNA are applied for numerical efficiency of the anchor bolt modeling. Combined beam and solid elements are used to reflect the tension state at internal part of anchor bolt due to torques. The clamping forces due to torques are considered by introducing a compression for a nut plane modeled by beam elements. The numerical examples show good agreement with different element types. Parametric studies are focused on the various effects of different element types on the induced axial and shear forces of anchor bolts considering clamping forces.

• 한국벤처창업학회:학술대회논문집
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• 2016.04a
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• pp.67-69
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• 2016

이 연구는 경영학과 MBA교육과정이 세상의 모든 제품과 기업에 공통적으로 적용되듯이, 세상의 어떤 분야의 제품이든 그 시작인 한 개 착안에서부터 시장력 확보를 위해 시도 되는 도전행위의 매개인 모든 착안과 아이디어가 기업이 되는 과정인 제벤처행위에 공통적으로 적용되는 학문이 될, MVA(PH-MVA, master of venture arming, 벤처무장학)학의 개념적 모델링의 시작에 필요로하는 정의론과 개념론으로, MBA에 있어 경영학원론이 개론화되듯, MVA에 있어 그 개론서가 될 벤처학원론서 설계에 있어서의 시작인 1편 기초론을 구성하는 내용을 벤처창업이나 기업의 신제품개발 부서에의 취업을 희망하는 학생들과 제벤처 생태계의 모든 직간접 관련 직무자 들이 공통적으로 무장하면 벤처적 행위에 필요로하는 여러 가지 직무자들 같이 소통력은 물론 직무매칭력 등의 분업 협업력이 매우 높아 질 것이라는 주장을 바탕으로한다. 그리고 제시하는 정의와 개념을 제벤처 생태계 전체의 표준으로 참고 삼아, 누구의 어떤 모델이든, 창조경제의 일부로서 미생들의 벤처(창업, 기업만들기 도전)행위나 완생기업들의 신제품개발 모두에 두루 적용 될 수 있는, 누구나가 이해, 공감, 교감, 습득이 용이한 벤처학 개발이 왕성하게 활성화될 수 있도록 하는 것이 곧 창조경제 활성화를 위한 학자들의 사명이자 새로운 성장동력 모델의 발굴이기도하다는 측면에서의 동참이 될 수 있기를 바라는 마음이다. 아울러, 이러한 정의와 개념을 바탕으로 전개되어, 벤처생태계 전반에서 수행 될 교육이 개인들의 창업(기업만들기)을 목표로하는 공부가 되기도하고 연장에, 완생기업들이 필요로하는 신제품개발에 있어서의 기본적인 능력과 자질을 갖춘 인재선발적 취업준비공부도 될 수 있는 통합적 교육이되어야한다는 취지를 가지고있다. 또 연구를 통해 제벤처(기업의 신제품개발 도전협업행위 포함) 생태계에서의 직무자들의 직무매칭력 및 협업행위에 있어서의 다양한 용어와 정의와 개념들의 제각각으로 부터 발생되는 상치(相馳, 제각각, 불통, 협업마찰, 대립, 갈등, 등)력을 해소하는 것이 역설적으로 협업력을 최적으로 활성화 할 수 있다는 사실을 모두가 인지, 수용토록 하고자 함을 목적으로한다. 이러한 연구를 전벤처단계의 벤처기초학을 바탕으로하는 제벤처생태계 개념을 일원화 통합화하는 연장에 전개되는 공통무장교육 모델화를 목적으로한다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.469-485
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• 2016

The failure of rock mass around deep tunnel, different from shallow tunnel largely affected by discontinuities, is dominated by magnitudes and directions of stresses, and the failures dominated by stresses can be divided into ductile and brittle features according to the conditions of stresses and the characteristics of rock mass. It is important to know the range and the depth of the V-shaped notch type failure resulted from the brittle failure, such as spalling, slabbing and rock burst, because they are the main factors for the design of excavation and support of deep tunnels. The main features of brittle failure are that it consists of cohesion loss and friction mobilization according to the stress condition, and is progressive. In this paper, a three-dimensional numerical model has been developed in order to simulate the brittle behavior of rock mass around deep tunnel by introducing the bi-linear failure envelope cut off, elastic-elastoplastic coupling and gradual spread of elastoplastic regions. By performing a series of numerical analyses, it is shown that the depths of failure estimated by this model coincide with an empirical relation from a case study.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.3
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• pp.241-249
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• 2004

There is an over head hoist transporter(OHT) by the system for delivering the wafer in semiconductor processing. The transfer system consist of carrier, vehicle, rail and support. The Tail supporting the wafer and the transfer system should maintain enough strength and stiffness. To achieve lightness and enough strength and stiffness, optimization algorithm should be introduced in design process. In this study, two kinds of section shapes as L-type, C-type is carried out the structure analysis and optimization. Total weight of rail is to be minimized while displacement should not exceed limit. To improve the initial model, topology optimization is done by the plain problem. Size optimization is done with 3D solid element and PLBA algorithm, the RQP algorithm. The weight of optimum model as L-type, C-type is decreased by 2.3%, 10% respectively. It is improved better than the initial model in the strength and stiffness of the structure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.545-550
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• 2016

The main purpose of this study is to analyze and evaluate the feasibility of ligthweight pavement system with pile foundation on soft soil by laboratory small chamber test. In order to verify the stability of lightweight pavement system, the 1/30 scaled downed model system was tested at lab. The soft soil condition was simulated and group piles for skin friction resistance were used. Within the limited lab test, the settlements of pavement system were 0.86 mm for Case A, 0.70 mm for Case B, and 0.50 mm for Case C. The converted maximum settlement differential settlement were 25.8 mm and 10.8 mm. These values meet the inside of specification of Bridge Design Guide in Korea. The use of lightweight pavement systems on soft soils could be an alternative construction method on soft soils to reduce the challenges of conventional design and constructions.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.121-127
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• 2007

Direct acting pressure relief valve applicable to propellant tank of launch vehicle is modeled in this study The flow resistance of the partially opened valve is modeled as a function of the distance of the valve stem from the resting position. The position of the valve varies transiently as a function of its mass, the spring force, sliding friction, and the pressure differential. Choking at valve throat and compressibility are considered for the analysis. This study presents systematic analysis method for pressure relief valve applicable to propellant tank of liquid rocket. The results shows transient flow resistance caused by stem motion and the importance of choking at valve throat for pressure relief valve design.

• Journal of the Korean Institute of Gas
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• v.19 no.5
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• pp.13-19
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• 2015

This paper presents a hydraulic fracture propagation model to describe propagation more realistically. In propagating the hydraulic fractures, we have used two criteria: maximum tangential stress to determine the fracture initiation angle and whether a hydraulic fracture intersects a natural fracture. The model was validated for the parameters relevant to fracture propagation, such as initiation angle and crossing ability through natural fracture. In order to check whether a hydraulic fracture crosses a natural fracture, the model results on crossing state excellently matched with the experimental data. In the sensitivity analysis for direction of maximum horizontal stress, frictional coefficient of fracture interface, and natural fracture orientation, the results show that hydraulic fracture intersects natural fracture, and then, propagated suitably with theoretical results according to fracture interaction criterion. In comparison of this model against vertical fracture approach, it was ascertained that there are discrepancies in fracture connectivity and stimulated reservoir volume.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.239-239
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• 2019

상수도시설 중 배수관망시설은 해당 지역의 영향을 민감하게 받는 시설이므로 설계시 해당시설의 특성을 충분히 고려해야 한다. 배수시설은 설치된 해당지역에 따라 그 특성이 매우 다르기 때문에, 설계지표 또한 해당 도시마다 다르게 설정될 수 있다. 도시의 규모가 크거나, 그 특성이 해당 구역에 따라 다른 경우에는 같은 도시의 경우라도 대상구역에 따라 다른 지표를 사용하는 경우도 있다. 따라서 이런 상수도관망의 설계 및 관리를 위해서는 장기간 현장여건에 맞는 관측자료를 통한 정밀한 수리분석이 요구되며 국내의 경우 일반적으로 Hazen-Williams 공식을 사용하고, 이때 관내면의 마찰손실계수 C는 유속계수라 한다. 이러한 유속계수는 상수관로의 물리적 특성을 나타내며 관로 내의 흐름해석, 펌프 및 관로의 설계, 최적 운영 방안, 통수능력 및 관 노후도 평가 등에 사용되거나 영향을 미치는 중요한 요소라 평가되고 있다. 또한 다수의 현장 관측 자료를 확보하여도 분기 구간과 펌프 및 밸브 등으로 인한 손실 등의 오차가 발생하므로 유속계수 산정 시 발생되는 많은 오차들을 줄여 보다 신뢰성 있는 유속계수를 산정해야 하고, 현장 관측 자료를 이용하여 유속계수를 산정하기 어려운 구간에 대해서는 관망해석 모델링을 통하여 결정하고 있다. 본 연구에서는 전주권 광역상수도의 계통 특성에 맞는 관로의 유속계수를 결정하기 위해 관리주체에서 기존에 설치한 수압계와 유량계 및 관망도를 이용하여 기초자료를 수집하고 Hazen-Williams 공식을 이용하여 유속계수를 산정하였다. 계산된 상수관로 유속계수는 전주시의 10개 계통에서 최소 107.06, 최대 145.02, 평균 127로 계산되었으며, 유속계수에 영향을 미치는 물리적 요소들의 관계를 파악하고자 상관성 분석 실행하였다. 그 결과 관경과 경과년수의 상관계수 R은 0.011 관경과 유속계수의 상관계수는 -0.009로 두변수간의 상관성이 거의 없고, 경과년수와 유속계수의 상관계수는 -0.776로 음의 상관성을 갖는 것으로 분석되었다. 이와 같이 제시한 유속계수는 해당 지역의 참고자료나 기준으로서 활용할 수 있을 것으로 판단되며 비 대상 지역에서도 현장자료가 부족한 곳의 유속계수를 산정할 경우 보다 신뢰성 있게 유속계수를 산정할 수 있는 방법을 제시하고자 한다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.4
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• pp.305-330
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• 2023

Unlike NATM tunnels, Shield TBM tunnels have split linings. Therefore, the stress distribution of the lining is different even if the lining is under the same load. Representative methods for analyzing the stress generated in lining in Shield TBM tunnels include Non-joint Mode that does not consider connections and a 2-ring beam-spring model that considers ring-to-ring joints and segment connections. This study is an analysis method by Break-joint Mode. However, we do not consider the structural role of segment lining connections. The effectiveness of the modeling is verified by analyzing behavioral characteristics against vibration loads by modeling with segment connection interfaces to which vertical stiffness and shear stiffness, which are friction components, are applied. Unlike the Non-joint mode, where the greatest stress occurs on the crown for static loads such as earth pressure, the stress distribution caused by contact between segment lining and friction stiffness produced the smallest stress in the crown key segment where segment connections were concentrated. The stress distribution was clearly distinguished based on segment connections. The results of static analysis by earth pressure, etc., produced up to seven times the stress generated in Non-joint mode compared to the stress generated by Break-joint Mode. This result is consistent with the stress distribution pattern of the 2-ring beam-spring model. However, as for the stress value for the train vibration load, the stress of Break-joint Mode was greater than that of Non-joint mode. This is a different result from the static mechanics concept that a segment ring consisting of a combination of short members is integrated in the circumferential direction, resulting in a smaller stress than Non-joint mode with a relatively longer member length.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.4
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• pp.257-266
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• 2000

A vertically-averaged, two-dimensional version of the Princeton Ocean Model has been applied to the South Sea to simulate the circulation driven by tides and inflows/outflows across open boundaries. To incorporate both forcing properly, a two-step modeling approach is adopted, in which the tidal circulation is first simulated by specifying the tides along the open boundaries, and then both the calculated tidal currents and the observed steady mean currents are prescribed across the open boundaries. Model results show that the steady, subtidal circulation of the South Sea is different from the residual circulation due to tidal rectification, and subtidal currents become locally as strong as tidal currents. The Cheju Current entering the model domain across the Cheju Strait flows eastward in general while shifting onshore or offshore areas following local isobaths. The Tsushima Current entering across the southern boundary reaches farther to the north in the eastern vicinity of Cheju-Do as compared to that entering across other parts of the southern boundary. The Tsushima Current turns to the east, merges with the Cheju Current, and both the Cheju and Tsushima Current exit to the East Sea through the western channel of the Korea Strait. An intensification of the outflow occurs over the deep trough adjacent to the Tsushima Island, which appears to be due to the formation of the frictional boundary layer in order to remove excess positive relative vorticity generated by an increase in the layer thickness. The circulation driven by both the tidal and inflows/outflows is different from that driven by each forcing separately in coastal areas, which implies that both forcings should be considered simultaneously in the simulation of more realistic coastal circulation.