• Journal of Korean Society of Steel Construction
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• v.22 no.2
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• pp.139-150
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• 2010

Reinforced-concrete (RC) columns are frequently designed and constructed. other types of columns includes composite types such as concrete-filled tube columns (CFT). Hollow RC columns may be effective in reducing both the self weight of columns and total amount of materials used. This is due to the fact that a hollow RC column possesses larger moment of inertia than that of solid RC columns of same cross sectional area. Despite the effectiveness the hollow RC column has not been popular because of its poor ductility performance. While the transverse reinforcements are effective in controlling the brittle failure of the outside concrete, they are not capable of resisting the failure of concrete of inner face which is in unconfined state of stress. To overcome these drawbacks, the internally confined hollow reinforced concrete (ICH RC), a new column type, was proposed in the previous researches. In this study, the fire resistance performance of the ICH RC columns was analyzed through a series of extensive heat transfer analyses using the nonlinear-material model program. Also, effect of factors such as the hollowness ratio, thickness of the concrete, and thickness of the internal tube on the fire resistance performance were extensively studied. Then the factors that enhance the fire-resistant performance of ICH RC were presented and analyzed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1441-1446
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• 2014

In the present paper, the effects of the thickness and width of a curved wide-plate, the crack length, and the strain hardening exponent on the crack-tip constraint of the curved wide-plate were investigated. To accomplish this, detailed three-dimensional elastic-plastic finite element (FE) analyses were performed considering various geometric and material variables. The material was characterized by the Ramberg-Osgood relationship, and the Q-stress was employed as a crack-tip constraint parameter. Based on the present FE results, the variations in the Q-stress of the curved wide-plate with the geometric variables and material properties were evaluated. This revealed that the effect of out-of-plane constraint conditions on the crack-tip constraint was closely related to the in-plane constraint conditions, and out-of-plane constraint conditions affected the crack-tip constraint more than in-plane constraint conditions.

• Journal of Oral Medicine and Pain
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• v.24 no.3
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• pp.245-257
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• 1999

일상 생활에서 우리는 스트레스에 항상 노출되어 있으며, 스트레스는 생체의 신경계, 내분비계 및 면역계의 변화를 수반한 항상성의 파괴로 수많은 정신적, 육체적 질병을 야기시킨다. 특히 구강안면영역에서도 다양한 구강점막질환과 구강건조증 등을 발생시킨다. 스트레스를 제거하는 방법으로는 약물요법 및 상담, 명상요법, 종교요법 등 다양한 방법이 제시되고 있는데, 다소의 부작용이 나타나거나 꾸준히 시행하기가 쉽지 않으며 스트레스의 원인을 근본적으로 제거하기가 현실적으로 용이하지 않은 경우가 많아 스트레스에 대한 해결책에 대하여 많은 관심이 집중되고 있다. 이에 본인은 스트레스가 가해졌을 때 백서 악하선에서 관철되며 apoptosis에 대하여 세포보호작용을 하는 clusterin(SGP-2)을 이용하여 구속스트레스를 가하기에 앞서 오랫동안 경험적으로 사용되어 왔고 부작용이 적은 전통약물인 보혈안신탕을 투여하고 스트레스에 의한 타액선의 조직변화를 관찰하여 그 효과를 확인해 보고자하였다. Sprague-Dawley계 응성 백서(200-230g/bw) 33마리를 정상 대조군(3마리), 구속스트레스군(15마리) 및 보혈안신탕 투여 후 구속스트레스군(15마리)으로 나누고 이틀을 각각 구속장치에 구속한 후 0, 1, 3, 5, 7일에 회생시켜 악하선을 적출하였으며, 면역조직화학법 및 Northern Blot을 이용하여 clusterin의 변화를 관찰하였다. 그 결과는 다음과 같다. 1. 구속스트레스군의 악하선 조직에서 clusterin 단백질과 mRNA는 실험 즉일군에서만 미약하게 관찰되었으며 실험 3일과 5일 후에 핵붕괴 및 핵농축 등의 핵변화를 동반한 apoptosis가 관찰 되었다. 2. 보혈안신탕 투여 후 구속스트레스군의 악하선 조직에서 실험 5일군까지 clusterin 이 증가한 후 실험 7일군에서는 감소하였다. 3. 보혈안신탕 투여 후 구속스트레스군의 악하선 조직에서는 apoptosis가 관찰되지 않았다. 4. 보혈안신탕 투여 후 구속스트레스군의 악하선 조직에서 clusterin mRNA가 실험 전군에 걸쳐 미약하게 관찰되었다. 이상의 결과로 타액선 조직은 스트레스 단백질인 clusterin을 생산하여 세포를 보호함으로써 스트레스 상황에 적응하지만, 생리적 적용한계를 넘는 스트레스에 노출될 때는 apoptosis됨이 확인되었다. 그리고 보혈안신탕은 스트레스 상황에서 세포의 생리적 적응력을 높여 세포의 apoptosis를 억제하는 효과를 나타냄이 확인되었다. 따라서 본 연구결과는 구강건조증등의 스트레스성 타액선 질환의 병리기전을 규명하는데 도움이되리라 생각되며, 향후 항스트레스 효과를 가진 보혈안신탕등의 한약재를 임상에 적용함으로써 스트레스로 인한 신체의 병리적 변화를 다소나마 차단할 수 있을 것으로 사료된다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.3
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• pp.48-56
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• 2021

Due to the recent earthquake that has occurred worldwide, interest in seismic reinforcement of structures is increasing. In order to improve the seismic performance of the structure, the seismic reinforcement of the column should be made. Various seismic retrofit methods are being developed to improve the seismic performance of columns. In this study, in order to improve the seismic performance of RC columns, an numerical study was conducted to evaluate the seismic performance of the columns by applying a surface constrained pressure. For the numerical study, the experimental study on the column was used, and the failure shape and behavior characteristics of the experimental results and the numerical results were compared. As a result of the numerical study, the ductile behavior of the RC columns occurred according to the strength of the surface constraining stress. In addition, ductile behavior occurred almost constant above a certain surface constrained pressure. Compared with the numerical results and the experimental results, he reinforcing effect of the used seismic reinforcement of the column in experimental study was compared with the value of the surface constrained pressure for the RC column, and the seismic reinforcing effect was examined as the surface constrained pressure value for the RC column. In conclusion, in this work, surface constrained stress and constrained strength for ductile behavior of RC columns are derived. Based on the results derived, it is believed that it can be used as basic data on the review of seismic design methods and seismic performance complementary effects using ductile behavior induction of RC columns.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.549-552
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• 2009

본 논문에서는 재료적 성능이 우수하며 경량재료로서 최근 건설구조물에 활용하고자 하는 연구가 활발히 진행되고 있는 섬유보강재료(FRP : Fiber Reinforced Polymer)를 이용한 합성구조인 CFFT(Concrete Filled FRP Tube)의 설계프로그램을 개발하여 제안하고자 하였다. 먼저, CFFT구조는 FRP관에 의해 철근콘크리트가 구속되는 구조로서 기둥과 같이 축력이 도입되는 경우 포아송효과에 의한 변형을 FRP관이 구속효과를 줌으로써 콘크리트의 역학적 거동을 개선하게 되는데 본 연구에서는 실험에 의해 검증된 식을 제시하였으며 이를 바탕으로 CFFT구조를 설계하는 알고리즘을 제안하였다. 또한 CFFT구조는 FRP관의 구속으로 인해 고강도콘크리트와 긴장재의 도입이 가능한 구조로서 이에 대한 설계도 포함하였다. 그러나 이방성재료인 FRP의 설계와 동시에 FRP관에 의한 구속효과를 고려하는 CFFT구조의 설계는 일반 실무설계자들에게는 다소 난해한 작업으로써 전산화 설계프로그램의 필요성이 대두되어 본 연구에서 CFFT구조의 설계프로그램을 개발하였다. 개발된 설계프로그램의 검증을 위해 일반 철근콘크리트기둥, CFFT기둥, 고강도콘크리트와 PS긴장재를 도입한 CFFT기둥을 설계한 결과, 매우 실용적이며 타당한 설계가 수행될 수 있음을 확인하였다.

• Journal of Navigation and Port Research
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• v.28 no.6
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• pp.469-474
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• 2004

In this paper, we study the posture control of an underwater vehicle with nonholonomic constraint. Generally, systems with nonholnomic constraints cannot be stabilized to an equilibrium points by smooth state feedback control. For the nonholonomic underwater vehicle system, we applied coordinate transformation to get multi-chained system We proposed non smooth feedback controller using backstepping method for stabilizing the multi chained form system Applying inverse input transformation to the non smooth feedback controller, we can get posture controller of the underwater vehicle with nonholonomic constraint. The proposed control scheme is applied to the posture control qf an underwater vehicle and verified the effectiveness of control strategy by numerical simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.333-338
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• 2007

An infernally confined hollow reinforced concrete pier (ICH RC pier) is hollow RC pier which has a internal steel tube to enhance its ductility and stiffness by internal confinement. In this study, the internal steel tube were changed to investigate the behavior of ICH RC pier. The behavior of internally confined hollow reinforced concrete piers were evaluated with safety ratio, ductility, total material cost, the total weight of the pier, etc. As a result of analytical study, the usage of a minimum necessary thickness of the internal steel tube the most effective. The ICH RC pier has decrease of weight compare to Solid RC pier.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.8
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• pp.102-106
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• 2007

To apply the flux-lock type superconducting fault current limiter(SFCL) into power system, its current and voltage ratings are required to increase. Especially, in case of series connection of SFCLs, the countermeasure for simultaneous quenches must be considered. The structure, which each flux-lock type SFCL unit was wound in series on the same iron core, can induce the simultaneous quench of superconducting elements. Through the fault current limiting experiment for the suggested structure, it was confirmed that the even voltage burden among the superconducting elements comprising SFCLs could be made.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.11
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• pp.911-918
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• 2014

In this paper, a selective activation strategy of cohesive elements using user subroutine UMPC was studied as an efficient solution for the added compliance problem in cohesive zone model crack propagation analyses. The cohesive elements were inserted between every bulk elements in region where cracks were expected to initiate and propagate, but initially not activated by tying the cohesive nodes using multi-point constraints. During analyses, the cohesive elements for which specified criterion was met were selectively activated by releasing the constraints. The effect of initial cohesive stiffness and the release criterion on the crack propagation behavior was carefully investigated.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.311-320
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• 2009

This paper presents the experimental results of an experiment on the current rectangular CFT columns and rectangular CFT columns additionally confined by carbon fiber sheets(CFS) under axial loading. The main experimental parameters were the layer numbers of the CFS and the depth-to-thickness ratio. Nine specimens were prepared according to the experimental parameter plans, and axial compression tests were conducted. From the tests, the failure procedure, the load-axial deformation curve, the maximum axial strength, and the deformation capacity of the CFT columns and the confined CFT columns were compared. Finally, it was seen that the maximum axial strengths of the CFT increased more significantly than that of the current CFT columns because of delayed local buckling.