• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.1-8
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• 2004

For the linearized differential algebraic equation of the nonlinear constrained system, exact initial values of the acceleration are needed to solve itself. It may be very troublesome to perform the inverse operation for obtaining the incremental quantities since the mass matrix contains the zero element in the diagonal. This fact makes the mass matrix impossible to be positive definite. To overcome this singularity phenomenon the mass matrix needs to be modified to allow the feasible application of predictor and corrector in the iterative computation. In this paper the proposed numerical algorithm based on the modified mass matrix combines the conventional implicit algorithm, Newton-Raphson method and Newmark method. The numerical example presents reliabilities for the proposed algorithm via comparisons of the 4th order Runge-kutta method. The proposed algorithm seems to be satisfactory even though the acceleration, Lagrange multiplier, and energy show unstable behaviour. Correspondingly, it provides one important clue to another algorithm for the enhancement of the numerical results.

• Structural Engineering and Mechanics
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• 제87권5호
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• pp.431-450
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• 2023

In this study, it is intended to perform nonlinear time-history analyses of nuclear power plant structures (NPP) under near-fault earthquakes showing directivity pulse and fling-step characteristics. Simulation procedures based on cycloidal pulse and far-fault ground motions are also used to simulate near-fault motions showing forward-directivity and fling-step characteristics and the structural responses are compared with those of the recorded near-fault ground motions. Because it is aimed to determine specifically the pulse type characteristics of near-fault ground motions on NPPs, all the ground motions are normalized to have a PGA of 0.3 g. Depending on the obtained results it can be underlined that although near-fault ground motion has the potential to cause damage mostly on structural systems having larger periods, it may also have noticeable effects on the responses of rigid structures, like NPP containment buildings. On the other hand, simulated near-fault motions can help us to get an insight into the near-fault mechanism as well as an approximate visualization of the structural responses under near-fault earthquakes.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.68-75
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• 2009

In this study, aeroelastic response analyses have been conducted for a 3D wind turbine blade model. Advanced computational analysis system based on computational fluid dynamics(CFD) and computational structural dynamics(CSD) has been developed in order to investigate detailed dynamic responsed of wind turbine blade. Vibration analyses of rotating wind-turbine blade have been conducted using the general nonlinear finite element program, SAMCEF (Ver.6.3). Reynolds-averaged Navier-Stokes (RANS)equations with spalart-allmaras turbulence model are solved for unsteady flow problems of the rotating turbine blade model. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3D turbine blade for fluid-structure interaction (FSI) problems. Detailed dynamic responses and instantaneous Mach contour on the blade surfaces considering flow-separation effects are presented to show the multi-physical phenomenon of the rotating wind-turbine blade model.

• 한국재난정보학회 논문집
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• 제13권2호
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• pp.249-257
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• 2017

최근 당진-평택시에 위치한 서해대교에서 낙뢰로 인한 케이블 단선사고가 발생하였다. 이것은 자연발생 사고로 결론이 났지만 케이블교량의 단선으로 인하여 안전문제를 재검토하는 과정이 매우 중요한 일임을 상기하게 된 사건이다. 즉, 케이블 교량에서 케이블의 역할은 구조물의 안전에 지대한 영향을 미치며 이로 인해 전체구조체계에 대한 영향을 파악할 필요가 대두 되었다. 케이블 교량은 주 탑을 세우고 바닥판을 케이블로 지지하는 경제적 교량으로 케이블의 영향은 주 부재로써 전 교량시스템의 안전에 영향이 큰 부재이다. 사장교에서 케이블은 케이블의 장력이 변할 때 발생하는 사하중으로 인한 처짐의 변화 때문에 비선형 성을 가진다. 동적해석은 변형 된 사하중 접선강도행렬을 사용하여 되며 새로운 개념은 전체 교량에 대한 케이블 진동 (면내 및 스윙 모두)의 효과를 연구하기 위해 케이블을 여러 요소로 분할하였다. 이 연구의 결과는 전반적인 교량 역학에 케이블 진동의 중요성을 보여준다.

• 한국전산구조공학회논문집
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• 제26권4호
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• pp.247-254
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• 2013

본 논문에서는 해상 시추작업을 위한 heave compensation system의 시뮬레이션 모델을 개발하였다. 우선 시뮬레이션을 위하여, 다물체계 동역학 커널을 개발하였다. 다물체계 동역학 커널은 입력 받은 heave compensation system 시뮬레이션 모델의 운동학적 정보를 이용하여 recursive Newton-Euler formulation 방법을 기반으로 운동방정식을 자동으로 구성하고, 수치적으로 해를 계산하는 기능을 한다. 그리고 해상 시추선에 작용하는 외력을 계산하기 위하여 유체 정역학적 힘과 유체 동역학적 힘을 계산하는 모듈을 개발하였다. 이와 같이 개발한 커널과 모듈들을 적용하여 해상 시추선의 hoisting system 동적거동 해석을 수행하고, 관절에서의 구속력을 계산하였다.

• Computers and Concrete
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• 제12권1호
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• pp.37-51
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• 2013

The responses of reinforced concrete slabs subject to an impact loading near the ultimate load range are explored. The analysis is carried out on a simply supported rectangular reinforced concrete slab using a nonlinear explicit dynamic procedure and considering three material models: Drucker-Prager, modified Drucker-Prager, and concrete damaged plasticity, available in the commercial finite element software, ABAQUS/Explicit. For comparison purposes, the impact force-time response, steel reinforcement failure, and concrete perforation pattern are verified against the existing experimental results. Also, the effectiveness of mesh density and damage wave propagation are studied independently. It is shown that the presently adopted finite element procedure is able to simulate and predict fairly accurate the behavior of reinforced concrete slab under impact load. More detailed investigations are however demanded for the justification of effects coming from an imperfect projectile orientation as well as the load and structural surface conditions, including the impulsive contacted state, which are inevitable in an actual impact environment.

• Earthquakes and Structures
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• 제15권3호
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• pp.335-350
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• 2018

This paper presents numerical modelling, modal testing, finite element model updating, linear and nonlinear earthquake behavior of a reinforced concrete building model. A 1/2 geometrically scale, two-storey, reinforced concrete frame model with raft base were constructed, tested and analyzed. Modal testing on the model using ambient vibrations is performed to illustrate the dynamic characteristics experimentally. Finite element model of the structure is developed by ANSYS software and dynamic characteristics such as natural frequencies, mode shapes and damping ratios are calculated numerically. The enhanced frequency domain decomposition method and the stochastic subspace identification method are used for identifying dynamic characteristics experimentally and such values are used to update the finite element models. Different parameters of the model are calibrated using manual tuning process to minimize the differences between the numerically calculated and experimentally measured dynamic characteristics. The maximum difference between the measured and numerically calculated frequencies is reduced from 28.47% to 4.75% with the model updating. To determine the effects of the finite element model updating on the earthquake behavior, linear and nonlinear earthquake analyses are performed using 1992 Erzincan earthquake record, before and after model updating. After model updating, the maximum differences in the displacements and stresses were obtained as 29% and 25% for the linear earthquake analysis and 28% and 47% for the nonlinear earthquake analysis compared with that obtained from initial earthquake results before model updating. These differences state that finite element model updating provides a significant influence on linear and especially nonlinear earthquake behavior of buildings.

• 한국실내디자인학회논문집
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• 제18권1호
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• pp.64-71
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• 2009

The modern society is rapidly changing through the development of computer network technology. By generation a collapse of boundaries between may important social institutions, computer networking has affected culture, economy and the physical environment. Because of this, people face a switchover from a simple society, to a compound society. It will also increase the diversity if society's demand, though, and experience. This change is not an exception in the exhibition space. People are more interested in civilized pastimes and also demand diverse thinking. So as a necessary consequence, the function of museum space Is offended and that there are various attempt to increase information and demand of that space. The purpose of this study is try to find a solution a countermeasure of modern society's mobile situation. Researchers analyzed structural qualities of Hyper-text; non-boundary, interaction and nonlinear and deduce nine kinds of methods to apply in space. Also, Researchers looked at the examples in museum space and derived like this expression way; dynamics, mobility, a non-materiality, continuity, complexity from analysis of expression way.

• Structural Engineering and Mechanics
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• 제72권1호
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• pp.83-97
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• 2019

In this research, the vulnerability of some reinforced concrete frames with different stories are studied based on the Park-Ang Damage Index. The damages of the frames are investigated under various earthquakes with nonlinear dynamic analysis in IDARC software. By examining the most important characteristics of earthquake parameters, the damage index and vulnerability of these frames are investigated in this software. The intensity of Erias, velocity spectral intensity (VSI) and peak ground velocity (PGV) had the highest correlation, and root mean square of displacement ($D_{rms}$) had the lowest correlation coefficient among the parameters. Then, the particle swarm optimization (PSO) algorithm was used, and the sinusoidal waves were equivalent to the used earthquakes according to the most influential parameters above. The damage index equivalent to these waves is estimated using nonlinear dynamics analysis. The comparison between the damages caused by earthquakes and equivalent sinusoidal waves is done too. The generations of sinusoidal waves equivalent to different earthquakes are generalized in some reinforced concrete frames. The equivalent sinusoidal wave method was exact enough because the greatest difference between the results of the main and artificial accelerator damage index was about 5 percent. Also sinusoidal waves were more consistent with the damage indices of the structures compared to the earthquake parameters.

• Wind and Structures
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• 제31권6호
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• pp.495-508
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• 2020

To investigate the structural behaviour of grouped tanks under wind loads, 2 problems need to be figured out, wind pressures on tank shells and critical loads of the shell under these pressure distribution patterns. Following the wind tunnel tests described in the companion paper, this paper firstly seeks to obtain wind loads on the external wall in a squarely-arranged cylindrical tank group by numerical simulation, considering various layouts. The outcomes demonstrate that the numerical method can provide similar results on wind pressures and better insights on grouping effects through extracted streamlines. Then, geometrically nonlinear analyses are performed using several selected potentially unfavourable wind pressure distributions. It is found that the critical load is controlled by limit point buckling when the tank is empty while excessive deformations when the tank is full. In particular, significant reductions of wind resistance are found on grouped full tanks compared to the isolated tank, considering both serviceability and ultimate limit state, which should receive special attention if the tank is expected to resist severe wind loads with the increase of liquid level.