• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2003.09a
• /
• pp.411-418
• /
• 2003

This paper presents the results of experimental studies on the equipment isolation effect in the nuclear containment. for this Purpose, shaking table tests were performed. The natural rubber bearing (NRB) and high damping rubber bearing (HDRB) were selected for the isolation. Peak ground acceleration, damping characteristics of isolation system and frequency contents of selected earthquake motions were considered. finally, it is presented that the NRB and HDRB systems are effective for the small equipment isolation and the damping of isolation systems can be affected to the seismic isolation effect.

• Journal of the Korea Concrete Institute
• /
• v.12 no.4
• /
• pp.79-89
• /
• 2000

In this paper, the seismic analysis and the modeling techniques have been introduced for aseismic performances assessment, when seismic isolation bearings are applied on a real bridge. Nonlinear time-history analysis is carried out using finite element analysis program. In this study, EI Centro earthquake(1940, N00W), Mexico earthquake(1985, N90W), and earthquake simulation from modified SIMQKE are used as earthquake ground excitations. The seismic response of seismically isolated bridge is compared with that of a bridge using conventional Pot Bearings, after obtaining the displacements of the deck, the deformations of the piers, shear forces and moments of the bottoms of the piers. The analytical analysis results show that seismic isolation bearing, especially seismic isolation bearings with sliding mechanism, could reduce earthquake forces.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11a
• /
• pp.247-251
• /
• 2001

Nowadays, base isolation systems such as lead-rubber bearing, elastomer bearing and sliding bearing have been installed to the various structures to prevent the disaster from seismic. The performance of base isolation system have been well proved by model-scale experiments and numerical analysis. However. the seismic response data measured at real large base-isolated structures is still insufficient. This paper presents a seismic monitoring system, acquiring real-time acceleration signals up to 32 channels, displaying time history and spectrum of the signals, storing the acquired data at a PC hard disk, and replaying the saved data. Moreover, the system can be operated without any limitation for monitoring period by automatic management of stored data file. The developed system has been installed at a real base-isolated building using lead-rubber bearings and we expect its seismic response data with ground motion signal can be well licquired in case of earthquake occurrence.

• Nuclear Engineering and Technology
• /
• v.51 no.2
• /
• pp.600-606
• /
• 2019

Studies on the application of the lead rubber bearing (LRB) isolation system to nuclear power plants are being carried out as one of the measures to improve seismic performance. Nuclear power plants with isolation systems require seismic probabilistic safety assessments, for which the seismic fragility of the structures, systems, and components needs be calculated, including for beyond design basis earthquakes. To this end, seismic response analyses are required, where it can be seen that the behaviors of the isolation system components govern the overall seismic response of an isolated plant. The numerical model of the LRB used in these seismic response analyses plays an important role, but in most cases, the extreme performance of the LRB has not been well studied. The current work therefore develops an extreme nonlinear numerical model that can express the seismic response of the LRB for beyond design basis earthquakes. A full-scale LRB was fabricated and dynamically tested with various input conditions, and test results confirmed that the developed numerical model better represents the behavior of the LRB over previous models. Subsequent seismic response analyses of isolated nuclear power plants using the model developed here are expected to provide more accurate results for seismic probabilistic safety assessments.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.5
• /
• pp.601-611
• /
• 2016

The research, development and use of seismic isolation systems have been increasing with the gradual development of structure safety assurance methods for earthquakes. The High Damping Rubber Bearing (HDRB), one type of seismic isolation system, is a Laminated Rubber Bearing using special High Damping Rubber. However, as its damping function is slightly lower than that of the Lead Rubber Bearing, a similar seismic isolation system, its utilization has not been high. However, the HDRB has a superior damping force to the Natural Rubber Bearing, which has similar materials and shapes, and the existing Lead Rubber Bearing has a maleficence problem in that it contains lead. Thus, studies on HDRBs that do not use lead have increased. In this study, a test targeting the HDRB was done to examine its various dependence properties, such as its compressive stress, frequency and repeated loading. To evaluate the HDRB's seismic performance in response to several earthquake waves, the shaking table test was performed and the results analyzed. The test used the downscaled bridge model and the HDRB was divided into seismic and non-seismic isolation. Consequently, when the HDRB was applied, the damping effect was higher in the non-seismic case. However, its responses on weak foundations, such as in Mexico City, represented increased shapes. Thus, its seismic isolator.

• Computational Structural Engineering
• /
• v.7 no.1
• /
• pp.83-90
• /
• 1994

This study presents the nonlinear dynamic analysis method of the bridge with the seismic isolation bearing. Also the numerical analyses are performed for investigating the response characteristics of the bridge isolated with the lead-rubber bearing under the ground motions compatible to Korea bridge design response spectra. It is found that the pier design force can be considerably smaller than the one for the bridge with the fixed bearing. It is observed that the lead-rubber bearing has the great effectiveness for reducing the longitudinal seismic force in case of the bridges with low and medium periods. Therefore the seismic isolation bearing can be used instead of the fixed bearing for the economic and safe design of the bridge.

• Earthquakes and Structures
• /
• v.7 no.6
• /
• pp.1141-1169
• /
• 2014

This study is aimed to investigate the seismic performance of low-rise precast wall system with base isolation. Three types of High Damping Rubber Bearing (HDRB) were designed to provide effective isolation period of 2.5 s for three different kinds of structure in terms of vertical loading. The real size HDRB was manufactured and tested to obtain the characteristic stiffness as well as damping ratio. In the vertical stiffness test, it was revealed that the HDRB was not an ideal selection to be used in isolating lightweight structure. Time history analysis using 33 real earthquake records classified with respective peak ground acceleration-to-velocity (a/v) ratio was performed for the remaining two types of HDRB with relatively higher vertical loading. HDRB was observed to show significant reduction in terms of base shear and floor acceleration demand in ground excitations having a/v ratio above $0.5g/ms^{-1}$, very much lower than the current classification of $0.8g/ms^{-1}$. In addition, this study also revealed that increasing the damping ratio of base isolation system did not guarantee better seismic performance particularly in isolation of lightweight structure or when the ground excitation was having lower a/v ratio.

• Computers and Concrete
• /
• v.21 no.5
• /
• pp.495-504
• /
• 2018

The possibility of earthquakes in vulnerable regions indicates that efficient technique is required for seismic protection of buildings. During the recent decades, the concept is moving towards the insertion of base isolation on seismic prone buildings. So, investigation of structural behavior is a burning topic for buildings to be isolated in base level by bearing device. This study deals with the incorporation of base isolation system and focuses the changes of structural responses for different types of Lead Rubber Bearing (LRB) isolators. A number of sixteen model buildings have been simulated selecting twelve types of bearing systems as well as conventional fixed-base (FB) scheme. The superstructures of the high-rise buildings are represented by finite element assemblage adopting multi-degree of freedoms. Static and dynamic analyses are carried out for FB and base isolated (BI) buildings. The dynamic analysis in finite element package has been performed by the nonlinear time history analysis (THA) based on the site-specific seismic excitation and compared employing eminent earthquakes. The influence of the model type and the alteration in superstructure behavior of the isolated buildings have been duly assessed. The results of the 3D multistory structures show that the lateral forces, displacement, inertia and story accelerations of the superstructure of the seismic prone buildings are significantly reduced due to bearing insertion. The nonlinear dynamic analysis shows 12 to 40% lessening in base shear when LRB is incorporated leading to substantial allowance of horizontal displacement. It is revealed that the LRB isolators might be potential options to diminish the respective floor accelerations, inertia, displacements and base shear whatever the condition coincides. The isolators with lower force intercept but higher isolation period is found to be better for decreasing base shear, floor acceleration and inertia force leading to reduction of structural and non-structural damage. However, LRB with lower isolator period seems to be more effective in dropping displacement at bearing interface aimed at reducing horizontal shift of building structure.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03b
• /
• pp.229-232
• /
• 1999

The seismic isolation technology has appeared to be increasingly necessary for highway brides LNG tank nuclear power plant and building structures in view of recent frequent earthquake vibrations in Korea. Also high-technology industries required effective seismic protection. The LRB(Lead Rubber Bearing) systen has been counted as the most effective way for seismic isolation which is now under development and widely used in industries. Hear the commercial FEM software for nonlinear analysis MARC has provided force-displacement curves on the rubber system. The analysis has been carried out about four cases ; 29.5mm and 59mm horizontal dislacements with/without a center hole. The unknown constants of the strain energy function of Ogden model have been obtained by a tension test,

• Journal of the Earthquake Engineering Society of Korea
• /
• v.21 no.2
• /
• pp.95-103
• /
• 2017

In order to modeling seismic isolation system such as lead-rubber bearing (LRB), bilinear model is widely used by many researchers. In general, an actual force-displacement relationship for LRB has a smooth hysteretic shape. So, Bouc-Wen model with smooth hysteretic shape represents more accurately actual hysteretic shape than bilinear model. In this study, seismic responses for seismically isolated nuclear power plant (NPP) with LRB modelled by Bouc-Wen and bilinear models are compared with those of NPP without seismic isolation system. To evaluate effect of earthquake characteristics for seismic responses of NPP isolated by LRB, 5 different site class earthquakes distinguished by Geomatrix 3rd Letter Site Classification and artificially generated earthquakes corresponding to standard design spectrum by Reg. Guide 1.60 are used as input earthquakes. From the seismic response results of seismically isolated NPP, it can be observed that maximum displacements of seismic isolation modelled by Bouc-Wen model are larger than those by bilinear model. Seismic responses of NPP with LRB is significantly reduced than those without LRB. This reduction effect for seismic responses of NPP subjected to Site A (rock) earthquakes is larger than that to Site E (soft soil) earthquakes.