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

• Structural Engineering and Mechanics
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• v.43 no.4
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• pp.475-502
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• 2012

In this paper, the seismic analysis modeling technologies for sodium-cooled fast reactor (SFR) are presented with detailed descriptions for each structure, system and component (SSC) model. The complicated reactor system of pool type SFR, which is composed of the reactor vessel, internal structures, intermediate heat exchangers, primary pumps, core assemblies, and core support structures, is mathematically described with simple stick models which can represent fundamental frequencies of SSC. To do this, detailed finite element analyses were carried out to identify fundamental beam frequencies with consideration of fluid added mass effects caused by primary sodium coolant contained in the reactor vessel. The calculation of fluid added masses is performed by detailed finite element analyses using FAMD computer program and the results are discussed in terms of the ways to be considered in a seismic modeling. Based on the results of seismic time history analyses for both seismic isolation and non-isolation design, the functional requirements for relative deflections are discussed, and the design floor response spectra are proposed that can be used for subsystem seismic design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.1
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• pp.13-20
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• 2021

Recently, various piloti structures have been constructed in Korea to secure residential and parking spaces. However, these piloti structures have been constructed in the form of protruding columns without walls to secure parking spaces on the first floor. In this form, when an earthquake occurs, the column is relatively easily damaged compared to general structures, and such damage can lead to the collapse of the structure. Therefore, in this study, a study on securing the safety of the piloti structure using the MPS (Multi Performance System) seismic isolation device was conducted. Nonlinear dynamic analysis according to the presence or absence of MPS seismic isolation device was performed on the existing piloti structure, and analysis results were compared and analyzed. Finally, each seismic performance evaluation was performed and the superiority of the MPS seismic isolation device was verified.

• Earthquakes and Structures
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• v.7 no.6
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• pp.1223-1240
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• 2014

Seismic isolation has been established as an effective earthquake-resistant design method and the lead rubber bearings (LRBs) are among the most commonly used seismic isolation systems. In the scientific literature, a sharp bilinear model is often used for capturing the hysteretic behaviour of the LRBs in the analysis of seismically isolated structures, although the actual behaviour of the LRBs can be more accurately represented utilizing smoothed plasticity, as captured by the Bouc-Wen model. Discrepancies between these two models are quantified in terms of the computed peak relative displacements at the isolation level, as well as the peak inter-storey deflections and the absolute top-floor accelerations, for the case of base-isolated buildings modelled as multi degree-of-freedom systems. Numerical simulations under pulse-like ground motions have been performed to assess the effect of non-linear parameters of the seismic isolation system and characteristics of both the superstructure and the earthquake excitation, on the accuracy of the computed peak structural responses. Through parametric analyses, this paper assesses potential inaccuracies of the computed peak seismic response when the sharp bilinear model is employed for modelling the LRBs instead of the more accurate and smoother Bouc-Wen model.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.417-423
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• 2006

The seismic characteristics with 3-Dimensional isolation systems have been studied using a shaking table system. In this study, we made nuclear power plant main control room floor systems and several seismic shaking table tests with and without isolation systems were conducted to evaluate floor isolation effectiveness. Isolation systems have showed large reduction effectiveness in acceleration and response spectra with x and z direction respectively, but horizontal isolation is more effective than vertical one It is required to make isolation systems of which design frequency is below 1Hz when applied to main control room of NPP, but considering much difficulties in making such isolation systems, it is recommended that much consideration should be taken into account when applied to main control room of NPP.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.424-431
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• 2000

After the Kobe earthquake(1995) in Japan, the Izmit earthquake(1997) in Turkey and the Chi-chi earthquake(1999) in Taiwan, the small-to-medium-sized earthquakes occurred in the Koreans peninsula and this shows the fact that Korea is not located in the safety zone of earthquake. The main concept of base isolation system is to reduce the member forces by decreasing the earthquake forces transmitted to superstructure instead of the conventional techniques of strengthening the structural members. This study investigates the effect of seismic response attenuation of computer floors using base isolation systems

• 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.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.3
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• pp.51-60
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• 1998

Base isolation is an innovative design strategy that provides a practical alternative for the seismic design of structures. Base isolators, mainly employed to isolate large structures subjected to earthquake ground excitations and to rehabilitate structures damaged by past earthquakes, deflect and absorb the seismic energy horizontally transmitted to the structures. This study demonstrated that the base isolation system may offer effective performance for bridges during severe seismic events through shaking table tests. Two base isolation systems using laminated rubber bearings with and without hydraulic dampers are tested. The test results strongly show that the laminate rubber bearings cause the natural period of the bridge structure increased considerably, which results in the deck acceleration and the shear forces on the deck acceleratino and the shear forces on the piers reduced significantly. The results also demonstrate that the hydraulic dampers enhance the system's capacity in dissipating energy to reduce the relative displacement between the bridge deck and the pier.

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

• International Journal of High-Rise Buildings
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• v.4 no.3
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• pp.181-189
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• 2015

Shimizu Corporation Tokyo Headquarters, one of the city's leading office buildings, features many pioneering technologies that contribute to a sustainable society through environmental stewardship and a sophisticated disaster management facility. In terms of structural engineering, a seismic isolation system incorporating reinforced concrete core walls and precast concrete perimeter frames create a robust structure in the event of a large earthquake. In addition to the seismic resistance of the structure, several pioneering construction methods and materials are adopted. This office building can serve as a basis for new design and construction approaches and methodologies to ensure safe and economical structures.