• 한국구조물진단유지관리공학회 논문집
• /
• 제17권4호
• /
• pp.75-83
• /
• 2013

본 연구에서는 탄소섬유판을 이용하여 표면매입 보강된 철근콘크리트 부재의 내화성능에 관한 연구로서 온도변화에 따른 탄소섬유 판의 인장시험, 에폭시의 상태변화 실험, 그리고 온도변화에 따른 부착성능에 관한 일련의 실험연구를 실시하였다. 실험연구로부터, 부착강도의 측면에서 콘크리트를 보강하기 위한 효율적인 보강방법은 표면매입 보강이며, 이 보강법은 상온에서는 그 효과가 매우 높지만, 비록 낮은 온도일지라도 주변온도가 높아질 경우에는 보강효과가 현저히 저하될 수 있음을 확인하였다. 특히, 주변 온도가 에폭시의 화학적 성질이 변화하기 시작하는 유리전이 온도에 근접할 경우, 부착기능이 상실되기 시작하므로 구조물의 안전한 내화설계를 위해서는 부착용으로 사용되는 에폭시의 성능을 개선시키고 또한 섬유보강재의 성능개선이 시급한 것으로 사료된다.

• Steel and Composite Structures
• /
• 제51권2호
• /
• pp.153-172
• /
• 2024

Due to the fast development of constructions in recent years, there has been a rapid consumption of fresh water and river sand. In the production of concrete, alternatives such as sea water and sea sand are available. The near surface mounted (NSM) technique is one of the most important methods of strengthening. Aluminum alloy (AA) bars are non-rusting and suitable for usage with sea water and sand concrete (SSC). The goal of this study was to enhance the shear behaviour of SSC-beams strengthened with NSM AA bars. Twenty-four RC beams were cast from fresh water river sand concrete (FRC) and SSC before being tested in four-point flexure. All beams are the same size and have the same internal reinforcement. The major factors are the concrete type (FRC or SSC), the concrete degree (C25 or C50 with compressive strength = 25 and 50 MPa, respectively), the presence of AA bars for strengthening, the direction of AA bar reinforcement (vertical or diagonal), and the AA bar ratio (0, 0.5, 1, 1.25 and 2 %). The beams' failure mechanism, load-displacement response, ultimate capacity, and ductility were investigated. Maximum load and ductility of C25-FRC-specimens with vertical and diagonal AA bar ratios (1%) were 100,174 % and 140, 205.5 % greater, respectively, than a matching control specimen. The ultimate load and ductility of all SSC-beams were 16-28 % and 11.3-87 % greater, respectively, for different AA bar methods than that of FRC-beams. The ultimate load and ductility of C25-SSC-beams vertically strengthened with AA bar ratios were 66.7-172.7 % and 89.6-267.9 % higher than the unstrengthened beam, respectively. When compared to unstrengthened beams, the ultimate load and ductility of C50-SSC-beams vertically reinforced with AA bar ratios rose by 50-120 % and 45.4-336.1 %, respectively. National code proposed formulae were utilized to determine the theoretical load of tested beams and compared to matching experimental results. The predicted theoretical loads were found to be close to the experimental values.

• 콘크리트학회논문집
• /
• 제25권1호
• /
• pp.37-43
• /
• 2013

최근 FRP 판을 이용한 표면매입 보강공법에서 FRP와 콘크리트 사이의 계면파괴를 연구하기 위한 실험 및 이론적인 연구가 국내외에서 수행되고 있다. 그 결과 보강재의 형상과 콘크리트 강도 그리고 부착길이 등에 대한 일련의 연구가 수행되었지만, 보강재의 부착길이에 따른 각 보강재의 적정 간격, 그리고 무리효과 등과 같은 영향인자들에 대한 연구 필요성이 제기되고 있다. 이에 따라 이 연구에서는 부착길이와 보강재인 FRP 판의 보강간격을 변수로 부착실험을 실시하고 그에 따른 부착성능의 변화를 연구하고자 한다. 또한 표면매입 보강된 FRP 판의 계면파괴시 강도를 산정하기 위한 기존 제안식과의 비교를 통하여 그 적용성을 평가하고자 한다. 연구 결과, 매입된 FRP의 간격이 넓어질수록 FRP판의 인장파단과 함께 내력이 증가하는 양상을 보이는 반면에 FRP판의 간격이 좁을수록 콘크리트 할렬파괴가 지배하는 것으로 나타났다. 기존 제안식을 이용하여 실험 결과를 비교한 결과, FRP의 부착길이와 무리효과를 고려한 기존 제안식을 사용하여 표면매입 보강된 FRP의 부착강도를 적절히 예측할 수 있는 것으로 나타났다.

• Archives of Plastic Surgery
• /
• 제45권3호
• /
• pp.229-238
• /
• 2018

Background Nipple-sparing mastectomies (NSMs) are increasingly performed to obtain the best aesthetic and psychological outcomes in breast cancer treatment. However, merely preserving the nipple-areolar complex (NAC) does not guarantee a good outcome. Darkly pigmented NACs and a tendency for poor scarring outcomes are particular challenges when treating Asian patients. Herein, we review the reconstructive outcomes following NSM at Singapore General Hospital. Methods All breasts reconstructed following NSM over an 11-year period from 2005 to 2015 were reviewed. Information was collected from the patients' records on mastectomy indications, operative details, and complications. Patient satisfaction, breast sensation, and aesthetic outcomes were evaluated in 15 patients. Sensation was quantified using the Semmes-Weinstein monofilament test. Results A total of 142 NSMs were performed in 133 patients for breast cancer (n=122, 85.9%) or risk reduction (n=20, 14.1%). Of the procedures, 114 (80.2%) were autologous reconstructions, while 27 (19.0%) were reconstructions with implants. Complications occurred in 28 breasts (19.7%), with the most common complication being NAC necrosis, which occurred in 17 breasts (12.0%). Four breasts (2.8%) had total NAC necrosis. The overall mean patient satisfaction score was 3.0 (good). The sensation scores were significantly diminished in the skin envelope, areola, and nipple of breasts that had undergone NSM compared to non-operated breasts (P<0.05). Half of the subset of 15 patients in whom aesthetic outcomes were evaluated had reduced nipple projection. Conclusions Immediate reconstruction after NSM was performed with a low complication rate in this series, predominantly through autologous reconstruction. Patients should be informed of potential drawbacks, including NAC necrosis, reduced nipple projection, and diminished sensation.

• 한국구조물진단유지관리공학회 논문집
• /
• 제26권6호
• /
• pp.238-246
• /
• 2022

본 논문은 목재 보의 휨성능을 향상시키기 위한 CFRP 판의 보강상세 개발과 보강성능평가를 정리한 것이다. 본 연구에서 EBM 공법에 의한 CFRP 판으로 목재 보를 보강하는 상세로서 고력볼트에 의한 단부구속보강상세를 개발하였다. 이에 대한 휨성능을 평가하기 위하여 단부 구속이 없는 EBM 공법과 NSM 공법 등의 보강 상세와 함께 휨실험을 실시하였다. 실험결과로부터, 단부구속되지 않은 CFRP 판 보강실험체는 CFRP 판의 부착파괴와 목재의 쪼갬파괴가 동시에 일어났으며, 고력볼트로 단부구속된 CFRP 판 보강실험체는 목재의 쪼개짐에 의해 최종파괴되었다. 하중-변위곡선에서 무보강 실험체들은 선형탄성거동을 하다가 최대하중 이후 취성파괴되는 거동을 나타내었으며, EBM 공법으로 보강된 실험체들은 탄성변형후 휨강성 기울기가 감소되며 최대하중에 도달하는 거동을 나타내었다. EBM 공법으로 보강된 실험체들의 최대하중은 무보강 실험체들에 비하여 31.5~63.0% 증가하였으며, 고력볼트의 단부구속에 따른 최대하중은 24.0% 증가효과를 나타내었다. 동일한 CFRP 판의 보강량을 기준으로 EBM 보강이 NSM 보강에 비하여 최대하중 증가율에서 2.67배 크게 나타났다.

• Structural Engineering and Mechanics
• /
• 제65권5호
• /
• pp.535-546
• /
• 2018

The objective of this study is to understand the behaviour of hollow core slabs strengthened with FRP and hybrid techniques through numerical and analytical studies. Different strengthening techniques considered in this study are (i) External Bonding (EB) of Carbon Fiber Reinforced Polymer (CFRP) laminates, (ii) Near Surface Mounting (NSM) of CFRP laminates, (iii) Bonded Overlay (BO) using concrete layer, and (iv) hybrid strengthening which is a combination of bonded overlay and NSM or EB. In the numerical studies, three-dimensional Finite Element (FE) models of hollow core slabs were developed considering material and geometrical nonlinearities, and a phased nonlinear analysis was carried out. The analytical calculations were carried out using Response-2000 program which is based on Modified Compression Field Theory (MCFT). Both the numerical and analytical models predicted the behaviour in agreement with experimental results. Parametric studies indicated that increase in the bonded overlay thickness increases the peak load capacity without reducing the displacement ductility. The increase in FRP strengthening ratio increased the capacity but reduced the displacement ductility. The hybrid strengthening technique was found to increase the capacity of the hollow core slabs by more than 100% without compromise in ductility when compared to their individual strengthening schemes.

• Corrosion Science and Technology
• /
• 제10권1호
• /
• pp.1-5
• /
• 2011

The major purpose of the present study is to evaluate the performance of various galvanized (GI) or galvannealed (GA) mild steels and AHSS in stamping applications. Finite Element Analysis (FEA) of selected stamping operations was conducted to estimate the critical pressure boundary conditions that exist in practice. Using this information, laboratory tribotests, e.g. Twist Compression (TCT), Deep Drawing (DDT) and Strip Drawing (SDT) Tests, were developed to evaluate the performance of selected lubricants and die materials/coatings in forming galvanized steels of interest. The sheet materials investigated included mild steels and AHSS (e.g. DP600 GI/GA, DP780 GI/GA, TRIP780 GA and DP980 GI/GA). Experimental results showed that galvanized material resulted in more galling, while galvannealed material showed more powdering and flaking. The surface roughness and chemical composition of galvanized sheet materials affected the severity of galling under the same testing conditions, i.e. lubricants and die materials/coatings. The results of this study helped to determine the critical interface pressure that initiates lubricant failure and galling in stamping selected galvanized sheet materials. Thus, to prevent or postpone the critical interface conditions, the results of this study can be used to select the optimum combination of galvanized sheet, die material, die coating and lubricant for forming structural automotive components.

• 한국컴퓨터정보학회논문지
• /
• 제3권3호
• /
• pp.23-30
• /
• 1998

ODBC는 동적인 클라이언트/서버 환경에서 특히 효과적이다. ODBC는 멀티미디어데이터를 처리할 수 있는 특징 때문에 멀티미디어 서버로 지원할 수 있다. 본 논문에서는 관계형 DBMS 위한 ODBC 드라이버를 개발하였다. 이 드라이버는 클라이언트 모듈과 서버 모듈로 구성되었다. 클라이언트 모듈은 SRM 이라 하고 서버모듈은 CSM 이라 하였다. 이들 두 모듈은 NSM 이라 부르는 네트워크 모듈을 통해서 연결된다. 본 논문에서 개발한ODBC 드라이버 테스트는 기능과 정보처리 상호 운용 가능성을 테스트하였으며, 그 결과 드라이버는 클라이언트 DBMS 툴로서 성공적이었고, 멀티미디어 데이터 처리가 가능할 뿐만 아니라 DBMS 툴을 포함하는 클라이언트 응용 프로그래밍 인터페이스를 지원할 수 있는 것으로 나타났다.

• Computers and Concrete
• /
• 제20권4호
• /
• pp.439-448
• /
• 2017

Reinforced concrete (RC) infrastructures often require strengthening due to error in design, degradation of materials properties after prolong utilization and increases load carrying capacity persuaded by new use of the structures. For this purpose, a newly proposed Side Near Surface Mounted (SNSM) composite technique was used for flexural strengthening of RC beam specimens. Analytical and non-linear finite element modeling (FEM) using ABAQUS were performed to predict the flexural performance of RC specimens strengthened with S-NSM using steel bars as a strengthening reinforcement. RC beams with various SNSM reinforcement ratios were tested for flexural performance using four-point bending under monotonic loading condition. Results showed significantly increase the yield and ultimate strengths up to 140% and 144% respectively and improved failure modes. The flexural response, such as failure load, mode of failure, yield load, ultimate load, deflection, strain, cracks characteristic and ductility of the beams were compared with those predicted results. The strengthened RC beam specimens showed good agreement of predicted flexural behavior with the experimental outcomes.

• 대한건축학회논문집:구조계
• /
• 제35권11호
• /
• pp.137-146
• /
• 2019

Recently, the Near-Surface-Mounting method using Fiber reinforced polymer (FRP) has been developed and applied to the reinforcement of many concrete structural members. However, as a part of the fire resistance design, there is a lack of research related to fire insulation for the areas reinforced with FRP. In case of NSM reinforcement, there is a difference in the transferred temperature from the external surface to the groove corresponding to the location of the groove where the FRP is embedded, and the effect of this should be reflected in the fireproof insulation design. Therefore, in this study, after forming grooves for surface embedding in concrete blocks, fireproof insulation reinforcement was performed using Calcium Silicate (CS) fireproof board and an experiment to evaluate the temperature transfer was performed. By observing the temperature at these groove positions, the reduction of temperature transfer according to fireproof insulation detail was studied. As a result, when the NSM-FRP is properly fire-insulated using the CS-based fireproof board, the epoxy inside the groove does not reach its glass transition temperature until the external temperature reaches $800^{\circ}C$.