• Journal of KSNVE
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• v.9 no.2
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• pp.248-257
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• 1999

This paper presents the model updating of an equipment panel by using modal test and sensitivity analysis. The equipment panel is one of the major structures of communication satelite, on which broadcasting and communication equipments are mounted. For high rigidity and light weight, the panel was designed as an aluminum honeycomb sandwich panel. In addition, heat pipes were embedded in the panel for thermal control. It is essential to improve the finite element model of a spacecraft structure by using modal test in order to verify that the satellite is designed and fabricated with adequate margin under launch environment. In this paper, Young's modulus of aluminumfacesheet was selected as a modified parameter in the sensitivity analysis. The effect of boundary conditions on model improvement was also investigated.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.472-476
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• 2024

It is important that radioactive and nuclear wastes are immobilized in a glass composition with lower melting temperatures due to their economy. In this study, the elastic and mechanical properties of sodium borate-based vitrified radioactive waste were measured using ultrasonic techniques. Many ultrasonic parameters, such as elastic moduli, Poisson's ratio, and microhardness, were calculated by measuring the ultrasonic velocities of the glasses. The ultrasonic velocity data, the density, the calculated elastic moduli, micro-hardness, softening temperature, and Debye temperature depending on the glass composition were evaluated, and the relation with the structure was clarified. It was observed that the elastic modulus and Poisson ratio increased as the Cs₂O content increased in glasses containing Cs waste. This result shows that the rigidity of the network structure of these glasses increases in contrast to the glass containing Sr.

• Interaction and multiscale mechanics
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• v.5 no.4
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• pp.369-383
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• 2012

In this paper, soil-structure interaction analysis has been presented for beams resting on multilayered geosynthetic-reinforced granular fill-soft soil system. The soft soil and geosynthetic reinforcements are idealized as nonlinear springs and elastic membranes, respectively. The governing differential equations are solved by finite difference technique and the results are presented in non-dimensional form. It is observed from the study that use of geosynthetic reinforcement is not very effective for maximum settlement reduction in case of very rigid beam. Similarly the reinforcements are not effective for shear force reduction if the granular fill has very high shear modulus value. However, multilayered reinforced system is very effective for bending moment and differential settlement reduction.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.185-193
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• 1997

본 연구는 각종 제진재료를 이용하여 진동을 억제할 수 있는 콘크리트를 개발하여 각종 건설공사에서 흔히 발생할 수 있는 진동공해문제를 억제하고자 하며 아울러 폐기물의 재활용차원에서 폐자재를 이용하여 유용한 제진콘크리트를 개발하고자 하는데 그 목적이 있다. 우선, 제진재료를 이용한 압축강도 (200kg/$\textrm{cm}^2$)이상의 콘크리트 배합비를 찾기 위하여 24배치의 예비실험을 수행하였으며, 선정된 적정배합비에 따른 제진재료를 이용한9개의 진동시험체보를 제작하여 보의 구조적 및 재료적 동적특성 즉 1차 공명진동수와 동적 휨강성 및 감쇠비를 측정하여 제진효과를 조사하였다. 그리고 압축강도에 의한 각 시험체의 균열모멘트를 추정하여 재하하중과 균열모멘트비(M/Mcr)에 따른 하중단계별 동적특성값을 살펴보았다. 제진재료로서는 라텍스(Latex), 고무분말(Rubber Powder)그리고 플라스틱 레진( Plastic Resin)등을 사용하였고, 재료적, 구조적 진동감쇠효과를 파악하고자 KS F2437규정과 진동파의 속도법을 사용하였으며, 감쇠비 측정은 Frequency Spectrum 곡선에 대한 Polynomial Curvefitting 방법과 기하학적 해석방법을 이용하여 각각의 결과를 비교.분석하였다.

• Journal of the Korean Wood Science and Technology
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• v.25 no.4
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• pp.29-38
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• 1997

The effect and control of wood property of reconstituted composite panels for improved board properties by wood-waste materials and development of combination method for heterogeneous materials have been of interest to the wood science researchers. The purpose of this study is to consider the properties in relation to hot pressing conditions and to develope the optimum hot pressing condition with waste wood and waste tire for the manufacturing of composite boards. The study of composite boards for recycling of wood and waste tire is nothing up to the present. Physical and mechanical properties such as specific gravity, moisture content, swelling coefficient, modulus of rupture and modulus of elasticity in bending test were studied. The condition of 3-stage press time for the lowest moisture content of composite board was $4{\rightarrow}3{\rightarrow}3$ minutes. Specific gravity of composite panels was affected mainly by the amount of rubber chip. Because of the low rigidity and high elasticity in rubber chip, it is considered the composite panel was adequate material in the place of compression load, but not bending load. Therefore, it was concluded that a use of rubber-based wood composite panel is proper to the interior materials such as floor a room than exterior materials. From the test results, the most optimum hot pressing conditions were $4{\rightarrow}3{\rightarrow}3$ minutes for 3-stage press time and $45{\rightarrow}20{\rightarrow}5kg/cm^2$ for 3-stage press pressure. The rubber-based wood composite panel was very excellent in elasticity by combination of rubber chip in comparison with existing other wood-based materials. Therefore, it was considered that rubber-based wood composites can be applicable to every interior materials such as floor a room and will be expected to effective reuse and recycle of waste tires and wood-waste materials, and will be contribute to protection of environment pollution in earth.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.3
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• pp.191-198
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• 2013

In this paper, the effects of uncertain material constant on the nonlinear behavior of steel frames with semi-rigid joints are examined. As to the probabilistic model, a normal distribution is assumed to simulate the uncertain elastic modulus of steel material. A nonlinear structural analysis program, which can consider both semi-rigidity in joints of the steel frames and uncertainty in the material constant, is developed. Including the geometric, material and connection nonlinearites which are the parameters of nonlinear behavior of steel frames, probabilistic analysis is conducted based on the Monte-Carlo simulation. In the probabilistic analyses, we consider the three different cases for random variables. The deterministic analysis results are shown to be in good agreement with those of the previous research results in the literature. As to the probabilistic analyses, it is observed that the coefficient of variation(COV) of displacements increases as the loading increases, and that the values of COV are dependent on the structural features of the frames.

• Composites Research
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• v.19 no.6
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• pp.23-31
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• 2006

We measured mechanical properties, including Young's modulus, effective bending modulus and nominal fracture strength of nanohoneycomb structures using an Atomic Force Microscope(AFM) and a Nano-Universal Testing Machine(UTM). Anodic aluminum oxide(AAO) films are well suited as nanohoneycomb structures because of the simple fabrication process, high aspect ratio, self-ordered hexagonal pore structure, and simple control of pore dimensions. Bending tests were carried out for cantilever structures by pressing AFM tips, and the results were compared with three-point bending tests and tensile tests using a Nano-UTM. One side of the AAO films is clogged by harrier layers, and looks like a face material of conventional sandwich structures. Analysis of this layer showed that it did not influence the bending rigidity, and was just a crack tip. The present results can act as a design guideline in applications of nanohoneycomb structures.

• Structural Engineering and Mechanics
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• v.44 no.6
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• pp.735-751
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• 2012

Although being one of the most popular strengthening techniques in reinforced concrete beams, the use of steel plates bonded to the soffit raises problems of ductility. This study aims at investigating the influence of the use of perforated steel plates instead of solid steel plates on the ductility of reinforced concrete beams. A total of nine reinforced concrete beams were tested. In addition to an unplated beam, eight beams with perforated steel plates of two different thicknesses (3 mm and 6 mm) were subjected to monotonic loading. Effect of bonding the plates to the beams with anchor bolts and with additional side plates bonded to the sides of the beam with and without anchors is also investigated. The use of bolts in addition to epoxy was found to greatly contribute to the ductility and energy absorption capacity of the beams, particularly in specimens with thick plates (6 mm) and the use side plates in addition to the bottom plate was found to be ineffective in increasing the ductility of a concrete beam unless the side plates are attached to the beam with anchors bolts. The thickness of the plate was found to have little effect on the bending rigidity of the beam.

• Steel and Composite Structures
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• v.18 no.2
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• pp.305-324
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• 2015

In this study, two common types of laterally supported castellated beams are considered as design problems: beams with hexagonal openings and beams with circular openings. The main goal of manufacturing these beams is to increase the moment of inertia and section modulus, which results in greater strength and rigidity. These types of open-web beams have found widespread use, primarily in buildings, because of great savings in materials and construction costs. Hence, the minimum cost is taken as the design objective function and the Colliding Bodies Optimization (CBO) method is utilized for obtaining the solution of the design problem. The design methods used in this study are consistent with BS5950 Part 1 and Part 3, and Euro Code 3. A number of design examples are considered to optimize by CBO algorithm. Comparison of the optimal solution of the CBO algorithm with those of the Enhanced Charged System Search (ECSS) method demonstrate the capability of CBO in solving the present type of design problem. It is also observed that optimization results obtained by the CBO algorithm for three design examples have less cost in comparison to the results of the ECSS algorithm. From the results obtained in this paper, it can be concluded that the use of beam with hexagonal opening requires smaller amount of steel material and it is superior to the cellular beam from the cost point of view.

• Carbon letters
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• v.1 no.3_4
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• pp.165-169
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• 2001

The C-type mesophase pitch-based carbon fiber (C-MPCF) was prepared throuch C-type spinnerette and compared the mechanical properties to those of round type mesophase pitch fiber (R-MPCF) and C-type isotropic pitch fiber (C-iPCF). The tensile strength and modulus of C-MPCF were about 18.6% and 35.7% higher than those of R-MPCF. The tensile strength of C-MPCF was 62% higher than that of C-iPCF of the same $8{\mu}m$ thickness because of more linear transverse texture, which could be easily converted to graphitic crystallinity during heat treatment. The torsional rigidity of C-MPCF was 2.37 times higher than that of R-MPCF. The electrical resistivity of C-MPCF was $8{\mu}{\Omega}{\cdot}m$. The C-iPCF shows far lower electrical resistivity than R-iPCF as well as the mesophase carbon fiber because of better alignment of texture to the fiber axis.