외부구속자켓의 구속비와 강도비에 따른 콘크리트 부착거동의 특성

최은수,정춘성,Choi, Eunsoo,Jung, Chunsung 대한토목학회 2014 대한토목학회논문집 Vol.34 No.1

이 연구에서는 형상기억합금과 강재로 구속된 콘크리트의 부착응력을 외부자켓의 구속비 및 강도비를 이용하여 분석하였다. 이를 위해서 직경 1.0 mm 형상기억합금 와이어와 두께 1.0 mm와 1.5 mm 강판을 사용하여, 구속비 및 강도비의 차이를 유발하여 각 변수의 차이에 따른 부착강도 및 부착거동을 분석하였다. 외부자켓 구속에 의해서 콘크리트의 부착강도는 증가하였으며, 파괴형태도 쪼갬파괴에서 뽑힘파괴로 전환되어 구속효과가 있음을 알 수 있었다. 콘크리트 부착강도는 구속비와 강도비가 증가함에 따라 증가하는 현상을 보이지만, 특정 시점부터는 부착강도가 거의 증가하지 않고 일정한 값을 나타내는 결과를 보였다. 그러나 강도비의 증가에 따라 발생하는 원주방향 최대 변형율은 거의 선형적으로 감소하는 결과를 보였다. This study analyzes the characteristics of bond behavior of concrete, which is confined by external jackets such as shape memory alloy (SMA) and steel, according to confinement and stiffness ratios of the external jackets. For this purpose, SMA wires with 1.0 mm diameter and steel plates with 1.0 and 1.5 thickness are used to induce difference on confinement and stiffness ratios and, then, bond strength and behavior are analyzed considering the two factors. When external jakcets are used for the concrete cylinders, bond strengths of specimens increase and their bond failures are transferred from splitting failure to pull-out failure and, thus, the external jackets show confining effect. Bond strenght of concrete increase with increasing confinement and stiffness ratios of the external jackets. However, maximal circumferential strains decrease linearly with increasing the two values.

그라우팅이 필요 없는 RC기둥 강판보강 기법

최은수,조성철,정영수,조백순,Choi, Eun Soo,Cho, Sung Chul,Chung, Young Soo,Cho, Baik Soon 한국강구조학회 2008 韓國鋼構造學會 論文集 Vol.20 No.1

본 연구에서는 주철근의 겹침이음으로 인해 효과적인 내진성능을 충분히 확보하지 못한 RC기둥 보강 기법의 개발을 위해 횡방향외부압력을 도입한 강판으로 RC기둥을 보강하는 기법을 제시하였다. 제시된 기법의 성능 검증을 위해 설계강도를 변수로 하여 콘크리트 공시체 45개를 제작하여 외부압력을 도입하여 강자켓으로 보강하였다. 본 연구에서 소개하는 강자켓팅 기법은 기존의 방법과 달리 강판과 콘크리트 사이에 그라우팅이 필요 없는 기법이다. 보강된 시편과 무보강 시편의 압축실험을 수행하여 각각의 결과를 비교, 분석하였 다. 본 연구를 통해 횡방향 외부압력을 도입한 강판보강은 콘크리트 시편의 강도 및 연성도 증가에 매우효과적인 것으로 나타났고 설계강도가 낮은 시편에서 강도증가현상이 두드러지게 나타났다. 두꺼운 강판은 더 큰 강도 증진효과가 있었다. 본 연구에서는 제시한 보강기법은 RC기둥에 적용하여 강도 및 연성도을 증진시키는 효과가 있을 것으로 기대된다. This study introduced a new method to retrofit RC columns with lap splice that do not have enough ductility during an earthquake. The new method used mechanical external pressure and split steel plates around the RC columns. The introduced method does not require grouting the gap between jacket and concrete surface. In this study, 45 concrete cylinders were manufactured with varyingstrengths and part of them was retrofitted with split steel jackets under a lateral confining stress. The effect of the new method was verified by comparing the results from the compressive tests of retrofitted and unretrofitted cylinders. The steel jacket that was built following the new method showed good results of increasing the compressive strength and ductility of concrete cylinders. The thicker steel jackets showed larger compressive strength, however, the ductility at failure depends on their welding quality.

Seismic base isolation for highway steel bridges using shape memory alloys

최은수,전준창,Choi, Eun Soo,Jeon, Jun Chang Korean Society of Steel Construction 2004 韓國鋼構造學會 論文集 Vol.16 No.1

Conventional lead-rubber bearings may be unstable in case of strong ground motions. To address this problem, this paper proposed a new concept of isolation device wherein shape memory alloy wires were incorporated in an elastomeric bearing. A three-span continuous steel bridge was used for seismic analyses to compare the performance of lead-rubber and proposed bearings. The proposed bearings showed almost the same performance as the lead-rubber bearings. In particular, the proposed bearings limited relative displacement effectively with strong ground motions and recovered its original undeformed shape. 기존교량의 내진성능개선 및 신설교량의 지진보호에 납-고무 베어링은 좋은 효과를 보여주고 있다. 그러나 납-고무 베어링은 사용상에 있어 문제점이 있으며, 이를 개선하기 위하여 형상기억합금(shape memory alloy)을 이용한 면진장치를 본 연구에서 제시하였다. 3경간 연속 고속도로 강교량의 지진해석을 통하여 납-고무베어링과 고무베어링 및 형상기억합금 와이어와의 조합 면진장치의 지진거동을 비교하였다. 해석결과 형상기억합금 와이어+고무베어링 시스템이 납-고무베어링과 거의 유사한 거동을 보여주었으며, 특히 제시된 면진장치는 상대변위의 제어 및 잔류변형에 있어 기존의 납-고무 베어링에 비해 성능이 우수했다.

펨토초 레이저와 미세각막절삭기를 이용한 근시교정수술에서 임상성적 비교

최은수,정희진,이경헌,Yun Su Choi,M,D,Hee Jin Jung,M,D,Kyung Hun Lee,M,D 대한안과학회 2007 대한안과학회지 Vol.48 No.8

Purpose: To compare results between in femtosecond laser and microkeratome LASIK correction of myopia Methods: We retrospectively analyzed the result of 94 eyes of 47 patients in the femtosecond group (F) and 103 eyes of 52 patients in the microkeratome group (M). All patients had undergone LASIK using either a femtosecond laser or a microkeratome for making of flap. Patients were divided into groups I (6D≤) and II (≥6D) according to preoperative myopia. Each patient was followed up for over 6 months with measurements of uncorrected visual acuity and manifest refraction at 1 week and 1, 3, and 6 months after operation. Complications during and after the operation were reviewed retrospectively in two groups 6month after the operation. Results: In groups F-I, F-II, M-I, and M-II, postoperative 6-month uncorrected visual acuity was 0.98±0.08, 0.96±0.09, 0.97±0.03, 0.98±0.09. At the 6-month follow-up, there were no significant differences between the two groups in uncorrected visual acuity and mean spherical equivalent. Corneal opacity was found in 3 eyes in group M and complication related with flap was found 1 eye in group F and 4 eyes in group M. Conclusions: During a 6-month follow up, LASIK using either a femtosecond laser or a microkeratome has an similar effect in uncorrected visual acuity and mean spherical equivalent. Thus LASIK for using femtosecond laser can be used as an alternative procedure to correct myopia.

철도교용 고무패드 설치에 따른 판형교의 동적 거동 분석

최은수,김현민,오지택,김성일,Choi, Eun Soo,Kim, Hyun Min,Oh, Ji Taek,Kim, Sun Gil 한국강구조학회 2005 韓國鋼構造學會 論文集 Vol.17 No.3

본 연구에서는 '철도교용 고무패드의 강성추정기법'에서 결정된 각 고무패드의 강성과 가정된 감쇠비를 이용하여 두 판형교에서의 동적 거동을 분석하였다. 또한 패드에 의한 판형교의 동적 거동 변화가 철도교량의 거동의 한계를 규정하고 있는 규준에 적합한지도 판단하였다. 고무패드를 교좌로 판형교에 설치하면 판형교의 동적 처짐은 증가하였다. 그러나 처짐이 증가하더라도 규정에 있는 한계를 넘지는 않아 차량의 안정적 주행에 영향을 주지는 않는다. 천연고무나 크로로프렌 고무패드는 변형이 크게 발생하여 교좌로서 활용이 부적합하나, 폴리우레탄 고무패드는 변형이 작게 나타나 사용성이 우수한 것으로 판단되었다. 그러나 고속 주행을 위해서는 패드의 면적을 증가 시켜서 패드변형을 제한해야 하는 것으로 나타났다. 고무패드의 강성증가 및 감쇠비 증가가 교량의 동적 거동에 미치는 영향에 대해서 분석을 실시하였다. 고무패드의 감쇠비 증가는 교량의 동적 거동에 거의 영향을 주지 않았다. 패드의 강성 증가는 상대적으로 자중이 크고 강성이 작은 교량에서는 응답 개선 효과가 적지만, 자중이 작고 강성이 큰 즉 경간이 짧은 교량에서 상대적으로 응답 개선 효과가 크게 나타났다. In this study, the dynamic characteristics of the two open-steel-plate-girder bridges was analyzed using the pads' stiffness estimated in the previous accompanying paper.Also, it was determined that the variation in the dynamic behavior of the two bridges due to the pads corresponds to the codes describing the restriction for the steel bridges' behavior.The pads installed at the bridges increase the displacement at mid-span.However, the increase does not exceed code restrictions and does not have an adverse effect on the riding quality of the running trains. The natural and Chloroprene rubber pads are not suitable for bridge bearings since they are more deformed than the code regulated ones.

결막하 스파르가눔증 1예

최은수,한상엽,박동원,노주헌,Eun-Su Choi,Sang-Youp Han,Dong-Won Park,Ju-Hun Rho 대한안과학회 2005 대한안과학회지 Vol.46 No.12

Purpose: The subconjunctival sparganosis is rare tissue helminthiasis which developed frequently in abdominal, urethral, ureteral and vertebral cases. Authors report a case of sparganosis in the subconjunctival mass. Methods: A 51-year-old man with reddish non painful mass in his left eye on the subconjunctiva that was unresponsive to medications for 6months was evaluated and treated surgically. On surgical exploration, a white thread-like plerocercoid 0.2×4.7 cm in size was extracted from the subconjunctival mass and actively motile in the bottle filled with saline. It was confirmed as a typical sparganum under histologic examination. Three months after surgery, the lesion disappeared completely. Results: Although rare, parasitic disease should be suspected in a palpable subconjuntival mass unresponsive to the medical treatment.

쯔쯔가무시병에서 발생한 전포도막염 1예

최은수,문상정,김호숭,이경헌,Eun Su Choi,Sang Jeong Moon,Ho Soong Kim,Kyung Hun Lee 대한안과학회 2010 대한안과학회지 Vol.51 No.10

Purpose: To report a single case of tsutsugamushi disease with anterior uveitis and eschars on the upper eyelid. Case summary: A 56-year-old female patient complained of ocular pain and gradually decreasing visual acuity in her right eye. On physical examination, lymphadenopathy was palpable on the right side of the neck, and eschars were observed on the forehead and upper eyelid. On slit lamp examination, conjunctival injection, episcleral vessel dilations and severe intraocular inflammatory reaction were observed. Fundus examination showed no abnormal findings. A blood test was submitted for analysis, and tsutsugamushi disease was diagnosed. The patient’s ocular manifestations responded well to treatment with steroids. After three weeks, the patient showed improvement on ocular examination, and no problems were observed at the six-month follow-up. Conclusions: Although ocular manifestation of tsutusgamushi disease with conjunctivitis and limbitis has previously been reported, ocular manifestation of tsutusgamushi disease with anterior uveitis has not been reported. Anterior uveitis may respond satisfactorily to steroid treatment, along with improvement in systemic conditions. J Korean Ophthalmol Soc 2010;51(10):1414-1418

소아에서 위장관내 이물질의 임상적 고찰

최은수,이호균,최수진나,정상영,Choi, Eunsoo,Lee, Hyo Gyun,Choi, Soo Jin Na,Chung, Sang Young 대한소아외과학회 2014 소아외과 Vol.20 No.1

Foreign body ingestion is a common problem among paediatric populations. Most of the ingested foreign bodies spontaneously pass through the gastrointestinal tract, but approximately less then 10% of them remain without being discharged, and trigger complications. Therefore, proper evaluation and treatment according to the situation is required. In this study, clinical progress and complications were analyzed according to the clinical features and treatment in children who ingested foreign bodies. Among pediatric patients under 18 who were admitted to Chonnam National University Hospital after ingesting foreign bodies between January 2008 to June 2012, only the patients who had their foreign body in the gastrointestinal tract were included in this study. Based on medical records, age, type of foreign body, time spent till admission, and whether the endoscopy was done or not, complication were researched retrospectively. According to symptoms and plain abdomen X-ray findings, treatment was chosen and conducted among endoscopy, observation and emergency operation. Among 273 patients, 9 (3.3%) of them had surgical removal. Seven (2.6%) of them had an emergency operation on the day of admission, and the rest 2 (0.7%) had operation during observation. Removal through initial endoscopic approach was tried in 157 (57.5%) patients. Eleven (70.8%) of them had their foreign body removed at the initial trial, and 5 (4.9%) of them at the second trial. Among 109, who were on observation status, 9 (8.3%) of them needed endoscopic removal, and 2 (1.8%) of them suffered from surgical removal. It is thought to be better to approach slowly considering the type, size and symptoms in foreign body ingestion of pediatric patients, rather than immediate and invasive removal.

폴리우레탄 고무 스프링의 압축 강성도 추정 및 적용

최은수,박승진,우대승,Choi, Eunsoo,Park, Seungjin,Woo, Daeseung 한국강구조학회 2017 韓國鋼構造學會 論文集 Vol.29 No.3

The purpose of this study is to investigate the behavior and characteristics of rubber springs and calculate the compressive stiffness by performing dynamic compression tests of rubber springs. In order to carry out the dynamic compression test of rubber spring, total 9 rubber springs were tailored by calculating the shape factor of L80-D55, L90-D58, and L100-D60, and used for the experiments. Experiments were performed by controlling the compression according to the length of the rubber spring, and the compression was increased in the order of 5%, 10%, 15%, 20% and 25% of the strain. From the experimental results, the force-strain curves were obtained and it was confirmed that strength decrease and strength increase phenomenon occurred as the strain increased. In addition, it was confirmed that the decrease of stiffness and the increase of stiffness were clearly observed according to the size and diameter of the rubber spring, and the effective compression stiffness was estimated using the slope of the force-strain curve. By using the effective compressive stiffness, design values that can be used in actual design were presented. 이 연구에서는 고무스프링의 동적 압축실험을 수행하여 고무스프링의 거동 및 특성을 규명하고 압축 강성도를 계산하여 실제 설계값에 대해 알아보고자 하였다. 고무스프링의 동적 압축실험을 수행하기 위하여, L80-D55, L90-D58, L100-D60의 고무스프링의 형상계수를 구하여 총 9개의 고무스프링을 주문 제작 하여 실험에 사용하였다. 실험은 고무스프링의 길이에 따라 기압축을 제어하여 수행하였으며, 기압축은 변형률의 5%, 10%, 15%, 20%, 25% 순서로 증가시켰다. 실험결과를 통해 힘-변형률 곡선을 얻을 수 있었고, 변형률의 증가함에 따라 강도감소 현상과 강도증가 현상이 발생함을 확인하였다. 또한 고무스프링의 크기와 지름에 따라 강성저하 및 강성증가 현상이 확연하게 나타남을 확인하였고, 힘-변형률 곡선에서 할선기울기를 이용하여 유효 압축강성도를 추정하였다. 유효압축강성도를 이용하여 실제 설계에 사용할 수 있는 설계값을 제시하였다.

디스크 받침에 의한 철도 판형교의 고유진동수 및 동적 거동 변화

최은수,이희업,김성일,김이현,Choi, Eun Soo,Lee, Hee Up,Kim, Sung Il,Kim, Lee Hyeon 한국강구조학회 2006 韓國鋼構造學會 論文集 Vol.18 No.4

철도판형교는 한국철도 교량에서 약 40%를 차지하고 있는 중요교량 형식중의 하나이다. 그러나 판형교의 대표적인 교량받침은선받침으로 거동 및 유지관리에 상당한 문제들을 발생시키고 있다. 이러한 문제를 해결하기 위한 방안연구의 일환으로 본 연구에서는 판형교의 실교량을 선정하여 선받침을 폴리우레탄 디스크 받침으로 교체하였다. 폴리우레탄 디스크 받침은 탄성받침의 일종으로 폴리우레탄 패드를 사용하여 탄성을 구현한다. 철도 판형교에 이와 같이 탄성받침을 설치하는 경우 실교량의 동특성의 변화 및 동적 거동의 변화를 디젤기관차 재하실험 및 운행차량에 의한 거동 계측을 통해서 분석 평가하였다. 탄성받침에 의해서 판형교의 1차모드 고유진동수가 3% 감소하였으며, 2차 및 3차모드의 고유진동수는 7 및 15% 감소하였다. 디스크 받침에 의해서 판형교의 동적 수직 처짐은 증가하였으나, 디스크의 변형을 제거한 교량의 순수 변형에 의한 처짐은 거의 증가하지 않는다. 교축직각방향의 변위는 디스크 받침의 전단핀 역할에 의해서 감소하는 경향을 보였다. 또한, 수평방향의 가속도도 탄성 받침에 의해서 거의 변화가 없었다. Open-steel-plate-girder(OSPG) bridges are one of the most prevalent bridge types among Korean railway bridges. They account for about 40% of all Korean railway bridges. However, the line-type bearings used for OSPG bridges generate several problems with respect to the bridges' dynamic behavior and maintenance. The replacement of the existing bearings with polyurethane disk bearings could be a possible solution to this problem. This type of disk bearing is an elastic bearing using a polyurethane disk. This study estimated the variations in the natural frequency of a bridge when disk bearings were installed and the bridge's dynamic behavior with a running locomotive and running trains. The first natural frequency of the bridge was 3% lower than that of the as-built bridge after the installation of the disk lower, respectively. Also, the second and third frequencies were 7 and 15% lower, respectively. The disk bearings increased the vertical displacement of the bridge, but the pure displacement, excluding the disk deformation, did not vary. The vertical acceleration did not increase when the disk bearing was installed, with trains running. The shear pin in the disk bearing reduced the lateral displacement and the acceleration of the bridge.