• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.1
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• pp.63-69
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• 1998

A rotating shaft system subjected to seismic motions has been investigated for the various operating modes at start-up. During an earthquake excitation, the rotor may hit the stator of machines due to the excessive deformation of shaft, and thus the response of rotating shaft system of which foundation is supported by the vibration isolation devices has been simulated. In order to examine the transient response of the rotating shaft system at the start-up to both the various operating conditions and the seismic excitation simultaneously, nonlinear equations of motion are derived and solved numerically using Runge-Kutta method. The response of the rotating shaft system is calculated according to the operating modes as recommended by the machine and the system parameters such as the spring stiffness of isolation devices.

• Earthquakes and Structures
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• v.10 no.1
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• pp.25-51
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• 2016

In this study, graph product rules are applied to the dynamic analysis of regular skeletal structures. Graph product rules have recently been utilized in structural mechanics as a powerful tool for eigensolution of symmetric and regular skeletal structures. A structure is called regular if its model is a graph product. In the first part of this paper, the formulation of time history dynamic analysis of regular structures under seismic excitation is derived using graph product rules. This formulation can generally be utilized for efficient linear elastic dynamic analysis using vibration modes. The second part comprises of random vibration analysis of regular skeletal structures via canonical forms and closed-form eigensolution of matrices containing special patterns for symmetric structures. In this part, the formulations are developed for dynamic analysis of structures subjected to random seismic excitation in frequency domain. In all the proposed methods, eigensolution of the problems is achieved with less computational effort due to incorporating graph product rules and canonical forms for symmetric and cyclically symmetric structures.

• Journal of the Korean Society of Safety
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• v.37 no.6
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• pp.81-88
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• 2022

It is necessary to better understand the effect of age-related degradation on the performance of reinforced concrete shear walls in nuclear power plants in order to ensure their structural safety in the event of earthquakes. Therefore, this paper studies seismic fragility of the typical shear wall in nuclear power plants under earthquake excitation Reinforced concrete shear wall is composed of wall, horizontal and vertical flanges. Due to characteristics of its geometry, it is difficult to predict the ultimate behavior of shear wall under earthquake excitation. In this study, for more realistic numerical simulation, the Latin Hyper-Cube (LHC) simulation technique was used to generate uncertain variables for the material properties of concrete shear walls. The effects of crack, characteristics of inelastic behavior of concrete, and loss of cross section were considered in the nonlinear finite element analysis. The effects of aging-related deterioration were investigated on the performance of reinforced concrete shear walls through analysis of undegraded concrete shear walls and degraded concrete shear walls. The resulting seismic fragility curves present the change of performance of concrete shear wall due to age-related degradation.

• Structural Engineering and Mechanics
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• v.81 no.6
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• pp.691-703
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• 2022

To obtain the seismic response of lead-cored rubber, shape memory alloy (SMA)-rubber isolation Plate-shell Integrated Concrete Liquid-Storage Structure (PSICLSS), based on a PSICLSS in a water treatment plant, built a scale experimental model, and a shaking table test was conducted. Discussed the seismic responses of rubber isolation, SMA-rubber isolation PSICLSS. Combined with numerical model analysis, the vibration characteristics of rubber isolation PSICLSS are studied. The results showed that the acceleration, liquid sloshing height, hydrodynamic pressure of rubber and SMA-rubber isolation PSICLSS are amplified when the frequency of seismic excitation is close to the main frequency of the isolation PSICLSS. The earthquake causes a significant leakage of liquid, at the same time, the external liquid sloshing height is significantly higher than internal liquid sloshing height. Numerical analysis showed that the low-frequency acceleration excitation causes a more significant dynamic response of PSICLSS. The sinusoidal excitation with first-order sloshing frequency of internal liquid causes a more significant sloshing height of the internal liquid, but has little effect on the structural principal stresses. The sinusoidal excitation with first-order sloshing frequency of external liquid causes the most enormous structural principal stress, and a more significant external liquid sloshing height. In particular, the principal stress of PSICLSSS with long isolation period will be significantly enlarged. Therefore, the stiffness of the isolation layer should be properly adjusted in the design of rubber and SMA-rubber isolation PSICLSS.

• Steel and Composite Structures
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• v.11 no.1
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• pp.21-38
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• 2011

This study examines the influence of curved, steel, I-girder bridge configuration on girder end reactions and cross frame member forces during seismic events. Simply-supported bridge finite element models were created and examined under seismic events mimicking what could be experienced in AASHTO Seismic Zone 2. Bridges were analyzed using practical ranges of: radius of curvature; girder and cross frame spacings; and lateral bracing configuration. Results from the study indicated that: (1) radius of curvature had the greatest influence on seismic response; (2) interior (lowest radius) girder reactions were heavily influenced by parameter variations and, in certain instances, uplift at their bearings could be a concern; (3) vertical excitation more heavily influenced bearing and cross frame seismic response; and (4) lateral bracing helped reduce seismic effects but using bracing along the entire span did not provide additional benefit over placing bracing only in bays adjacent to the supports.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.455-462
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• 2000

In this study seismic response of a base-isolated bridge for soil types is compared. Bilinear model is used for lead rubber bearing(LRB). Accelerograms whose response spectrum matches the design spectrum for soil types are used as earthquake ground excitation. Nonlinear time history analyses using the SAP2000 program is performed. The results show that seismic response of a base-isolated bridge is increased as the soil becomes soft.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.216-222
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• 1998

Effects of translational and rotational motions of the foundation on the dynamic behaviors of a bridge under seismic excitations are examined by utilizing a simplified 3 degree-of-freedom of system. To consider the nonlinear characteristics of the RC pier, a hysteresis model is adapted, which can simulate the inelastic motion of the pier with the stiffness degradation. From results, the portion of the total displacement due to rotational motion of the foundation becomes larger as applied seismic excitation increases.

• Smart Structures and Systems
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• v.2 no.4
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• pp.329-337
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• 2006

This paper illustrates an analytical investigation of the vibration parameters of buildings on sliding seismic isolation bearings with elastic limiters of the relative displacement. The installation scheme of sliding bearings and elastic limiters for the separate unit of a 4 storey hospital building with brick walls is designed. The analysis of the vibrations of the hospital building is conducted for harmonic base excitation.

• Smart Structures and Systems
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• v.23 no.3
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• pp.243-261
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• 2019

This paper introduces an appropriate technique to estimate the weighting matrices used in the linear quadratic regulator (LQR) method for active structural control. For this purpose, a parameter is defined to regulate the relationship between the structural energy and control force. The optimum value of the regulating parameter, is determined for single degree of freedom (SDOF) systems under seismic excitations. In addition, the suggested technique is generalized for multiple degrees of freedom (MDOF) active control systems. Numerical examples demonstrate the robustness of the proposed method for controlled buildings under a wide range of seismic excitations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.157-165
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• 2011

Base isolation system is widely used for reduction of dynamic responses of structures subjected to seismic load. Recently, research on a smart base isolation system that can effectively reduce dynamic responses of the isolated structure without accompanying increases in base drifts has been actively conducted. In this study, a smart base isolation system was applied to an arch structure subjected to seismic excitation and its control performance for reduction of seismic responses was evaluated. In order to make a smart base isolation system, 4kN MR dampers and low damping elastomeric bearings were used. Seismic response control performance of the proposed smart base isolation system was compared to that of the optimally designed lead-rubber bearing(LRB) isolation system. To this end, an artificial ground motion developed based on KBC2009 design response spectrum was used as a seismic excitation. Fuzzy control algorithm was used to control MR damper in the smart base isolation system and multi-objective genetic algorithm was employed to optimize the fuzzy controller. Based on numerical simulation results, it has been shown that the smart base isolation system can drastically reduce base drifts and seismic responses of the example arch structure in comparison with LRB isolation system.