• Structural Engineering and Mechanics
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• 제64권4호
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• pp.515-526
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• 2017

Dynamic response of functionally graded Carbon nanotubes (FG-CNT) reinforced pipes conveying viscous fluid under accelerated moving load is presented. The mixture rule is used for obtaining the material properties of nano-composite pipe. The radial force induced by viscous fluid is calculated by Navier-Stokes equation. The material properties of pipe are considered temperature-dependent. The structure is simulated by Reddy higher-order shear deformation shell theory and the corresponding motion equations are derived by Hamilton's principal. Differential quadrature (DQ) method and the Integral Quadrature (IQ) are applied for analogizing the motion equations and then the Newmark time integration scheme is used for obtaining the dynamic response of structure. The effects of different parameters such as boundary conditions, geometrical parameters, velocity and acceleration of moving load, CNT volume percent and distribution type are shown on the dynamic response of pipe. Results indicate that increasing CNTs leads to decrease in transient deflection of structure. In accelerated motion of the moving load, the maximum displacement is occurred later with respect to decelerated motion of moving load.

• Structural Engineering and Mechanics
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• 제52권6호
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• pp.1193-1208
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• 2014

A simulation of failures on responsible elements is only one form of the extreme structural behavior analysis. By understanding the dynamic behavior in incidental situations, it is possible to make a special structural design from the point of the largest axial force, stress and redundancy. The numerical realization of one such simulation analysis was performed using FEM in this paper. The boundary parameters of transient analysis, such as overall structural damping coefficient, load accelerations, time of load fall and internal forces in the responsible structural elements, were determined on the basis of the dynamic experimental parameters. The structure eigenfrequencies were determined in modal analysis. In the study, the basic incidental models were set. The models were identified by many years of monitoring incidental situations and the most frequent human errors in work with heavy structures. The combined load models of structure are defined in the paper since the incidents simply arise as consequences of cumulative errors and failures. A feature of a combined model is that the single incident causes the next incident (consecutive timing) as well as that other simple dynamic actions are simultaneous. The structure was observed in three typical load positions taken from the crane passport (range-load). The obtained dynamic responses indicate the degree of structural sensitivity depending on the character of incident. The dynamic coefficient KD was adopted as a parameter for the evaluation of structural sensitivity.

• 한국항공우주학회지
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• 제30권1호
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• pp.132-138
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• 2002

오늘날 여러 가지 측면에서 전략적으로 고성능의 위성 본체를 개발하는 것은 매우 중요하다. 본 연구에서는 부분구조합성법의 하나인 구속모드법을 이용한 연성하중해석 기법 및 모달 과도해석법을 사용하여 위성체 구조부재에 대한 최적화를 수행하였다. 제안된 방법은 초기 설계시, 일반적으로 사용되고 있는 준정적 하중을 이용하지 않고, 동종의 발사체에 대해 유사한 위성과의 연성하중해석 자료를 이용함으로써, 각 구조부재에 대해 보다 정확한 결과를 얻을 수 있는 장점이 있다. 예제를 통해 제안된 기법이 초기단계의 위성체 구조 부재의 효율적인 최적설계 및 중량 감소를 위해 적용될 수 있음을 확인하였다.

• 한국산업정보학회논문지
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• 제15권5호
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• pp.97-104
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• 2010

본 논문에서는 그리드 데이터베이스에서의 부하 분산 문제를 복제 데이터 간 메쉬 연결 구조를 이용하여 해결한다. 그리드 데이터베이스의 데이터는 성능 향상을 위해 여러 노드에 복제 저장되어 있다. 따라서 사용자 질의는 목적 데이터를 포함하는 노드들의 작업 부하를 평가하여 노드를 선택함으로써 구성 노드들 간의 부하를 분산하여야 한다. 기존의 기법은 노드의 작업 부하가 한계를 넘게 되었을 때 다른 연결 노드를 선택하여 질의를 처리하게 하는 수동적 부하 분산 기법을 사용하기 때문에 노드의 수가 많고 질의가 유동적인 그리드 데이터베이스에 적용하기에는 비효율적이다. 제안 기법은 각각의 동일 복제본이 포함된 노드들을 하나의 메쉬 구조로 연결하여 사용자 질의가 발생하였을 때 연결 노드 중 부하가 가장 적은 노드를 선택하여 질의 처리를 할 수 있도록 한다. 제안 기법은 성능 평가를 통해 기존의 기법보다 향상된 성능을 가짐을 보였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.740-743
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• 2001

Sandwich structure is widely used in various fields of industry due to its excellent strength and stiffness compared with weight. We studied the sandwich structure which has honeycomb core type. We are concerned about its buckling and bending stress with respect to its side length, thickness and the height ratio of its unit core. After obtaining the buckling critical load of unit core, we applied it to the sandwich structure to observe the bending behavior. When we compared the buckling with bending stress under buckling critical load, we observed that models of which length ratio of unit honeycomb core, A, is lower than 0.04 and the thickness of core, t, is thicker than 0.09 mm, is subjected to the ultimate stress by bending before buckling.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.812-818
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• 2001

The drop type impact test and finite element analysis are established for examining the buckling behavior of a square tube under the lateral impact load. Based on these results, the effects by the boundary conditions for supporting the structure are reviewed, which are as follows. One is pinned condition by screw; the other is fixed by welding. The critical impact force and acceleration by test are nearly same between two cases. However, the critical impact velocity of the pinned condition is higher than that of the fixed case. Therefore, the dynamic buckling behavior of a pinned structure is better than the fixed condition in view of critical impact velocity. These test and analysis results will be adaptable for predicting the dynamic structural integrity of a tube structure not only the axial impact event but the lateral impact event.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.357-362
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• 2000

Allowable stress design(ASD) method has been widely used to design steel structures such as boiler and heat recovery steam generator(HRSG) of power plant. However, many researchers are recently intrested in road and resistance factor design(LRFD) method which may take the place of ASD. In this work, the weight calculation of steel structure was compared when ASD and LRFD were applied respectively. For the calculation of weight of steel structure, computer program was developed and applied to obtain beam weight. Using this program and GTSTRUDL, structural design program, weight of steel structure is calculated. As a result of weight calculation, maximum 5.4% of weight reduction is achieved among examples of this study by applying LRFD comparing with the result of ASD, and those results quite dependent on the applied load and member classification.

• 한국공간구조학회논문집
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• 제17권3호
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• pp.65-73
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• 2017

Recently, the trend is emerging a variety of irregular tall buildings. It is important to design the building for lateral load according to this trend. Fluid Structure Interaction(FSI) simulation can be performed to understand the vibrations of the structure against dynamic wind loads. In order to make the physical characteristics of the actual structure and the analytical model the same, we studied core inserting equivalent stiffness modeling method. As a result of this analysis, the stiffness of the structure can be set similar to that of the two axes of the structure, and turbulence can be reproduced through the acceleration tendency.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.277-284
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• 2003

One of important problem, in large space structure, is to overcome the self-weight of roof structure. This problem can be solved with using tension members effectively. Thus the rapid progress of hybrid structure, that makes effective use of the means of settling, has a good effect on realizing the large space. These systems of hybrid structure have the advantages of light weight and its own internal redundancy, but are occurred unstable phenomenon such as bifurcation or snap-through buckling, when the load level is come to the critical point. Among the hybrid structure, cable dome is shown the strong nonlinearity of unstable phenomenon in accordance with the external force. Therefore, the purpose of this study is to analyze and verify comparatively the unstable phenomenon of the Geiger and Flower type cable dome structures under axismmetric load.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.149-154
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• 2001

In case of high capacity load force as millions of tons, it is difficult to measure the force with load cell. But we can measure and calculate the force with applied pressure and ram area of hydraulic jack. The 5,200 ton compression load tester is composed of thirteen hydraulic jack with 400 ton capacity. This paper explains the method of measuring the vertical compression load and provides characteristics of unit jack, and displacement of upper structure under maximum load condition.