• Smart Structures and Systems
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• 제30권5호
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• pp.463-477
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• 2022

In this paper, a hybrid vibration-impedance-based damage monitoring approach is experimentally evaluated for prestressed concrete (PSC) structures with local strand breakage. Firstly, the hybrid monitoring scheme is designed to alert damage occurrence from changes in vibration characteristics and to localize strand breakage from changes in impedance signatures. Secondly, a full-scale PSC anchorage is experimented to measure global vibration responses and local impedance responses under a sequence of simulated strand-breakage events. Finally, the measured data are analyzed using the hybrid monitoring framework. The change of structural condition (i.e., damage extent) induced by the local strand breakage is estimated by changes in a few natural frequencies obtained from a few accelerometers in the structure. The damaged strand is locally identified by tomography analysis of impedance features measured via an array of PZT (lead-zirconate-titanate) sensors mounted on the anchorage. Experimental results demonstrate that the strand breakage in the PSC structure can be accurately assessed by using the combined vibration and impedance features.

• 한국강구조학회 논문집
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• 제26권5호
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• pp.397-405
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• 2014

본 연구에서는 적층복합 T형 보의 휨 해석을 위해 전단에 유연한 보 요소를 제안한다. 1차 전단변형 보 이론을 사용해 유도된 보 요소는 ? 전단변형과 재료의 비등방성 성질에 따른 모든 연계성을 고려한다. 지배방정식의 해를 구하기 위해 절점 당 7개의 자유도를 갖는 2절점, 3절점, 4절점의 세 가지 보 요소를 제안한다. 제안된 보 요소의 활용성과 정확성을 검증하기 위해 등분포하중과 집중하중을 받는 대칭 및 역대칭 앵글프라이 복합 T형 보에 대해 수치해석을 수행한다. 다른 적층순서에 대해 화이버 각과 전단변형의 영향을 조사한다. 적층 복합 T형 보의 휨 해석에 대해 3절점과 4절점 보 요소의 유효성을 입증하였다.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2006년도 정기학술발표대회 논문집
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• pp.355-360
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• 2006

기능분석과 아이디어 창조과정수행은 동일한 VE job Plan을 적용하여 제조분야에서 단위 부위 및 요소별로 실시하고 있으며 건설 분야에서는 프로젝트의 프로세스, 규모, 공간, 위치, 단위요소, 요구성능 등 복합적이며 종합적인 기능을 가진 구조물에 적용하고 있다. 이에 따라 기능분석단계와 후속단계인 창조단계와의 비연속성 등의 문제가 있으나 이를 대체할 방법론이 아직 명확히 개발되어 있지 않아 건설에서 적용할 수 있는 고유의 모델 개발이 필요하다. VE워크샵 실무과정에서의 기능분석의 부적절한 적용 및 수행 VE적용의 부적합성을 해결하기 위해서 통합 기능계동도(FI FAST)와 계층적 컨셉모듈(HVECM)을 순차적으로 사용하여 선정된 1, 2차의 기능정의 Champion을 바탕으로 아이디어 창출이 연속적으로 원활하게 진행되도록 하는 모델을 개발하는데 목표를 두고 있다. 이를 위하여 기 수행되었던 사례에 대하여 본 모델에 의한 방법을 적용 ${\cdot}$ 검증함으로써 건설 분야에서 기능분석과 창조과정에서의 통합적이며 특정적인VE적용 가능성에 대하여 제안하고자 한다. 따라서 본 논문은 그 동안 국내에 적용된 VE수행 자료를 동해 기능분석과 아이디어 창조과정에서의 연계성을 검증하고, 기능분석단계에서의 복합기능분석과 HVECM의 활용모델에 대한 적합성 및 신뢰성을 검증, 성공적인 건설VE적용의 수행을 위한 발판이 되고자 한다.

• 한국가스학회지
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• 제6권4호
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• pp.1-7
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• 2002

인적 오류(human error)는 공장설비의 설계, 제작, 건설, 운전, 유지$\cdot$보수의 모든 단계에서 발생할 수 있으며 사고의 대부분이 인적 오류의 영향과 관계되어 있는 것으로 조사되고 있다. 본 연구에서는 현장의 작업자 행동 특성 및 오류 메커니즘을 확인하고, 평가분류 쉬트를 활용하여 공정에서 발생하는 인적 오류를 분석하였다. 또한 ASEP HRA 절차를 이용하여 인적 오류 확률(HEP) 산정 알고리즘을 구축하여 현장에서 쉽게 인적 오류를 분석할 수 있는 ASEP HEP 프로그램을 개발하였다. 이를 이용하여 화학공장에서의 가능한 인적 오류사고를 예방하고 보다 체계적인 인적 오류 방지대책을 수립할 수 있다고 판단된다.

• 전기학회논문지
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• 제57권2호
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• pp.155-163
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• 2008

This paper presents a novel framework for analysis of power system wide-area blackout based on so called fault cascading scenarios. For a given power system operating state, "triggering" faults or a "seed faults" are chosen based on the probabilities estimated from the hazard rates. The fault probabilities reflect both the load and the weather conditions. Effects of hidden failures in protection systems are also reflected in establishing the fault propagation scenarios since they are one of the major causes for the wide-area blackouts. A tree type data structure called a PS-BEST(Power System Blackout Event Scenario Tree) is proposed for construction of the fault cascading scenarios, in which nodes represent various power system operating states and the arcs are the events causing transitions between the states. Arcs can be either probabilistic or deterministic. For a given initial fault, the total probability of leading to wide-area blackout is estimated by aggregating the individual probability of each fault sequence route leading to wide-area blackout. A case study is performed on the IEEE RTS-79(24 bus) system based on the fault data presented by the North American Electrical Reliability Council(NERC). Test results demonstrate the potentials and the effectiveness of the proposed technique for the future wide-area blackout analysis.

• BMB Reports
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• 제37권5호
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• pp.527-532
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• 2004

A subtracted cDNA library specific to osmotic stress of Haloxylon ammodendron (Mey.) Bge seedlings was constructed by suppression subtractive hybridization (SSH) and T/A cloning. SSH was performed between two groups of H. ammodendron seedlings, one was cultivated in Hoagland (H) solution as a driver and the other group was treated with osmotic stress of the Hoagland solution by the addition of 400 mM mannitol (M), as a tester. The library consisted of about 400 recombinant clones, with the average size being of 500 bp, ranging from 300 bp to 1500 bp. Using a PCR-select differential screening kit, 100 recombinant clones were randomly chosen from the subtracted cDNA library and hybridized with forward,reverse subtracted and unsubtracted probes for two rounds. As a result, 21 positive clones specific to osmotic stress were obtained and some of them were verified by Northern blot analysis. The sequencing analysis of 6 positive clones and the following homology comparison to GenBank [blastx] non-redundant databases characterized that two sequences obtained in this experiment may contribute to novel drought-related genes.

• Structural Engineering and Mechanics
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• 제28권6호
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• pp.695-713
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• 2008

The aim of this contribution is to present a new link/beam finite element suitable for electrothermo-structural analysis of uni-axially graded materials. Continuous polynomial variation of geometry and material properties will be considered. The element matrix and relations for solution of Joule's heat (and its distribution to the element nodes) have been established in the sense of a sequence method of a coupled problem solution. The expression for the solution of nodal forces caused by a continuously distributed temperature field has also been derived. The theoretical part of this contribution is completed by numerical validation, which proves the high accuracy and effectiveness of the proposed element. The results of the performed experiments are compared with those obtained using the more expensive multiphysical link element and solid element of the FEM program Ansys. The proposed finite element could be used not only in the multiphysical analysis of the current paths and actuators but also in analysis of other 1D construction parts made of composite or uni-axially graded materials.

• Geomechanics and Engineering
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• 제13권5호
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• pp.881-892
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• 2017

Design and management of concrete slabs in concrete-faced rock-fill dams are crucial issues for stability and overall dam safety since cracks in the concrete face induced by stress, shrinkage, and deterioration can cause severe leakage from the reservoir into the dam. Especially, the increase of dam height to a certain level to enhance the storage capacity and to improve hydraulic stability can lead to undesirable deformation behavior and stress distribution in the existing dam body and in the concrete slabs. In such conditions, simulation of a concrete slab with a numerical method should involve the use of an interface element because the behavior of the concrete slab does not follow the behavior of the dam body when the dam body settles due to the increase of dam height. However, the interfacial properties between the dam body and the concrete slab have yet to be clearly defined. In this study, construction sequence of a 125 m high CFRD in South Korea is simulated with commercial FDM software. The proper interfacial properties of the concrete slab are estimated based on a comparison to monitored vertical displacement history obtained from the concrete slab. Possibility of shear strength failure under the critical condition is investigated based on the simplified model. Results present the significance of the interfacial properties of the concrete slab.

• Advances in environmental research
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• 제9권2호
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• pp.109-121
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• 2020

Phenol is frequently present as the hazardous pollutant in petrochemical and pesticide industry wastewater. Because of its high toxicity and carcinogenic potential, a proper treatment is needed to reduce the hazards of phenol carrying effluent before being discharged into the environment. Phenol biodegradation with microbial consortium offers a very promising approach now a day's. This study focused on the formulation of phenol degrading bacterial consortium with three bacterial isolates. The bacterial strains Bacillus cereus strain VCRC B540, Bacillus cereus strain BRL02-43 and Oxalobacteraceae strain CC11D were isolated from detergent contaminated soil by soil enrichment technique and was identified by 16s rDNA sequence analysis. Individual cultures were degrade 100 μl phenol in 72 hrs. The formulated bacterial consortium was very effective in degrading 250 μl of phenol at a pH 7 with in 48 hrs. The study further focused on the analysis of the products of biodegradation with Fourier Transform Infrared Spectroscopy (FT/IR) and Gas Chromatography-Mass Spectroscopy (GC-MS). The analysis showed the complete degradation of phenol and the production of Benzene di-carboxylic acid mono (2-ethylhexyl) ester and Ethane 1,2- Diethoxy- as metabolic intermediates. Biodegradation with the aid of microorganisms is a potential approach in terms of cost-effectiveness and elimination of secondary pollutions. The present study established the efficiency of bacterial consortium to degrade phenol. Optimization of biodegradation conditions and construction of a bioreactor can be further exploited for large scale industrial applications.

• 한국강구조학회 논문집
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• 제27권1호
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• pp.43-52
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• 2015

구조물의 기둥은 층에 따라 받는 내력이 상이함에도 시공의 오차를 줄이고 구조설계의 편의를 위해 상부층부터 하부층의 기둥단면은 동일하게 설계되고 있다. 그럼에도 불가피하게 상하부의 기둥의 단면이 상이하는 경우가 발생된다. 예를들어 초고층 구조물 또는 증축 및 보수에 의해 기둥을 보강할 경우이다. 이렇듯. 선 기둥과 후 피복이 되는 기둥을 피복충전형 콘크리트 충전기둥이라 할 때, 가력조건이 다르므로 재하상태를 나뉘어 구조적 안정성을 확인할 필요가 있다. 그럼에도 국내외적으로 가력조건에 따른 합성기둥에 대한 내력과 변형연구는 전무한 상태에 있다. 따라서 본 연구에서는 구조실험을 통해 가력조건 및 콘크리트 강도, 피복두께 변화에 의한 피복충전형 콘크리트 각형 기둥의 내력과 거동을 분석하였다.