• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.258-265
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• 1998

Seismic isolation has developed to the point where it may be considered as a viable design alternate for a wide range of building structures. However, it needs to consider various aspects to adopt a suitable isolation system for buildings practically. This report presents the basis for the preliminary design procedure which has been developed for the seismic isolation system using the lead rubber bearings. The design procedures have been developed to ensure that the bearings will safely support the maximum gravity load throughout the life of the structure while they provide a period shift and hysteretic damping during the design earthquake.

• 한국구조물진단유지관리공학회 논문집
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• 제4권3호
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• pp.137-144
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• 2000

Judging from the occasional occurrences of minor and major earthquakes in Korean peninsula, it is generally considered that Korean peninsula is not located in safe zone from earthquake any more. The worldwide damages from earthquake in public buildings such as bridges are also urging the necessity for an appropriate earthquake proof action. The elastomeric bearings have been used in seismic isolation design of bridges. and elastomeric bearings are quite ideal ones which allow movement and rotation in all directions without restraining superstruture. Within the limits of this study on dynamic behavior of the LBR for seismic isolation design, the reaearch results revealed that the Laminated Rubber Bearing(LRB) is useful in bridges for seismic isolation design. In addition, the relationship between the shape factor and compressive strength is linear. It was also found that the compressive strength gets higher as the shape factor increases.

• 한국지진공학회논문집
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• 제21권6호
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• pp.265-275
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• 2017

In order to improve the seismic performance of structures, friction pendulum system (FPS) is the most commonly used seismic isolation device in addition to lead rubber bearing (LRB) in high seismicity area. In a nuclear power plant (NPP) with a large self weight, it is necessary to install a large number of seismic isolation devices, and the position of the center of rigidity varies depending on the arrangement of the seismic isolation devices. Due to the increase in the eccentricity, which is the difference between the center of gravity of the nuclear structure and the center of stiffness of the seismic isolators, an excessive seismic response may occur which could not be considered at the design stage. Three different types of eccentricity models (CASE 1, CASE 2, and CASE 3) were used for seismic response evaluation of seismically isolated NPP due to the increase of eccentricity (0%, 5%, 10%, 15%). The analytical model of the seismic isolation system was compared using the equivalent linear model and the bilinear model. From the results of the seismic response of the seismically isolated NPP with increasing eccentricity, it can be observed that the effect of eccentricity on the seismic response for the equivalent linear model is larger than that for the bilinear model.

• Earthquakes and Structures
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• 제9권3호
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• pp.657-671
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• 2015

The level of ductility is determined by depending on the intended use of the building, the region's seismic characteristics and the type of structural system when buildings are planned by engineers. Major portion of seismic energy is intended to be consumed in the plastic zone in structural systems of high ductility, so the occurrence of damages in load bearing and non-load bearing structural elements is accepted in planning stage under severe earthquakes. However, these damages must be limited among specific values in order not to endanger buildings in terms of the bearing capacity. Isolators placed between the basement and upper structure make buildings behave elastically by reducing the effects of seismic loads and improving seismic performance of building significantly. Thus, damages can be limited among desired values. In this study, the effectiveness of seismic isolation is investigated on both fixed based and seismic isolated models of a hospital building with high ductility level with regard to lateral displacements, internal forces, structural periods and cost of the building. Layered rubber bearings are interposed between the base of the structure and foundation. Earthquake analysis of the building are performed using earthquake records in time domain (Kocaeli, Loma Prieta and Landers). Results obtained from three-dimensional finite element models are presented by graphs and tables in detail. That seismic isolation reduces significantly the destructive effects of earthquakes on structures is seen from the results obtained by seismic analysis.

• 한국지진공학회논문집
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• 제20권5호
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• pp.319-329
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• 2016

The Eradi Quake System (EQS) is a seismic isolation bearing system designed to minimize forces and displacements experienced by structures subjected to ground motion. The EQS dissipates seismic energy through friction of Poly Tetra Fluoro Ethylene (PTFE) disk pad. In general, a force-displacement relationship of EQS has post yield stiffness hardening during large inelastic displacement. In this study, seismic responses of seismically isolated nuclear power plant (NPP) subjected to design basis earthquake (DBE) and beyond design basis earthquakes (150% DBE and 167% DBE) are compared considering the post yield stiffness hardening effect of EQS. From the results, it can be observed that if the post-yield stiffness hardening effect of EQS is increased, the displacement response of EQS is reduced, and the acceleration and shear responses of containment structures of NPP is increased.

• 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.

• 한국구조물진단유지관리공학회 논문집
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• 제25권6호
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• pp.19-26
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• 2021

교량 받침장치부는 상부구조의 수직하중을 지지하여 하부구조에 전달하고, 교량의 붕괴사고를 방지하는 역할을 한다. 하지만, 포항지진에 의하여 총 12개 도로교량의 받침장치 몰탈 파손, 받침장치 파손 및 쐐기 손상이 보고되었다. 본 연구에서는 지진시 교량 받침장치부의 구조 시스템 특성을 고려하여 교각의 코핑부와 무수축몰탈을 포함한 면진받침 장치 실험체의 전단 거동특성 및 손상모드를 평가하였다. 받침장치 쐐기에 대한 영향을 확인하기 위하여 쐐기 설치 유무를 변수로 설정하였으며, 압축-전단 실험을 실시하여 면진장치의 전단 거동특성과 손상모드를 확인하였다. 또한 유한요소해석을 통하여 받침장치의 거동특성 및 각 구성요소별 손상원인을 분석하였다. 실험결과, 쐐기의 충돌 및 손상 발생 이후 급격한 하중변화가 발생하였으며, 받침장치와 무수축몰탈 경계부를 따라 균열이 발생하였다. 쐐기 유무에 따른 쐐기, 앵커 소켓 및 무수축볼탈의 응력거동을 비교함으로써 지진시 교량받침장치부의 손상원인을 규명하였다.

• Earthquakes and Structures
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• 제4권6호
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• pp.587-606
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• 2013

The given paper presents a new approach in design of seismic isolation systems of base isolated buildings. The idea is to install not one big size rubber bearing under the columns and/or shear walls, or one by one with certain spacing under the load-bearing walls, but to install a group/cluster of small size bearings, in order to increase the overall effectiveness of the isolation system. The advantages of this approach are listed and illustrated by the examples. Also the results of analyses of some buildings where the approach on installation of clusters of rubber bearings was used in their isolation systems are given for two cases: i) when the analyses are carried out based on the provisions of the Armenian Seismic Code, and ii) when the time history analyses are carried out. Obtained results are compared and discussed. Paper also presents, as an example, detailed analysis and design of the 18-story unique building in one of the residential complexes in Yerevan. Earthquake response analyses of this building were carried out in two versions, i.e. when the building is base isolated and when it is fixed base. Several time histories were used in the analyses. Comparison of the obtained results indicates the high effectiveness of the proposed structural concepts of isolation systems and the need for further improvement of the Seismic Code provisions regarding the values of the reduction factors. A separate section in the paper dedicated to the design of high damping laminated rubber-steel bearings and to results of their tests.

• Earthquakes and Structures
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• 제24권6호
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• pp.415-428
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• 2023

Low-cost techniques with seismic isolation performance and excellent resilience need to be explored in the case of rural low-rise buildings because of the limited buying power of rural residents. As an inexpensive and eco-friendly isolation bearing, scrap tire pads (STPs) have the issue of poor resilience. Thus, a seismic isolation system under a column (SISC) integrated with STP needs to be designed for the seismic protection of low-rise rural buildings. The SISC, which is based on a simple exterior design, maintains excellent seismic performance, while the mechanical behavior of the internal STP provides elastic resilience. The horizontal behaviors of the SISC are studied through load tests, and its mechanical properties and the intrinsic mechanism of the reset ability are discussed. Results indicate that the average residual displacement ratio was 24.59%, and the reset capability was enhanced. Comparative experimental and finite element analysis results also show that the load-displacement relationship of the SISC was essentially consistent. The dynamic characteristics of isolated and fixed-base buildings were compared by numerical assessment of the response control effects, and the SISC was found to have great seismic isolation performance. SISC can be used as a low-cost base isolation device for rural buildings in developing countries.

• 한국소음진동공학회논문집
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• 제23권2호
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• pp.185-191
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• 2013

This paper presents a new method for roller design of IRB(isolation roller bearing) seismic isolation device using experimental evaluation. Three layered plate is adopted for the IRB in which the upper plate is placed on x direction and the lower plate is placed on y direction. The rollers placed in each plate make a plate movement. The roller is then optimally designed using variable geometric conditions. Stress distribution depends on the diameter and length of the roller and hence this is used for the determination of optimal geometry of the roller. In the experimental evaluation, it is observed that stress concentration at the end sides of roller is decreased and geometric coefficients depend on crowning dimension. In addition, in order to determine optimal design parameters of the roller the plastic deformation and friction are experimentally identified.