• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.480-485
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• 1996

A numerical method for perdicting the behavior of a reinforced concrete column under biaxial loading is proposed, using the layered finite element method. Concrete is assumed to exhibit strain softening and steel reinforcement is elastic-plastic. The bending theory assumptions are used and bond slip of reinforcement is meglected. To perdict the entire load-deformation characteristics, displacement control method is used. This method consider not only combined effect due to axial load and bending moment but also that due to bending moments. Predicted behaviors of reinforced concrete columns under biaxial loading through the numerical method proposed in this study show good agreements with test results.

• 대한전기학회논문지
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• 제41권7호
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• pp.712-722
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• 1992

Several voltage instability/collapse problems that have occurred in the electric utility industry worldwide have gained the attention of engineers and researchers of electric power systems. This paper proposes an effective calculation scheme of the extreme loading point and nose curves(P-V curves) using modified Newton-Raphson(N-R) load flow method and the Continuation Method. This method provides detail and visual information of the power system voltage profile and operating margin ro operators and planners. In this paper, a modified load flow claculation method for ill-conditioned power systems is introduced for the purpose of seeking more precise load flow solutions and nose curves, and the Continuation Method is also used as a part of the solution algorithm for the calculation of extreme loading point and nose curves. The conventional polar coordinate based N-R load flow program is modified to avoid numerical difficulties caused by the singularity of the Jacobian matrix occuring in the vicinity of extreme loading point of heavily loaded systems. Application results of the proposed method to Klos-Kerner 11-bus system and modified IEE-30-bus system are presented to assure the usefulness of the approach.

• Journal of Mechanical Science and Technology
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• 제19권8호
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• pp.1554-1567
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• 2005

When multiple robotics systems with several sub-chains grasp a common object, the inherent force redundancy provides a chance of utilizing internal loading. Analysis of grasping space based internal loading is proposed in this work since this method facilitates understanding the physical meaning of internal loadings in some applications, as compared to usual operational space based approach. Investigation of the internal loading for a triple manipulator has been few as ,compared to a dual manipulator. In this paper, types of the internal loading for dual and triple manipulator systems are investigated by using the reduced row echelon method to analyze the null space of those systems. No internal loading condition is derived and several load distribution schemes are compared through simulation. Furthermore, it is shown that the proposed scheme based on grasping space is applicable to analysis of special cases such as three-fingered and three-legged robots having a point contact with the grasped object or ground.

• 동력기계공학회지
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• 제13권3호
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• pp.40-46
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• 2009

This study on the bolt elongation and torque measuring method by ultrasonic nod-destructive method. In the past, The dial gage was used for the elongation measurement of gas turbine bolts. The purpose of this study is to improve the traditional bolt elongation measurement method. The old method using dial gage measures the elongation of the gas turbine bolt. If the length differences among the loading bolts are within the required range, The loading torques of bolts consider as acceptable. But this method can not give the information about torque differences among the loading bolts. It could bring out vibration of turbine due to loading torque differences among the bolts. So the elongation and torque must be measured simultaneously. The new technology using ultrasonic non-destructive method can give the information about bolt elongation and torque. The ultrasonic method basically measures the speed in the bolt material for the calculation the bolt elongation. But the ultrasonic speed varies according to temperature and loading torque of bolts. So the factors of temperature and loading power were investigated and reflected to the calculation of bolt elongation and torque. The results of this study shows the big difference among the bolts torque in the old method and the torque differences among the bolts can be adjusted by reflecting the result of this study. And this torque adjusting method can decrease gas turbine vibration problem due to torque difference among the bolts. So this paper shows ultrasonic method is better than old method for the measurement of bolt elongation and torque.

• 동력기계공학회지
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• 제17권6호
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• pp.33-39
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• 2013

It is very important to analyze the dynamic responses of the shell structures from the viewpoint of the design of shell structures with a variety of axisymmetric loadings. In this paper, the computational algorithm for the dynamic response analysis of an cylindrical shell with axisymmetric loading is formulated by the transfer mass coefficient method based on the transfer of mass coefficient. After the computational programs for obtaining the dynamic responses of cylindrical shells with axisymmetric loading are made by the transfer mass coefficient method and the finite element method, the computational results by both methods are compared. From the computational results, we can confirm that the transfer mass coefficient method has the effectiveness in the dynamic response analyses of cylindrical shells with a variety of axisymmetric loadings.

• 콘크리트학회논문집
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• 제16권1호
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• pp.88-93
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• 2004

철근콘크리트 구조 부재에 발생되는 균열은 구조체의 미관, 내구성 및 구조적 측면에서 보수를 요하게 되며, 에폭시 주입 균열보수공법은 최근 국내에서 가장 널리 사용되는 균열 보수공법 중의 하나이다. 에폭시 주입공법의 성능은 사용되는 에폭시의 물성과 균열의 폭에 기인하게 된다. 본 연구에서는 균열을 발생시키는 하중의 크기를 변수로 하고, 재하 중 보수한 경우와 하중을 제거한 후 보수한 경우를 비교 분석하도록 하였다. 총 5개의 실험체에 대하여 공칭 휨강도의 $70\%$ 및 $90\%$의 하중을 가력하여 균열을 발생시킨 후 에폭시 주입공법으로 보수하고, 보수 이후 부재의 거동을 실험적으로 연구하였다. 실험결과, 에폭시 주입공법에 의한 균열의 보수는 양호한 구조성능의 회복을 나타내었으며, 극심한 하중 하에서 보수된 실험체는 에폭시의 강도특성으로 인하여 오히려 강도 및 강성이 증가되는 현상을 나타내었다.

• 한국수정란이식학회지
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• 제19권1호
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• pp.27-34
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• 2004

This study evaluated the efficiency and compared with different materials of loading vessels for vitrification-plastic/glass, copper grid and nylon. The loading method, vitrification, cryop-reservation and warming method of the oocytes were examined. The loading samples prepared in manual or company-made and sterilized, loaded the COCs selected on each samples and cultured for maturation during 40 hours, and then exposed sequentially to ethylene glycol solution. Thawing method was reversely treated and exposed for warmed oocytes. After oocytes were thawed, fertilized and cultured in vitro for 3-4 hours, rates of development and morphological appearance were examined. The results were as summarized: ㆍOPS from company-made or hand-made of the hematocrit micropipettes, NLS from fishing line and EMG from company-made for EM were used for loading oocytes, respectively. ㆍThe efficiency of freezing method and loading convenience were orderly higher in OPS, NLS and EMG. The optimal capacity per vessel was orderly lowered in NLS, EMG and OPS, respectively. ㆍAfter oocytes were warmed, the recovery rate, morphology and rate of development were orderly higher in OPS, NLS and EMG, respectively. ㆍIn conclusion, OPS has the advantages of achieving a little more survival and preserving results than other two loading methods.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.804-809
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• 2001

Optimal design of a portable structure which supports impact loading is presented. The structure requires impact loading capability, stiffness and minimum weight for portability. A collapsible tripod structure with locking mechanism is suggested. Taguchi method has been used to identify the most important design variables and the initial design. Subsequent optimization yields additional weight reduction under stress and displacement constrains.

• Steel and Composite Structures
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• 제13권5호
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• pp.451-471
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• 2012

Concrete filled steel tube (CFST) structures have been used widely in high-rise buildings and bridges due to the efficiency of structurally favourable interaction between the steel tube and the concrete core. In the current design codes only one loading condition in the column members is considered, i.e., the load is applied on the steel tube and concrete core at the same time. However, in engineering practice the tube structures may be subjected to various loading conditions such as loading on the concrete core only, preloading on the steel tube skeleton before filling of concrete core, and so on. In this research, a series of comparative experiments were carried out to study the structural performance of concrete filled circular steel tube columns subject to four concentric loading schemes. Then, a generalized prediction method is developed to evaluate the ultimate load capacity of CFST columns subject to various loading conditions. It is shown that the predictions by the proposed method agree well with test results.

• 한국산학기술학회논문지
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• 제12권10호
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• pp.4642-4647
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• 2011

평면 변형률 상태에 있는 탄성지반의 해를 변분법을 적용하여 유도하여 보았다. 변분법 적용시 종방향 변위분포 함수는 선형함수를 고려하였다. 탄성지반상에 작용하는 하중조건은 집중하중과 분포하중을 고려하였는데 집중하중 작용시 탄성지반의 종방향 변위분포양상은 하중 작용점에서 멀어질수록 변위가 급격하게 감소하는 양상을 나타내었다. 등분포하중 작용시 지표면 변위는 압축층 두께에 대한 재하폭의 반의 비(B/H)값이 클수록 하중재하부분 아래에서 보다 균등하게 발생하였다. 또한 하중재하부분을 벗어난 영역에서는 B/H 값이 커질수록 하중재하 모서리 부분으로부터 짧은 거리에서 변위가 0에 수렴하였다.