• Structural Engineering and Mechanics
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• 제71권4호
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• pp.377-390
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• 2019

A method for estimating the floor response spectra (FRS) of elastic structures under earthquake excitations is proposed. The method is established based on a previously proposed direct estimation method for single degree of freedom systems, which generally overestimates the FRS of a structure, particularly in the resonance period range. A modification factor is introduced to modify the original method; the modification factor is expressed as a function of the period ratio and is determined through regression analysis on time history analysis results. Both real and artificial ground motions are considered in the analysis, and it is found that the modification factors obtained from the real and artificial ground motions are significantly different. This suggests that the effect of ground motion should be considered in the estimation of FRS. The modified FRS estimation method is further applied to a 10-story building structure, and it is verified that the proposed method can lead to a good estimation of FRS of multi-story buildings.

• 한국정밀공학회지
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• 제29권4호
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• pp.433-440
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• 2012

Various studies to improve the physical abilities of the human have been steadily continued from the past to the present. Only recently such technology has been realized, and those are expected to replace or complement human beings in large part. In this paper, the current status of developed wearable robots is investigated and studies were conducted in order to apply the types of robots in industry spot. In order to apply wearable exoskeleton robot to industry which enhances human physical capability, driving range of the robot's degrees of freedom were selected by analyzing working motion, and augmentative exoskeleton structure design process is presented by analyzing require torque and power during selected working motion. At the end of this paper, the designed mock-up is introduced to validate the feasibility of designed robot.

• Structural Engineering and Mechanics
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• 제32권4호
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• pp.517-529
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• 2009

A passive vibration mitigation architecture is proposed to damp transverse vibrations of guyed masts. The scheme is based on a number of pendula attached to the mast and tuned to the vibration modes to be controlled. This scheme differs from the well-known autoparametric pendulum absorber system. The equations of motion of the guyed mast with an arbitrary number of pendula are obtained. The leading bending behaviour of a typical truss mast is described by an equivalent beam model whereas the guys are conveniently modeled as equivalent transverse springs whose stiffness comprises the elastic and geometric stiffness. By assuming a mast with an inertially and elastically isotropic cross-section, a planar model of the guyed mast is investigated. The linearization of the equations of motion of the mast subject to a harmonic distributed force leads to the transfer functions of the structure without the dampers and with the dampers. The transfer functions allow to investigate the mitigation effects of the pendula. By employing one pendulum only, tuned to the frequency of the lowest mode, the effectiveness of the passive vibration potential in reducing the motion and acceleration of the top section of the mast is demonstrated.

• 대한기계학회논문집B
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• 제28권2호
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• pp.174-180
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• 2004

Failure of tube bundles due to excessive flow-induced vibrations continues to affect the performance of nuclear power plant Early experimental studies concentrated on rigid structures and later investigators dealt with elastic structures because of their importance in many engineering fields. On the other hand, much less numerical work has been carried out, because of the numerical complexity associated with the problem. Conventional approaches usually decoupled the flow solution from the structural problem. The present numerical study proposes the methodology in analyzing the fluidelastic instability occurring in tube bundles by coupling the Computational fluid Dynamics (C%) with the tube equation of motions. The motion of the structures is modeled by a spring-damper-mass system that allows transnational motion in two directions (a two-degree-of-freedom system). The fluid motion and the cylinder response are solved in an iterative way, so that the interaction between the fluid and the structure can be accounted for property. The aim of the present work is to predict the fluidelstic instability of tube bundles and the associated phenomena, such as the response of the cylinder, the unsteady lift and drag on the cylinder, the vortex shedding frequency.

• 한국해안해양공학회지
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• 제19권3호
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• pp.237-243
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• 2007

잔교식 안벽구조물의 확률론적 지진위험도 해석을 수행하였다. 부지응답해석을 통해 증폭된 지표 지진이 구조물에 가해질 때 강관파일의 조합응력비와 최대수평변위가 한계상태를 초과하는 확률을 지진취약도 곡선으로 표현하였다. 해당 지역의 지진발생확률은 항만설계기준의 지진재해도를 이용하여 최대지반가속도의 초과확률을 구할 수 있었다. 구조물의 최종적인 지진위험도는 지진취약도와 지진재해도를 이용하여 산정하였으며 수치해석 예제를 통해 그 결과를 제시하였다.

• Structural Engineering and Mechanics
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• 제62권2호
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• pp.163-170
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• 2017

This study presents a particle-wall filtration model for predicting the particle motion behavior in a typical rotational flow field-filtration in blower system of cooker hood. Based on computational fluid dynamics model, air flow and particles has been simulated by Lagrangian-particle/ Eulerian-gas approaches and get verified by experiment data from a manufacturer. Airflow volume, particle diameter and local structure, which are related to the particle filtration has been studied. Results indicates that: (1) there exists an optimal airflow volume of $1243m^3/h$ related to the most appropriate filtration rate; (2) Diameter of particle is the significant property related to the filtration rate. Big size particles can represent the filtration performance of blower; (3) More than 86% grease particles are caught by impeller blades firstly, and then splashed onto the corresponding location of worm box internal wall. These results would help to study the micro-particle motion behavior and evaluate the filtration rate and structure design of blower.

• Wind and Structures
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• 제16권5호
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• pp.411-431
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• 2013

A computational study of vortex-induced transverse vibrations of a cylinder with low mass-damping is presented. An Arbitrary Lagrangian-Eulerian (ALE) formulation of the Unsteady Reynolds-Averaged Navier-Stokes equations (URANS), along with the Spalart-Allmaras (SA) one-equation turbulence model, are coupled conservatively with rigid body motion equations of the cylinder mounted on elastic supports in order to study the amplitude and frequency response of a freely vibrating cylinder, its flow-induced motion, Vortex Street, near-wake flow structure, and unsteady loading in a moderate range of Reynolds numbers. The time accurate response of the cylinder from rest to its limit cycle is studied to explore the effects of Reynolds number on the start of large displacements, motion amplitude, and frequency. The computational results are compared with published physical experiments and numerical studies. The maximum amplitudes of displacements computed for various Reynolds numbers are smaller than the experimental values; however, the overall agreement of the results is quite satisfactory, and the upper branch of the limit-cycle displacement amplitude vs. reduced velocity response is captured, a feature that was missed by other studies. Vortex shedding modes, lock-in phenomena, frequency response, and phase angles are also in agreement with experiments.

• 한국지반공학회논문집
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• 제22권4호
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• pp.105-111
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• 2006

본 연구에서는 먼저 지표면을 비롯하여 구조물 곳곳에 가속도계가 설치된 깊은 직접기초 구조물 2개를 선정하였다. 이어서 구조물에 기록된 실지진 데이터를 사용하여 주파수 영역에서 Transmissibility 함수를 사용하는 기법으로 기초 위치에서와 자유지표면에서의 지반운동 사이의 차이를 산정하였고 실지진기록을 사용하여 산정된 이 변환함수를 기존의 간편식과 비교하여 검증하였다. 비록 강성 기초저면, 연직으로 전파되는 지반운동을 가정하는 간편식의 전제조건은 실제 조건과 차이가 있지만, 그럼에도 불구하고 실지진기록으로부터 산정된 변환함수와 매우 양호한 유사성을 보여주므로 간편식을 설계실무에서 사용할 수 있을 것으로 판단된다.

• 한국컴퓨터산업학회논문지
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• 제10권5호
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• pp.221-226
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• 2009

폐쇄된 계 내부에서 강체 입자의 회전 운동에는 회전시키는 주체가 되는 몸체와 회전을 당하는 입자로 나눌 수 있다. 이 경우 입자가 몸체에 대해서 구속 될(bounded) 경우 홀로노믹(HOLONOMIC) 시스템으로서 지금까지 동역학에 소개되는 모든 수식이 잘 맞게 해석되고 수식에 의한 구조 또 한 현실과 잘 맞다. 그러나 그 구조가 비흘로노믹 시스템 이면 기존 회전 운동 방정식에서 벗어난다. 본 논문의 목적은 회전 운동 시 홀로노믹 시스템과 비흘로노믹 시스템과의 차이를 장치로 구분 하고 특히 비 홀로노믹 시스템의 현실에서 나타나는 현상을 컴퓨터 시뮬레이션 모델에 수식 화 하는 것이다. 그 수식으로부터 닫힌 회전운동의 질량중심(center of mass) 이동과 외부의 마찰에 대한 갇힌 운동(confined motion)의 표현법을 컴퓨터 그래픽 운동 방법에 응용 할 수 있도록 한다.

• Structural Engineering and Mechanics
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• 제33권6호
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• pp.725-745
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• 2009

In this paper, probabilistic seismic performance assessment of a typical non-seismic RC frame building representative of a large inventory of existing buildings in developing countries is conducted. Nonlinear time-history analyses of the sample building are performed with 20 large-magnitude medium distance ground motions scaled to different levels of intensity represented by peak ground acceleration and 5% damped elastic spectral acceleration at the first mode period of the building. The hysteretic model used in the analyses accommodates stiffness degradation, ductility-based strength decay, hysteretic energy-based strength decay and pinching due to gap opening and closing. The maximum inter story drift ratios obtained from the time-history analyses are plotted against the ground motion intensities. A method is defined for obtaining the yielding and collapse capacity of the analyzed structure using these curves. The fragility curves for yielding and collapse damage levels are developed by statistically interpreting the results of the time-history analyses. Hazard-survival curves are generated by changing the horizontal axis of the fragility curves from ground motion intensities to their annual probability of exceedance using the log-log linear ground motion hazard model. The results express at a glance the probabilities of yielding and collapse against various levels of ground motion intensities.