• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.25-28
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• 2004

Many highway bridges in Korea need seismic retrofit because only one decade has passed since the seismic design criteria was introduced. In this experimental study, the effectiveness of base isolation bearings was discussed for the seismic retrofit of the highway bridges. Four real scale RC pier specimens were constructed for the test. These RC piers didn't have seismic details. Except for one RC pier for the pilot test, three types of bearings such as Pot bearing, Rubber bearing (RB), Lead-rubber bearing (LRB) were applied to the other RC piers respectively. The RC pier with Pot bearing means current state of the prototype bridge that is not retrofitted seismically. And two RC piers with RB or LRB mean assumed states of the prototype bridge that are retrofitted seismically. To simulate dynamic behavior of these RC piers under earthquake loads, Pseudo-dynamic test method was used.

• Structural Engineering and Mechanics
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• v.67 no.1
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• pp.69-78
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• 2018

The study presented herein focused on the change in hysteretic force-deformation behavior of lead rubber bearings (LRBs). The material model used to idealize response of LRBs under cyclic motion is capable of representing the gradual attrition in strength of isolator unit on account of lead core heating. To identify the effect of loading history on the hysteretic response of LRBs, a typical isolator unit is subjected to cyclic motions with different velocity, amplitude and number of cycles. Furthermore, performance of an LRB isolated single degree of freedom system is studied under different seismic input levels. Finally, the significance of lead core heating effect on LRBs is discussed by considering the current design approach for base isolated structures. Results of this study show that the response of an LRB is governed strongly by the amplitude and number of cycles of the motion and the considered seismicity level.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.747-748
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• 2005

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.4 s.50
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• pp.77-84
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• 2006

Recently, as large structures such as high-rise building and long span bridge become lighter and more flexible, the necessity of structural control for reducing excessive dynamic response due to seismic excitation is increased. In this study, a semi-active base isolation system using Magneto-Sensitive (MS) rubbers is proposed to effectively protect structures against earthquakes. MS Rubber is a class of smart controllable materials whose mechanical properties change instantly by the application of a magnetic field. To demonstrate the performance of this device, the MS Rubber isolation system is compared to Lead-Rubber Bearing (LRB) isolation systems and judged based on computed responses to several historical earthquakes. The MS Rubber isolation system is shown to achieve notable decreases in base drifts over comparable passive systems with no accompanying increase in base shears or in accelerations imparted to the superstructure. The proposed MS Rubber system is shown to perform better than the passive isolation system.

• Computers and Concrete
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• v.13 no.5
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• pp.603-619
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• 2014

Soft storey buildings are characterised by having a storey that has a large amount of open space. This soft storey creates a major weak point during an earthquake. As the soft stories are typically associated with retail spaces and parking garages, they are often on the lower levels of tall building structures. Thus, when these stories collapse, the entire building can also collapse, causing serious structural damage that may render the structure completely unusable. The use of special soft storey is predominant in the tall building structures constructed by several local developers, making the issue important for local building structures. In this study, the effect of the incorporation of an isolator on the seismic behaviour of tall building structures is examined. The structures are subjected to earthquakes typical of the local city, and the isolator is incorporated with the appropriate isolator time period and damping ratio. A FEM-based computational relationship is proposed to increase the storey height so as to incorporate the isolator with the same time period and damping ratio for both a lead rubber bearing (LRB) and high-damping rubber bearing (HDRB). The study demonstrates that the values of the FEM-based structural design parameters are greatly reduced when the isolator is used. It is more beneficial to incorporate a LRB than a HDRB.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.133-138
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• 2008

In this study, the seismic behavior of arch structure with lead rubber bearing(LRB) is analyzed. The arch structure is the simplest structure and has the basic dynamic characteristics among large spatial structures. Also, Large spatial structures have large vertical response by horizontal seismic vibration, unlike seismic behavior of normal rahmen structures. When horizontal seismic load is applied to the large spatial structure with isolation systems, the horizontal acceleration response of the large spatial structure is reduced and the vertical seismic response is remarkably reduced.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.442-448
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• 2003

최근 장대교량의 건설이 증가하고 지진에 대한 관심이 고조되면서 교략의 내진설계와 면진설계가 교량설계의 주요항목으로 자리잡게 되었다. 특히 최근 ILM교량과 같은 다경간 장대교의 경우 지진시 교량의 상부구조와 하부구조를 격리시켜 주기를 변화시키는 LRB를 이용한 면진설계가 주로 이루어지고 있다. 그러나 아직까지 국내에는 Mt5의 거동과 기본성능에 대한 실험데이터가 절대적으로 부족하며, 따라서 그 특성을 엄밀히 검증하지 못한 채 고속도로 및 국도상의 교량에 LRB를 다수 사용하고 있는 현실이다. 본 연구에서는 실교량에 사용될 LRB에 대하여 기본성능 중의 하나인 피로마모시험을 수행함으로써 온도하중과 같은 반복하중에 대한 LRB의 피로거동을 모사하고 피로시험 전.후의 기본성능의 변화를 파악하였다. 이러한 LRB의 기본성능에 대한 실험온 LRB의 성능에 대한 검증과 함께 LRB의 거동에 대한 불확실성을 줄일 수 있는 기본 자료로 축적할 수 있으며, 현재 한국도로공사 도로교통기술원에서 마련중인 지진격리장치(LRB) 성능시험기준(안)의 정립에 기초 자료로참고하고자 한다.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.4
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• pp.15-23
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• 2009

An experimental study was performed to evaluate seismic reduction performance and the applicability of 2-dimensional floor isolation system to the main control room of a nuclear power plant. A lead-rubber bearing (LRB) and a friction pendulum system (FPS) were designed and fabricated for a 2-dimensional floor isolation system. A partial experimental model of a main control room with the LRB and FPS was tested using a shaking table. The experimental model consisted of a control panel, a 2.5m${\times}$2.5m access floor, and four LRB and FPS. The artificial time histories based on the horizontal floor response spectrums (OBE, SSE) of the main control room were used as earthquake input signals. Compared to the non-isolated system, the seismic response of experimental models using a 2-dimensional floor isolation system showed considerable seismic reduction performance against an earthquake.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.04a
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• pp.116-121
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• 1994

지금까지 대형 구조물에 널리 사용되고 있는 Base Isolator는 특히, 지진하중에 대하여 상부 구조물의 지반분리(base isolation)을 이용한 지진제어를 목적으로 하기 때문에 Seismic Isolator라 한다. 일반적으로 면진베어링에는 LRB(Laminated Rubber Bearing) 방식과 R-FBI(resilient-friction base isolator) 방식으로 크게 나눌 수 있다. LRB 방식은 가장 널리 사용되는 면진베어링으로써 방진고무를 주된 재료로 하고 수직강성을 보강하기 위하여 steel plate를 조합하여 제작하며, 초기강성 및 에너지 소산능력을 증가시키기 위하여 단면중앙에 납(lead plug)를 삽입하기도 한다. R-FBI 방식은 방진고무 적층판 내부에 미끄럼판을 가지고 있으므로 LRB 방식에 비하여 더 큰 수평변위를 발생시킬 수 있다. 이번에 설계 제작한 면진베어링은 LNG 저장탱크의 Seismic Isolation을 목적으로 적용대상의 사양에 맞추어 설계 제작하고 성능평가 시험을 수행하여 LNG 저장탱크, 원자로, 대형 건축물등 지진으로부터 보호되어야 하는 대형구조물의 방진재로 적용할 수 있는가를 평가하고자 한다. 본 논문에서는 제작된 면진베어링의 설계를 검증하고 방진고무(HDR)재료의 물리적 특성시험, 축소모델에 의한 정적, 동적시험을 통하여 시험방법을 소개하고 이러한 시험결과를 기초로 하여 면진베어리의 성능을 평가하였으며, 면진베어링의 온도변화, 외부 수직하중의 변화등에 따른 특성변화와 LNG 저장탱크와 면진베어링의 체결방법에 따른 시험으로 체결방법을 검증하였으며, 대상물의 사양에 적합한가를 고찰하였다.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.383-390
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• 2002

The new seismic isolation system (StLRB) is developed, which can separate non-seismic displacements which come from the thermal expansion etc. in LRB design. The StLRB has 3 components, sliding system (PTFE + stainless plate), LRB (lead rubber bearing) and STU (shock transmit units). In this project, the StLRB is designed to apply to the bridge structure by analyzing the characteristics of each component and also the dynamic behavior of the structure was analyzed by non-linear analysis. The verification test was performed to show the two stages separated by STU units. Test results show the effectiveness of both the separation and the seismic isolation performance.