• Structural Engineering and Mechanics
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• v.55 no.4
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• pp.785-799
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• 2015

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies of hyperboloidal shells free at the top edge and clamped at the bottom edge like a hyperboloidal cooling tower by the Ritz method based upon the circular cylindrical coordinate system instead of related 3-D shell coordinates which are normal and tangent to the shell midsurface. The Legendre polynomials are used as admissible displacements. Convergence to four-digit exactitude is demonstrated. Natural frequencies from the present 3-D analysis are also compared with those of straight beams with circular cross section, complete (not truncated) conical shells, and circular cylindrical shells as special cases of hyperboloidal shells from the classical beam theory, 2-D thin shell theory, and other 3-D methods.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.348-358
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• 2008

Unlike structures in the air, the vibration analysis of a submerged or floating structure such as offshore structures is possibly only when the fluid-structures is understood, as the whole or part of the structure is in contact with water. Through the comparision between the experimental result and the finite element analysis result for a simple cylindrical model, it was verified that an added mass effects on the cylindrical structure. Using the commercial FEA program ANSYS(v.11.0), underwater added mass was superposed on the mass matrix of the structure. A frequency response analysis of forced vibration in the frequency considered the dynamic load was also performed. It was proposed to find the several important modes of resonance peak for these fixed cylindrical type structures. Furthermore, it is expected that the analysis method and the data in this study can be applied to a dynamic structural design and dynamic performance evaluation for the ground and marine purpose of power generator by wind.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1031-1034
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• 2007

Electric transmission lines pass through a variety of area. Foundation supporting the conductors and tower are selected properly in accordance with external load, for example dead load, wind load, snow load, construction load etc, and topography and geology condition. Typical types of foundation are as follows: pad foundation for small load and hard soil or rock in mountainous area, pile foundation for medium or large load and soft soil in plain field area. This paper introduced cylindrical foundation design & construction for large load and mountainous area. This foundation failure mode against pulling-out show splitting failure by tensile force toward circumferential direction.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.2
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• pp.67-81
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• 1988

The purpose of the present study is to set up an efficient optimum design method for the large-scale reinforced concrete cylindrical shell structures like intake tower of reservoir and to establish a solid foundation for the automatic optimum structural design combined with finite element analysis. The major design variables are the dimensions and steel areas of each member of the structures. The construction cost which is composed of the concrete, steel, and form work costs, respectively, is taken as the objective function. The constraint equations for the design of intake-tower are derived on the basis of the working stress design method. The corresponding design guides including the standard specification for concrete structures have been also employed in deraving the constraint conditions. The present nonlinear optimization problem is solved by SUMT method. The reinforced concrete intake-tower is decomposed into three major substructures. The optimization is then conducted for both the whole structure and the substructures. The following conclusions can be drawn from the present study. 1. The basis of automatic optimum design of reinforced concrete cylindrical shell structures which is combined with finite element analysis was established. 2. The efficient optimization algorithms which can execute the automatic optimum desigh of reinforced concrete intake-tower based on the working stress design method were developed. 3. Since the objective function and design variables were converged to their optimum values within the first or second iteration, the optImization algorithms developed in this study seem to be efficient and stable. 4. The difference in construction cost between the optimum designs with the substructures and with the entire structure was found to be small and thus the optimum design with the substructures,rnay conveniently be used in practical design. 5. The major active constraints of each structural member were found to be the tensile stress insteel for salb, the minimum lonitudinal steel ratio constraints for tower body and the shearing stress in concrete, tensile stress in steel and maximum eccentricityconstraints for footing, respectively. 6. The computer program develope in the present study can be effectively used even by an unexperienced designer for the optimum design of reinforced concrete intake-tower.

• International journal of steel structures
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• v.18 no.4
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• pp.1318-1324
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• 2018

This paper evaluates the effects of door opening, collar stiffener, and initial imperfection on the ultimate strength of a 10 MW wind tower. The lower segment of the tower was modeled to investigate the ultimate strength using steel cylindrical shell elements of finite element program ABAQUS. The wind tower was classified into three categories; without opening nor stiffener (C1), with opening but no stiffener (C2), and with opening and stiffener (C3). The C2 and C3 were further divided into long axis and short axis categories depending on the position of the opening. Result from linear and nonlinear analyses shows that the bigger the opening the bigger the reduction in strength and the same thing goes for the initial imperfection ratio or ovality of the shell. Also, there is a significant decreased in strength as the initial imperfection ratio increases by as high as 18.08%.

• Journal of Korean Society of Steel Construction
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• v.29 no.2
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• pp.123-134
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• 2017

Ultimate axial strength of longitudinally stiffened cylindrical steel shells for wind turbine tower was investigated by applying the geometrically and materially nonlinear finite element method. The effects of radius to thickness ratio of shell, shape and amplitude of initial imperfections, area ratio between effective shell and stiffener, and stiffener spacing on the ultimate axial strength of cylindrical shells were analyzed. The ultimate axial strengths of stiffened cylindrical shells by FEA were compared with design buckling strengths specified in DNV-RP-C202. The shell buckling modes obtained from a linear elastic bifurcation FE analysis as well as the weld depression during fabrication specified in Eurocode 3 were introduced in the nonlinear FE analysis as initial geometric imperfections. The radius to thickness ratio of cylindrical shell models was selected to be in the range of 50 to 200. The longitudinal stiffeners were designed according to DNV-RP-C202 to prevent the lateral torsional buckling and local buckling of stiffeners.

• Journal of Korean Society of Steel Construction
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• v.27 no.1
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• pp.109-118
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• 2015

Ultimate flexural buckling strength of cylindrical steel shells for the wind turbine tower structure was investigated by applying the geometrically and materially nonlinear finite element method. The effects of initial imperfection, radius to thickness ratio, and type of steel on the ultimate flexural strength of cylindrical shell were analyzed. The flexural strengths of cylindrical shells obtained by FEA were compared with design flexural strengths specified in Eurocode 3 and AISI. The shell buckling modes recommended in DNV-RP-C202 and the out-of-roundness tolerance and welding induced imperfections specified in Eurocode 3 were used in the nonlinear FE analysis as initial geometrical imperfections. The radius to thickness ratios of cylindrical shell in the range of 60 to 210 were considered and shells are assumed to be made of SM520 or HSB800 steel.

• International Journal of Safety
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• v.3 no.1
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• pp.15-19
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• 2004

A new tower internal, which is called CSE, is presented. The CSE is composed of a nozzle perforated in its bottom along the entire periphery and equipped with a multi vane axial swirler at the inlet and hollow cylindrical separator at the outlet of the nozzle. According to the experimental work for obtaining the necessary hydraulic information of the CSE, which is used for preliminary design of a separation column, the CSE showed a stable operation over the wide rage of gas/liquid ratio. However, it caused large pressure drop due to the high gas velocity which should carry liquid droplets through the element. The high pressure drop may cause problems in energy recovery and the application of the CSE can be limited to the high pressure columns. Assuming that the tray efficiency of the CSE is the same with the existing separation columns, the results of the column design showed the size reduction of the column diameters by 30 to $40\%$ and investment cost saving, depending on operating conditions. The application of the CSE to separation column may also contribute to the de-bottlenecking the existing column.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.258-261
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• 2002

In this study, micro tools(WC) to produce micro-structure and parts, were fabricated ell a cylindrical grinding machine using ELID(Electrolytic In-process Dressing) technique. The shape of the micro-carbide tool was square, corn. The size of the micro-carbide tool was measured less than 10$\mu\textrm{m}$ respectively by SEM(Scanning Electron Microscope). Furthermore, we fabricated micro structure by different processing methods on the desk top cylindrical grinding machine. The manufactured shape was like a tower and the measurement showed that the endpoint of micro structure was $50{\times}50$$\mu{\textrm}{m}$.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.3
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• pp.82-94
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• 1988

A growing attention has been paid to the optimum design of structures in recent years. Most studies on the optimum design of reinforced concrete structures has been mainly focussed to the design of structural members such as beams, slabs and columns, and there exist few studies that deal with the optimum design of large-scale concrete shell structures. The purpose of the present investigation is, therefore, to set up an efficient optimum design method for the large-scale reinforced concrete cylindrical shell structures like intake tower of reservoir. The major design variables are the dimensions and steel areas of each member of structures. The construction cost which is compo8ed of the concrete, steel, and form work costs, respectively, is taken as the objective function. The constraint equations for the design of intake-tower are derived on the basis of strength design method. The results obtained are summarized as follows 1. The efficient optimlzation algorithrns which can execute the automatic optimum design of reinforced concrete intake tower based on the strength design method were developed. 2. Since the objective function and design variables were converged to their optimum values within the first or second iteration, the optimization algorithms developed in this study seem to be efficient and stable. 3. When using the strength design method, the construction cost could be saved about 9% compared with working stress design method. Therefore, the reliability of algorithm was proved. 4. The difference in construction cost between the optimum designs with substructures and with entire structure was found to be small and thus the optimum design with substructures may conveniently be used in practical design. 5. The major active constraints of each structural member were found to be the 'bending moment constraint for slab, the minimum longitudinal steel ratio constraint for tower body and the shearing force, bending moment and maximum eccentricity constraints for footing, respectively. 6. The computer program developed in the present study can be effectively used even by an uneiperienced designer for the optimum design of reinforced concrete intake-tower on the basis of strength design method.