• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 추계 학술발표회논문집
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• pp.505-512
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• 2003

As large structures such as highrise buildings and cable-stayed bridges become lighter and more flexible, the necessity of structural control for reducing excessive displacement and acceleration due to seismic excitation is increased. As a means to minimize seismic damages, various base isolation systems are adopted or considered for adoption. In this study, the seismic performance of M dampers are studied and compared with that of the NZ system as a base isolation system As the control algorithm of the MR damper, the clipped-optimal control(applied LQR method) is employed. A five-story building is modeled and the seismic performance of the two systems subjected to three different earthquakes is compared. The results show that the M damper system can provide superior protection than the NZ system for a wide range of ground motions.

• 한국구조물진단유지관리공학회 논문집
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• 제17권1호
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• pp.55-63
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• 2013

본 연구는 우리나라에서 가장 일반적인 중소규모의 비내진 상세를 가진 건축물을 대상으로, 노후도를 고려하여 내진성능을 평가하였다. 평가결과, 준공 후 24년이 경과되었으나 노후도는 대체로 양호한 것으로 평가되었고, 1차, 2차 내진성능평가는 기준지표를 만족하지 못하는 것으로 나타났다. 3차 내진성능평가에서는 층간변위비를 기준으로 목표성능은 만족하지만 보강이 필요한 것으로 판단되었다. 대상 건축물에 벽체보강, 가새보강, 댐퍼보강을 한 후 내진성능평가를 실시한 결과, 보강방법에 상관없이 층간변위비는 현저히 감소하여 즉시거주수준을 만족하는 수준으로 나타났다. 그러나 벽체보강의 경우 밑면전단력이 2배 이상 증가되어 기존기초에 대한 검토가 필요하다.

• Earthquakes and Structures
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• 제16권5호
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• pp.523-532
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• 2019

Different types of gas reservoir such as Liquid Natural Gas (LNG) are among the strategic infrastructures, and have great importance for any government or their private owners. To keep the tank and its contents safe during earthquakes especially if the contents are of hazardous or flammable materials; using seismic protection systems such as base isolator can be considered as an effective solution. However, the major deficiency of this system can be the large deformation in the isolation level which may lead to the failure of bearing system. In this paper, as a solution, the efficacy of an optimally designed combined vibration control system, the combined laminated rubber isolator and rotational friction damper, is investigated to evaluate the enhancement of an existing metal tank response under both far- and near-field earthquakes. Responses like impulsive and convective accelerations, base shear, and sloshing height are studied herein. The probabilistic framework is used to consider the uncertainties in the structural modeling, as well as record-to-record variability. Due to the high calculation cost of probabilistic methods, a simplified structural model is used. By using the Mont-Carlo simulation approach, it is revealed that this combined isolation system is a highly reliable system which provides considerable enhancement in the performance of reservoir, not only leads to the reduction of probability of catastrophic failure of the tank but also decrease the reservoir damage during the earthquake. Moreover, the relative displacement of the isolation level is controlled very well by this combined system.

• Structural Engineering and Mechanics
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• 제78권3호
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• pp.333-350
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• 2021

Motivated by the demand of seismic protection of museum collections and development of performance-based seismic design guidelines, this paper investigates the seismic fragility of sliding artifacts based on incremental dynamic analysis and three-dimensional finite element model of the artifact-showcase-museum system considering nonlinear behavior of the structure and contact interfaces. Different intensity measures (IMs) for seismic fragility assessment of sliding artifacts are compared. The fragility curves of the sliding artifacts in both freestanding and restrained showcases placed on different floors of a four-story reinforced concrete frame structure are developed. The seismic sliding fragility of the artifacts within a real-world museum subjected to bi-directional horizontal ground motions is also assessed using the proposed IM and engineering demand parameter. Results show that the peak floor acceleration including only values initiating sliding is an efficient IM. Moreover, the sliding fragility estimate for the artifact in the restrained showcase increases as the floor level goes higher, while it may not be true in the freestanding showcase. Furthermore, the artifact is more prone to sliding failure in the restrained showcase than the freestanding showcase. In addition, the artifact has slightly worse sliding performance subjected to bi-directional motions than major-component motions.

• Earthquakes and Structures
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• 제5권5호
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• pp.499-526
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• 2013

Seismic isolation is an effective method for the protection of buildings and their contents during strong earthquakes. This research work aims to assess the appropriateness of the linear and nonlinear models that can be used in the analysis of typical low-rise base isolated steel buildings, taking into account the inherent nonlinearities of the isolation system as well as the potential nonlinearities of the superstructure in case of strong ground motions. The accuracy of the linearization of the isolator properties according to Eurocode 8 is evaluated comparatively with the corresponding response that can be obtained through the nonlinear hysteretic Bouc-Wen constitutive model. The suitability of the linearized model in the determination of the size of the required seismic gap is assessed, under various earthquake intensities, considering relevant methods that are provided by building codes. Furthermore, the validity of the common assumption of elastic behavior for the superstructure is explored and the alteration of the structural response due to the inelastic deformations of the superstructure as a consequence of potential collision to the restraining moat wall is studied. The usage of a nonlinear model for the isolation system is found to be necessary in order to achieve a sufficiently accurate assessment of the structural response and a reliable estimation of the required width of the provided seismic gap. Moreover, the simulations reveal that the superstructure's inelasticity should be taken into account, especially if the response of the structure under high magnitude earthquakes is investigated. The consideration of the inelasticity of the superstructure is also recommended in studies of structural collision of seismically isolated structures to the surrounding moat wall, since it affects the response.

• 한국공간구조학회논문집
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• 제20권3호
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• pp.81-89
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• 2020

As the damage caused by earthquakes gradually increases, seismic retrofitting for existing public facilities has been implemented in Korea. Several types of structural analysis methods can be used to evaluate the seismic performance of structures. Among them, for nonlinear dynamic analysis, the hysteresis model must be carefully applied because it can significantly affect the behavior. In order to find a hysteresis model that predicts rational behavior, this study compared the experimental results and analysis results of the existing non-seismic reinforced concrete frames. For energy dissipation, the results were close to the experimental values in the order of Pivot, Concrete, Degrading, and Takeda models. The Concrete model underestimated the energy dissipation due to excessive pinching. In contrast, the other ones except the Pivot model showed the opposite results with relatively little pinching. In the load-displacement curves, the experimental and analysis results tended to be more similar when the column axial force was applied to columns.

• 한국화재소방학회논문지
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• 제34권1호
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• pp.47-54
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• 2020

본 논문은 협소공간인 피트 내부에 설치되는 기존 입상관 흔들림방지버팀대의 설치 및 시공 상의 문제점을 개선하고, 수평지진하중(X축, Y축)에 대한 지지역할과 더불어 추가적으로 수직지진하중(Z축)을 지지할 수 있는 협소공간전용 바닥고정형 입상관 버팀대 개발에 관한 연구이다. 솔리드웍스 시뮬레이션을 이용한 구조해석 결과 1차 설계모델의 경우 수직방향에서 앵커 위치에 따른 편심하중이 발생하였고, 수평 및 수직 방향에서 모두 재질의 허용응력을 초과하는 문제가 나타났다. 2차 설계모델의 경우 1차 설계모델에서 발생하였던 수직방향으로의 편심하중에 의한 변형이 발생되지 않았고, 최대변형률이 0.17%로 1차 설계모델(최대변형률 13.01%)보다 약 12.84% 감소하는 것으로 나타나 구조적인 안정성 및 내구성이 향상된 것을 확인할 수 있었다. 시제품에 대한 압축 및 인장 하중시험결과 모든 시제품이 기준에서 정한 성능기준에 적합한 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제82권3호
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• pp.325-341
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• 2022

Previous major earthquakes indicated that the earthquake induced ground motions are typical non-stationary processes, which are non-stationary in both amplification and frequency. For the convenience of aseismic design and analysis, it usually assumes that the ground motions at structural supports are stationary processes. The development of time-frequency analysis technique makes it possible to evaluate the non-stationary responses of engineering structures subjected to non-stationary inputs, which is more general and realistic than the analysis method commonly used in engineering. In this paper, the wavelet-based stochastic vibration analysis methodology is adopted to calculate the non-stationary responses of multi-support structures. For comparison, the stationary response based on the standard random vibration method is also investigated. A frame structure and a two-span bridge are analyzed. The effects of non-stationary spatial ground motion and local site conditions are considered, and the influence of structural property on the structural responses are also considered. The analytical results demonstrate that the non-stationary spatial ground motions have significant influence on the response of multi-support structures.

• 한국공간구조학회논문집
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• 제23권2호
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• pp.53-60
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• 2023

Recently, a novel cast-in specialty insert was developed in Korea as an anchor for lightweight pipe supports, including fire-protection pipes. As these pipe supports and anchors play a critical role in transferring loads of fire-protection pipes to structural members, it is crucial to evaluate their seismic performance before applying the newly developed insert. In this study, the seismic shear performance of the insert anchors was evaluated through cyclic loading tests based on the loading protocols of ACI 355.2 and FEMA 461. Initially, five monotonic loading tests were conducted on the insert anchors in cracked concrete, followed by cyclic loading tests based on the monotonic test results. The findings revealed that the insert anchors exhibited negligible decrease in shear strength even after cyclic loading. Furthermore, a comparison of the maximum load and displacement of the insert anchors obtained under the loading protocols of ACI 355.2 and FEMA 461 was performed to investigate the applicability of the FEMA 461 loading protocol for anchor performance evaluation.

• 한국구조물진단유지관리공학회 논문집
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• 제15권3호
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• pp.106-115
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• 2011

본 연구에서는 비선형 지진응답해석을 이용하여 유도된 전단 및 휨파괴형 부재가 혼합된 저층 철근콘크리트(RC) 건물의 비선형 요구내력스펙트럼을 수식화하여, 특정 연성률 별로 지진입력수준과 내진성능잔존률을 산정하여, 건물의 지진손상정도를 정량적으로 평가 가능한 새로운 내진성능 평가법을 제안하였다. 또한 저층 RC 건물을 대상으로 본 연구의 내진성능 평가법을 적용하여 평가한 결과와 보다 정밀한 부재수준의 비선형 동적해석을 실시하여 그 결과를 각각 비교 검토함과 동시에, 내진진단기준에서 입력지진동 0.2g 수준에 대해서 구조체에 대규모이상의 지진피해를 막기 위한 임계값으로 설정한 내진성능판정지표값 (Es=0.6)과의 상관관계를 분석하여 본 연구에서 제안한 내진성능 평가법의 타당성 및 그 적용가능성을 검증하였다. 본 평가법은 비선형해석 또는 능력스펙트럼법 등의 상세 내진성능 평가법을 수행하지 않고도 대상건물에 대한 연성률 단계별의 입력지진 수준, 지진손상도를 정량적으로 평가할 수 있다. 향후 전단 및 휨파괴형 부재가 혼합된 저층 RC 건물의 내진성능을 효과적으로 평가하기 위한 자료로서 활용이 가능하다고 판단된다.