• 한국항해항만학회지
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• 제36권3호
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• pp.225-232
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• 2012

본 연구에서는 수상위에 진수된 콘크리트 플로팅 폰툰에 상부골조를 단계별로 시공함에 따라 발생하는 추가 처짐이 상부골조에 발생하므로 추가변형에 의한 상부골조의 추가 모멘트량을 산정하는 해석절차를 제시하였으며 제시된 절차에 따라 3층 예제 철골 건물을 해석하고 분석하였다. 제시된 시공단계를 고려한 해석 방법과 비교하여, 폰툰의 변형을 고려하지 않는 해석 방법은 수직하중에 의한 변형을 무시하여 설계하중을 과소평가 하며, 플로팅 구조물을 전 층을 모델링하고 하중을 동시에 작용시키는 모델은 과대 처짐의 영향으로 설계하중을 과대평가함을 알게 되었다.

• Steel and Composite Structures
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• 제44권3호
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• pp.371-388
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• 2022

The present study tackles the problem of forced vibration of imperfect axially functionally graded shell structure with truncated conical geometry. The linear and nonlinear large-deflection of the structure are considered in the mathematical formulation using von-Kármán models. Modified coupled stress method and principle of minimum virtual work are employed in the modeling to obtain the final governing equations. In addition, formulations of classical elasticity theory are also presented. Different functions, including the linear, convex, and exponential cross-section shapes, are considered in the grading material modeling along the thickness direction. The grading properties of the material are a direct result of the porosity change in the thickness direction. Vibration responses of the structure are calculated using the semi-analytical method of a couple of homotopy perturbation methods (HPM) and the generalized differential quadrature method (GDQM). Contradicting effects of small-scale, porosity, and volume fraction parameters on the nonlinear amplitude, frequency ratio, dynamic deflection, resonance frequency, and natural frequency are observed for shell structure under various boundary conditions.

• Advances in concrete construction
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• 제15권3호
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• pp.161-170
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• 2023

Ultra-high-performance concrete (UHPC) is produced using high amount of cementitious materials, very low water/cementitious materials ratio, fine-sized fillers, and steel fibers. Due to the dense microstructure of UHPC, it possesses very high strength, elasticity, and durability. Besides that, the UHPC exhibits high ductility and fracture toughness due to presence of fibers in its matrix. While the high ductility of UHPC allows it to undergo high strain/deflection before failure, the high fracture toughness of UHPC greatly enhances its capacity to absorb impact energy without allowing the formation of severe cracking or penetration by the impactor. These advantages with UHPC make it a suitable material for construction of the structural members subjected to special loading conditions. In this research work, the UHPC mixtures having three different dosages of steel fibers (2%, 4% and 6% by weight corresponding to 0.67%, 1.33% and 2% by volume) were characterized in terms of their mechanical properties including facture toughness, before using these concrete mixtures for casting the slab specimens, which were tested under high-energy impact loading with the help of a drop-weight impact test setup. The effect of fiber content on the impact energy absorption capacity and central deflection of the slab specimens were investigated and the equations correlating fiber content with the energy absorption capacity and central deflection were obtained with high degrees of fit. Finite element modeling (FEM) was performed to simulate the behavior of the slabs under impact loading. The FEM results were found to be in good agreement with their corresponding experimentally generated results.

• 한국자기학회지
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• 제18권2호
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• pp.71-74
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• 2008

본 논문에서는 4분할 광 검출기 상에 입사된 광점의 크기에 따른 optical beam deflection방식에서의 변위 측정감도의 변화에 대해 살펴보았다. 3mW의 헬륨-네온 레이저를 사용하여 optical beam deflection방식의 광학적 변위 측정 장치를 제작하였으며 광 검출기에 도달하는 광점의 크기를 변화시켜가며 제작된 변위 측정 장비가 나타내는 변위 측정감도를 관찰하였다. 또한 광 검출기에 도달하는 optical beam power를 원형의 균일한 분포를 지닌 광점으로 설정하여 광점 크기의 변화에 따른 변위 측정감도를 계산하였다. 측정된 결과와 계산을 통하여 검출기 상에 입사하는 광점의 크기가 작을수록 변위 측정감도가 증가함을 알 수 있었으며 이는 나노미터 급의 변위측정 장비 개발에 있어 광 검출기에 도달하는 광점의 크기를 최소화함으로써 변위 측정감도를 최적화 할 수 있음을 나타낸다.

• 대한조선학회논문집
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• 제33권3호
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• pp.103-111
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• 1996

이미 저자들에 의해 기존의 경사처짐법을 일반화하여 일반화 경사처짐법을 정립하였으며, 일차적으로 횡강도 해석 측면에서 그 유용성을 확인하기 위해 유조선을 대상으로 frame modeling을 통한 횡강도 해석을 수행한 바 있다. 본 연구에서는 설계 측면에서의 일반화 경사처짐법의 유용성을 확인하기 위해 일반화 경사처짐법과 이산화 변수를 고려한 최적화 기법을 결합하여 최소 중량 설계 프로그램을 개발하였다. 이 프로그램을 통해 주어진 설계 조건하에서 최소 중량을 주는 유조선의 설계 치수를 결정할 수 있었으며, 실적선에 비해 상당한 양의 선각 중량이 감소가 되는 설계가 가능함을 보여 주었다.

• 한국군사과학기술학회지
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• 제12권1호
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• pp.8-17
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• 2009

This paper proposes robust ship wake search method in the target evasion environment. Moving surface ships generate a long trailing wake in the rear of a surface ship. Wake homing torpedo sensing this wake can detect the surface target and engage it automatically. In wake homing torpedo, wake search method is important element to maximize effectiveness of wake homing torpedo. This paper proposes one-side, two-side and centering mode according to passing wake boundary scenarios. Also, wake deflection angle is deduced by using the principle of deflection angle of acoustic torpedo. The representative experimental results using monte-carlo simulation demonstrate that the searching method using one-side mode is superior to two-side and centering mode in the target evasion environment.

• 한국정밀공학회지
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• 제24권9호
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• pp.119-129
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• 2007

The residual life expectancy of the container crane which has been operated more or less 39 years is examined carefully, especially on the boom structure. The basic load and load combination need to be considered for to analyse the boom structure. Various parts of container crane are modeled for to analyse stress, the deflection and the fatigue. Analysis results show that the boom is stable in the stress and deflection but the boom vertical member is over the fatigue life. The rail support beam and boom bottom chord are approximately near the fatigue life. Analysis results show that the residual life of rail support beam and the boom bottom chord would be 2.2 years and 6.8 years, respectively.

• 대한기계학회논문집
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• 제12권2호
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• pp.206-214
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• 1988

본 논문에서는 엔드 밀링에서 황삭 작업시 비교적 절삭 모델의 정립이 용이한 하향 밀링(down milling)의 경우를 대상으로, 가공면 오차의 주 원인인 공구와 공작물 사이의 처짐과 절삭력의 특정한 동적관계를 유도하고, 그 절삭력을 일정하게 유지하도록 공구의 이송속도를 온라인으로 제어하였다.

• 한국정밀공학회지
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• 제17권4호
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• pp.173-180
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• 2000

In the process of grinding a long slender type workpiece, such as ballscrew, by the external cylindrical grinding machine, the cylindricity of the workpiece depends on the distance of rests, the stiffness of supports, the diameter and material of workpiece. Conventionally the process needs to be supported by one or more rests to prevent static deflection and vibration. In this paper, the optimal position of the rests was investigated in order to minimize the cylindricity due to the static deflection, by taking compliance of the workpiece and structure into account. In order to obtain the optimal position of rests, a new modeling that is considering the spring effect of all support elements was established. Since it is so complicated to obtain the optimal position analytically for various conditions due to discontinuity, a genetic algorithm u as utilized.

• 콘크리트학회논문집
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• 제11권5호
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• pp.131-137
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• 1999

The use of higher strength materials with the strength methed of design has resulted in more slender member and shallower sections. For this reason, it is necessary to satisfy the requirements of serviceability even though the structural safety is the most important limit state. This paper is only concerned with the control of deflections in the serviceability. In this study, an analytical model is presented to predict the deflections of reinforced concrete beams to given loading and environmental conditions. This model is based on the finite element approach in which a finite element is generally divided into a number of stiffening effect due to cracking, creep and shrinkage. Comparisons are made with available measured deflections reported by others to assess the capability of the layered beam model. The calculated values of instantaneous and long-term deflection show good agreement with experimental results in the range of tension stiffening parameter $\beta$ between 2.5 and 3.0.