• 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.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.537-544
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• 2006

In this study, performance level evaluation tests have been actually performed on laminated rubber seismic isolation bearings (LRB) made in Korea. To provide basic data for setting up fabrication criteria and performance evaluation criteria three real scale LRB were tested and the test results were analysised. Accordingly, a large capacity test device has been designed and manufactured to implement the tests. The device selected for evaluation is a circular LRB actually applied in bridges. Evaluation tests were conducted using full-scale LRB with diameter of 851mm in the rubber part and total height of 215mm of which the effective horizontal stiffness and equivalent damping ratio have been measured during the experiments.

• Journal of Korean Association for Spatial Structures
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• v.17 no.2
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• pp.71-77
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• 2017

In this study, the boundary non-linear analysis of the sky bridge subjected to walking load and running load is performed. The sky bridge is installed in the mid-story between two buildings and the walking load and running load induced by pedestrians are measured by load cell. LRB is modeled as a non-linear hysteresis model to accurately represent the behavior of LRB. For the serviceability evaluation of sky bridge, the acceleration responses of sky bridge are analyzed based on ISO 2631-2 and the velocity response are analyzed based on standards Bachmann &Amann. In serviceability evaluation of this sky bridge, the pedestrian can not perceive the vibration except for resonance running loads consequently. Therefore, it is concluded that this sky bridge haven't problem in the serviceability.

• Earthquakes and Structures
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• v.24 no.5
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• pp.333-343
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• 2023

Various seismic isolation and reduction devices have been applied to suppress the longitudinal vibration of continuous girder bridges. As representative devices, lead rubber bearing (LRB) and fluid viscous damper (FVD) might suffer from deterioration during the long-term service. This study aims to evaluate the impact of device deterioration on the seismic responses of continuous girder bridges and investigate the seismic behavior of deteriorated LRBs and FVDs. Seismic performance of a simplified bridge model was investigated, and the influence of device deterioration was evaluated by the coefficient of variation method. The contribution of LRB and FVD was assessed by the Sobol global sensitivity analysis method. Finally, the seismic behaviors of deteriorated LRBs and FVDs were discussed. The result shows that (i) the girder-pier relative displacement is the most sensitive to the changes in the deterioration level, (ii) the deterioration of FVD has a greater effect on the structural responses than that of LRB, (iii) FVD plays a major role in energy dissipation with a low degradation level while LRB is more essential in dissipating energy when suffering from high degradation level, (iv) the deteriorated devices are more likely to reach the ultimate state and thus be damaged.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.1-10
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• 2001

In this study, the horizontal loading tests of 10ton and 200ton capacity of LRB(lead-rubber bearing) were performed for the evaluation of the dynamic properties of the LRB. It is noted from the test results that dynamic properties of the LRB are dependent on the loading frequency, vertical load and shear strain. A Slender bearing subjected to large deformation will tend to develop plastic hinges in the end regions of the lead plug which will cause the failure of the lead plug. It is recommended that the appropriate mechanical properties of LRB considering the level of structural response and input ground motion should be used in the design of base isolated structures.

• Structural Engineering and Mechanics
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• v.50 no.1
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• pp.89-103
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• 2014

According to experimental studies made so far, design formula of shear characteristics suggested by ISO 22762 and JEAG 4614, representative design code for Lead Rubber Bearing(LRB) shows dependence caused by changes in compressive stress. Especially, in the case of atypical special structure, such as a nuclear power structure, placement of seismic isolation bearing is more limited compared to that of existing structures and design compressive stress is various in sizes. As a result, there is a difference between design factor and real behavior with regards to shear characteristics of base isolation device, depending on compressive stress. In this study, a full-scale low hardness device of LRB, representative base isolation device was manufactured, analyzed, and then evaluated through an experiment on shear characteristics related to various compressive stresses. With design compressive stress of the full-scale LRB (13MPa) being a basis, changes in shear characteristics were analyzed for compressive stress of 5 MPa, 10 MPa, 13 MPa, 15 MPa, and 20 MPa based on characteristics test specified by ISO 22762:2010 and based on the test result, a regression analysis was made to offer an empirical formula. With application of proposed design formula which reflected the existing design formula and empirical formula, trend of horizontal characteristics was analyzed.

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

• 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.

• Journal of Korean Association for Spatial Structures
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• v.19 no.2
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• pp.51-61
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• 2019

The objective of this study is to analysis the seismic response of 200m spanned honeycomb lattice domes under horizontal and up-down ground motion of El Centro earthquake. For the analysis of seismic response of the honeycomb lattice domes by rise/span ratio, the time history analysis is used for the estimation of the dynamic response. The low rise lattice dome is less deformed and less stressed than the high rise lattice dome for the earthquake ground motion. The 3-dimensional earthquake response is not significantly different the dynamic response of one directional ground motion. The earthquake response of domes with LRB isolation system is significantly reduced for the asymmetric vertical deformation and the horizontal and vertical accelerations.

• Journal of Korean Association for Spatial Structures
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• v.18 no.4
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• pp.81-88
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• 2018

Seismic isolation systems have typically been used in the form of base seams in mid-rise and low-rise buildings. In the case of high-rise buildings, it is difficult to apply the base isolation. In this study, the seismic response was analyzed by changing the installation position of the seismic isolation device in 3D high - rise model. To do this, we used 30-story and 40-story 3D buildings as example structures. Historic earthquakes such as Mexico (1985), Northridge (1994) and Rome Frieta (1989) were applied as earthquake loads. The installation position of the isolation device was changed from floor to floor to floor. The maximum deformation of the seismic isolation system was analyzed and the maximum interlaminar strain and maximum absolute acceleration were analyzed by comparing the LB model with seismic isolation device and the Fixed model, which is the base model without seismic isolation device. If an isolation device is installed on the lower layer, it is most effective in response reduction, but since the structure may become unstable, it is effective to apply it to an effective high-level part. Therefore, engineers must consider both structural efficiency and safety when designing a mid-level isolation system for high-rise buildings.