• 한국해양공학회지
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• 제32권6호
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• pp.427-432
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• 2018

Tidal current power is one of the energy sources of the ocean. Electricity can be generated by converting the flow energy of the current into the rotational energy of a turbine. Unlike tidal barrage, tidal current power does not require dams, which have a severe environmental impact. A floating-type tidal current power device can reduce the expensive support and installation cost, which usually account for approximately 41% of the total cost. It can also be deployed in relatively deep water using tensioned wires. The dynamic behavior of a floater and turbine force are coupled because the thrust and moment of the turbine affect the floater excursion, and the motion of the floater can affect the incoming speed of the flow into the turbine. To maximize the power generation and stabilize the system, the coupled motion of the floater and turbine must be extensively analyzed. However, unlike pile-fixed devices, there have been few studies involving the motion analysis of a moored-type tidal current power device. In this study, the commercial program OrcaFlex 10.1a was used for a time domain motion analysis. In addition, in-house code was used for an iterative calculation to solve the coupled problems. As a result, it was found that the maximum mooring load of 200 kN and the floater excursion of 5.5 m were increased by the turbine effect. The load that occurred on the mooring system satisfied the safety factor of 1.67 suggested by API. The optimum mooring system for the floating tidal current power device was suggested to maximize the power generation and stability of the floater.

• 대기
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• 제18권2호
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• pp.83-95
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• 2008

In this study we have investigated the preceding eighteen large-scale climate indices with a lead time from zero to twelve months that have an influence on the variability of temperature and precipitation in Korea in order to understand which climate indices are overall available as predictors for long-range forecasting. We also have studied the dynamic link between preceding large-scale climate indices and regional climate using singular value decomposition analysis (SVDA) and correlation analysis (CA). Based on the coupled mode between large-scale circulation and regional climate, and correlation pattern between the preceding large-scale climate indices and large-scale circulation, the level of significance on climate indices as a predictor for monthly mean temperature and precipitation was evaluated for 5 and 1% level.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.3-26
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• 2009

Superloading yield surface concept is newly introduced together with subloading yield surface conception in order to describe full gradation continuously of the mechanical behavior of soils from typical sand through intermediate soil to typical clay (All Soils). Finite deformation theory has been applied to the soil skeleton-pore water coupled continuum mechanics, which enables us to discuss things in a perpetual stream from stable state to unstable state like from deformation to failure and vice versa like from liquefaction to post liquefaction consolidation of sand (All States). Incremental form of the equation of motion has been employed in the continuum mechanics in order to incorporate a rate type constitutive equation, which is "All Round" enough to predict ground behavior under both static and dynamic conditions. The present paper is the shortened version of the lecture note delivered in 2008 Theoretical and Applied Mechanics Conference, Science Council Japan, but with newly developed application examples.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.785-787
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• 2005

This paper addresses the small-signal analysis of the multi-phase interleaved boost converter with the coupled inductors operated in the continuous inductor current mode. The generalized and analytical expressions for the transfer functions of interest are derived for various inductor couplings. The dynamic characteristics are analyzed according to the inductor couplings and verified experimentally. The proposed frequency models will be very useful to design the dynamic controllers of the multi-phase interleaved boost converters.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.300-306
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• 2004

This paper is concerned with the application of perturbation method to the dynamic analysis of free-free beam. In general, the rigid-body motions and elastic vibrations are analyzed separately. However, the rigid-body motions cause vibrations and elastic vibrations also affect rigid-body motions in turn, which indicates that the rigid-body motions and elastic vibrations are coupled in nature. The resulting equations of motion are hybrid and nonlinear. We can discretize the equations of motion by means of admissible functions but still we have to cope with nonlinear equations. In this paper, we propose the use of .perturbation method to the coupled equations of motion. The resulting equations consist of zero-order equations of motion which depict the rigid-body motions and first-order equations of motion which depict the perturbed rigid-body motions and elastic vibrations. Numerical results show the efficacy of the proposed method.

• 한국소음진동공학회논문집
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• 제16권9호
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• pp.937-948
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• 2006

In this study, a fluid/structure coupled analysis system for simulating complex flow-induced vibration (FIV) phenomenon of cascades has been developed. The flow is modeled using Euler and Wavier-Stokes equations with different turbulent models. The fluid domains are modeled using the unstructured grid system with dynamic deformations due to the motion of structural boundary. The Spalart-Allmaras (S-A) and the SST ${\kappa}-{\omega}$ turbulent models are used to predict the transonic turbulent flows. A fully implicit time marching scheme based on the Newmark direct integration method is used in order to solve the coupled governing equations for viscous flow-induced vibration phenomena. For the purpose of validation for the developed FIV analysis system, comparison results for computational analyses of steady and unsteady aerodynamics and flutter analyses are presented in the transonic flow region. In addition, flow-induced vibration analyses for the isolated cascade and multi-blades cascade models have been conducted to show the physical fluid-structure interaction effects in the time domain.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.793-802
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• 2006

In this study, a fluid/structure coupled analysis system for simulating complex flow-induced vibration (FIV) phenomenon of cascades has been developed. The flow is modeled using Euler and Wavier-Stokes equations with different turbulent models. The fluid domains are modeled using the unstructured grid system with dynamic deformations due to the motion of structural boundary. The Spalart-Allmaras (S-A) and the SST ${\kappa}-{\omega}$ turbulent models are used to predict the transonic turbulent flows. A fully implicit time marching scheme based on the Newmark direct integration method is used in order to solve the coupled governing equations for viscous flow-induced vibration phenomena. For the purpose of validation for the developed FIV analysis system, comparison results for computational analyses of steady and unsteady aerodynamics and flutter analyses are presented in the transonic flow region. In addition, flow-induced vibration analyses for the isolated cascade and multi-blades cascade models have been conducted to show the physical fluid-structure interaction effects in the time domain.

• Steel and Composite Structures
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• 제20권1호
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• pp.107-125
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• 2016

Steel shear wall system has been used in recent years in tall buildings due to its appropriate behavior advantages such as stiffness, high strength, economic feasibility and high energy absorption capability. Coupled steel plate shear walls consist of two steel shear walls that are connected to each other by steel link beam at each floor level. In this article the frames of 3, 10, and 15 of (C-SPSW) floor with rigid connection were considered in three different lengths of 1.25, 2.5 and 3.75 meters and link beams with plastic section modulus of 100% to the panel beam at each floor level and analyzed using three pairs of accelerograms based on nonlinear dynamic analysis through ABAQUS software and then the performance of walls and link beams at base shear, drift, the period of structure, degree of coupling (DC) and dissipated energy evaluated. The results show that the (C-SPSW) system base shear increases with a decrease in the link beam length, and the drift, main period and dissipated energy of structure decreases. Also the link beam length has different effects on parameters of coupling degrees.

• Coupled systems mechanics
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• 제8권4호
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• pp.351-375
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• 2019

The present work investigates the use of a rigid rocking block as a tool to reduce vibrations in a frame structure. The study is based on a simplified model composed by a 2-DOF linear system, meant to represent a general M-DOF frame structure, coupled with a rocking rigid block through a linear visco-elastic device, which connects only the lower part of the 2-DOF system. The possibility to restrain the block directly to the ground, by means of a second visco-elastic device, is investigated as well. The dynamic response of the model under an harmonic base excitation is then analysed in order to evaluate the effectiveness of the coupling in reducing the displacements and the drift of the 2-DOF system. The nonlinear equations of motion of the coupled assemblage 2-DOF-block are obtained by a Lagrangian approach and then numerically integrated considering some reference mechanical and geometrical quantities as variable parameters. It follows an extensive parametric analysis, whose results are summarized through behaviour maps, which portray the ratio between the maximum displacements and drifts of the system, with and without the coupling with the rigid block, for several combinations of system's parameters. When the ratio of the displacements is less than unity, the coupling is considered effective. Results show that the presence of the rocking rigid block improves the dynamics of the system in large ranges of the characterizing parameters.

• Structural Engineering and Mechanics
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• 제82권3호
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• pp.385-400
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• 2022

Sky-bridges between adjacent buildings can enhance lateral stiffness and limit the impact of lateral forces. This study analysed the structural capabilities and dynamic performances of sky-bridge-coupled buildings under various sets of ground motions. Finite Element (FE) analyses were carried out with the link being iteratively repositioned along the full height of the structures. Incremental dynamic analysis (IDA) and probabilistic damage distribution were also applied. The results indicated that the establishment of sky-bridges caused a slight change in the natural frequency and mode shapes. The sky-bridge system was shown to be efficient in controlling displacement and Inter-Storey Drift Ratio (%ISDR) and reducing the probability of damage in the higher floors. The most efficient location of the sky-bridge, for improving its rigidity, was found to be at 88% of the building height. Finally, the effects of two types of materials (steel and concrete) and end conditions (hinged and fixed) were studied. The outcomes showed that coupled buildings with a sky-bridge made of steel with hinged connection could withstand ground motions longer than those made of concrete with fixed connection.