• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.145-152
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• 2009

In performing a risk analysis on structure for earthquake, it is imperative to identify the vulnerability of structures associated with various stages of damage. And the earthquake resisting capability is needed for structures like bridge. So the damage analysis of bridges with or without isolator for earthquake effects is necessary. In this paper, the risk analysis of seismic isolated LRB bridges considering earthquake effects such as PGA, PGV, SA, SV, and SI is performed using fragility curves to assure the earthquake resisting capability of the structures. And, the stability of fragility curve is investigated with respect to input earthquake.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.2
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• pp.23-33
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• 2011

In this study, a CFPBS (Cone-type Friction Pendulum Bearing System) was developed which controls the acceleration delivered to the structure to prevent damage and degradation of the critical communication equipment in case of an earthquake. The isolation performance of the CFPBS was evaluated by numerical analysis. The CFPBS was manufactured in the shape of a cone differenced from the existing FPS (Friction Pendulum System), and a pattern was engraved on the friction surface. The natural frequencies of the CFPBS were evaluated from a free-vibration test with the seismic isolator system consisting of four CFPBSs. In order to verify its earthquake-resistant performance, a numerical analysis program was created from the equation of the CFPBS induced from the equations of motion. A simplified theoretical equation of the CFPBS was proposed to manufacture the equipment which could demonstrate the necessary performance. Artificial seismic waves satisfying the maximum earthquake scale of the Korean Building Code-Structural (KBC-2005) were created and verified to review the earthquake-resistant performance of the CFPBS by numerical analysis. The superstructural mass of the CFPBS and skew angle of the friction surface were considered for numerical analysis with El Centro NS (1940), Kobe NS (1995) and artificial seismic waves. The CFPBS isolation performance evaluation was based on the results of numerical analysis and the executed comparative analysis between the results from numerical analysis and the simplified theoretical equation under the same conditions.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.426-431
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• 2001

Seismic performance of base isolated rigid-mass model were studied through shaking table tests. Friction pendulum systems (FPS), pure-friction systems with laminated rubber bearing (LRB) were selected for the comparison of performance. Performance of specially designed isolation systems were tested statically using actuator and dynamically using shaking table. Numerical methods were developed to simulate the nonlinear behavior of the frictional base isolation systems. Two models were considered. one is modified Bouc-Wen model considering breakaway coefficient of friction and the other is classical Coulomb model. The results of numerical methods are found to be in very good agreement with test results.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.433-441
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• 2003

In this paper, a study on the nonlinear modeling of lead rubber bearings(LRBs) by a neural network theory was carried out. The random tests on the LRB were used for a training of neural network model. Numerical simulations using the neural network model were peformed on a scaled structural model with the LRBs excited by three type of seismic loads and compared with the shaking table tests. As a result, it was shown that the neural network model would be useful to a numerical modeling of LRB.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.175-182
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• 2008

In performing a risk analysis of structure for earthquake, it is imperative to identify the vulnerability of structures associated with various stages of damage. And the earthquake resisting capability is needed for structures like bridge. So the damage analysis of bridges with or without isolator for earthquake effects is necessary. In this paper, the risk analysis of seismic isolated LRB bridges considering earthquake effects such as PGA, PGV, SA, SV, and SI is performed using fragility curves to assure the earthquake resisting capability of the structures. And, the stability of fragility curve is investigated with respect to elastic modulus.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.4
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• pp.213-219
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• 2021

Polytetrafluoroethylene (PTFE) is a commercialized friction material in friction pendulum systems used for earthquake hazard mitigation in structures, and it has excellent chemical resistance and frictional performance. However, PTFE has a relatively low wear resistance for the friction pendulum systems in service. As an alternative to PTFE, a cost-effective frictional material, polyvinylidene fluoride (PVDF) strengthened by magnesium oxide (MgO), with enhanced wear resistance performance is proposed in this study. The frictional performance of the developed PVDF/MgO was evaluated through experiments and compared with that of PTFE. Accordingly, a friction pendulum system was designed using the measured friction coefficient. The performance of this friction pendulum system was evaluated via nonlinear time history analyses of bridges. Subsequently, the plausibility of using PVDF/MgO as an alternative to PTFE as a friction material for friction pendulum systems was discussed.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.4
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• pp.67-74
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• 2001

Structural engineers lately have an interest in the safety for equipments and facility in buildings subjected to earthquake. The stability of cultural assets was not considered for the earthquake induced vibration, while the integrity of structure has been considered through the resistant earthquake design. The purpose of this study aimed to analyze the behavior of isolation device named as \"Isolation table system\" and to evaluate its isolation performance through the experiment study. Isolation table is one of isolation systems to reduce the vibration which was transferred from slab to exhibition table. Experimental result shows that isolation table can reduce the vibration by 80-90% and its behavior is very stable within its maximal stroke.al stroke.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.124-135
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• 2011

The capacity of bearings installed at abutments and piers for continuous bridges is usually determined by the magnitude of the maximum vertical reaction at each support and the capacity of bearings placed at piers is higher than that at abutments. In this study, the possibility of the improved seismic performance of base-isolated continuous skew bridges was investigated by analysing the variation of the seismic behavior of them according to three arrangements of bearings. Based on the conventional arrangement of bearings(Case A), three arrangements of bearings such as Case A, Case B and Case C were selected considering the variation of the horizontal stiffness of the lead rubber bearing(LRB) installed at the pier. The seismic behavior of the total 36 skew bridges was investigated by conducting the response spectrum analysis using the hybrid response spectrum considered the effect of LRB's damping. Results of analyses show that a more desirable seismic behavior of base-isolated continuous skew bridges can be obtained by reducing the magnitude of the horizontal stiffness of LRB placed at the pier to similar to or less than that of LRB installed at abutments. The variation of LRB's stiffness at the pier brings about period elongation and the change of mode shapes of base-isolated skew bridges and results in the reduction of the total base shear, the maximum base shear at the pier and the girder stresses. Although positive effects on the seismic behavior of base-isolated skew bridges caused by the change of arrangement of bearings decreased slighty with an increase in the flexibility of the substructure, the proposed arrangements of bearings bring about the improved seismic performance of base-isolated continuous skew plate girder bridges with less than 10m height of piers.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5A
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• pp.417-424
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• 2010

The dynamic properties of laminated rubber bearings used as isolators in structures could be significantly deteriorated because of the change of microstructure in rubber caused by thermal aging. As a result, a catastrophic failure of bridges and buildings unexpectedly occurs when they are subjected to earthquake attack. Here, the dynamic properties of laminated rubber bearings before and after different of compression-shear loading and repeated cycles loadings, ultimated failure test with thermal aging were first measured and compared to each other. The experimental results, the effects of thermal aging on the shear stiffness, energy absorption, and equivalent damping coefficient of laminated rubber bearings are investigated. It is found that the deterioration of dynamic properties of laminated rubber bearings caused by thermal aging is significant and should be taken into account in designing rubber bearings.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.855-864
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• 2013

The dynamic characteristics of natural rubber bearings, which are used as isolator, are dependent on the main rubber's dynamic behaviors and nonlinear properties. Rubber materials tend to undergo an aging process under the influence of mechanical or environmental factors, so they inevitably end up facing damage. A main cause of aging like this is known to be oxidization, which occurs through the heat of reaction at high temperatures. Accordingly, in this study an accelerated thermal aging test was carried out in order to compare the characteristic values of the bearings before and after thermal aging occurs. As a result of this experiment, it was found that a thermal aging phenomenon could have some effects on shear stiffness, energy absorption, and equivalent damping coefficients of the bearings. Furthermore, a deterioration in the dynamic properties of the natural rubber bearings caused by the thermal aging was applied to an actual bridge and then the effects of such thermal aging on the seismic performance of the bridge were also compared and analyzed based on numerical analysis. As a result of this analysis, it was found that the changes in the basic properties of the natural rubber bearings caused by the thermal aging bring only a minor effect on the seismic performance of bridges.