• Steel and Composite Structures
• /
• 제30권2호
• /
• pp.185-199
• /
• 2019

Modular construction is an emerging technology to accommodate the increasing restrictions in terms of construction period, energy efficiency and environmental impacts, since each structural module is prefabricated offsite beforehand and assembled onsite using industrialized techniques. However, some innate structural drawbacks of this innovative method are also distinct, such as connection tying inaccessibility, column instability and system robustness. This study aims to explore the theoretical and numerical stability analysis of a tenon-connected square hollow section (SHS) steel column to address the tying and stability issue in modular construction. Due to the excellent performance of composite structures in fire resistance and buckling prevention, concrete-filled steel tube (CFST) columns are also taken into account in the analysis to evaluate the feasibility of adopting composite sections in modular buildings. Characteristic equations with three variables, i.e., the length ratio, the bending stiffness ratio and the rotational stiffness ratio, are generated from the fourth-order governing differential equations. The rotational stiffness ratio is recognized as the most significant factor, with interval analysis conducted for its mechanical significance and domain. Numerical analysis using ABAQUS is conducted for validation of characteristic equations. Recommendations and instructions in predicting the buckling performance of both SHS and CFST columns are then proposed.

• Structural Engineering and Mechanics
• /
• 제77권6호
• /
• pp.705-720
• /
• 2021

Reinforced concrete (RC) columns are the primary type of vertical support used in building structures that sustain vertical loads. However, their strength may be insufficient due to fire, earthquake or volatile environments. The load demand may be increased due to new functional usages of the structure. The deformability of concrete columns can be greatly reduced under high axial load conditions. In response, a novel steel encasement that distinguishes from the traditional steel jacketing that is assembled by welding or bolt is developed. This novel strengthening method features easy installation and quick strengthening because direct fastening is used to connect the four steel plates surrounding the column. This new connection method is usually used to quickly and stably connect two steel components by driving high strength fastener into the steel components. The connections together with the steel plates behave like transverse reinforcement, which can provide passive confinement to the concrete. The confined column along with the steel plates resist the axial load. By this way, the axial load capacity and deformability of the column can be enhanced. Eight columns are tested to examine the reliability and effectiveness of the proposed method. The effects of the vertical spacing between adjacent connections, thickness of the steel plate and number of fasteners in each connection are studied to identify the critical parameters which affect the load bearing performance and deformation behavior. Lastly, a theoretical model is proposed for predicting the axial load capacity of the strengthened RC columns.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2023년도 봄 학술논문 발표대회
• /
• pp.83-84
• /
• 2023

Wall structure smart modular is a building construction method where modules are manufactured in a factory and assembled on-site. This method is gaining popularity in the construction industry as it reduces construction time and mitigates risks such as material supply and labor costs. Wall structure smart modular is necessary as it provides comfortable temporary classroom space during renovation and remodeling of aging school buildings. The structure and characteristics of each type of temporary classroom modular were compared, and wall structure modular showed superior performance in terms of height and weight competitiveness compared to mixed structures. With these advantages, wall structure modular can ensure economic efficiency and recyclability as a temporary classroom. In the future, we aim to compare and analyze the standards such as inter-floor noise and heat transfer coefficient for wall structure and mixed structures.

• Steel and Composite Structures
• /
• 제37권3호
• /
• pp.273-289
• /
• 2020

Due to the unique construction method of modular steel buildings (MSBs) with units prefabricated fully off the site and assembled quickly on the site, the inter-module connection for easy operation and overall performance of the system were key issues. However, it was a lack of relevant research on the system-level performance of MSBs. This study investigated the seismic performance of two-storey modular steel structure with a proposed vertical rotary inter-module connection. Three full-scale quasi-static tests, with and without corrugated steel plate and its combination, were carried out to evaluate and compare their seismic behaviour. The hysteretic performance, skeleton curves, ductile performance, stiffness degradation, energy dissipation capacity, and deformation pattern were clarified. The results showed that good ductility and plastic deformation ability of such modular steel structures. Two lateral-force resistance mechanisms with different layout combinations were also discussed in detail. The corrugated steel plate could significantly improve the lateral stiffness and bearing capacity of the modular steel structure. The cooperative working mechanism of modules and inter-module connections was further analyzed. When the lateral stiffness of upper and lower modular structures was close, limited bending moment transfer may be considered for the inter-module connection. While a large lateral stiffness difference existed initially between the upper and lower structures, an obvious gap occurred at the inter-module connection, and this gap may significantly influence the bending moments transferred by the inter-module connections. Meanwhile, several design recommendations of inter-module connections were also given for the application of MSBs.

• 청정기술
• /
• 제19권1호
• /
• pp.22-29
• /
• 2013

본 연구는 염료감응형 태양전지의 구성요소 중 핵심 소재로 주목받고 있는 티타니아($TiO_2$) 나노입자의 크기와 결정구조에 따른 광전 효율을 비교하고자 하였다. 나노입자의 크기는 용매열법(solvothermal method)을 이용하여 출발 용액의 pH를 조절하고 결정구조의 차이는 솔-젤법에 의해 얻어진 무정형의 티타니아를 온도를 달리하여 소성함으로써 조절되었다. 그 결과, 용매법으로는 8.9, 12.8 그리고 20.2 nm의 크기를 가지는 세 종류의 아나타제 티타니아를, 솔-젤법으로는 세 종류의 아나타제-루타일(anatase-rutile) 혼합결정구조를 가지는 티타니아를 얻었다. 여섯 종류의 샘플 중 20.2 nm 크기의 아나타제 결정구조의 티타니아를 광 전극으로 사용한 염료감응형 태양전지 단위 셀에서 8.6%로 가장 좋은 광전 효율을 얻었다.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2004년도 학술대회지
• /
• pp.90-98
• /
• 2004

Nano/micro-scale studies on friction properties were conducted on Si (100) and three self-assembled monolayers (SAMs) (PFOTC, DMDM, DPDM) coated on Si-wafer by chemical vapor deposition technique. Experiments were conducted at ambient temperature $(24{\pm}1^{\circ}C)$ and humidity $(45{\pm}5\%)$. Nano-friction was evaluated using Atomic Force Microscopy (AFM) in the range of 0-40nN normal loads. In both Si-wafer and SAMs, friction increased linearly as a function of applied normal load. Results showed that friction was affected by the inherent adhesion in Si-wafer, and in the case of SAMs the physical/chemical structures had a major influence. Coefficient of friction of these test samples was also evaluated at the micro-scale using a micro-tribotester. It was observed that SAMs had superior frictional property due to their low interfacial energies. In order to study of the effect of contact area on friction coefficient at the micro-scale, friction was measured for Si-wafer and DPDM against Soda Lime balls (Duke Scientific Corporation) of different radii 0.25 mm, 0.5 mm and 1 mm at different applied normal loads $(1500,\;3000\;and\;4800{\mu}N)$. Results showed that Si-wafer had higher friction coefficient than DPDM. Furthermore, unlike that in the case of DPDM, friction was severely influenced by wear in the case of Si-wafer. SEM evidences showed that solid-solid adhesion to be the wear mechanism in Si-wafer.

• KSTLE International Journal
• /
• 제5권2호
• /
• pp.37-43
• /
• 2004

Abstract : Nano/micro-scale friction properties were investigated on Si (100) and three self-assembled monolayers (SAMs) (PFOTC, DMDM, DPDM) coated on Si-wafer by chemical vapor deposition technique. Experiments were conducted at ambient temperature(24$pm$1$circ$C) and humidity(45$pm$5%). Friction at nano-scale was measured using Atomic Force Microscopy (AFM) in the range of 0-40nN normal loads. In both Si-wafer and SAMs, friction increased linearly as a function of applied normal load. Results showed that friction was affected by the inherent adhesion in Ssi-wafer, and in the case of SAMs the physical/chemical structures had a major influence. Coefficient of friction of these test samples at the micro-scale was also energies. In order to study the effect of contact area on coefficient of friction at the micro-scale, friction was measured for Si-wafer and DPDM against Soda Lime balls (Duke Scientiffic Corporation) of different radii (0.25 mm, 0.5 mm and 1 mm) at different applied normal loads (1500, 3000 and 4800 mN). Results showed that Si-wafer had higher coefficient of friction than DPDM. Further, unlike that in the case of DPDM, friction in Si-wafer was severely influenced by its wear. SEM evidences showed that solid-solid adhesion was the wear mechanism in Si-wafer.

• 한국공간구조학회:학술대회논문집
• /
• 한국공간구조학회 2008년도 춘계 학술발표회 논문집
• /
• pp.49-52
• /
• 2008

목재자원을 효율적으로 활용하기 위한 목적으로 개발된 공학목재는 기존에 구조용으로 사용되어 오던 목재제품에 비해 강도가 높으면서도 안정적인 장점을 가지고 있다. 또한 설계 상세에 따라 부재를 주문 제작이 가능하며, 대규모 건축물에도 주요 구조체로 사용되어져 오고 있다. 장 스팬이 요구되는 재료로 구조용 집성재나 목재 I형장선, 단판적층재(LVL) 등을 활용하여 사용되고 있다. 본 프로젝트는 공학목재 중에서 집성재 및 막재를 이용한 구조 시스템으로, 강원도 뿌리기념관 공원공사 중 "야외무대 지붕공사"로 구조 재료, 구조설계 및 시공에 관한 내용으로 구성되어 있다. 지붕 구조재는 PVF/PFLT(테드라 필름코팅) 소재의 막이 사용되었다. 기둥 및 경사 부재는 강재(SS400)를 사용하였고, 캔틸레버 보 부재는 비대칭 구성 집성재(10S-28B)를 이용하였다.

• 마이크로전자및패키징학회지
• /
• 제7권1호
• /
• pp.25-28
• /
• 2000

분자선에피택시법에 의하여 GaAs(100)기판 위에 InAs 자발형성양자점을 성장하였다. InAs 양자점은 1, 3, 6, 10, 15 및 20층 등으로 다양하게 적층되어졌고, GaAs 층과 InAs 양자점 층은 각각 20 MLs와 2 MLs의 두께를 갖도록 하였다. 이 양자점의 나노구조적 특성은 PL과 STEM을 사용하여 분석하였다. 가장 높은 PL 강도는 6층의 적층구조를 갖는 시편에서 나타났고 PL 피크의 에너지가 적층회수가 증가함에 따라 분리됨을 알 수 있었다. STEM분석결과, 6충의 적층구조에서는 결함이 거의 없이 수직으로 형성된 구조를 보여준 반면에 10층 이상의 적층구조를 가질 때 그 성장 방향에 따라 volcano형상을 갖는 결함이 수직하게 성장되어졌다.

• 한국지반신소재학회논문집
• /
• 제22권1호
• /
• pp.1-7
• /
• 2023

본 연구에서는 화학적 박리를 통해 흑연분말로부터 분리한 산화그래핀의 전기적특성을 개선시키기 위해 자가조립단층막 기술을 활용하였다. 반응물질로는 황산알루미늄(Al₂(SO₄)₃)을 적용하였으며, 시멘트를 기반으로 한 건설구조물의 자가센싱에 적용하기 위한 기초연구를 수행하였다. 전기저항 측정결과 대조군인 표준공시체와 대비할 때 GO 및 Al-GO가 함유된 공시체에서 각각 10.2%, 15.9% 개선되어 도체로서의 활용 가능성을 확인하였다. 미세구조분석 결과 Al-GO의 첨가에 따라 Al(OH)₃ gel형성을 확인하였으며, 이로 인해 공시체의 밀도를 향상시켜 전류의 흐름을 원활하게 개선시킨 것으로 판단된다. 이는, 단순 구조물이 아닌 구조물 자체로서 활용성을 지닐 수 있음을 시사하며, 스마트 건설자재로서의 가능성을 확인하였다.