• 한국강구조학회 논문집
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• 제22권2호
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• pp.173-183
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• 2010

본 논문은 I형 강재와 프리캐스트 콘크리트 바닥판으로 구성된 비합성 합성아치 생태교량에 대한 해석 및 실험 연구이다. 범용유한 요소해석 프로그램 ABAQUS(2007)를 사용하여 단위거더, 단위합성거더, 3거더 아치, 3거더 합성아치 등 4종류의 해석모델이 검토되었으며, 해석 결과를 토대로 모델별 거동특성을 분석하고, 3거더 합성아치 모형실험체에 설치될 응력 및 변형률 게이지 위치를 결정하였다. 본 연구의 정적파괴 하중실험에 사용된 실험체는 3개의 I형강 거더와 14개의 PC패널로 구성되어 있다. 모형실험체 정적파괴실험결과로부터 강거더 하부플랜지가 항복응력에 도달하는 시기의 재하하중은 유한요소해석을 통해 얻어진 정적하중과 17%정도의 차이를 나타내고 있으며, 실험체 파괴하중은 1,961kN으로 AASHTO LRFD 교량설계기준 (2007)의 단면 소성모멘트를 이용한 작용가능하중은 1,380kN으로 본 실험체는 충분한 내하력을 나타내고 있다. 해석결과와 실험결과를 토대로 새로운 형식의 비합성 합성아치 교량의 안전성과 강도가 충분히 발휘됨을 확인할 수 있었다.

• 한국강구조학회 논문집
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• 제15권2호
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• pp.167-174
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• 2003

본 연구는 보 플랜지와 스티프너의 용접부 양단, 기둥 모서리 부분 스티프너에 라운드를 두는 방법 등을 통하여 총 7개 시험체에 실물대 반복하중실험을 실시한 결과를 나타낸 것이다. 실험 결과를 통하여 다음과 같은 결론을 얻을 수 있었다. (1) 필레(fillet)를 둠으로써 응력집중을 줄여 내진성능을 크게 향상 시킬 수 있다. (2) 스티프너 폭의 증가로 접합부의 강성 및 강도는 증가하였지만 에너지 소산 능력은 감소하였다. (3) 모든 시험체는 규준에서 강진지역의 내진구조에 대해 요구하는 총 0.04 radian의 회전각을 발휘할 수 있는 것으로 나타났다.

• Steel and Composite Structures
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• 제19권1호
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• pp.173-190
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• 2015

This study presents an analytical investigation on the seismic response of a medium-rise buckling-restrained braced frame (BRBF) under the near-fault ground motions. A seven-story BRBF is designed as per the current code provisions for five different combinations of brace configurations and beam-column connections. Two types of brace configurations (i.e., Chevron and Double-X) are considered along with a combination of the moment-resisting and the non-moment-resisting beam-to-column connections for the study frame. Nonlinear dynamic analyses are carried out for all study frames for an ensemble of forty SAC near-fault ground motions. The main parameters evaluated are the interstory and residual drift response, brace displacement ductility, and plastic hinge mechanisms. Fragility curves are developed using log-normal probability density functions for all study frames considering the interstory drift ratio and residual drift ratio as the damage parameters. The average interstory drift response of BRBFs with Double-X brace configurations significantly exceeded the allowable drift limit of 2%. The maximum displacement ductility characteristics of BRBs is efficiently utilized under the seismic loading if these braces are arranged in the Double-X configurations instead of Chevron configurations in BRBFs located in the near-fault regions. However, BRBFs with the Double-X brace configurations exhibit the higher interstory drift and residual drift response under near-fault ground motions due to the formation of plastic hinges in the columns and beams at the intermediate story levels.

• International Journal of Concrete Structures and Materials
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• 제9권4호
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• pp.401-413
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• 2015

In this study the progressive collapse resisting capacity of a RC beam-column subassemblage with and without strengthening was investigated. Total of five specimens were tested; two unreinforced specimens, the one designed as gravity load-resisting system and the other as seismic load-resisting system, and three specimens reinforced with: (i) bonded strand, (ii) unbonded strand, and (iii) side steel plates with stud bolts. The two-span subassemblages were designed as part of an eight-story RC building. Monotonically increasing load was applied at the middle column of the specimens and the force-displacement relationships were plotted. It was observed that the gravity load-resisting specimen failed by fractures of re-bars in the beams. In the other specimens no failure was observed until the maximum displacement capacity of the actuator was reached. Highest strength was observed in the structure with unbonded strand. The test result of the specimen with side steel plates in beam-column joints showed that the force-displacement curve increased without fracture of re-bars. Based on the test results it was concluded that the progressive collapse resisting capacity of a RC frame could be significantly enhanced using unbonded strands or side plates with stud bolts.

• 한국강구조학회 논문집
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• 제14권1호
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• pp.31-40
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• 2002

적층된 박벽 복합재료 보의 자유 진동에 관한 연구를 수행하였다. 박벽 C형강 복합재료의 동적 거동에 적용 가능한 일반적인 해석 모델을 개발하였다. 이 모델은 classical lamination theory를 기초로 두고 있으며, 임의의 적층 상태의 구성 즉, 대칭뿐만 아니라 비대칭의 적층 상태, 그리고 다양한 경계조건에 따른 휨과 비틀림 형상의 연계(coupling)을 설명하였다. 변위를 기반으로 한 일차원 유한 요소 모델은 박벽 복합재료 보의 고유 진동수와 그에 대응하는 진동 모드를 예측하기 위해 개발되었다. 운동방정식은 Hamiton의 원리로부터 유도되었으며, 수치적인 결과는 박벽 복합재 보에서 복합재료의 진동수와 모드 형상에 대해 적층각, 계수비, 그리고 경계조건의 영향을 얻을 수 있었다.

• 전산구조공학
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• 제2권3호
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• pp.69-75
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• 1989

브레이싱재를 사용하는 목적은 본 골조체계 즉 기둥과 보에 비해 단면(강성)이 작은 부재로 보강하여 횡력에 대한 강성효과를 크게 향상시키기 위함이다. 브레이싱재의 단면이 기둥과 보의 단면에 비해 월등히 작기 때문에 압축력에 의한 좌굴의 위험성과 휨량의 크기에 비례하여 부재 중앙에 발생되는 추가 모멘트(P-.DELTA. Effect)에 의한 불리한 영향 및 해석상의 어려움 때문에 브레이싱의 설계에 있어서 브레이싱재는 압축력을 받지 않는 것으로 간주하여 왔다. 그러나 최근 들어 구조물 해석에 정확도가 요구되어짐에 따라 브레이싱재의 정확한 거동에 대한 연구가 실험을 통해 활발히 진행되어 왔고, 특히 탄성한계를 지난 소성상태에서 반복하중에 의한 거동 규명이 큰 관심을 끌고 있다. 본 논문에서는 반복하중을 받는 강재 브레이싱재의 비선형 거동을 해석적 방법에 의해 규명했고, 그 결과를 실험결과와 비교하였다.

• Steel and Composite Structures
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• 제45권2호
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• pp.293-303
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• 2022

In order to improve the seismic resilience of coupled wall structure, coupling beam with fuse has been developed to reduce the post-earthquake damage. However, the fuses often have a build-up I-shaped section and are relatively heavy to be replaced. Moreover, the fuse and the beam segments are usually connected by bolts and it is time-consuming to replace the damaged fuse. For reducing the repair time and cost, a novel quickly replaceable coupling beam with buckling-restrained energy dissipaters is developed. The fuse of the proposed coupling beam consists of two chord members and bar-typed energy dissipaters placed at the corners of the fuse. In this way, the weight of the energy dissipater can be greatly reduced. The energy dissipaters and the chords are connected with hinge and it is convenient to take down the damaged energy dissipater. The influence of ratio of the length of coupling beam to the length of fuse on the seismic performance of the structure is also studied. The seismic performance of the coupled wall system with the proposed coupling beam is compared with the system with reinforced concrete coupling beams. Results indicated that the weight and post-earthquake repair cost of the proposed fuse can be reduced compared with the typical I-shaped fuse. With the increase of the ratio of the beam length to the fuse length, the interstory drift of the structure is reduced while the residual fuse chord rotation is increased.

• Earthquakes and Structures
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• 제14권3호
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• pp.249-259
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• 2018

This paper aims to assess the seismic risk of a plane moment-resisting frames (MRFs) consisting of concrete-filled double skin steel tube (CFDST) columns and I-section steel beams. Firstly, three typical limit performance levels of CFDST structures are determined in accordance with the cyclic tests of seven CFDST joint specimens with 1/2-scaled and the limits stipulated in FEMA 356. Then, finite element (FE) models of the test specimens are built by considering with material degradation, nonlinear behavior of beam-column connections and panel zones. The mechanical behavior of the concrete material are modeled in compression stressed condition in trip-direction based on unified strength theory, and such numerical model were verified by tests. Besides, numerical models on 3, 6 and 9-story CFDST frames are established. Furthermore, the seismic responses of these models to earthquake excitations are investigated using nonlinear time-history analyses (NTHA), and the limits capacities are determined from incremental dynamic analyses (IDA). In addition, fragility curves are developed for these models associated with 10%/50yr and 2%/50yr events as defined in SAC project for the region on Los Angeles in the Unite State. Lastly, the annual probabilities of each limits and the collapse probabilities in 50 years for these models are calculated and compared. Such results provide risk information for the CFDST-MRFs based on the probabilistic risk assessment method.

• Steel and Composite Structures
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• 제19권5호
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• pp.1167-1184
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• 2015

Despite considerable life casualty and financial loss resulting from past earthquakes, many existing steel buildings are still seismically vulnerable as they have no lateral resistance or at least need some sort of retrofitting. Passive control methods with decreasing seismic demand and increasing ductility reduce rate of vulnerability of structures against earthquakes. One of the most effective and practical passive control methods is to use a shear panel system working as a ductile fuse in the structure. The shear Panel System, SPS, is located vertically between apex of two chevron braces and the flange of the floor beam. Seismic energy is highly dissipated through shear yielding of shear panel web while other elements of the structure remain almost elastic. In this paper, lateral behavior and related benefits of this system with narrow-flange link beams is experimentally investigated in chevron braced simple steel frames. For this purpose, five specimens with IPE (narrow-flange I section) shear panels were examined. All of the specimens showed high ductility and dissipated almost all input energy imposed to the structure. For example, maximum SPS shear distortion of 0.128-0.156 rad, overall ductility of 5.3-7.2, response modification factor of 7.1-11.2, and finally maximum equivalent viscous damping ratio of 35.5-40.2% in the last loading cycle corresponding to an average damping ratio of 26.7-30.6% were obtained. It was also shown that the beam, columns and braces remained elastic as expected. Considering this fact, by just changing the probably damaged shear panel pieces after earthquake, the structure can still be continuously used as another benefit of this proposed retrofitting system without the need to change the floor beam.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.192-195
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• 2004

Recently, the development of construction materials is rapidly advancing. Especially, the rate of development of cement based construction materials is much quicker than steel or composite materials. In order to optimize the ductility and strength of cement based materials, Micro-mechanics based fiber concrete called Engineered Cement Composite (ECC) is developed and studied extensively by many researchers in the field. Due to ECC's remarkable flexural strain and strength capacities, many leading nation (i.e., US, Japan, and European countries) are currently using ECC in actual constructions. In this study, ECC with internationally competitive material capacities is manufactured using domestic materials. Then, unreinforced concrete beams are repaired using ECC with $10\%,\;20\%,\;30\%$ of concrete specimen height Using 4 point bending test, the flexural strength of repaired flexural members are determined. The results show that ECC manufactured with domestic materials can be effectively used for repairing materials.