• 한국전산구조공학회논문집
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• 제33권2호
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• pp.137-144
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• 2020

본 논문에서는 시공단계에서 서포트가 필요 없는 UHPC 충전형 상현재를 활용한 트러스 데크플레이트 시스템을 제안하고자 한다. 제안된 시스템은 기존의 시스템과 동일한 절대 층고를 유지하면서 증대된 강성과 강도를 보유하며 효과적으로 처짐을 제어한다. 제안된 시스템 및 기존의 시스템의 구조 성능을 평가하기 위해 4.6m의 순 스팬을 갖는 5개의 실험체를 제작하였고 점진적으로 하중을 증가시키며 4점 휨 실험을 수행하였다. 실험을 토대로 실험체별 하중-처짐 그래프를 도출하였고 변수에 따른 비교 및 분석을 진행하였다. 그리고 실험을 기준으로 수행한 비선형 3차원 유한요소해석결과와의 비교를 진행하였다. 비교 및 분석 결과, 기존의 트러스 데크플레이트를 제외한 모든 실험체들이 시공단계 하중에서 건축구조설계기준 및 강구조설계기준에서 제한하는 처짐 기준을 만족하였으며, 실험과 유한요소해석의 결과가 서로 유사한 것을 확인하였다.

• 한국항공우주학회지
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• 제48권7호
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• pp.505-511
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• 2020

원형 복합재 튜브를 고고도 장기체공 무인기의 주요 스파에 사용하였다. 본 논문에서는 수정된 Brazier 방법을 이용하여 비대칭으로 보강된 원형 스파의 파단하중을 예측할 수 있는 이론적인 모델을 제안하였다. 이 모델을 이용하여 비대칭으로 보강된 원형스파의 최대 허용 굽힘 모멘트를 예측하였다. 해석 결과로부터 원형 스파의 상단에 위치한 보강된 캡은 최대 허용 굽힘 모멘트를 증가시키는 것을 알 수 있다. 4점 굽힘 실험을 수행하여 스파 캡이 파손하중에 미치는 영향을 평가하였고 제안된 모델과 비교하였다. 그리고 수치해석을 수행하여 보강된 원형 스파의 거동을 분석하였다. 제안된 이론적인 모델은 실험 및 수치해석 결과와 잘 일치함을 보였다.

• Computers and Concrete
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• 제4권2호
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• pp.83-100
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• 2007

Applying a direct formulation for the enrichment of the displacement field an extended finite element (XFEM) scheme for modeling of cohesive crack growth is developed. Only elements cut by the crack is enriched and the scheme fits within the framework of standard FEM code. The scheme is implemented for the 3-node constant strain triangle (CST) and the 6-node linear strain triangle (LST). Modeling of standard concrete test cases such as fracture in the notched three point beam bending test (TPBT) and in the four point shear beam test (FPSB) illustrates the performance. The XFEM results show good agreement with results obtained by applying standard interface elements in FEM and with experimental results. In conjunction with criteria for crack growth local versus nonlocal computation of the crack growth direction is discussed.

• Journal of the Korean Wood Science and Technology
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• 제48권5호
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• pp.676-684
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• 2020

This study was carried out in order to evaluate the bending creep deflection of glulams and bolted glulams beam-to-beam connection with steel-gusset plates and bolts under changing relative humidity. The two types of glulam beams (130 mm in width, 175 mm in thickness, and 3000 mm in length) used in this study were made from domestic larch and composed of seven layers. The gussets were made of 8-mm-thick steel plates. Creep testing was conducted under constant loads in an uncontrolled environment. The test was carried out in a room that was well ventilated through a window. The creep test specimens were loaded for 33,000 hours. A bending creep test for the glulams was conducted through four-point loading. The applied stresses were 20% and 30% of the MOR in the static bending test for the glulam and bolted glulam, respectively. After 33,000 hours, the creep deflection of the glulam at a 20% stress level increased by 39% to 99%, while the creep deflection of the glulam at a 30% stress level increased by 27% to 67%, as compared with instantaneous elastic deflection. The relative creep increased during autumn and winter, and recovered during spring and summer. The relative creep of the bolted glulams was changed abruptly by loading up to 5,000 hours, but stabilized after 5,000 hours, and then gradually increased until 33,000 hours. The relative creep of the bolted glulam increased 2.11 times on average after 33,000 hours.

• 구강회복응용과학지
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• 제16권3호
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• pp.221-227
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• 2000

Provisional fixed partial dentures(FPDs) are an important part of many prosthodontic treatment procedures. These provisional fixed prostheses must fulfill biologic, mechanical, and esthetic requirements to be considered successful. Consideration of all these factors and requirements are important because provisional resin restorations may be worn over a long period to assess the results of periodontal and endodontics therapies, and also during the restorative phase of implant reconstructive procedures. This in vitro study examined flexual strength of four resins commonly used for fixed provisional prostheses. The effects of polymerization conditions were also evaluated. The four resins tested were : Caulk Temporary bridge resin(L.D. Caulk Co. Dentsply International Millford), Jet(Lang Dental Mfg. Co. Chicago. ILL. U.S.A), Alike (Coe Laboratories. Inc. Chicago. ILL. U.S.A) and Tokuso Curefast (Coe Laboratories. Inc. Chicago. ILL. U.S.A) The test specimens were 65mm long, 14mm wide, and 3.5mm thickness. 10 specimens of four resins were cured for 15 minutes at atmospheric pressure and 10 specimens of four resins were cured at an additional pressure of approximately 20 psi. A total of 80 specimens were prepared. The flexual strength was determined by three-point bending test. Data were analysed with the Paired samples T-test and Tukey student-range test Within the limitations imposed in this study, the following conclusions can be drawn : 1. Under the condition of bench curing, Caulk Temporary bridge resin showed the highest flexual strength. In decreasing order, the flexual strength of the other materials was as follows : Jet, Tokuso Curefast, Alike, and Caulk Temporary bridge resin demonstrated significantly higher strength than other resins. 2. Under the condition of pressure curing, Jet showed the highest flexual strength. In decreasing order, the flexual strength of the other materials was as follows : Caulk Temporary bridge resin, Tokuso Curefast, and Alike. There were all statistically significant differences among four resins 3. There was a statistically significant difference between bench- and pressure-cured specimens in all four materials.

• 콘크리트학회논문집
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• 제24권5호
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• pp.525-533
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• 2012

이 연구에서는 UHPCC에서 섬유혼입률에 따른 초기균열강도 및 휨인장강도의 변화를 0~5 vol.% 범위에서 조사하였으며, 노치의 여부에 따른 영향을 파악하기 위해 노치가 없는 보에 대한 4점 재하실험 및 노치 낸 보에 대한 3점 재하실험을 같이 실시하였다. 실험 결과로부터 섬유혼입률이 증가함에 따라 휨인장강도는 선형적으로 강도가 향상됨을 확인할 수 있었고, 초기균열강도의 경우에는 1 vol.% 이상에서는 강도향상을 나타내었으나 그 이하의 섬유혼입에서는 강도향상 효과가 거의 없는 것으로 나타났다. 노치 유무에 따른 휨 실험으로부터 구한 UHPCC의 초기균열발생강도 및 휨 인장강도를 비교했을 때, 섬유혼입률에 따라 노치의 영향이 변하는 것으로 나타났다. 섬유혼입률이 증가함에 따라 노치에서의 응력집중의 영향이 감소하여 강도 차이가 점차 줄어들었으며, 높은 섬유혼입률에서는 노치에 의한 응력집중효과는 없어지고 균열면의 상태 및 크기효과의 영향이 지배적으로 작용하여 노치낸 보의 강도가 좀 더 크게 나타났다.

• 마이크로전자및패키징학회지
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• 제27권3호
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• pp.55-60
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• 2020

최근 참단 반도체 패키징 기술은 고성능 SIP(system in packaging) 구조로 발전해 가고 있고, 이를 실현시키기 위해서 구리 대 구리 접합은 가장 핵심적인 기술로 대두되고 있다. 구리 대 구리 접합 기술은 아직 구리의 산화 특성과 고온 및 고압력 공정 조건, 등 해결해야 할 문제점들이 남아 있다. 본 연구에서는 아르곤과 질소를 이용한 2단계 플라즈마 공정을 이용한 저온 구리 접합 공정의 접합 계면 품질을 정량적 접합 강도 측정을 통하여 확인하였다. 2단계 플라즈마 공정은 구리 표면에 구리 질화막을 형성하여 저온 구리 접합을 가능하게 한다. 구리 접합 후 접합 강도 측정은 4점 굽힘 시험법과 전단 시험법으로 수행하였으며, 평균 접합 전단 강도는 30.40 MPa로 우수한 접합 강도를 보였다.

• Steel and Composite Structures
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• 제18권6호
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• pp.1423-1450
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• 2015

The paper presents the details and results of an experimental study on bolted end-plate joints of industrial type steel building frames. The investigated joints are commonly used in Lindab-Astron industrial buildings and are optimized for manufacturing, erection and durability. The aim of the research was to provide an experimental background for the design model development by studying load-bearing capacity of joints, bolt force distribution, and end-plate deformations. Because of the special joint details, (i.e., joints with four bolts in one bolt-row and HammerHead arrangements), the Eurocode 3 standardized component model had to be improved and extended. The experimental programme included six different end-plate and bolt arrangements and covered sixteen specimens. The steel grade of test specimens was S355, the bolt diameter M20, whereas the bolt grade was 8.8 and 10.9 for the two series. The end-plate thickness varied between 12 mm and 24 mm. The specimens were investigated under pure bending conditions using a four-point-bending test arrangement. In all tests the typical displacements and the bolt force distribution were measured. The end-plate plastic deformations were measured after the tests by an automatic measuring device. The measured data were presented and evaluated by the moment-bolt-row force and moment-distance from centre of compression diagrams and by the deformed end-plate surfaces. From the results the typical failure modes and the joint behaviour were specified and presented. Furthermore the influence of the end-plate thickness and the pretension of the bolts on the behaviour of bolted joints were analysed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.539-541
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• 2005

The purpose of this study is to accurately understand the flexural behavior in RC beam with strrup on repair thickness of DFRCC. Using a four-point bending test, the shear strengths and shear stress-deflection relations of DFRCC repair RC specimens are obtained. The results show that DFRCC can be effectively used for repairing materials for concrete structures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.635-638
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• 2000

This experimental were carried out in order to investigate the equivalent strength of SFRC (Steel Fiber Reinforced Concrete). Tow hundred and tenh SFRC beeam (size: 150x150x550) were used in the tests the relationships between loading and mid-point deflections of the beams were observed four oint bending loading. From the test results, prediction formulas for the equivalent strength of SFRC beams are suggested.