• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.11-20
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• 2004

This paper focused on square steel tubular column to H-beam connections (concrete filled tubular) with an outside-type diaphragm. Based on the yield line theory and the nonlinear static FEM analysis the specification equations were evaluated by comparing them with previous result of the simplified tensile experiment[please check. The yield line theory applied to the mechanical model theory revised by K. Morita, the nonlinear static FEM analysis using abaqus/standard, the ultimate strength equation in the specification equation using the factor for long-time loading, and the yield ratio according to material. The allowable strength in the specification equations applied the safety factors of 2.2 and 2.6 in the cases with and without filled concrete, respectively. Therefore, the evaluation of strength(for the previous result of the simplified tensile experiment in this study) was considered possible through the yield line theory, the nonlinear static FEM analysis, and the specification equations. Likewise, the specification equations were seen to be an underestimate of the previous result of the simplified tensile experiment. The strength and displaced mesh in the FEM analysis approximated the previous result of the simplified tensile experiment.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.113-125
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• 2007

Improved numerical method to obtain the exact stiffness matrices is newly proposed to perform the spatially coupled elastic and stability analyses of non-symmetric and open/closed thin-walled beam on elastic foundation. This method overcomes drawbacks of the previous method to evaluate the exact stiffness matrix for the spatially coupled stability analysis of thin-walled beam-column This numerical technique is accomplished via a generalized eigenproblem associated with 14 displacement parameters by transforming equilibrium equations to a set of first order simultaneous ordinary differential equations. Next polynomial expressions as trial solutions are assumed for displacement parameters corresponding to zero eigenvalues and the eigenmodes containing undetermined parameters equal to the number of zero eigenvalues are determined by invoking the identity condition. And then the exact displacement functions are constructed by combining eigensolutions and polynomial solutions corresponding to non-zero and zero eigenvalues, respectively. Consequently an exact stiffness matrix is evaluated by applying the member force-deformation relationships to these displacement functions. In order to illustrate the accuracy and the practical usefulness of this study, the numerical solutions are compared with results obtained from the thin-walled beam and shell elements.

• Parasites, Hosts and Diseases
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• v.32 no.3
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• pp.171-176
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• 1994

Wistar rats were induced of Pneumowstis cayinii infection by injection with methyl-prednisolone to correlate the cyst counts and numbers of nuclei. Seven sections of the lungs were examined by impression smears and also whole lung homogenates were screened for nucleus counting for each rat. At the first week of the experiment, all of the Impression smears except one were cyst negative but trophic forms were counted around 106. At the third week, the cysts appeared one per 20 Immersion oil lens fields. The nuclei were on the order of 107 at this period, and this amount of Pc is regarded as the limit of cyst detection on Impression smears. When the nuclei were over 109 in the lungs, the cysts were counted about 50 in 20 microscopic fields. The organisms were distributed in the lungs without any predilection focus. The present data suggest that the trophic forms, proliferate first and the cysts appear later in the lungs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.949-954
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• 2013

Generally, structural plates under axial compression should be stiffened by longitudinal stiffeners in order to enhance the buckling strength. Though U-shaped ribs would be more efficient for the stiffened plate system, there is in the absence of a proper design guides or relevant research results. Thus this study is aimed to examine the local buckling behavior of stiffened plates with U-section ribs. 3-dimensional analysis models which include 3 types of U-shaped longitudinal stiffeners were simulated by using the finite element code ABAQUS. The bifurcation analysis were conducted and then the buckling analysis results are compared with the theoretical equation values. It is found that the rotational constraint effect provided by the U-ribs should increase the local buckling strength. Some features drawn from a series of parametric study results are summarized.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.3
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• pp.237-250
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• 2003

Since an orthotropic steel deck bridge has large number of design variables and shows complex structural behavior, it would be very difficult and impractical to directly use a Conventional Single Level (CSL) optimization algorithm for its optimum design. Thus, in this paper, an Improved Multi Level Design Synthesis (IMLDS) optimization algorithm is proposed to improve the computational efficiency. In the proposed IMLDS algorithm, a coordination method is introduced to divide the bridge into main girders and orthotropic steel deck with preserving the characteristics of the structural behavior. For an efficient optimization of the bridge, the IMLDS algorithm incorporates the various crucial approximation techniques such as constraints deletion, Automatic Differentiation (AD), stress reanalysis, and etc. In the case of orthotropic steel deck system, optimum design problems are characterized by mixed continuous discrete variables and discontinuous design space. Thus, a modified Genetic Algorithm (GA) is also applied to optimize discrete member design for orthotropic steel deck. From the numerical example, the efficiency and convergency of the IMLDS algorithm proposed in this paper is investigated. It may be positively stated that the IMLDS algorithm will lead to more effective and practical design compared with previous algorithms.