• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.124-132
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• 2013

Damage location and extent could be detected by the inverse analysis on dynamic response of the damaged structure. In general, detection of damage location is possible by the observation of the mode shape difference between undamaged and damaged structure and assessment of stiffness reduction is possible by the observation of the natural frequency difference of them. The study on damage detection by the dynamic response in civil structures is reported enough and in practical use, but in building structures it is reported seldom due to several problems. The purpose of this study is to present the damage detection method on shear building structures by mode shape. The damage location index using 1st mode shape is observed theoretically to find out damage location. The damage detection method is applied to numerical analysis model such as MATLAB and MIDAS GENw for the verification. Finally the shaking table test on 3 story shear building is performed for the examination of the damage detection method. In shaking table results, as the story stiffness decrease by 25% the 1st mode frequency increase by 12%, and the damage location index represents minus at damaged story.

• Journal of Korean Port Research
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• v.10 no.1
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• pp.37-51
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• 1996

2차의 섭동법과 경계요소법에 기초한 시간영역해석법은 불규칙파의 파동장에 있어서 파-구조물의 비선형간섭을 해석할 수 있는 해석법이지만. 파와 구조물의 운동이 정상상태에 도달하기까지 시간스텝으로 계산을 수행하여야 하므로 계산시간이 매우 길어지고, 각 성분파와 그에 의한 운동요소를 평가하는 것이 어렵다. 반면에 주파수영역해석법은 계산시간이 짧고, 각 성분요소들의 변화특성을 쉽게 판단할 수 있지만, 불규칙파동장으로의 적용이 현실적으로 어렵다는 단점을 가진다. 본 연구에서는 잠제 등에 대해서 전개되어 있는 주파수영역해석법을 임의형상의 부체 구조물에 대해 새롭게 수식의 전개를 수행하고, 압축공기주입 부체구조물에 적용하여 실험 및 이론해석결과로부터 그의 타당성을 확인한다. 이 때 압축공기의 거동은 Boyle법칙을 사용하여 평가한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.107-114
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• 2004

In this paper, a simple improved 8-node finite element for the finite element analysis of fibrous composite plates is presented by using the direct modification. We drive explicit expressions of shape functions for the 8-node element with bilinear element geometry, which is modified so that it can represent any quadratic fields in Cartesian coordinates. The refined first-order shear deformation theory is proposed, which results in parabolic through-thickness distribution of the transverse shear strains and stresses from the formulation based on the third-order shear deformation theory. It eliminates the need for shear correction factors in the first-order theory. This finite element is further improved by combined use of assumed strain, modified shape function, and refined first-order theory. To show the effectiveness of our simple modification on the 8-node finite elements, numerical studies are carried out the static, buckling and free vibration analysis of fibrous composite plates.

• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.93-103
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• 2009

The concept of the effective moment of inertia has been generally used for the deflection estimation of reinforced concrete flexural members. The KCI design code adopted Branson's equation for simple calculation of deflection, in which a representative value of the effective moment of inertia is used for the whole length of a member. However, the code equation for the effective moment of inertia was formulated based on the results of beam tests subjected to uniformly distributed loads, which may not effectively account for those of members under different loading conditions. Therefore, this study aimed to verify the influences of moment shapes resulting from different loading patterns by experiments. Six beams were fabricated and tested in this study, where primary variables were concrete compressive strengths and loading distances from supports, and test results were compared to the code equation and other existing approaches. A method utilizing variational analysis for the deflection estimation has been also proposed, which accounts for the influences of moment shapes to the effective moment of inertia. The test results indicated that the effective moment of inertia was somewhat influenced by the moment shape, and that this influence of moment shape to the effective moment of inertia was not captured by the code equation. Compared to the code equation, the proposed method had smaller variation in the ratios of the test results to the estimated values of beam deflections. Therefore, the proposed method is considered to be a good approach to take into account the influence of moment shape for the estimation of beam deflection, however, the differences between test results and estimated deflections show that more researches are still required to improve its accuracy by modifying the shape function of deflection.

• Journal of computational fluids engineering
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• v.3 no.1
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• pp.1-10
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• 1998

서로 섞이지 않는 두 비압축성 유체의 유동을 해석하기 위하여 VOF 방법에 기초한 수치 기법을 개발하였다. 유체간의 계면형상의 거동은 유동장내의 유체의 점유체적비의 변화에 의해 묘사되는데 이를 지배하는 이동방정식을 풀기 위한 새로운 대류항 계산법을 고안하였다. 대류항은 유체계면의 방향에 따라 풍상법과 역풍상법의 적절한 조합을 취하여 계산하는데 여기에 대각방향의 상류효과를 포함시켜 시간에 대한 2차 정확도를 갖도록 하였다. 또한 이 방법을 유량보정수송(FCT)법과 결합시켜 해의 단조성을 보장하였다. 몇 가지 단순 문제에 대한 시험 결과 이 기법이 수치오차에 의한 계면형상의 변형과 파손을 감소시킴을 확인하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.257-266
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• 1993

Computer Simulation based of divided element method was done to predict strip shape in20-high Sendzimir Mill and has been used to find a way for preventing quarter waves occurring in the wide and thin gaged strip rolling. The simulation showed that it was difficult to prevent quarter waves by the existing methods of controlling actuators such as the shifting of the first intermediate roll and the profile control of As-U-Roll in back up roll. It was, however, confirmed analytically and experimentally that quarter waves could be effectively reduce by changing taper mode at the barrel-end taper radius of the first intermediate roll.

• Journal of the Korea Convergence Society
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• v.10 no.12
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• pp.281-286
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• 2019

To repair the underside of the car, a repairman has to enter under the car body. But this work can make it difficult for him to fix it and the injuries can occur. To solve these difficult problems, the developed equipment is the automotive lift. In this study, three kinds of lift models 1, 2 and 3 were designed and the material properties of the structural steel were applied. As the same load were applied under the same conditions on all models, the structural analyses were conducted. Models 2 and 3 were shown to have the structural deformation less than model 1. Also, models 2 and 3 were shown to be more stable than model 1 structurally. By utilizing the design data on a convergence research through durability analysis according to the configuration of automotive lift obtained on the basis of this result, the esthetic feeling can be shown by being converged onto the automotive repair equipment parts at actual life.

• Composites Research
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• v.16 no.5
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• pp.28-38
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• 2003

In this study, the analytical investigation of orthotropic rectangular plate is presented. The loaded edges are assumed to be simply supported and the unloaded edges could have elastically restrained boundary conditions including the extreme boundary condition such as simple, fixed, and free. Using the closed-form solutions, the buckling analyses of orthotropic plate with arbitrary boundary conditions are performed. Based on the data obtained by conducting numerical analysis, the simplified form of equation for finding the buckling coefficient of plate with elastically restrained boundary conditions at the unloaded edges is suggested as a function of aspect ratio, elastic restraint. and material properties of the plate. The results of buckling analyses by closed-form solution and simplified form of solution are compared for various orthotropic material properties. It is confirmed that the difference of results is less than 1.5%.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.12
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• pp.1017-1024
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• 2012

The aerodynamic design and analysis on advanced propeller with blade sweep was performed for recent turboprop aircraft. HS1 airfoil series are selected as a advanced propeller blade airfoil. Adkins method is used for aerodynamic design and performance analysis with respect to the design point. Adkins method is based on the vortex-blade element theory which design the propeller to satisfy the condition for minimum energy loss. Propeller geometry is generated by varying chord length and pitch angle at design point of target aircraft. Advanced propeller is designed by apply the modified chord length, the tip sweep which is based on the geometry of conventional propeller. The aerodynamic characteristics of the designed Advanced propeller were verified by CFD(Computational Fluid Dynamic) and evaluated to be properly designed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.37-42
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• 2010

The objective of this study is to find heat emission characteristics on the natural convection radiator in a heating system when the aspect ratio of radiator is changed. In addition the computer simulation method is used in order to find the characteristics of heat transfer. When the width of the radiator is long and the height of radiator is short, the temperature difference from the floor level 0.5m to about 2.7m above the floor is small. It shows that thermal environment in heating space is good than the other case. For the future, I hope to compare the results between the computer simulation and experimental method for reliability.