• Structural Engineering and Mechanics
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• v.3 no.1
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• pp.61-74
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• 1995

A linearly tapered, doubly symmetric thin-walled closed member, such as power-transmission towers and tourist towers, are often characterized by local variation in mass and/or rigidity, due to additional mass and rigidity. On the preliminary stage of design the closed-form solution is more effective than the finite element method. In order to propose approximate solutions, the discontinuous and local variation in mass and/or rigidity is treated continuously by means of a usable function proposed by Takabatake(1988, 1991, 1993). Thus, a simplified analytical method and approximate solutions for the free and forced transverse vibrations in linear elasticity are demonstrated in general by means of the Galerkin method. The solutions proposed here are examined from the results obtained using the Galerkin method and Wilson-${\theta}$ method and from the results obtained using NASTRAN.

• Journal of Astronomy and Space Sciences
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• v.23 no.2
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• pp.117-126
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• 2006

The Diurnal variation of galactic cosmic ray (GCR) flux intensity observed by the ground Neutron Monitor (NM) shows a sinusoidal pattern with the amplitude of $1{\sim}2%$ of daily mean. We carried out a statistical study on tendencies of the local times of GCR intensity daily maximum aad minimum. To test the influences of the solar activity and the location (cut-off rigidity) on the distribution in the local times of maximum and minimum GCR intensity, we have examined the data of 1996 (solar minimum) and 2000 (solar maximum) at the low-latitude Haleakala (latitude: 20.72 N, cut-off rigidity: 12.91 GeV) and the high-latitude Oulu (latitude: 65.05 N, cut-off rigidity: 0.81 GeV) NM stations. The most frequent local times of the GCR intensity daily maximum and minimum come later about $2{\sim}3$ hours in the solar activity maximum year 2000 than in the solar activity minimum you 1996. Oulu NM station whose cut-off rigidity is smaller has the most frequent local times of the GCR intensity maximum and minimum later by $2{\sim}3$ hours from those of Haleakala station. This feature is more evident at the solar maximum. The phase of the daily variation in GCR is dependent upon the interplanetary magnetic field varying with the solar activity and the cut-off rigidity varying with the geographic latitude.

• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.593-604
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• 2005

In this paper, the parametric study on the local displacement and the local moment due to a concentrated load is performed for stiffened plates with open ribs and the orthotropic rigidity ratio of stiffened plates is selected as the parameter. For estimating the local behavior, stiffened plates loaded on the center of plates between the ribs were considered and for the global behavior, stiffened plates loaded on the rib at the center of plates were analyzed. The Analyzed results for the local behavior of stiffened plates show that the increasing ratio of the local moment according to rib sizes is constant regardless of rib spaces and the ratio of the local displacement to the global displacement can be expressed as a function of the rib space and the rigidity ratio. The application of functions to examples shows good accuracy in comparison with the local behavior of stiffened plates loaded on the center of plates and the application to the orthotropic analysis of stiffened plates improves accuracy. Therefore, using functions proposed in this study, the local behavior can easily be estimated from the global behavior of stiffened plates with open ribs.

• Journal of Korean Society of societal Security
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• v.3 no.1
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• pp.33-42
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• 2010

This study predicts the stress history for truss bridge with local damages by using global-local model combination method. For this end, the global structure is modeled by 3D frame elements and the selected local details are modeled by shell elements. Then superposition principle enable the global-local model to be combined interactively. Because the frame model cannot consider the rigidity of gusset plate and the interation of structural members due to the complexity of stress distribution in truss connection. The section modification factors are proposed to calibrate the stiffness of global frame element. The global-local model combination is verified by comparing the numerical results with experimental data obtained from the proof loading test to the operating truss bridge. Furthermore, stress histrories of the truss bridge are generated in the consideration of the rigidity of truss connection with local damage by using the combination method.

• Journal of Power System Engineering
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• v.2 no.1
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• pp.52-58
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• 1998

An immune system has powerful abilities such as memory, recognition and learning to respond to invading antigens, and is applied to many engineering algorithm recently. In this paper, the combined optimization algorithm is proposed for multi-objective problem by introducing the capability of the immune system that controls the proliferation of clones to the genetic algorithm. The optimizing ability of the proposed algorithm is identified by using multi-peak function which have many local optimums and identification of the flexural rigidity for wire rope model.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.354-361
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• 2002

This paper propose section properties factor to generate stress history for fatigue analysis and safety inspection of steel bridge. A methodology is described for the computation of numerical stress histories in the steel truss bridge, caused by the vehicles using section properties factor. The global 3-D beam model of bridge is combined with the local shell model of selected details. Joint geometry is introduced by the local shell model. The global beam model takes the effects of joint rigidity and interaction of structural elements into account. Connection nodes in the global beam model correspond to the end cross-section centroids of the local shell model. Their displacements are interpreted as imposed deformations on the local shell model. The load cases fur the global model simulate the vertical unit force along the stringers. The load cases fer the local model are imposed unit deformations. Combining these, and applying vehicle loads, numerical stress histories are obtained. The method is illustrated by test load results of an existing bridge.

• Journal of the Korean Mathematical Society
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• v.46 no.5
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• pp.895-905
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• 2009

Let $B^{n+1}$ be the unit ball in the complex vector space $\mathbb{C}^{n+1}$ with the standard Hermitian metric. Let ${\Sigma}^n={\partial}B^{n+1}=S^{2n+1}$ be the boundary sphere with the induced CR structure. Let f : ${\Sigma}^n{\hookrightarrow}{\Sigma}^N$ be a local CR immersion. If N < 3n - 1, the asymptotic vectors of the CR second fundamental form of f at each point form a subspace of the CR(horizontal) tangent space of ${\Sigma}^n$ of codimension at most 1. We study the higher order derivatives of this relation, and we show that a linearly full local CR immersion f : ${\Sigma}^n{\hookrightarrow}{\Sigma}^N$, N $\leq$ 3n-2, can only occur when N = n, 2n, or 2n + 1. As a consequence, it gives an extension of the classification of the rational proper holomorphic maps from $B^{n+1}$ to $B^{2n+2}$ by Hamada to the classification of the rational proper holomorphic maps from $B^{n+1}$ to $B^{3n+1}$.

• Wind and Structures
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• v.11 no.2
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• pp.153-178
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• 2008

Based on the empirical formulas for power spectra of generalized modal forces and local fluctuating wind forces in across-wind and torsional directions, the wind-induced lateral-torsional coupled response analysis of a representative rectangular tall building was conducted by setting various parameters such as eccentricities in centers of mass and/or rigidity and considering different torsional to lateral stiffness ratios. The eccentricity effects on the lateral-torsional coupled responses of the tall building were studied comprehensively by structural dynamic analysis. Extensive computational results indicated that the torsional responses at the geometric center of the building may be significantly affected by the eccentricities in the centers of mass and/or rigidity. Covariance responses were found to be in the same order of magnitude as the along-wind or across-wind responses in many eccentricity cases, suggesting that the lateral-torsional coupled effects on the overall wind-induced responses can not be neglected for such situations. The calculated results also demonstrated that the torsional motion contributed significantly to the total responses of rectangular tall buildings with mass and/or rigidity eccentricities. It was shown through this study that the framework presented in this paper provides a useful tool to evaluate the wind-induced lateral-torsional coupled responses of rectangular buildings, which will enable structural engineers in the preliminary design stages to assess the serviceability of tall buildings, potential structural vibration problems and the need for a detailed wind tunnel test.

• Journal of Industrial Technology
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• v.1
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• pp.9-16
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• 1981

In the steel Structural design, buckling is the main factor to determine size, particularly in compression member. Buckling may sometimes occur in the form of wrinkles in thin elements, such as webs, flanges, and other parts that make up a section. This phenomenon is called local buckling. The strength of the steel and the rigidity of the frame are considerably deteriorated by the local buckling. The specimens used for this experiments, H-Shape Steel beams composed by fillet-welding, are dessified classified into two groups, ie one for web test and another for flange fest. The aim of this study is to define the influences by the local bucking on the vesisting forces, deformation and the phenomena of the internal forces in the section, and to collect the basic data for design of steel beams.

• Smart Structures and Systems
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• v.8 no.2
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• pp.157-172
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• 2011

A new method for both local damage(s) identification and input excitation force identification of beam structures is presented using the dynamic response sensitivity-based finite element model updating method. The state-space approach is used to calculate both the structural dynamic responses and the responses sensitivities with respect to structural physical parameters such as elemental flexural rigidity and with respect to the force parameters as well. The sensitivities of displacement and acceleration responses with respect to structural physical parameters are calculated in time domain and compared to those by using Newmark method in the forward analysis. In the inverse analysis, both the input excitation force and the local damage are identified from only several acceleration measurements. Local damages and the input excitation force are identified in a gradient-based model updating method based on dynamic response sensitivity. Both computation simulations and the laboratory work illustrate the effectiveness and robustness of the proposed method.