• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.19-26
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• 2021

The seismic isolation system have been applied in order to protect the collapse of bridge by seismic load and the vertical load transmitted from the superstructure. However, the failure and damages of non-shrinkage mortar, isolator and wedge in total 12 bridge were reported by Pohang Earthquake. In this study, the damage mechanism and behavior characteristics of elastomeric bearing by an earthquake were evaluated to consider the seismic isolation system including non-shrinkage mortar and the seat concrete of pier. To discuss the effect of installed wedge and damage mode of elastomeric bearing, the compressive-shear tests were carried out. Also, the mechanical behaviors and damage mechanism for each component of elastomeric bearing were evaluated by using finite element analysis. From the test results, the cracks were created at boundary between non-shrinkage mortar and seismic isolator and the shear loads were rapidly increased after bump into wedge. The cause for damage mechanism of seismic isolation system was investigated by comparing stress distribution of anchor socket and non-shrinkage mortar depending on wedge during earthquake.

• Smart Structures and Systems
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• v.8 no.4
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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.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.2
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• pp.89-95
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• 2013

Structures in a nuclear power system are designed to be elastic even under an earthquake excitation. However a structural component such as an isolator shows inelastic behavior inherently. For the seismic assessment of nonlinear structures, response history analysis should be performed. In this study, the response of base isolation system was analyzed by response history analysis for the seismic performance assessment. Firstly, several seismic assessment criteria for a nuclear power plant structure were reviewed for the nonlinear response history analysis. Based on these criteria, the spectrum matched ground motion generation method modifying a seed earthquake ground motion time history was adjusted. Using these spectrum matched accelerograms, the distribution of displacement responses of the simplified base isolation system was evaluated. The resulting seismic responses excited by the modified ground motion time histories and the synthesized time history generated by stochastic approach were compared. And the response analysis of the base isolation system considering the different intensities in each orthogonal direction was performed.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.1
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• pp.47-62
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• 1998

The laminated elastomeric bearing and the lead-rubber bearing were designed to isolate one bay-two story steel frame which is designed for only gravity load. The seismic performance is evaluated for the designed steel frame before and after application of these seismic isolators between the super structure and the foundation. These isolators can improve the seismic capacity of the steel frame. Especially, by inserting the lead plug into the center of the laminated elastomeric bearing, the initial stiffness of th bearing can be increased, thus rather large lateral displacement can be prevented under the frequent service lateral load. During the strong earthquake, yielding of the lead can increase the capacity of the energy dissipation.

• Earthquakes and Structures
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• v.26 no.6
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• pp.463-475
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• 2024

The study aims to investigate the pounding that occurs between the isolator's ring and slider of isolated structures resulting from excessive seismic excitation, while considering soil-structure interaction. The dynamic responses and poundings of structures subjected a series seismic records were comparatively analyzed for three different soil types and fixed-base structures. A series of parametric studies were conducted to thoroughly discuss the effects of the impact displacement ratio, the FPB friction coefficient ratio, and the radius ratio on the structural dynamic response when considering impact and SSI. It was found that the pounding is extremely brief, with an exceptionally large pounding force generated by impact, resulting in significant acceleration pulse. The acceleration and inter-story shear force of the structure experiencing pounding were greater than those without considering pounding. Sudden changes in the inter-story shear force between the first and second floors of the structure were also observed. The dynamic response of structures in soft ground was significantly lower than that of structures in other ground conditions under the same conditions, regardless of the earthquake wave exciting the structure. When the structure is influenced by pulse-type earthquake records, its dynamic response exhibits a trend of first intensifying and then weakening as the equivalent radius ratio and friction coefficient ratio increase. However, it increases with an increase in the pounding displacement ratio, equivalent radius ratio, friction coefficient ratio, and displacement ratio when the structures are subjected to non-pulse-type seismic record.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.3
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• pp.133-143
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• 2015

It is very important to assure the seismic performance of equipment as well as building structures in seismic design of nuclear power plant(NPP). Seismically isolated structures may be reviewed mainly on the horizontal seismic responses. Considering the equipment installed in the NPP, the vertical earthquake responses of the structure also should be reviewed. This study has investigated the vertical seismic demand of seismically isolated structure by lead rubber bearings(LRBs). For the numerical evaluation of seismic demand of the base isolated NPP, the Korean standard nuclear power plant (APR1400) is modeled as 4 different models, which are supported by LRBs to have 4 different horizontal target periods. Two real earthquake records and artificially generated input motions have been used as inputs for earthquake analyses. For the study, the vertical floor response spectra(FRS) were generated at the major points of the structure. As a results, the vertical seismic responses of horizontally isolated structure have largely increased due to flexibility of elastomeric isolator. The vertical stiffness of the bearings are more carefully considered in the seismic design of the base-isolated NPPs which have the various equipment inside.

• Smart Structures and Systems
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• v.20 no.3
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• pp.303-309
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• 2017

Structural control through seismic isolation using elastomeric rubber bearing, which is also known as High Damping Rubber Bearing (HDRB), has seen an increase in use to provide protective from earthquake, especially for new buildings in earthquake zones. Besides, HDRB has also been used in structural rehabilitation of older yet significant buildings, such as museums and palaces. However, the present design approach applied in normal practice has often resulted in dissimilar HDRB dimension requirement between structural designers and bearing manufacturers mainly due to ineffective communication. Therefore, in order to ease the design process, most HDRB manufacturers have come up with catalogs that list all necessary and relevant product lines specifically for structural engineers to choose from. In fact, these catalogs contain physical dimension, compression property, shear characteristic, and most importantly, the total rubber thickness. Nonetheless, other complicated issues, such as the relationship between target isolation period and displacement demand (which determines the total rubber thickness), are omitted due to cul-de-sac fixing of these values in the catalogs. As such, this paper presents a formula, which is derived and extended from the present design approach, in order to offer a simple guideline for engineers to estimate the required HDRB size. This improved design formula successfully minimizes the discrepancies stumbled upon among structural designers, builders, and rubber bearing manufacturers in terms of variation order issue at the designing stage because manufacturer of isolator is always the last to be appointed in most projects.

• Structural Monitoring and Maintenance
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• v.5 no.3
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• pp.325-343
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• 2018

This study aims to propose a performance-based design method of a novel passive base isolation system, BIO isolation system, which is inspired by an energy dissipation mechanism called 'sacrificial bonds and hidden length'. Fragility functions utilized in this study are derived, indicating the probability that a component, element, or system will be damaged as a function of a single predictive demand parameter. Based on PEER framework methodology for Performance-Based Earthquake Engineering (PBEE), a systematic design procedure using performance and fragility objectives is presented. Base displacement, superstructure absolute acceleration and story drift ratio are selected as engineering demand parameters. The new design method is then performed on a general two degree-of-freedom (2DOF) structure model and the optimal design under different seismic intensities is obtained through numerical analysis. Seismic performances of the biologically inspired (BIO) isolation system are compared with that of the linear isolation system. To further demonstrate the feasibility and effectiveness of this method, the BIO isolation system of a 4-storey reinforced concrete building is designed and investigated. The newly designed BIO isolators effectively decrease the superstructure responses and base displacement under selected earthquake excitations, showing good seismic performance.

• Earthquakes and Structures
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• v.12 no.1
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• pp.35-45
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• 2017

The current paper investigates the effect of the seismic pounding of neighboring buildings on the response of structures isolated by Triple Friction Pendulum Bearing (TFPB). To this end, a symmetric three-dimensional single story building is modeled for analysis with two specified levels of top deck and base deck, to capture the seismic response of the base isolators and building's roof. Linear elastic springs with different level of gaps are employed to calculate the impact between the buildings. Nonlinear Dynamic Time History Analyses (NDTHA) are conducted for seismic evaluation. Also, five different sizes with four different sets of friction coefficients are assumed for base isolators to cover a whole range of base isolation systems with various geometry configurations and fundamental period. The results are investigated in terms of base shear, buildings' drift and top deck acceleration of the superstructure. The results also indicate the profound effect of the stiffness of the adjacent buildings on the value of the impact they impose to the superstructure. Also, in situations of potential pounding, the increment of the fundamental period of the TFPB base isolator could intensify the impact force up to nearly five-fold.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.855-860
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• 2002

This paper is about seismic performance of the StLRB(S.T.U＋PETE＋LRB) system, that is among various base isolator. A rational modeling of StLRB system has been presented that used Nllink element. We get theoretical solutions of equation of motion of the system and compared with numerical solutions using a finite element program, Thus, a verified modeling can be applied bridge structure of multi-degree-of-fredoom systems.