• 플랜트 저널
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• 제15권4호
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• pp.30-35
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• 2019

미세먼지 감축에 대한 사회적 요구 증가와 강화되는 대기오염물질 배출허용기준을 충족시키기 위해 구조적 제약조건을 갖는 500 MW급 석탄화력발전소 탈황설비의 성능개선 방안을 제시하였다. 탈황설비 흡수탑을 통과하는 배기가스가 선회하도록 내부 설비를 개조하여 난류를 형성시켜 물질전달효율을 증가시키고 반응 면적 및 시간을 증가시킴으로써 황산화물 저감 및 먼지 포집 능력을 향상시킬 수 있었다. 개선결과 황산화물 제거효율은 91.61%에서 98.43%로 향상되었고 먼지 제거성능은 77.4%에서 87.08%로 향상되었다. 배출농도는 황산화물 7.85 ppm, 먼지 4.67 mg/㎥이 배출되어 2023년의 대기오염물질 배출허용기준인 황산화물 25 ppm, 먼지 5 mg/㎥을 만족하는 수준이다. 본 연구의 성능 개선 방식은 유사한 제약조건을 갖는 다른 석탄화력발전소에도 효과적으로 적용될 수 있으리라 기대된다.

• 한국구조물진단유지관리공학회지
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• 제18권1호
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• pp.42-48
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• 2014

• 한국구조물진단유지관리공학회지
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• 제20권4호
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• pp.15-20
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• 2016

• Nuclear Engineering and Technology
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• 제39권6호
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• pp.737-746
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• 2007

A spacer grid, which is one of the most important structural components in a PWR fuel assembly, supports its fuel rods laterally and vertically. Based on in-house design experience, scrutiny of the design features of advanced nuclear fuels and the patents of other spacer grids, KAERI has devised its own spacer grid shapes and acquired patents. In this study, a performance evaluation of KAERI's spacer grid shapes was carried out from mechanical/structural and thermohydraulic view points. A comparative performance evaluation of commercial spacer grid shapes was also carried out. The comparisons addressed the spring characteristics, fuel rod vibration characteristics, fretting wear resistance, impact strength characteristics, CHF enhancement, and the pressure drop level of the spacer grid shapes. The results show that the performances of KAERI's spacer grid shapes are as good as or better than those of the commercial spacer grid shapes.

• 국제초고층학회논문집
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• 제1권3호
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• pp.195-201
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• 2012

Today, a great effort to develop PBSD procedure to be utilized in Korea is given by domestic structural engineers, academics, and governmental organizations. After Great East Japan Earthquake (2011) took place, lots of clients in Korea became to concern of their buildings so that requests of seismic performance evaluation and seismic rehabilitation for existing buildings have been gradually increased. Such interests in seismic events initiated a rapid development of a series of guidelines for seismic performance evaluation and seismic performance enhancement. For new buildings, however, design guidelines for PBSD are yet well prepared in Korea and prescriptive design methods are dominant design procedure still. Herein, seismicity demands used in seismic performance evaluation and some important design parameters in NLRH are introduced. Some project examples for seismic performance evaluation and rehabilitation applying passive energy dissipation devices are also described in the latter part of paper.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제18권3호
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• pp.51-59
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• 2012

Over a past century, the continuity in post-earthquake serviceability of medical facilities has been demonstrated to be essential for sustaining a society and/or a nation stable. However, not many countries including Korea have paid appropriate attention to such a lesson learned from the previous experiences of the countries located in high seismicity for various reasons, one of which may be the lack of social consensus in allocating a portion of the resources to the earthquake preparedness. As a result, an earthquake-related policy might have been pushed away out of the list of priority in the government agenda. Therefore, the present paper attempts to persuade the public general, experts and government officials together to seek a way to upgrade the seismic safety of the country a step forward by enhancing the seismic performance of medical facilities. For this the framework of seismic design codes and standards for medical facilities, and Californian experience in managing the seismic performance enhancement program and U.S.-Italian collaborative study to improve the seismic safety of Italian hospitals are reviewed. Finally, a list of further researches and practices to perform for seismic enhancement of medical facilities in Korea are suggested.

• Advances in concrete construction
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• 제5권3호
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• pp.201-219
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• 2017

With the rapid growth in construction sector, it becomes all the more important to assess the amount of Construction and Demolition (C&D) waste being generated and analyze the practices needed to handle and use this waste before final disposal. This serves waste management and disposal issues, paving way to waste utilization in construction industry from the sustainability point of view. C&D waste constitutes a major bulk of total solid waste produced in the world. In this work, an attempt is made to study the performance of concrete using water soaked Recycled Coarse Aggregates (RCA) in replacement levels of 0%, 25%, 50%, 75% and 100% to Natural Coarse Aggregates (NCA). Experiments were designed and conducted to study the performance of RCA based concrete. Further suitable performance enhancement techniques to RCA based concrete were attempted, to achieve compressive strength at least equal to or more than that for no RCA based concrete (control concrete). Performance enhancement study is reported here for 50% and 100% RCA based concretes. All four techniques attempted have given favorable results encouraging use of RCA based concretes with full replacement levels, to adopt RCA based concrete in structural applications, without any kind of concern to the stake holder. Further attempts have also been made to use Recycled Fine Aggregates (RFA) with appropriate modifications to serve as fine aggregates in mortar and concrete. Using RFA blended with river sand fractions as well as RFA with Iron Ore Tailings (IOT) fractions, have given good results to serve as fine aggregates to the extent of 100% replacement levels in mortars and concretes.

• 한국멀티미디어학회논문지
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• 제19권8호
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• pp.1248-1259
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• 2016

Classification methods based on dual energy X-ray absorptiometry, ultrasonic waves, and quantitative computed tomography have been proposed. Also, a classification method based on machine learning with bone mineral density and structural indicators extracted from the CT images has been proposed. We propose a method which enhances the performance of existing classification method based on bone mineral density and structural indicators by extending structural indicators and using principal component analysis. Experimental result shows that the proposed method in this paper improves the correctness of osteoporosis classification 2.8% with extended structural indicators only and 4.8% with both extended structural indicators and principal component analysis. In addition, this paper proposes a method of automatic phantom analysis needed to convert the CT values to BMD values. While existing method requires manual operation to mark the bone region within the phantom, the proposed method detects the bone region automatically by detecting circles in the CT image. The proposed method and the existing method gave the same conversion formula for converting CT value to bone mineral density.

• 한국지진공학회논문집
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• 제20권7_spc호
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• pp.509-516
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• 2016

Secure operation of hospitals during and right after earthquake is essential. Past lessons from earthquake damages have shown that most of the injured and the death occurred within 30 minutes after earthquake and the portion of nonstructural damage has become significant. However, hospital buildings in Korea have not prepared fully to address such rising issues. This paper is to study what type of damage patterns are related to hospital buildings and how to develop a preparedness plan to keep hospitals operational at all earthquakes if possible. This paper first reviews on past earthquake damages reported as critical to hospital buildings while classifying them into four groups: (1) structural element; (2) architectural-nostructural element; (3) medical equipments and contents; and (4) utility facility. Upon such classification, some detailed concerns can be specified under each group explicitly. Then a hierarchy for hospital building is also developed for the classified groups, which enables us to identify required things for the enhancement of seismic performance of hospital building that consists of heterogeneous elements. To upgrade the level of seismic performance for existing hospital buildings, the concept of performance-based approach can be adopted to address the heterogeneous problems in a systematic and stepwise manner. Finally a conceptual framework for the seismic risk assessment for hospital building is proposed toward the seismic enhancement of hospital buildings using performance-based approach.

• Structural Engineering and Mechanics
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• 제73권5호
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• pp.487-500
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• 2020

Stiffeners can be utilised to enhance the strength of thin-walled wind turbine towers in engineering practise, thus, structural performance of wind turbine towers by means of different stiffening schemes should be compared to explore the optimal structural enhancement method. In this paper two alternative stiffening methods, employing horizontal or vertical stiffeners, for steel tubular wind turbine towers have been studied. In particular, two groups of three wind turbine towers of 50m, 150m and 250m in height, stiffened by horizontal rings and vertical strips respectively, were analysed by using FEM software of ABAQUS. For each height level tower, the mass of the stiffening rings is equal to that of vertical stiffeners each other. The maximum von Mises stresses and horizontal sways of these towers with vertical stiffeners is compared with the corresponding ring-stiffened towers. A linear buckling analysis is conducted to study the buckling modes and critical buckling loads of the three height levels of tower. The buckling modes and eigenvalues of the 50m, 150m and 250m vertically stiffened towers were also compared with those of the horizontally stiffened towers. The numbers and central angles of the vertical stiffeners are considered as design variables to study the effect of vertical stiffeners on the structural performance of wind turbine towers. Following an extensive parametric study, these strengthening techniques were compared with each other and it is obtained that the use of vertical stiffeners is a more efficient approach to enhance the stability and strength of intermediate and high towers than the use of horizontal rings.