• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.9
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• pp.943-950
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• 2007

A new metallic sandwich panel with a quasi-Kagome truss core subjected to bending load has been analyzed. First, equations of the failure loads corresponding to the eight failure modes are presented. Then, non-dimensional forms of the equations are derived as functions of three geometric variables, one material parameter (yield strain), one load index and one weight index. Failure maps are presented for a given weight index. By using the dimensionless forms of equations as the design constraints, two kinds of optimization are performed. One is based on the weight, that is, the objective function, namely, the dimensionless load is to be maximized for a given weight. Another is based on the load, that is, the dimensionless weight is to be minimized for a given load. The results of the two optimization processes are found to agree each other. The optimized geometric variables are derived as a function of given weights or failure loads. The performance of the quasi-Kagome truss as the core of a sandwich panel is evaluated by comparison with those of honeycomb cored and octet truss cored panels.

• Smart Structures and Systems
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• v.12 no.3_4
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• pp.427-440
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• 2013

A growing need has developed in the United States to obtain more specific knowledge on the structural integrity of infrastructure due to aging service lives, heavier and more frequent loading conditions, and durability issues. This need has spurred extensive research in the area of structural health monitoring over the past few decades. Several structural health monitoring techniques have been developed that are capable of locating damage in structures using modal strain energy of mode shapes. Typically in the past, bending strain energy has been used in these methods since it is a dominant vibrational mode in many structures and is easily measured. Additionally, there may be cases, such as pipes, shafts, or certain bridges, where structures exhibit significant torsional behavior as well. In this research, torsional strain energy is used to locate damage. The damage index method is used on two numerical models; a cantilevered steel pipe and a simply-supported steel plate girder bridge. Torsion damage indices are compared to bending damage indices to assess their effectiveness at locating damage. The torsion strain energy method is capable of accurately locating damage and providing additional valuable information to both of the structures' behaviors.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.41 no.4
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• pp.395-404
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• 1996

This experiment was to evaluate the growth characteristics of lodging resistance cultivated at sandbed in rice varieties. Five varieties were used in this studies. The leaf area, leaf dry weight, culm dry weight and total dry weight of cultivated rice seedling at sandbed showed the maximal values at heading stage, but decreased according to growth development. The number of newly developed roots of rice seedlings cultivated at sand pot were the most at the 30 days seedling stage, but those were decreasing at 40 to 45 days seedling stage. Cheongmyungbyeo and Dongjinbyeo showed the most vigor in newly developed roots. The bending moment at breaking of rice internodes were the largest at the 4th node, but decreased at the top internodes. Cheongmyungbyeo and Dongjinbyeo were proved lodging resistant varieties by the bending moment. The weight of culm base was positively correlated with bending moment at breaking of rice culm, but lodging index was negatively correlated weight of culm base and root dry weight, respectively.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.556-563
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• 2005

This paper proposed a new substructural identification method to estimate the bending stiffness of a bridge deck, a fundamental structural health index of a super-structure. The proposed method can estimate the bending stiffness without considering actual supporting conditions by using substructural identification method while most of conventional methods need reasonable assumptions on supporting conditions which are hard to be assessed in a real bridge in operation. The mathematical formulation is derived and the results of laboratory tests are summarized. It was verified that the proposed method gives consistent estimation results regardless of actual supporting conditions.

• Advances in materials Research
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• v.6 no.1
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• pp.45-63
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• 2017

In this article, static deflection and buckling of functionally graded (FG) nanoscale beams made of porous material are carried out based on the nonlocal Timoshenko beam model which captures the small scale influences. The exact position of neutral axis is fixed, to eliminate the stretching and bending coupling due to the unsymmetrical material change along the FG nanobeams thickness. The material properties of FG beam are graded through the thickness on the basis of the power-law form, which is modified to approximate the material properties with two models of porosity phases. By employing Hamilton's principle, the nonlocal governing equations of FG nanobeams are obtained and solved analytically for simply-supported boundary conditions via the Navier-type procedure. Numerical results for deflection and buckling of FG nanoscale beams are presented and validated with those existing in the literature. The influences of small scale parameter, power law index, porosity distribution and slenderness ratio on the static and stability responses of the FG nanobeams are all explored.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.272-277
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• 2007

Generally railway vehicle runs on the rail with endless interaction between wheel and rail. Irregularity of rail causes the periodic motion of the vehicle. In association with this motion, the design of vehicle would be carried out in order to avoid the resonance between car-body and bogie. It may be seen that the first vertical bending mode of car-body contributes considerably to the vertical ride comfort level. In this paper to know the effect of the car-body first vertical bending mode on vertical ride comfort, the mode has been considered with dynamic model. I-DEAS program was used to get the car-body first vertical bending mode and VAMPIRE program was used to analyze ride comfort index(Wz) with FE interface file.

• Steel and Composite Structures
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• v.11 no.4
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• pp.341-358
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• 2011

This paper presents the effects of thermal environment and temperature-dependence of the material properties on axisymmetric bending of functionally graded (FG) circular and annular plates. The material properties are assumed to be temperature-dependent and graded in the thickness direction. In order to accurately evaluate the effect of thermal environment, the initial thermal stresses are obtained by solving the thermoelastic equilibrium equations. Governing equations and the related boundary conditions, which include the effects of initial thermal stresses, are derived using the virtual work principle based on the elasticity theory. The differential quadrature method (DQM) as an efficient and robust numerical tool is used to obtain the initial thermal stresses and response of the plate. Comparison studies with some available results for FG plates are performed. The influences of temperature rise, temperature-dependence of material properties, material graded index and different geometrical parameters are carried out.

• Steel and Composite Structures
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• v.52 no.5
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• pp.525-541
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• 2024

This study uses the state-space approach to study the bending behavior of Levy-type functionally graded (FG) plates sandwiched between two piezoelectric layers. The coupled governing equations are obtained using Hamilton's principle and Maxwell's equation based on the efficient four-variable refined plate theory. The partial differential equations (PDEs) are converted using Levy's solution technique to ordinary differential equations (ODEs). In the context of the state-space method, the higher-order ODEs are simplified to a system of first-order equations and then solved. The results are compared with those reported in available references and those obtained from Abaqus FE simulations, and good agreements between results confirm the accuracy and efficiency of the approach. Also, the effect of different parameters such as power-law index, aspect ratio, type of boundary conditions, thickness-to-side ratio, and piezoelectric thickness are studied.

• Structural Engineering and Mechanics
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• v.10 no.1
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• pp.37-51
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• 2000

Identification of damage location based on modal measurement is an important problem in structural health monitoring. The damage index method that attempts to evaluate the changes in modal strain energy distribution has been found to be effective under certain circumstances. In this paper two damage index methods using bending strain energy and shear strain energy have been evaluated for numerous cases at different locations and degrees of damage. The objective is to evaluate the feasibility of the damage index method to localize the damage on large span concrete bridge. Finite element models were used as the test structures. Finally this method was used to predict the damage location in an actual structure, using the results of a modal survey from a large concrete bridge.

• Computers and Concrete
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• v.26 no.1
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• pp.63-74
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• 2020

In this investigation, study of the bending response of functionally graded (FG) porous plates is presented using a cubic shear deformation theory. The properties of the FG-plate vary according to a power-law distribution which is modified to approximate material characteristics for considering the effect of porosities. The equilibrium equations are derived by using the principle of virtual work and solved by using Navier's procedure. Various numerical results are discussed to demonstrate the influence of the variation of the power index, the porosity parameter and the geometric ratios on the bending response of FG porous plates.