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철골연결재 및 고인성섬유복합체를(ECC) 이용한 프리캐스트 보-기둥 접합부의 거동에 관한 실험적 연구
최현기(Choi Hyun-Ki),류창희(Yoo Chang-Hee),최윤철(Choi Yun-Cheul),최창식(Choi Chang-Sik) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.4
The used of a precast concrete structural system has been limited primarily non-seismic areas. To promote the use of precast concrete in seismic areas, adequate methods between precast members need to be developed and they must have enough strength and ductility. In this study, new moment-resisting precast concrete beam-column joint was made up of hybrid steel concrete. It has square hollow tubular section in concrete column and connecting plat in precast U-beam. The steel elements of column and beam members be connected from bolt. And in order to prevent the premature failure of concrete in previous hybrid steel-concrete connection, we use the ECC(Engineered Cementitious Composite). An experimental study was carried out to investigate the joint behavior subjected to reversed cyclic loading and constant axial compressive load. Test data showed that properly designed precast beam-column connection maintained ductility, strength and energy-dissipation capacity when subjected to inelastic deformations under load reversals.
전단보강된 플랫 플레이트-기둥 외부접합부의 불균형 모멘트 강도
최현기(Choi Hyun-Ki),최윤철(Choi Yun-Cheul),최창식(Choi Chang-Sik) 대한건축학회 2009 大韓建築學會論文集 : 構造系 Vol.25 No.8
Flat plate slab has been widely used in high rise buildings for its remarkable advantages. However, punching shear failure has become increasingly important issue with the spread of flat plate slab. The intend of this research was to study the response of slab-column connections containing various types of shear reinforcement when subjected to combined gravity and cyclic lateral loading. The three test specimens were full-scale representations of exterior slab-column connections in a prototype Korea apartment building. The control specimen had no shear reinforcement, while the other specimens had CS-Bar(Curve steel) and SS-Bar(Curve steel) as shear reinforcement. The control specimen failed due to punching shear around the slab-column connection at 4.0% drift. None of the shear reinforcement specimen experienced punching failure during testing to 4.4% drift. The estimation for experimental data using the equation of ACI318-05 and CEB-FIP MC 90 represented the problem of application for eccentric shear stress and unbalanced moment. According to the variable analysis, it is needed to consider the variation of reinforcement ratio within effective width of slabs.
최현기(Choi Hyun-Ki),김준서(Kim Jun-Seo),최윤철(Choi Yun-Cheul),백영수(Back Young-Soo),진언식(Jin Eon-Sik),최창식(Choi Chang-Sik) 대한건축학회 2008 大韓建築學會論文集 : 構造系 Vol.24 No.8
There are many in utilizing the flat plate structure in reinforced concrete building. This structure has drawbacks as well because the structure is vulnerable to a punching shear failure at the column connections. This research is an experimental study on full-scale interior slab-column connections of flat-plate. Three types of shear reinforcements were proposed to prevent brittle punching shear failure that could result in collapse of whole flat plate structures. A series of four flat plate specimens including a specimen without shear reinforcement and three specimens with the reinforcements was tested. The dimension of the slabs was 2620*2725* 180㎜ and the specimens had a 600*800㎜ square column at the center of the slabs. The slabs were tested up to failure using monotonic vertical shear forces. The presences of the shear reinforcements substantially increased punching shear capacity and ductility of the interior slab-column connections.
최현기(Choi Hyun-Ki),김준서(Kim Jun-Seo),최윤철(Choi Youn-Cheul),최창식(Choi Chang-Sik),백영수(Back Young Soo) 대한건축학회 2007 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.27 No.1
Flat plate slab has been widely used in high rise buildings for its remarkable advantages. However, punching shear failure has become increasingly important issue with the spread of flat plate slab. A flat plate-column connection is susceptible to brittle punching shear failure, which may result in the necessity of shear reinforcement. In previous, experimental tests were performed to study the capacity of slab-column connections strengthened with various shear reinforcement, and the capacity of the specimens with curve steel reinforcement, experimental studies was performed. The results of an experiment program on punching shear performance of RC slab-column connection are presented in this paper. Specimens were full-scale representations of a one-story slab in a Korean apartment. The test results showed that failure mechanism of specimens governed by shear fracture and the strength of specimens were different according to the retrofitting strategies.
횡 하중 작용시 곡선형 철근으로 보강된 RC 플랫 플레이트 외부 접합부의 구조성능에 관한 실험적 연구
최현기(Choi Hyun-Ki),김준서(Kim Jun-Seo),최윤철(Choi Youn-Cheul),최창식(Choi Chang-Sik) 대한건축학회 2007 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.27 No.1
Flat plate slab has been widely used in high rise buildings for its remarkable advantages. However, punching shear failure has become increasingly important issue with the spread of flat plate slab. The results of an experiment program on punching shear performance of RC slab-column connection are presented in this paper. Specimens were full-scale representations of a one-story slab in a Korean apartment. The test results showed that failure mechanism of specimens governed by shear fracture and the strength of specimens were different according to the retrofitting strategies.
최현기(Choi Hyun-Ki),백성우(Beck Seong-Woo),최윤철(Choi Yun-Cheul),최창식(Choi Chang-Sik) 대한건축학회 2008 大韓建築學會論文集 : 構造系 Vol.24 No.5
Flat plate slab has been widely used in high rise buildings for its remarkable advantages. However, punching shear failure has become increasingly important issue with the spread of flat plate slab. The intend of this research was to study the response of slab-column connections containing various types of shear reinforcement when subjected to combined gravity and cyclic lateral loading. The three test specimens were full-scale representations of exterior slab-column connections in a prototype Korea apartment building. The control specimen had no shear reinforcement, while the other specimens had CS-Bar(Curve steel) and SS-Bar(Curve steel) as shear reinforcement. The control specimen failed due to punching shear around the slab-column connection at 4.0% drift. The two types of slab shear reinforcement proved equally effective in resisting punching shear failure for these connections subjected to relatively low levels of gravity load. The presence of shear reinforcement significantly increased the lateral load ductility of the connection. The test results showed that the strength and ductility of the specimens with the SS-Bar/CS-Bar shear reinforcement were improved by 23% and 13% those of the none of the shear reinforcement specimens, respectively.
금강밀과 dark northern spring밀의 기울과 배아에서 추출한 기름의 광산화 과정 중 천연산화방지성분의 변화
최현기(Hyunki Choi),최은옥(Eunok Choe) 한국식품과학회 2010 한국식품과학회지 Vol.42 No.1
금강밀과 Dark Northern Spring(DNS)밀의 제분 중 발생하는 기울과 배아로부터 추출한 기름(WBG oil)을 5℃, 1700 Lux로 12일 동안 광산화시킬때 토코페롤, 카로티노이드, 인지질 함량 변화를 측정하고 이들과 WBG oil의 광산화 관련성을 평가하였다. 토코페롤, 카로티노이드, 인지질은 WBG oil의 광산화 중 분해되었으며 DNS밀 WBG oil이 금강밀 WBG oil에서보다 토코페롤의 분해가 빨랐으나, 카로티노이드와 인지질 분해 속도는 느렸다. WBG oil의 광산화 정도와 산화방지성분의 상관관계는 매우 높았으며 인지질이 WBG oil의 광산화에 가장 큰 영향을 나타내었다. 금강밀 WBG oil에 비해 리놀레산 함량이 낮고 올레산 함량이 높았던 DNS밀 WBG oil은 지방산 조성은 물론 인지질의 높은 함량과 낮은 분해 속도에 기인하여 높은 광산화안정성을 나타내었다. 본 결과는 빛의 존재하에서 DNS밀 WBG oil보다는 금강밀 WBG oil이 토코페롤 source로 사용될 수 있는 가능성을 보여주었다. Naturally present antioxidants, tocopherols, carotenoids, and phospholipids in the bran and germ oils from Keumkang (K-WBG oil) and Dark Northern Spring wheats (DNS-WBG oil) were determined during storage under 1700lux light at 5℃ by HPLC. Oil oxidation was monitored by peroxide values (POV) and conjugated dienoic acid content. The results showed that antioxidants were degraded during storage of the WBG oils under light, with higher degradation rates for carotenoids and phospholipids in the K-WBG oil compared to the DNS-WBG oil. Light increased oil oxidation and the rate of oxidation was higher in K-WBG oil than in the DNS-WBG oil. There was a high correlation between POV and residual amounts of antioxidants during photo-oxidation, with phospholipids showing the greatest effects on POV. This study suggests that a higher amount and lower degradation rate of phospholipids in the DNS-WBG oil contributed to its higher photo-oxidative stability compared to the K-WBG oil.