• Steel and Composite Structures
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• 제1권3호
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• pp.295-312
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• 2001

The purpose of this paper is to propose a new type of steel reinforced concrete (SRC) beam-column joints and to examine the structural performance of the proposed joints, which simplify the construction procedure of steel fabrication, welding works, concrete casting and joint strengthening. In the proposed beam-column joints, the steel element of columns forms continuously built-in crossing of H-sections (${\Box}$), with adjacent flanges of column being connected by horizontal stiffeners in a joint at the level of the beam flanges. In addition, simplified lateral reinforcement (${\Box}$) is adopted in a joint to confine the longitudinal reinforcing bars in columns. Experimental and analytical studies have been carried out to estimate the structural performance of the proposed joints. Twelve cruciform specimens and seven SRC beam-column subassemblage specimens were prepared and tested. The following can be concluded from this study: (1) SRC subassemblages with the proposed beam-column joints show adequate seismic performances which are superior to the demand of the current code; (2) The yield and ultimate strength capacities of the beam-to-column connections can be estimated by analysis based on the yield line theory; (3) The skeleton curves and the ultimate shear capacities of the beam-column joint panel are predicted with a fair degree of accuracy by considering a simple stress transfer mechanism.

• 아동학회지
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• 제37권6호
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• pp.133-144
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• 2016

Objective: The purpose of this study was to identify the mediation effect of value of children in the relationship between maternal parenting stress and ideal number of children and to verify whether perception of the adequacy of national public childcare facilities moderates this mediation relationship. Methods: For the analysis, the 6th year results (2013) from the Panel Study on Korean Children by the Korean Institute of Child Care and Education were used. The main subjects of the study were 1,611 mothers with children aged 60 - 66 months. Results: First, there was a partial mediation effect of mother's parenting stress influencing the ideal number of children through the value of children. Second, the enhancing effect of the perception of the adequacy of national public childcare facilities moderating the value of children and ideal number of children was verified. Third, perception of the adequacy of national public childcare facilities had enforcing effects moderating the value of children and ideal number of children and mediation effects moderating the influence of maternal parenting stress on ideal number of children through the value of children. Conclusion: Based on the results, it was confirmed that the expansion of national public childcare facilities is a factor strengthening the maternal intention of birth.

• Journal of Preventive Medicine and Public Health
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• 제40권6호
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• pp.495-504
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• 2007

Objectives : This study attempts to show how studies using non-experimental data can strengthen causal inferences by applying propensity score and instrumental variable methods based on the counterfactual framework. For illustrative purposes, we examine the effect of having private health insurance on the probability of experiencing at least one hospital admission in the previous year. Methods : Using data from the 4th wave of the Korea Labor and Income Panel Study, we compared the results obtained using propensity score and instrumental variable methods with those from conventional logistic and linear regression models, respectively. Results : While conventional multiple regression analyses fail to identify the effect, the results estimated using propensity score and instrumental variable methods suggest that having private health insurance has positive and statistically significant effects on hospital admission. Conclusions : This study demonstrates that propensity score and instrumental variable methods provide potentially useful alternatives to conventional regression approaches in making causal inferences using non-experimental data.

• The Journal of Asian Finance, Economics and Business
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• 제9권7호
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• pp.109-121
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• 2022

The study aims to examine the interaction of formal and informal institutions for strengthening economic development, particularly entrepreneurship growth. The research will also assess the impact of control variables on political index within the formal and informal markets. The research is quantitative, which analyses panel data of 6 years in 22 countries comprising middle and high-income countries with diversified and unique political, economic, and social systems. The findings suggested that reducing the entry regulation and promoting the social capital within the formal and informal institutions would grow formal and informal entrepreneurship and be a greater source for new venture creation. Moreover, the political index, a control variable, was found significant in the relationship of institutional mix with formal and informal entrepreneurship. Entry regulations in formal and informal institutions are a complex phenomenon in the entrepreneurship literature, moderated by the political development index as tested by the current study. The time horizon for this paper is much longer since it analyzes 6 years (2014-2019) of data on 22 developing and developed countries to see the entrepreneurial growth across multiple regions on different income levels, geographic conditions, and contrasting political and social systems.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2022년도 추계학술대회
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• pp.9-9
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• 2022

The concept of food security has gained increasing attention during the food crisis period between 2006 and 2011. According to the FAO, food security is defined as an access by all people at all times to the food needed for healthy and active life. Achieving food security means that sufficient food is available, food supply is relatively stable, and those in need of food can afford food at a reasonable cost. After a short period of stable food prices the world is facing another food crisis due mainly to the COVID-19 pandemic and the Russian invasion over Ukraine. Food security has re-emerged as an urgent problem to the world. There have been two conflicting opinions about how to achieve food security. Agricultural exporting countries insist diversification of food sources and freer trade on the top of domestic self-reliance. On the other hand, food importing countries emphasize self-sufficiency of major food crops. This study investigates whether domestic agricultural production contributes to strengthening food security. The panel data analysis shows that the increase in food self-sufficiency raises the Global Food Security Index and lessens the probability of food riots, while lower import tariffs (implying freer trade) do not. Some related issues are discussed accordingly.

• 한국산학기술학회논문지
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• 제19권2호
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• pp.228-237
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• 2018

본 연구는 선행연구로부터 지역창조화 요인을 측정할 수 있는 지표를 개발하고, 우리나라 15개 시 도의 2008년부터 2012년까지 5년간의 지역창조화 균형패널자료를 구축하여 패널회귀분석법을 통해 지역창조화와 지역성장과의 관계를 실증분석하였다. 분석결과 첫째, 지역창조화 요인 중 기초자산 부문의 창조인력과 무형자산 영역, 경제주체 부문의 창조기업 영역, 지역공간 부문의 창조적 지역환경 영역, 핵심산업 부문의 융합산업과 창조산업은 GRDP(Gross Regional Domestic Product, 지역내총생산)와 의미있는 정(+)의 영향관계가 나타났다. 반면, 조직화 부문은 하위영역 모두 통계적으로 GRDP와 유의미한 영향관계를 확인할 수 없었다. 둘째, 지역창조화 요인 중 기초자산 부문의 창조인력과 조직화 부문의 창업과 기업가 정신 영역, 경제주체 부문의 창조기업 영역, 지역공간 부문, 핵심산업 부문의 융합산업 영역은 고용율과 의미있는 정(+)의 영향관계가 나타났다. 반면, 기초자산 부문의 유형 무형 창조자산 영역, 조직화 부문의 융합경영과 융합행정, 경제주체 부문의 대 중견 중소기업과 중앙정부 및 지자체 영역, 핵심산업 부문의 창조산업 영역은 고용율과 유의미한 영향관계를 확인할 수 없었다. 본 연구의 결과는 지역창조화를 위한 현황을 진단하고, 추진과정과 장단기성과를 점검하는데 시사점을 제공할 것이다. 또한, 중앙정부의 지방자치와 분권강화 정책을 견인할 수 있는 기초수단이 될 것이다.

• 한국강구조학회 논문집
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• 제29권6호
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• pp.411-422
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• 2017

본 연구에서는 콘크리트피복 원형충전강관 기둥을 적용한 합성구조 접합부의 거동특성과 내진성능을 평가하기 위하여, 기둥-플랜지 접합부에 대한 인장실험과 보-기둥 접합부에 대한 반복하중 실험을 수행하였다. 기둥-플랜지 인장실험은 피복콘크리트의 유무와 플랜지 폭, 인장철근 보강을 변수로 하여 5개의 실험체에 대하여 하중재하능력과 파괴모드를 분석하였다. 실험결과, 접합부에서의 플랜지 단부 폭을 200mm에서 350mm로 증가시킬 경우 연결부의 강도 및 강성이 각각 1.61배와 1.56배가 증가했고, 인장철근을 보강할 경우 추가적으로 강성과 강도가 각각 1.35배와 1.92배 증가했다. 접합부 반복하중 실험에서는 접합 상세를 변수로 3개의 외부접합부 실험체를 구성했다. 접합부 보강상세로는 인장철근 보강과 강관의 두께, 수직강판 보강을 고려하였다. 모든 접합부 실험체는 보에서 뚜렷한 휨항복이 발생하였으며 접합부의 손상은 제한적이었다. 특히, 강재보가 강관에 직접 용접되는 경우 보의 웨브를 통해서도 하중이 전달되기 때문에, 플랜지 인장실험 결과보다 보수적인 설계가 가능하며, 접합부 강관 두께를 증가시키거나 수직강판으로 보강한 경우에는 추가적으로 패널존의 전단내력이 증가하는 것으로 나타났다.

• 콘크리트학회논문집
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• 제16권4호
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• pp.493-500
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• 2004

FREP(Fiber Reinforced Epoxy Panel)는 고인장강도, 경량성, 내부식성 및 시공성 등의 우수한 성질을 가지고 있어 손상된 RC보의 보강에 이용되고 있다. 본 연구에서는 RE보에 대한 사용 전 휨보강의 경우와 사용 중 휨보강의 경우에 대한 구성방정식을 정립하여 그 차이를 규명하고, 보강재 단부의 응력집중으로 인해 발생하는 단부박리파괴(rip-off failure)의 역학적 특성을 밝힘으로써 휨보강 효과 성능을 평가하였다. 연구결과 FREP로 휨보강된 철근콘크리트 보의 지배적인 파괴모드는 단부박리파괴이며, 본 연구의 실험 및 해석조건을 기준으로 RC 보강보의 단부박리파괴에 대한 평가를 실시한 결과 FREP 보강두께의 과다로 인한 보강단부의 급격한 휨강성의 변화로 응력집중 현상이 발생하여 단부박리파괴가 생긴다는 것을 알 수 있었다. 이는 보강 설계 시 단부박리파괴에 대한 평가가 반드시 필요한 것을 의미한다. 또한 FREP의 보강시기에 따른 보강효과를 분석한 결과 사용 전 보강(I-Type)에 비해 사용 중 보강(P-Type)의 보강효과가 감소하는 것으로 나타났다. 따라서, 기존 구조물과 같이 사용 중인 구조물을 보강하는 경우에는 이미 작용하고 있는 보강전하중(응력)으로 인한 발생 응력을 보강설계 시 고려하여야 할 것으로 판단된다.

• 콘크리트학회논문집
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• 제18권1호
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• pp.73-82
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• 2006

최근까지의 거푸집 공법은 거푸집의 설치 및 탈형공정에 따른 공기연장, 인건비 상승에 따른 추가적인 비용소모, 거푸집 탈형후 발생되는 건설 폐자재로 인한 환경문제 유발 등의 직 간접적인 문제를 발생시켜 왔다. 따라서 본 연구에서는 이와 같은 문제점을 해결하고자 스테인레스 강섬유를 이용한 고성능 영구거푸집 공법에 대한 재료 및 구조적 거동특성을 분석하였다. 재료적 거동특성의 경우, 고성능 영구거푸집의 휨 거동에 있어 안정적인 연성거동 특성을 나타내었으며 후타설 콘크리트와의 부착성능도 우수한 것으로 나타났다. 구조적 거동특성의 경우, 고성능 영구거푸집의 압축단 및 인장단 거동특성이 분석되었으며 실험결과, 추가적인 보강성능 이외에 충분한 구조거동 특성을 발휘한 것으로 분석되었다.

• Earthquakes and Structures
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• 제12권2호
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• pp.237-250
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• 2017

There has been increasing attention in many countries on seismic retrofit of old fashioned RC structures in recent years. In such buildings, the joints lack transverse reinforcement and suffer inadequate seismic dimensional requirements and the reinforcement is plain bar. The behavior of the joints is governed by sliding of steel bars and diagonal shear failure is less influential. Different methods to retrofit beam-column joints have been proposed in the literature such as wrapping the joint by FRP sheets, enlargement of the beam-column joint, and strengthening the joint by steel sheets. In this study, an enlargement technique that uses external prestressed cross ties with steel angles is examined. The technique has already been used for substructures reinforced by deformed bars and has advantages such as efficient enhancement of seismic capacity and lack of damage to the joint. Three reference specimens and two retrofitted units are tested under increasing lateral cyclic load in combination with two levels of axial load. The reference specimens showed relatively low shear strength of 0.150${\surd}$($f_c$) and 0.30${\surd}$($f_c$) for the exterior and interior joints, respectively. In addition, relatively brittle behavior was observed and large deformations extended into the panel zone of the joints. The retrofit method has increased ductility ratio of the interior beam-column joints by 63%, and energy dissipation capacity by 77%, relative to the control specimen; For external joints, these values were 11%, and 94%. The retrofit method has successfully relocated the plastic joints far from the column face. The retrofit method has improved shear strength of the joints by less than 10%.