• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.07a
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• pp.109-110
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• 2015

강재 부표는 구조적 강도가 우수하고 철재의 절단, 용접 등의 간단한 가공으로 원하는 모양을 쉽게 만들 수 있는 장점은 있으나, 소재의 특성상 해수에 의한 부식과 흘러나오는 페인트로 인한 환경오염, 무거운 중량, 이에 따른 설치 비용과 유지보수 비용의 증가 등 여러 가지 극복하기 힘든 문제점과 한계점을 가지고 있다. 이 연구에서는 우리나라 표준형 부표의 기본 소재로 사용하고 있는 강재 대신 친환경적인 경량재질의 소재를 이용한 부표를 모듈 구조로 설계함으로써, 기존 강재 부표의 문제점과 한계점을 뛰어넘어 효율적인 유지관리와 운영이 가능하고, 해양환경 오염의 방지와 경량화를 실현시킬 수 있는 표체 개선 방안을 제시하고자 한다. 또한, 경량 재질을 이용한 부표의 안정성과 경제성 검토를 통해, 기존 강재 부표와 비교함으로써 안정성과 경제성을 평가하고자 한다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.111-116
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• 2022

Recently, building structures tend to be super high-rise and large-scale with the development of concrete technology. When high-rise building is constructed of reinforced concrete structure, it has a disadvantage that its own weight increases. Light weight aggregate(LWA) was developed to compensate for these shortcomings. Manufacturing concrete using these light weight aggregates has the advantage of reducing the self weight of the reinforced concrete structure, but has a disadvantage in that the strength of the concrete is reduced. In this study, an experimental study was conducted to investigate the strength characteristics of hardened cement according to the presence or absence of surface coating of lightweight aggregates. As a result, in terms of compressive strength, the surface-coated lightweight aggregate exhibited higher strength than the uncoated lightweight aggregate. Also, it was considered that this is because the interfacial voids of the surface coated lightweight aggregate mixed cement hardened body were filled with blast furnace slag fine powder particles.

• Korean Architects
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• v.4 no.11 s.11
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• pp.37-43
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• 1969

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.209-217
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• 2011

In recent days, while taller and more massive structures such as huge bridges and super skyscrapers have been welcomed, the structural stabilization in design and construction have been gradually limited due to the major weakness of current concrete which is relatively heavier when compared with its strength. To improve the weakness of the current concrete, The lightweight concrete with light weight and high strength should be used; however, not many researchers in Korea have studied on the lightweight concrete. Generally, artificial lightweight aggregate produced through high-temperature-plasticization has a possibility of its body-expansion with many bubbles. Therefore, depending on the size of aggregate, the effects of bubbles on the specific weight and strength of the lightweight concrete should be studied. In this study, considering grain-size, the mix design of the artificial lightweight aggregate produced through the high-temperature-plasticization and the body-expansion of waste and clay from the fire power plant in Korea was conducted. The experiment to analyze the variation in specific weight and strength of the lightweight concrete was followed. From these experiments, the optimized grain-size ratio of the artificial lightweight aggregate for the enhancement of high-strength from the lightweight concrete was revealed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.315-325
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• 2017

This study aims to provide information for the design and use of structural lightweight concrete (SLWC) for floating concrete structures in a marine environment. An experimental program was set up and comprehensive experimental campaign were carried out to determine SLWC mix proportions that can satisfy specified concrete strength, density, and slump values all of them were determined from previous research. Comparisons with previous SLWC mix designs that have been utilized for actual floating concrete structures were made. Key aspects needed to be considered regarding to the use of SLWC for floating marine concrete structures were discussed.

• Journal of Energy Engineering
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• v.29 no.3
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• pp.25-33
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• 2020

In this study, flow and structural computational analysis were performed to investigate the structural safety of the lightweight butterfly valve disc designed by topology optimization. After flow analysis, as the opening angle increased, the flow coefficient increased non-linearly and showed a gentle slop. When the opening angle was 12 degree, the cavitation could be predicted. After FE analysis, all FE von-Misses stresses of the lightweight disc were smaller than the yield strength of the material, and all FE maximum deformations were also smaller than the conservative deformation of the previous study. Ultimately, it was confirmed that the structural safety of the lightweight valve disc based on computational analysis is effective.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.4
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• pp.449-455
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• 2022

Concrete is the most widely used construction material. The heavy self-weight of concrete may offer an advantage when developing high compressive strength and good dimensional stability. However, it is limited in the construction of super-long bridges or very high skyscrapers owing to the substantially increased self-weight of the structure. For developing lightweight concrete, various lightweight aggregates have typically been utilized. However, due to the porous characteristics of lightweight aggregates, the strength at the composite level is generally decreased. To overcome this intrinsic limitation, this study aims to develop a construction material that satisfies both lightweight and high strength requirements. The developed cementitious composite was manufactured based on a high volume usage of hollow glass microspheres in a matrix with a low water-to-cement ratio. Regardless of the tested hollow glass microspheres from among four different types, compressive strength outcomes of more than 60 MPa and 80 MPa with a density of 1.7 g/cm³ were experimentally confirmed under ambient and high-temperature curing, respectively.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.201.2-201.2
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• 2012

위성용 초고주파신호분배기(이하, RFDU)는 위성에 장착된 두 개의 안테나와 두 개의 송수신기 사이에 위치하게 되며, 지상으로부터 송신된 제어신호와 위성의 상태 정보 신호를 전달/분배하는 RF 신호 경로를 제공하게 된다. 기존의 위성용 RFDU의 구조는 cavity 형태의 필터로 구성된 diplexer와 hybrid RF coupler 및 저역통과필터 들이 서로 SMA 케이블로 연결되어 있는 부피가 큰 구조이다. 또한 차세대 위용용 부품들은 위성을 경제성 등을 고려하여 소형/경량화 개발이 요구되고 있으며, 특히 위성용 S 대역 TC/TM 통신링크에서 RFDU와 트랜스폰더는 소형 경량화를 위해 단일 unit으로 개발되고 있다. 이에 따라 기존의 RFDU 또한 전기적 성능을 유지하면서 소형/경량화 개량 개발이 필요하다. 본 연구에서는 기존 RFDU의 소형 경량화를 위해 PCB와 housing을 이용하여 cavity 필터특성을 갖는 diplxer를 개발/구현 하였으며, PCB 페턴을 통한 내부 인터페이스용 SMA 케이블 제거 등을 적용하였다. 또한 microstrip 타입의 저역통과필터을 적용하여 소형 경량화를 이루었으며, 새로이 개발된 소형/경량의 RFDU는 전기적으로 기존의 그것과 유사하거나 동등한 특성을 갖는 것을 확인하였으며, 기존 RFDU 대비 무게 및 부피는 60 % 이상 감소하여 소형/경량화 개발을 성공하였다. 본 개발 결과물은 향후 차세대 위성용 RFDU 개발을 위한 기초 자료로 활용할 것이다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.21-28
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• 2017

The steel-plate concrete(SC) is used in a form of module assembly construction in the outer wall of nuclear-power plant and LNG containment. Since the steel-plate concrete modules are generally manufactured from the plant, the weight of SC has significantly effect on the total construction cost in the aspect of shipment. Therefore, the use of lightweight aggregates concrete(LWAC), which fill the inside of SC module can be a solution. However, the amount of used lightweight aggregates(LWA) is limited in the use of current concrete mixing process due to the concrete quality problems and it also determines the allowable minimum density of LWAC. In this research, the preplaced casting method is applied because of increasing the volume fraction of LWA significantly, which results from the producing process of pre-packing the LWA in the formwork and filling the interstitial voids between LWA using cement paste grout. The density and compressive strength of selected preplaced LWAC were $1,600kg/m^3$ and 30MPa and it was applied for the mock-up specimens of SC panel. It was used for the 3-point bending test for evaluating its structural performance. The results show that the preplaced LWAC can reduce the density of concrete with the adequate mechanical and structural performance.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.31-32
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• 2006

본 논문은 중형엔진 조립과정에서 실린더 프레임 회전 작업에 사용하는 지그의 구조해석을 수행한 후, 지그의 안전성을 검토하고 지그의 경량화를 통하여 실용적인 지그 설계안을 제안하였다. 현장 작업자가 들 수 있는 최대 무게를 넘는 지그를 구조해석 모델로 선정한 후, 해석모델은 지그, 실린더 프레임, 볼트, 너트, 샤클 핀을 3차원 입체요소로 구성하고 ABAQUS/Standard를 사용하여 재료 비선형 및 접촉을 고려한 구조해석을 수행하였다. 구조최적화를 위하여 응력이 상대적으로 낮은 부위와 작업성을 고려하여 설계변수를 선정하고, 실험계획법의 직교배열표를 활용하여 설계변수에 대한 각 부위의 민감도와 경량화 모델을 도출하였다.