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최현훈(Choi Hyun-Hoon),김진구(Kim Jin-Koo) 대한건축학회 2008 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.28 No.1(구조계)
To increase the effective damping force and to reduce the damper volume the magnifying system of the damper displacement such as toggle brace system and scissor-jack-damper configuration have been developed with increase in installation cost. In this study new installation scheme for dampers was proposed using cable. To verify the validity of the proposed method nonlinear dynamic analysis of model structures with viscoelastic dampers installed using the proposed configuration scheme was carried out. In the analysis three different earthquake records were used. According to the analysis results the proposed method resulted in significant reduction in the size of dampers compared with the conventional installation methods.
최현훈(Choi Hyun-Hoon),김진구(Kim Jin-Koo) 대한건축학회 2008 大韓建築學會論文集 : 構造系 Vol.24 No.11
In general passive energy dissipation devices (PEDD) such as viscous, viscoelastic, and friction devices are installed using diagonal or chevron braces. To increase the effective damping force and to reduce the damper volume the magnifying system of the damper displacement such as toggle brace system and scissor-jack-damper configuration have been developed with increase in installation cost. In this study new installation scheme for PEDD was proposed using cables installed in such a way that relative displacement occurs between the cable and the structure when the structure is subjected to lateral load. The cables can be installed continuously or discretely between base and top story of the structure. To verify the validity of the proposed method nonlinear dynamic analysis of model structures with viscoelastic dampers installed using the proposed configuration scheme was carried out using three different earthquake records and two sinusoidal forces. According to the analysis results the proposed method resulted in significant reduction in the size of dampers compared with the conventional installation methods.
분사제트 온도변화에 따른 벽면충돌 현상에 대한 실험적 연구
최현훈(Hyeonhun Choi),우루노유미(Yumi Uruno),김상호(Sangho Kim),정재원(Jaewon Chung) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
In order to remove dissolved oxygen and carbon dioxide from feedwater in power generation facilities, boilers and incinerators, deaerators are essential. In actual deaerator, temperature of spray is about 145°C and the surrounding temperature is about 177°C (steam temperature). It is necessary to analyze the temperature in order to improve the efficiency of deaerator. In this paper, splashed fraction and jet breakup according to the distance from nozzle were studied. Also, Liquid film shapes on the vertical wall are visualized and analyzed using highspeed camera. These were obtained at different temperature respectively. As temperature increases, ξ(splashed fraction) becomes smaller overall. Also, the value of ξ<SUB>max</SUB>(maximum of splashed fraction) decreases as the temperature increases. The Rayleigh regime, the first wind-induced regime, and the second wind-induced regime were confirmed by jet breakup images. The phenomenon that <SUB>max</SUB> decreased with increasing temperature was visualized and confirmed. It was confirmed that the diameter of the liquid film becomes larger as the temperature rises. That is, ξ decreases because droplets spread on the wall and the thickness of the liquid film becomes thinner. Therefore, when the temperature of water rises, ξ decreases. The results of this paper are used to increase the efficiency of actual deaerator and provide data for design and optimization.
최현훈(Choi Hyun-Hoon),박경훈(Park Kyoung-Hoon),전용(Jeon Yong),김진구(Kim Jin-Koo) 대한건축학회 2009 大韓建築學會論文集 : 構造系 Vol.25 No.12
In this study experiments were carried out to investigate the progressive collapse resisting capacity of RC beam-column subassemblages designed with and without seismic load. The two-span subassemblages were designed as part of an eight-story RC moment resisting frame. The right interior column was designed 1.5 times as large in size as the middle interior column to take into account the continuation of the girder. Monotonically increasing load was applied at the middle column of the specimens and the force-displacement relationships were plotted. It was observed that the non-seismic designed specimen failed by crushing of concrete at the exterior column-girder joint before catenary action was activated. However the force-displacement relationship of the specimen designed for seismic load kept increasing after fracture of the girder lower re-bars near the middle column due to the catenary action of the upper re-bars. Based on the test results it was concluded that RC moment-resisting buildings designed per current design code might have significant resisting capacity against progressive collapse initiated by sudden loss of a column.