• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.5
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• pp.203-209
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• 2022

A simplified method for earthquake response analysis of a rectangular liquid storage tank is proposed with fluid-structure interaction considered. In order to simplify the complex three-dimensional structural behavior of a rectangular liquid storage tank, it is assumed that structural deformation does not occur in the plane parallel to the direction in which the earthquake ground motion is applied but in the plane perpendicular to the direction. The structural deformation is approximated by combining the natural modes of the simple beam and the cantilever beam. The hydrodynamic pressure, the structure's mass and stiffness, and the hydrodynamic pressure's added mass are derived by applying the Rayleigh-Ritz method. The natural frequency, structural deformation, pressure, effective mode mass, and effective mode height of the rectangular liquid storage tank are obtained. The structural displacement, hydrodynamic pressure, base shear, and overturning moment are calculated. The seismic response analysis of an example rectangular liquid storage tank is performed using the proposed simplified approach, and its accuracy is verified by comparing the results with the reference solution by the finite element method. Existing seismic design codes based on the hydrodynamic pressure in rigid liquid storage tanks are observed to produce results with significant errors that cannot be ignored.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.6
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• pp.80-87
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• 2003

Tank structures in ships are in contact with various fluid. The vibration characteristics of those structures are strongly affected by the added mass due to containing fluid. It is important to predict vibration characteristics of tank structures, but it is difficult to do. That's because the interaction problem concerned with the free surface, the variation of water depth and stiffener is to be considered between the fluid and the structure. Many authors have studied vibration of rectangular tank structures containing water. Kito studied added mass effect of water in contact with thin elastic flat plates. Kim et al. studied flexural vibration of stiffened plates in contact with water. However, few researches on dynamic interaction tank walls with water are reported in the vibration of rectangular tanks recently. in the present report, the coupling effect of added mass of fluid and structural constraint between panels on each vibration mode changing breadth of elastic plate, and dynamic pressure distribution have investigated numerically and discussed.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2325-2334
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• 2023

To study the lubrication performance of tilting-pad thrust bearing (TPTBs) during start-up in nuclear pump, a hydrodynamic lubrication model of TPTBs was established based on the computational fluid dynamics (CFD) method and the fluid-structure interaction (FSI) technique. Further, a mesh motion algorithm for the transient calculation of thrust bearings was developed based on the user defined function (UDF). The result demonstrated that minimum film thickness increases first and then decreases with the rotational speed under start-up condition. The influence of pad tilt on minimum film thickness is greater than that of collar movement at low speed, and the establishment of dynamic pressure mainly depends on pad tilt and minimum film thickness increases. As the increase of rotational speed, the influence of pad tilt was abated, where the influence of the moving of the collar dominated gradually, and minimum film thickness decreases. For TPTBs, the circumferential angle of the pad is always greater than the radial angle. When the rotational speed is constant, the change rate of radial angle is greater than that of circumferential angle with the increase of loading forces. This study can provide reference for improving bearing wear resistance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.101-105
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• 2008

A flexible structure submerged in acoustic fluid is affected by its surrounding fluid. In transient response of a submerged structure, the coupled effect between structures and surrounding fluid emerges as damping and added mass at early and late time, respectively. Therefore, the characteristics of submerged structure such as natural frequencies and damping coefficients are changed by its surrounding fluid. In this paper, the analytic modal equation of a spherical shell surrounded by water and air is dealt with. Through the example, the damping coefficients and natural frequencies of flexible structures are studied for various external acoustic fluid and structures.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.7
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• pp.718-724
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• 2008

A flexible structure submerged in acoustic fluid is affected by its surrounding fluid. In this case, the coupling effects between structures and surrounding fluid have an effect on the submerged structure as external force and change impedance of acoustic domain. Therefore, the coupling effects by its surrounding fluid complicatedly change the characteristics of a submerged structure such as natural frequencies and damping coefficients. In this paper, using the analytic modal equation of a spherical shell surrounded by water and air, the complex changes of damping coefficients and natural frequencies of submerged structures are studied for various external acoustic fluid and structures.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.1
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• pp.21-32
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• 2024

This study performed the seismic response analysis of an LNG storage tank supported by a disconnected piled raft foundation (DPRF) with a load transfer platform (LTP). For this purpose, a precise analytical model with simultaneous consideration of Fluid-Structure Interaction (FSI) and Soil-Structure Interaction (SSI) was used. The effect of the LTP characteristics (thickness, stiffness) of the DPRF system on the seismic response of the superstructure (inner and outer tanks) and piles was analyzed. The analytical results were compared with the response of the piled raft foundation (PRF) system. The following conclusions can be drawn from the numerical results: (1) The DPRF system has a smaller bending moment and axial force at the head of the pile than the PRF system, even if the thickness and stiffness of the LTP change; (2) The DPRF system has a slight stiffness of the LTP and the superstructure member force can increase with increasing thickness. This is because as the stiffness of the LTP decreases and the thickness increases, the natural frequency of the LTP becomes closer to the natural frequency of the superstructure, which may affect the response of the superstructure. Therefore, when applying the DPRF system, it is recommended that the sensitivity analysis of the seismic response to the thickness and stiffness of the LTP must be performed.

• Journal of Ocean Engineering and Technology
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• v.6 no.2
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• pp.46-54
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• 1992

In this paper, behavior of rectangular storage structures under earthquake loadings are investigated. Linear sloshing is assumed in this study. The effect of the wall flexibility is considered. Eulerian and lagrangian approaches are presented. The Eulerian approach is carried out by solving the boundary value problem for the fluid motion. In the lagrangian approach, the fluid as well as the storage structure is modelled by the finite element method. The fluid region is discretized by using fluid elements. The (1 $\times$ 1)-reduced integration is carried out for constructing the stiffness matrices of the fluid elements. Seismic analysis of the coupled system is carried out by the response spectra method. The numerical results show that the fluid forces on the wall obtained by two approaches are in good agreements. By including the effect of the wall flexibility, the forces due to fluid motion can be increased very significantly.

• Geomechanics and Engineering
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• v.12 no.6
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• pp.949-963
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• 2017

The main purpose of the current study is to develop the new coefficients for consideration of soil-structure interaction effects to find the elevated tank natural period. Most of the recommended relations to find the natural period just assumed the fixed base condition of elevated tank systems and the soil effects on the natural period are neglected. Two different analytical systems considering soil-structure- fluid interaction effects are recommended in the current study. Achieved results of natural impulsive and convective period, concluded from mentioned models are compared with the results of a numerical model. Two different sets of new coefficients for impulsive and convective periods are developed. The values of the developed coefficients directly depend to soil stiffness values. Additional results show that the soil stiffness not only has significant effects on natural period but also it is effective on liquid sloshing wave height. Both frequency content and soil stiffness have significant effects on the values of liquid wave height.

• Wind and Structures
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• v.6 no.1
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• pp.41-52
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• 2003

Rain-wind induced vibrations of cables are a challenging problem in the design of cable-stayed bridges. The precise excitation mechanism of the complex interaction between structure, wind and rain is still unknown. A theoretical model that is able to accurately simulate the observed phenomena is not available. This paper presents a mathematical model describing rain-wind induced vibrations as movement-induced vibrations using the quasi-steady strip theory. Both, the vibrations of the cable and the movement of the water rivulet on the cable surface can be described by the model including all geometrical and physical nonlinearities. The analysis using the stability and bifurcation theory shows that the model is capable of simulating the basic phenomena of the vibrations, such as dependence of wind velocity and cable damping. The results agree well with field data and wind tunnel tests. An extensive experimental study is currently performed to calibrate the parameters of the model.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2829-2832
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• 2007

In this study, one-way fluid structure interaction analysis(FSI) on wind turbine blade was performed. Both a quantitative fluid analysis on 3-bladed wind turbine and a structural analysis using the surface pressure data resulting from fluid analysis were carried out. Streamlines and angle of attack was easily acquired from analysis results, we showed the inlet velocity that the stall begins to occur. In the structural analysis, structural displacement and maximum stress of the two comparative models was calculated. The location that has maximum stress was found. The pressure difference between back and front part of the blade increases as the inlet velocity increase. The torque and maximum with regard to inlet velocity was also presented.