• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1993년도 가을 학술발표회논문집
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• pp.106-112
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• 1993

This paper presents the optimum design of reinforced concrete conical shell which is fixed at the base and free at the top. The calculation of stresses is done using the SMAP(Segmented Matrix Analysis Package)program which uses the simple finite element method of analysis. The objective function contains the ratios of the unit cost of reinforcements and formwork to that of concrete. To Simplify the optimization procedure, the final optimum design of conical shell is obtained by combining the result of each element. The results are presented and discussed.

• 센서학회지
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• 제28권5호
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• pp.271-276
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• 2019

Pure and 0.5, 1, 2, 5, and 10 at% of Mo-doped $Co_3O_4$ yolk-shell spheres were synthesized by ultrasonic spray pyrolysis of droplets containing Co nitrate, ammonium molybdate, and sucrose and their gas sensing characteristics to 5 ppm trimethylamine (TMA), ethanol, p-xylene, toluene, ammonia, carbon monoxide, and benzene were measured at $225-325^{\circ}C$. The sensor using pure $Co_3O_4$ yolk-shell spheres showed the highest response to p-xylene and very low response to TMA at $250^{\circ}C$, while the doping of Mo into $Co_3O_4$ tended to increase the overall responses of gas sensors. In particular, the sensor using 5 at% Mo-doped $Co_3O_4$ yolk-shell spheres exhibited the high response to TMA with low cross-responses to other interfering gases. The high response and selectivity of Mo-doped $Co_3O_4$ yolk-shell spheres to TMA are attributed to the electronic sensitization by higher valent Mo doping and acid-base interaction between TMA and Mo components.

• 한국농공학회지
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• 제45권4호
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• pp.115-125
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• 2003

Shell structures are widely used in a variety of engineering application, and mathematical solution of shell structures are available only for a few special cases. The solution of shell structure is more complicated when it has such condition as winkler foundation, other problems. In this study many simplified methods (analogy of beam on elastic foudation, finite element method and transfer matrix method) are applied to analyze a hemisphere-cylindrical shell structures on elastic foundation. And the transfer matrix method is extensively used for the structural analysis because of its merit in the theoretical backgroud and applicability. Therefore, this paper presents the analysis of hemisphere-cylindrical shell structure base on the transfer matrix method. The technique is attractive for implementation on a numerical solution by means of a computer program coded in FORTRAN language with a few elements. To demonstrate this fact, it gives good results which compare well with finite element method.

• 대한기계학회논문집
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• 제18권3호
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• pp.777-784
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• 1994

A design expert system for the ship structural design is developed to support inexperienced designers. To establish the knowledge-base, an expert system development shell, Nexpert, is used. Knowledge is extracted from the rules of a classification society of ships, and also from an existing ship structural program that is being used by ship designers. This knowledge is systematized using the objectoriented concept. The design support system is constructed by adding additional functions which are required for the conventional engineering design work. Added functions are; calculation of longitudinal strength, database of existing ship designs, graphical user interface, and visualization of design results. It is observed that visualizing the relationships among the rules, which are activated to draw a certain design decision, is helpful. The system can easily be updated according to changes of the rule books of ship classification societies.

• 한국강구조학회 논문집
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• 제13권2호
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• pp.191-200
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• 2001

본 연구에서는 수치해석을 통하여 축하중을 받는 원통형 쉘의 좌굴해석을 수행하였다. 해석 식과의 비교를 통하여 수치모델 방법, 적절한 요소의 종류 및 요소의 개수등을 제시하였다. 매개변수 해석결과, 직경/두께비가 증가하면 좌굴응력은 크게 감소하나 높이/직경비가 증가하면 그 변화는 미세하며 이는 일반적인 기둥의 좌굴해석 결과와 상이하다. 높이/직경비가 커질수록 원주방향 좌굴모드의 파장수가 감소하였다. 바닥판의 두께가 증가하면 좌굴응력은 1~2% 증가한다. 따라서 그 영향은 거의 무시할 수 있다. 초기 형상결함의 크기가 증가하면 좌굴응력은 큰 감소를 보인다. 또한 회기분석을 통하여 좌굴응력을 간편하게 구할 수 있는 설계식을 도출하였으며, 수치해석 결과와 잘 일치하였다.

• Structural Engineering and Mechanics
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• 제50권6호
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• pp.797-816
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• 2014

Cooling tower is analyzed as an assembly of layered nonlinear shell elements. Geometric representation of the shell is enabled through layered nonlinear shell elements to define the different layers of reinforcements and concrete by considering the material nonlinearity of each layer for the cooling tower shell. Modal analysis using Ritz vector analysis and nonlinear time history analysis by direct integration method have been carried out to study the effects of the inclination of the supporting columns of the cooling tower shell on its dynamic characteristics. The cooling tower is supported by I-type columns and ${\Lambda}$-type columns supports having the different inclination angles. Relevant comparisons of the dynamic response of the structural system at the base level (at the junction of the column and shell), throat level and at the top of the tower have been made. Dynamic response of the cooling tower is found to be significantly sensitive to the change of the inclination of the supporting columns. It is also found that the stiffness of the structure system increases with increase in inclination angle of the supporting columns, resulting in decrease of the period of the structural system. The participation of the stiffness of the tower in structural response of the cooling tower is fund to be dependent of the change in the inclination angle and even in the types of the supporting columns.

• 한국공간구조학회논문집
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• 제17권1호
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• pp.49-58
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• 2017

The result of the previous work leads to the idea that the inner area of the hyperbolic shell generator should be minimized for the cooling tower with higher first natural frequency. In this study the inner area of the hyperbolic shell generator was graphically established under varying height of the throat and angle of the base lintel. From the graph, several shell geometries were selected and analysed in the aspect of the natural frequency. Three representative towers reinforced differently due to different first natural frequencies were analysed non-linearly and evaluated using a damage indicator based on the change of natural frequencies. The results demonstrated that the damage behaviour of the tower reinforced higher due to a lower first natural frequency was not necessarily advantageous than the others.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.794-801
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• 2006

The linkage framework of geometric modeling and analysis based on the NURBS technology is developed in this study. The NURBS surfaces are generated by interpolating the given set of data points or by extracting the necessary information to construct the NURBS surface from the IGES format file which is generated by the commercial CAD systems in the present study. Numerical examples shows the rate of displacement convergence according to the paramterization methods of the NURBS surface. NURBS can generate quadric surfaces in an exact manner. It is the one of the advantages of the NURBS. A trimmed NURBS surface that is often encountered in the modeling process of the CAD systems is also presented in the present study. The performance of the developed geometrically exact shell element integrated with the exact geometric representations by the NURBS equation is compared to those of the previous reported FE shell elements in the selected benchmark problems.

• 소음진동
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• 제4권4호
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• pp.469-478
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• 1994

This paper desfcribes the formulation for the analysis of the free vibration of a circular cylindrical shell with elastic supports by the transfer influence coefficient method. This method was developed on the base of the concept of the successive transmission of dynamic influence coefficients. The analysis algorithm for circular cylindrical shell elastically restrained by springs, which plays an important role in many industrial fields, is discussed. The supporting springs have the axial, circumferential, radial and rotational spring constants uniformly distributed along the circumference of the shell. The simple computational results on a personal computer demonstrate the validity of the present method, that is, the numerical high accuracy, the high speed analysis method and the flexibility for programming, compared with results of the transfer matrixmethod and reference. We also confirmed that the present algorithm could obtain the solutions of high accuracy for system with a number of intermediate rigid supports. And we could easily treat the intermediate support and all boundary conditions by adequately varying the values of spring constants.

• 대한산업공학회지
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• 제19권2호
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• pp.83-93
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• 1993

Conventional computer programs developed and used by practicing engineers can be considered to contain expert knowledge and design experience. If these conventional programs are converted into expert systems, the difficult and time consuming process of knowledge acquisition can be simplified. Also the constructed knowledge-base can have higher confidence level than that constructed by the usual knowledge acquisition method of interviews. An existing computer program which is being used by ship structural designers has been reformulated as a design expert system by applying an expert system development shell-Nexpert. Utilizing the callable interface provided by the development shell, external design tools have also been integrated. The interfaced external functions are a graphical user interface (GUI) for the design process control, and graphics functions for the visualization of design results. It is observed that the developed system for design support is useful in two aspects. The trace-back function shows what portion of design rules are applied in arriving at certain design decisions. Also the knowledge-base can be conveniently updated as design rules of the classification societies are updated.