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반응수정계수와 주기의 영향에 대한 철골모멘트저항골조 건물의 내진성능평가
신지욱,이기학,이도형 한국지진공학회 2008 한국지진공학회논문집 Vol.12 No.5
본 연구는 높은 지진의 위험이 내재된 지역에 위치한 3층, 9층 그리고 20층 철골 모멘트저항골조에 대한 반응수정계수와 주기의 영향을 평가하기 위한 것이다. 각 구조물들은 IBC 2000과 KBC 2005에서 제시하고 있는 8의 반응수정계수로 설계되었고 건물에 기대되는 최소의 성능과 최대의 성능을 평가하기 위해서 상한범위와 하한범위의 설계가 고려되었다. 또한 반응수정계수에 대한 영향을 조사하기 위하여 4개의 다른 반응수정계수들이(9, 10, 11, 12) 각 구조물에 대하여 적용되었고 각 구조물의 고유주기 값 외의 4개의 다른 주기를 추가로 적용하여 구조물의 동적거동시 주기에 대한 영향을 조사하였다. 총 150개의 해석모델들은 50년 동안 2%의 초과확률(재현 주기 2500년)을 가진 20개의 지반운동에 대하여 평가되었다. 구조물의 성능평가를 위하여 정적 Pushover와 비선형 시간이력해석이 수행되었으며 구조물의 연성능력을 평가하기 위해서 변위연성요구가 고려되었다. 3층과 9층 구조물은 변위연성요구 값이 비교적 안정적인 거동을 보인 반면 20층 구조물은 동적 불안정성을 야기하는 요소에 의해 민감하게 나타나는 것으로 조사되었다. This study was performed to evaluate the effect of Response modification factors (R-factor) in 3-, 9- and 20- story steel Moment Resisting Frame (MRF) buildings. Each structure was designed using a R-factor of 8, as tabulated in the 2000 International Building Code provision (IBC 2000) and Korea Building Code (KBC) 2008. In order to evaluate the maximum and minimum performance expected for such structures, an upper bound and lower bound design were adopted for each model. Next, each analytical model was designed using different R-factors (8, 9, 10, 11, 12) and four different structural periods with the original fundamental period. For a detailed case study, a total of 150 analytical models were subjected to 20 ground motions representing a hazard level with a 2% probability of being exceeded in 50 years. In order to evaluate the performance of the structures, static push-over and non-linear time history analysis (NTHA) were performed, and displacement ductility demand was investigated to consider the ductility capacity of the structures. The results show that the dynamic behaviors for the 3- and 9-story buildings are relatively stable and conservative, while the 20-story buildings show a large displacement ductility demand due to dynamic instability factors. (e.g. P-delta effect and high mode effect)
신지욱,이기학,정성훈,이한선,김진구 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.1
In this paper, Buckling-Restrained Knee Bracing (BRKB) system was developed through sub-assemblage tests. The core plate of the BRKB was restrained with two channel sections. Tests of the five BRKBs were carried out under cyclic loading as specified in the AISC (2005) Seismic Provisions. It was observed that the ductility and energy dissipation capacity of the BRKBs were mainly affected by the variables: size of core plate, size of channel sections, and size of end plate. Four out of five specimens satisfied the compression-strength adjustment factor and cumulative plastic ductility specified in the provisions. The BRKB, which showed the best performance among the test specimens, was applied to a piloti type reinforced concrete building. Static pushover and non-linear time history analyses were performed to confirm the retrofit effect. The analysis results showed that the installation of the BRKBs improved the seismic behavior of the building significantly in terms of strength and story drift.
폭발 하중에 대한 FRP 재킷 시스템이 보강된 철근콘크리트 기둥 해석 모델 개발
신지욱,Shin, Jiuk 한국공간구조학회 2021 한국공간구조학회지 Vol.21 No.2
This paper aims to develop numerical models for seismically-deficient reinforced concrete columns retrofitted using a fiber-reinforced polymer jacketing system under blast loading scenarios. To accomplish the research goal, a coupling model reproducing blast loads was developed and implemented to the column model. The column model was validated with a past experimental study, and the blast responses were compared to the numerical responses produced by past researchers. The validated modeling method was implemented to the non-retrofitted and retrofitted column models to estimate the effectiveness of the retrofit system. Based on the numerical responses, the retrofit system can significantly reduce the peak dynamic responses under a given blast loading scenario.
FRP 기둥 재킷 시스템이 보강된 지진 취약 철근콘크리트 건축물의 유한요소해석
신지욱,이상열,지동현,Shin, Jiuk,Lee, Sang-Youl,Ji, Dong-Hyun 한국공간구조학회 2021 한국공간구조학회지 Vol.21 No.2
This study develops finite element models for seismically-deficient reinforced concrete building frame retrofitted using fiber-reinforced polymer jacketing system and validates the finite element models with full-scale dynamic test for as-built and retrofitted conditions. The bond-slip effects measured from a past experimental study were modeled using one-dimensional slide line model, and the bond-slip models were implemented to the finite element models. The finite element model can predict story displacement and inter-story drift ratio with slight simulation variation compared to the measured responses from the full-scale dynamic tests.
연속 지진에 의하여 손상된 필로티 RC 건축물의 BRB 보강 전/후의 취약성 평가
신지욱,김준희,이기학 한국지진공학회 2013 한국지진공학회논문집 Vol.17 No.3
This paper presents the seismic evaluation and prediction of a damaged piloti-type Reinforced Concrete (RC) building before and after postretrofitting under successive earthquakes. For considering realistic successive earthquakes, the past records measured at the same station were combined. In this study, the damaged RC building due to the first earthquake was retrofitted with a buckling-restrained brace (BRB) before the second earthquake occurred. Nonlinear Time History Analysis (NTHA) was performed under the scaled intensity of the successive ground motions. Based on the extensive structural response data obtained form from the NTHA, the fragility relationships between the ground shaking intensity and the probability of reaching a pre-determined limit state was were derived. In addition, The the fragility curves of the pre-damaged building without and with the BRBs were employed to evaluate the effect of the successive earthquakes and the post-retrofit effect. Through the seismic assessment subjected to the successive records, it was observed that the seismic performance of the pre-damaged building was significantly affected by the severity of the damage from the first earthquake damages and the hysteresis behavior of the retrofit element.
비좌굴가새의 보강 전과 후의 철골 특수모멘트저항골조 건물의 R계수 평가
신지욱,이기학,조영욱 한국지진공학회 2013 한국지진공학회논문집 Vol.17 No.1
This research presents that seismic performance of steel moment resisting frame building designed by past provision(UBC, Uniform Building Code) before and after retrofitted with BRB (Buckling-Restrained Brace) was evaluated using response modification factor(R-factor). In addition, the seismic performance of the retrofitted past building was compared with that specified in current provision. The past building considered two different connections: bilinear connection, which was used by structural engineer for building design, and brittle connection observed in past earthquakes. The nonlinear pushover analysis and time history analysis were performed for the analytical models considered in this study. The R-factor was calculated based on the analytical results. When comparing the R-factor of the current provision with the calculated R-factor, the results were different due to the hysteresis characteristics of the connection types. After retrofitted with BRBs, the past buildings with the bilinear connection were satisfied with the seismic performance of the current provision. However, the past buildings with the brittle connection was significantly different with the R-factor of the current provision.