• Ocean Systems Engineering
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• 제2권1호
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• pp.69-81
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• 2012

Presented herein is a study on reducing the hydroelastic response of very large floating structures (VLFS) by altering their plan shapes. Two different categories of VLFS geometries are considered. The first category comprises longish VLFSs with different fore/aft end shapes but keeping their aspect ratios constant. The second category comprises various polygonal VLFS plan shapes that are confined within a square boundary or a circle. For the hydroelastic analysis, the water is modeled as an ideal fluid and its motion is assumed to be irrotational so that a velocity potential exists. The VLFS is modeled as a plate by adopting the Mindlin plate theory. The VLFS is assumed to be placed in a channel or river so that only the head sea condition is considered. The results show that the hydroleastic response of the VLFS could be significantly reduced by altering its plan shape.

• 농촌계획
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• 제17권1호
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• pp.13-27
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• 2011

This study analyzed the budget investment plans for the unit-project items(UPI) of 176 project districts for the rural village comprehensive development projects (RVCDP). This study classified the master plan reports of 176 project districts into 88 unit project items in aspect of project management, in order to analyze characteristics of distribution of budget in each project item. Most of all unit project items have similar types of uniform distribution with plus skewness in frequency pattern analysis except the total budget of the project district. This study analyzed the characteristics of budget distribution per province, year, and geographical types of region. Furthermore this paper also analyzed ratio of budget in unit project items to find out distribution pattern of each budget between project items over time. The hierarchical system for UPI of RVCDP consisted of three steps, which are 4 items of the first step on Strength of Rural-urban Exchange & Regional Capability (RURC), Green-income Infrastructure & Facility (GIF), Culture- health-welfare Facility, and Eco-environment & Landscape facility (ELF), 13 items for the second one, and 52 items for the third project items. From the results of the budget investment analysis for 5 years from 2004 to 2008, the budget investment ratios of RURC and ELF have steady state for every year, while GIF in decreasing and ELF in increasing over time. The ratios of UPI on infrastructure were decreased, whereas those on culture, health, and welfare were increased. Portion of tow project items among 52 items, which are community centers for village residents and rural experimental study facility, has 30% of total budget investment. Futhermore, the budget ratios of seven project items showed 50% of total budget. Average value of project budgets for five years was optimized as a type of exponential function in the case of decent array for ranking order.

• Structural Engineering and Mechanics
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• 제77권4호
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• pp.463-472
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• 2021

Fully rigid floor diaphragm is one of the main assumptions that are widely used in common practices due to its simple application. However, determining the exact degree of diaphragms flexibility cannot be easily accomplished without finite element modeling, which is an expensive and time-consuming procedure. Therefore, it is always possible that apparently rigid diaphragms, based on prescriptive limitations of seismic codes, experience some degrees of flexibility during the earthquakes. Since diaphragm flexibility has more uncertainties in asymmetric-plan structures, this study focuses on errors resulting from probable floor diaphragm flexibility of torsionally restrained structures. The analytical models used in this study were single-story buildings with asymmetric plan and RC shear walls. Although floor system is not considered explicitly, a wide range of considered diaphragm flexibility, from fully rigid to quite flexible, allows the results to be generalizable to a lot of lateral load resisting systems as well as floor systems. It has been shown that in addition to previously known effects of diaphragm flexibility, presence of orthogonal side elements during design procedure with rigid diaphragm assumption and rapid reduction in their absorbed forces can also be an important source to increase errors due to flexibility. Accordingly, from the obtained results the authors suggest designers to consider the possibility of diaphragm flexibility and its adverse effects, especially in torsionally restrained systems in their common designs.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.403-408
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• 2003

The objective of this study is to understand the variables affected the confinement for the transverse reinforcement of the reinforced concrete structural walls with the T-shaped cross section subjected to cyclic lateral loads. The structural performance of T-shaped walls was advanced by the transverse reinforcement which restrained the concrete subjected to compressive stress. If the arrangement of transverse reinforcement was not suitable for the confinement, T-shaped walls happened the brittle failure by web crushing or bucking of vertical reinforcement at the compression zone. It is necessary to confine transverse reinforcement in order to prevent the these failure. But the location of neutral axis and the magnitude of ultimate strain vary according to the section shape, a ratio of axial load, a ratio of wall cross sectional area to the floor-plan area, an aspect ratio and the reinforcement ratio. Therefore, the objective of this research is to grasp the location of neutral axis and the range which needs for the confinement of transverse reinforcement through the results of the sectional analysis which varies the ratio of axial load and the ratio of vertical reinforcement.

• Wind and Structures
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• 제29권3호
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• pp.209-223
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• 2019

The assessment of wind-induced vibration for tall reinforced concrete (RC) buildings requires the accurate estimation of their dynamic properties, e.g., the fundamental vibration periods and damping ratios. In this study, RC frame-shear wall systems designed under gravity and wind loadings have been evaluated by utilising 3D FE modelling incorporating eigen-analysis to obtain the elastic periods of vibration. The conducted parameters consist of the number of storeys, the plan aspect ratio (AR) of buildings, the core dimensions, the space efficiency (SE), and the leasing depth (LD) between the internal central core and outer frames. This analysis provides a reliable basis for further investigating the effects of these parameters and establishing new formulas for predicting the fundamental vibration periods by using regression analyses on the obtained results. The proposed constrained numerically based formula for vibration periods of tall RC frame-shear wall office buildings in terms of the height of buildings reasonably agrees with some cited formulas for vibration period from design codes and standards. However, the same proposed formula has a high discrepancy with other cited formulas from the rest of design codes and standards. Also, the proposed formula agrees well with some cited experimentally based formulas.

• 한국조경학회지
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• 제52권2호
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• pp.21-38
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• 2024

본 연구는 문헌 고찰을 통해 도시 열환경 개선 및 보행자 열쾌적성 증대를 위한 효율적인 가로녹지 조성방안을 제안하는 것이 목적이다. 특히, 녹지 계획 및 설계에 활용가능한 매개변수를 도출하고, 매개변수별로 열환경 완화 매커니즘을 분석한 후, 이를 바탕으로 녹지 계획 및 설계 시 활용가능한 수종선택 방법 및 녹지조성 방법을 제안하였다. 이를 위해 국내외 관련 논문 중 4단계 과정을 통해 고찰하고자 하는 61개의 논문을 선정하였으며, 선정된 논문을 분석하여 다음과 같은 주요 결과를 도출하였다. 열스트레스가 높은 종횡비 낮고 천공률이 높은 오픈된 거리협곡의 경우, 그늘의 양과 질을 높이기 위해 수관폭이 넓고, 수고가 높고, 지하고가 낮고, 엽면적 지수가 높고, 수관의 녹량이 많은 활엽수를 다열의 좁은 간격으로 다층식재하는 것이 열저감에 효과적이다. 반면 열스트레스가 비교적 적은 종횡비가 높고 천공률이 낮은 깊고 좁은 거리협곡의 경우, 거리협곡 내 환기력을 높이기 위해 수관폭이 좁고, 지하고가 높고, 수관높이가 낮고, 엽면적 지수가 낮은 활엽수를 넓은 간격으로 식재하는 것이 열저감에 효과적이다. 본 연구는 거리협곡 내 열환경 개선 및 보행자 열쾌적성 증대를 위한 가로녹지 조성의 기초자료로 활용할 수 있으며, 녹지의 위치 선정 및 우선순위 선정 시 기초자료로 활용할 수 있다. 나아가 기후변화 대응을 위한 녹지 계획 및 설계를 위한 가이드라인 작성 시 기초자료로 활용될 수 있을 것으로 기대한다.

• Structural Engineering and Mechanics
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• 제91권5호
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• pp.487-502
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• 2024

This study introduces a novel 'multi-mushroom' structural system designed to improve seismic performance in lowrise buildings. Traditional low-rise structures tend to favor sliding over rocking due to their smaller aspect ratios despite the rocking system's superior seismic response reduction. Rocking designs allow structures to pivot at their base during seismic events, reducing damage by dissipating energy. The proposed multi-mushroom system divides the building into four equal sections with small gaps in between, each capable of independent rocking. Numerical analyses are conducted using scaled earthquake records from far- and near-source events to evaluate this system's performance. The results indicated that the multimushroom system significantly reduces plastic hinge formation compared to conventional designs. The system also demonstrated enhanced beam performance and a robust base girder, contributing to reduced collapse vulnerability. The 3-story model exhibited the most favorable behavior, effectively mitigating peak roof drift values, where the rocking system achieved a 21% reduction in mean roof displacement for near-field records and 15% for far-field records. However, the 5-story configuration showed increased roof displacement, and the 7-story model recorded higher incidences of collapse prevention (CP) hinges, indicating areas for further optimization. Overall, the multi-mushroom system enhances seismic resilience by minimizing plastic hinge formation and improving structural integrity. While the system shows significant promise for low-rise buildings, challenges related to roof displacement and inter-story drift ratio in taller structures necessitate further research. These findings suggest that the multi-mushroom system offers a viable solution for seismic risk reduction, contributing to safer and more sustainable urban development in earthquake-prone areas.

• 콘크리트학회논문집
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• 제14권6호
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• pp.1001-1009
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• 2002

본 연구는 반복 수평하중을 받는 철근 콘크리트 T형 벽체의 횡철근의 구속범위를 제안하기 위한 것이다. 횡철근의 구속범위는 압축과 인장변형율 분포에 의해 좌우되는 중립축을 기준으로 압축변형율과 콘크리트 극한 변형율의 분포에 따라 결정된다. 압축변형율은 바닥층 평면적에 대한 벽 단면비, 형상비, 단면형상, 압축력, 그리고 철근비 등에 따라 다르게 나타난다. T형 벽체의 중립축은 플랜지의 영향으로 정가력과 부가력이 다르게 나타나며, T형 벽체의 중립축이 직사각형 벽체와 다르기 때문에 압축콘크리트를 구속하여 주는 횡철근의 구속범위가 다르게 나타날 것으로 판단된다. 또한, 좌우 대칭으로 배근되는 직사각형 벽체는 반복적인 수평하중에 대해 좌우 대칭인 구조적 특성을 나타내지만, T형 벽체의 경우는 좌우 비대칭적인 구조적 특성을 보인다. 즉, 복부 단부가 압축을 받는 정가력인 경우, 중립축 깊이(c)가 직사각형 벽체보다 크게 나타나며, 복부 단부가 인장을 받는 부가력인 경우, 중립축 깊이(c)가 직사각형 벽체보다 작게 나타난다. 그러므로, T형 벽체를 직사각형 벽체로 가정하여 좌우대칭으로 횡철근을 구속할 경우, 압축을 받는 복부 단부에서 요구되는 횡철근의 구속범위가 증가할 것으로 판단된다 따라서, 본연구에서는 T형 벽체의 구조적 특성을 파악하고, 실험값과 기존분석 및 단면해석을 비교함으로써 T형 벽체의 중립축 깊이를 제시하였다.