• Smart Structures and Systems
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• 제8권4호
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• pp.399-412
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• 2011

This study compares the performance of two smart isolation systems that utilize superelastic shape memory alloys (SMAs) for seismic protection of bridges using energy balance concepts. The first isolation system is a SMA/rubber-based isolation system (SRB-IS) and consists of a laminated rubber bearing that decouples the superstructure from the bridge piers and a SMA device that provides additional energy dissipation and re-centering capacity. The second isolation system, named as superelastic-friction base isolator (S-FBI), combines the superelastic SMAs with a flat steel-Teflon bearing rather than a laminated rubber bearing. Seismic energy equations of a bridge structure with SMA-based isolation systems are established by absolute and relative energy balance formulations. Nonlinear time history analyses are performed in order to assess the effectiveness of the isolation systems and to compare their performance. The program RSPMatch 2005 is employed to generate spectrum compatible ground motions that are used in time history analyses of the isolated bridge. Results indicate that SRB-IS produces higher seismic input energy, recoverable energy and base shears as compared to the S-FBI system. Also, it is shown that combining superelastic SMAs with a sliding bearing rather than rubber bearing significantly reduce the amount of the required SMA material.

• 한국지진공학회논문집
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• 제11권3호
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• pp.73-86
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• 2007

본 논문에서는 제4세대 소듐냉각고속로(Sodium-Cooled Fast Reactor)의 후보 노형으로 선정된 KALIMER-600에 대한 단순 지진해석모델을 개발하고 시간이력 지진응답해석을 수행하여 수평 면진설계(Seismic Isolation) 기술이 적용된 원자로건물의 주요기기 및 구조물에서의 지진응답 성능을 분석하였다. 개발된 단순 지진해석모델은 원자로건물, 원자로시스템, 주요 기기, 중간 열전달계통 배관, 그리고 면진장치를 포함하며 각각은 상세 유한요소해석을 통한 동특성 비교검증을 통하여 정확성을 검증하였다. 안전정지기준 0.3g의 설계인공지진 하중에 대한 시간이력 지진응답해석을 수행하여 면진설계와 비면진 설계조건에 따른 원자로 주요 부위에서의 층응답스펙트럼을 비교분석한 결과 KALIMER-600의 면진성능이 우수한 것으로 나타났다.

• 한국지반공학회논문집
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• 제34권1호
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• pp.5-16
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• 2018

본 연구에서는 지반에서 1차적인 면진작용을 할 수 있는 지반형 지진격리장치의 내진성능을 평가하였다. 테프론과 제강슬래그를 이용하여 지반형 지진격리장치를 조성한 후 그 위에 모형 상부구조물을 설치하고 1-G 진동대 실험을 수행하였다. 다양한 수준의 입력지진파에 대해 응답가속도와 응답스펙트럼을 분석하였으며, 지진격리장치가 없는 고정기초 구조물과 결과를 비교하였다. 연구결과, 제강슬래그형 지진격리장치가 가장 가속도 저감효과가 좋았으며, 테프론형 지진격리장치는, 중 약진 조건에서는 가속도 저감효과가 크게 없고 강진조건에서는 가속도 저감효과가 좋았다. 입력파가 상부질량(Mass)으로 전달되면서, 고정기초 구조물의 응답스펙트럼은 입력지진파에 비해 단주기영역에서 증폭하고, 테프론과 제강슬래그를 이용한 지진격리장치가 있는 구조물의 응답스펙트럼은 입력지진파에 비해 장주기 영역에서 증폭하였다. 이러한 주기특성 변화와 재료간의 마찰특성이 가속도 저감효과에 영향을 준 것으로 판단된다.

• 한국안전학회지
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• 제37권3호
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• pp.45-51
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• 2022

This paper focuses on a recently proposed asymmetric base-isolation coupling control system (ABiCS) for the vibration control of adjacent twin buildings. The ABiCS consists of inter-story diagonal dampers, a connecting damper between the two buildings, and a seismic isolation device at the base floor of one building. To investigate the control characteristics of ABiCS, a parametric study was performed by numerically simulating the 20-story twin buildings. In the parametric study, the control capacities of the inter-story diagonal dampers, connecting damper, and seismic isolation device were considered as varying parameters. The parametric study results indicate that the connecting damper between the two buildings reduces the responses of both buildings only at optimal or near-optimal capacity. In addition, adjusting the stiffness of the base isolation is found to be the most effective method for improving seismic performance and achieving cost-effectiveness. Accordingly, we presented a scenario-based performance improvement approach in which reducing the stiffness of the base isolation device could be an effective technique to improve the seismic performance of both buildings. However, note that checking the maximum allowable displacement of the base isolation device is essential.

• Structural Engineering and Mechanics
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• 제73권4호
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• pp.447-454
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• 2020

Seismic isolation technology has a wide application to protect bridges from earthquake damage, a new designed bridge pier with seismic isolation are provided for railways in seismic regions of China. The pier with rocking isolation is a self-centering system under small and moderate earthquakes, and the unbonded prestressed tendons are used to prevent overturning under strong earthquakes. A numerical model based on pseudo-static testing results is presented to evaluate the seismic performance of isolation bridge piers, and is validated by the shaking table test. It is found that the rocking response and the loss of prestressing for the bridge pier increase with the increase of earthquake intensity. Besides, the intensity and spectral characteristics of input ground motion have great influence on displacement of the top and bottom of the bridge pier, while have less influence on the bending moment of the pier bottom. Experimental and numerical results show that the rocking-isolated piers presented in this study have good seismic performance, and it provides an alternative way for the railway bridge in the regions with high occurrence of earthquakes. Therefore, we provide the detailed procedures for seismic design of the rocking-isolated bridge pier, and a case study of the seismic isolation design with rocking piers is carried out to popularize the seismic isolation methods.

• 한국지진공학회논문집
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• 제19권1호
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• pp.29-36
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• 2015

Base isolation is considered as a seismic protective system in the design of next generation Nuclear Power Plants (NPPs). If seismic isolation devices are installed in nuclear power plants then the safety under a seismic load of the power plant may be improved. However, with respect to some equipment, seismic risk may increase because displacement may become greater than before the installation of a seismic isolation device. Therefore, it is estimated to be necessary to select equipment in which the seismic risk increases due to an increase in the displacement by the installation of a seismic isolation device, and to perform research on the seismic performance of each piece of equipment. In this study, modified NRC-BNL benchmark models were used for seismic analysis. The numerical models include representations of isolation devices. In order to validate the numerical piping system model and to define the failure mode, a quasi-static loading test was conducted on the piping components before the analysis procedures. The fragility analysis was performed by using the results of the inelastic seismic response analysis. Inelastic seismic response analysis was carried out by using the shell finite element model of a piping system considering internal pressure. The implicit method was used for the direct integration time history analysis. In addition, the collapse load point was used for the failure mode for the fragility analysis.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.292-297
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• 2000

The seismic isolation technology has appeared to be increasingly necessary for highway bridges, LNG tank, nuclear power plant, and building structures in view of earthquake vibrations. Also high-technology industries require effective seismic protection. The Seismic Isolation Bearing - High Damping Rubber Bearing - system has been counted as the most effective way fur seismic isolation, which is now under development and widely used in industries. Here, the commercial FEM software for nonlinear analysis, MARC, has provided force-displacement curves on the rubber system. The analyses have been carried out about fourteen cases; 25%, 50%, 75%, 100%, 125% and 150% horizontal displacements with a different frequency - 0.01Hz and 0.50Hz - and 100% horizontal displacement with four different frequency - 0.01Hz, 0.16667Hz, 0.3333Hz and 0.50Hz. The unknown constants of the strain energy function of Ogden model have been obtained by a tension test and planar shear test.

• 한국구조물진단유지관리공학회 논문집
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• 제6권1호
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• pp.179-191
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• 2002

This paper presents a systematic approach to the seismic nonlinear analysis and retrofit strategies for existing bridges with isolation system using retrofit slate function newly proposed in this study. A seismic retrofit scheme using sliding base isolation system was presented to reduce the seismic hazard for bridge structures. In this study, two types of isolation systems such as lead bearings and sliding isolators were used. The behavior of sliding isolators was modeled by a triaxial interaction model. And three types of earthquakes such as El Centro, San Fernando, and the artificial were used as earthquake ground excitations. Seismic response analyses of the bridge before and after retrofit were effectively carried out by using a three-dimensional nonlinear seismic analysis program, IDARC-Bridge. Also, this paper proposes a retrofit state function for easily representing the efficiency of a retrofit scheme.

• Structural Engineering and Mechanics
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• 제87권5호
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• pp.405-418
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• 2023

This study focused on the effectiveness of seismic isolation technique in case of a reinforced concrete structure with soft story defined as the stiffness irregularity between adjacent stories. In this context, a seismically isolated 3-story reinforced concrete structure was analyzed by gradually increasing the first story height (3.0, 4.5, and 6.0 m). The seismic isolation system of the structure is assumed to be composed of lead rubber bearings (LRB). In the analyses, isolators were modeled by both deteriorating (temperature-dependent analyses) and non-deteriorating (bounding analyses) hysteretic representations. The deterioration in strength of isolator is due to temperature rise in the lead core during cyclic motion. The ground motion pairs used in bi-directional nonlinear dynamic analyses were selected and scaled according to codified procedures. In the analyses, different isolation periods (Tiso) and characteristic strength to weight ratios (Q/W) were considered in order to determine the sensitivity of structural response to the isolator properties. Response quantities under consideration are floor accelerations, and interstory drift ratios. Analyses results are compared for both hysteretic representations of LRBs. Results are also used to assess the significance of the ratio between the horizontal stiffnesses of soft story and isolation system. It is revealed that seismic isolation is a viable method to reduce structural damage in structures with soft story.

• Earthquakes and Structures
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• 제16권6호
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• pp.743-755
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• 2019

In this paper, a new system of seismic isolation for buildings - called suspended columns - is introduced. In this method, the building columns are placed on the hinged cradle seats instead of direct connection to the foundation. In this system, each of the columns is put on a seat hung from its surrounding area by a number of cables, for which cavities are created inside the foundation around the columns. Inside these cavities, the tensile cables are hung. Because of the flexibility of the cables, the suspended seats vibrate during an earthquake and as a result, there is less acceleration in the structure than the foundation. A Matlab code was written to analyze and investigate the response of the system against the earthquake excitations. The findings showed that if this system is used in a building, it results in a significant reduction in the acceleration applied to the structure. A shear key system was used to control the structure for service and lateral weak loads. Moreover, the effect of vertical acceleration on the seismic behavior of the system was also investigated. Effect of the earthquake characteristic period on the system performance was studied and the optimum length of the suspension cables for a variety of the period ranges was suggested. In addition, measures have been taken for long-term functioning of the system and some practical feasibility features were also discussed. Finally, the advantages and limitations of the system were discussed and compared with the other common methods of seismic isolation.