• Steel and Composite Structures
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• 제47권4호
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• pp.523-537
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• 2023

This paper proposed a new self-centering brace (SCB), which consists of four post-tensioned (PT) high strength steel strands and energy absorbing steel plate (EASP) clusters. First, analytical equations were derived to describe the working principle of the SCB. Then, to investigate the hysteretic performance of the SCB, four full-size specimens were manufactured and subjected to the same cyclic loading protocol. One additional specimen using only EASP clusters was also tested to highlight the contribution of PT strands. The test parameters varied in the testing process included the thickness of the EASP and the number of EASP in each cluster. Testing results shown that the SCB exhibited nearly flag-shape hysteresis up to expectation, including excellent recentering capability and satisfactory energy dissipating capacity. For all the specimens, the ratio of the recovered deformation is in the range of 89.6% to 92.1%, and the ratio of the height of the hysteresis loop to the yielding force is in the range of 0.47 to 0.77. Finally, in order to further understand the mechanism of the SCB and provide additional information to the testing results, the high-fidelity finite element (FE) models were established and the numerical results were compared against the experimental data. Good agreement between the experimental, numerical, and analytical results was observed, and the maximum difference is less than 12%. Parametric analysis was also carried out based on the validated FE model to evaluate the effect of some key parameters on the cyclic behavior of the SCB.

• Steel and Composite Structures
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• 제15권6호
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• pp.645-658
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• 2013

The objective of the study is to predict the moment anchorage capacity of the concrete filled steel box (CFSB) as footing by using the 3D finite element program CAMUI developed by authors' laboratory. The steel box is filled with concrete and concrete filled steel tube (CFT) column is inserted in the box. Numerical simulation of the experimental specimens was carried out after introducing the new constitutive model for post peak behavior of concrete in compression under confinement. The experimental program was conducted to verify the reliability of the simulation results by the FE program. The simulated peak loads agree reasonably with the experimental ones and was controlled by concrete crushing near the column. After confirming the reliability of the FEM simulation, effects of different parameters on the moment anchorage capacity of concrete filled steel box footing were clarified by conducting numerically parametric study.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.183.2-183.2
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• 2010

A three-dimensional numerical modeling using the finite element method for the suction caisson are described to decide suitability as foundation of offshore wind turbine in this paper. In the simulation, soil-structure interaction is defined by comparing experiment data. The reaction of monopod suction caisson is presented by moment loading which was calculated by FAST. Tendency of suction caisson appeared by difference of length and diameter of skirt under coupled loading. Length and diameter of skirt are suggested and evaluated as a offshore wind turbine.

• Computers and Concrete
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• 제14권6호
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• pp.635-656
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• 2014

A rational estimation of moisture distribution in structural concrete is vital for predicting the possible extent and rate of progression of impending degradation processes. The paper proposes a numerical scheme for analysing the evolution of moisture distribution in concrete subjected to wetting-drying exposure caused by intermittent periods of rainfall. The proposed paradigm is based on the stage wise implementation of non-linear finite element (FE) analysis, with each stage representing a distinct phase of a typical wet-dry cycle. The associated boundary conditions have been constituted to realize the influence of various meteorological elements such as rain, wind, relative humidity and temperature on the exposed concrete surface. The reliability of the developed scheme has been demonstrated through its application for the simulation of experimentally recorded moisture profiles reported in published literature. A sensitivity analysis has also been carried out to study the influence of critical material properties on simulated results. The proposed scheme is vital to the service life modelling of concrete structures in tropical climates which largely remain exposed to the action of alternating rains.

• 소성∙가공
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• 제10권6호
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• pp.456-464
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• 2001

Deep drawing and ironing are tile major process today in manufacturing of aluminum alloy battery case used in cellular phone. Most of these process require multi-stage ironing following the deep drawing and redrawing processes. The practical aspects of this technology are well known and gained through extensive experiment and production know-how. However, the fundamental aspects of these processes are relatively less known. Thus, it is expected that process analysis using FEM techniques would provide additional detailed information that could be utilized to improve the process condition. This paper illustrates the application of process modeling to deep drawing and redrawing operations. To verify the simulation results, the experimental investigations were also carried out on a real industrial product. The numerical analysis by FEM shows good agreement with the experimental results in view of the deformation shape of the product. A commercially available finite element code LS-DYNA3D was used to simulate deep drawing and redrawing operations.

• Journal of Magnetics
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• 제16권2호
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• pp.140-144
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• 2011

We report on a numerical calculation study of two new functional properties in magnetic tunnel junctions (MTJs), negative dynamic resistance and RF amplification. The magnetic dynamics in a conventional CoFeB/MgO/CoFeB MTJ with in-plane magnetization was investigated using a macro-spin model simulation. To examine the influence of thermal fluctuations, random external magnetic fields were also included. Using a voltage controlled bias circuit, the negative dynamic resistance was obtained from time averaged I-V characteristics at both 0 K and 300 K under appropriate external magnetic fields and bias voltages. Using this negative dynamic resistance property, we demonstrated RF amplification with a 100 MHz high frequency signal. Sizable RF amplification gain was observed without thermal fluctuation. However, at 300 K, the RF signal was not amplified because low frequency magnetization dynamics were dominant.

• Structural Engineering and Mechanics
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• 제12권3호
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• pp.297-312
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• 2001

The accurate finite element (FE) simulation of reinforced concrete (RC) slabs, having different boundary conditions and subjected to uniformly distributed loading, has led to the use of the developed FE models for generating results of ultimate loads from predictions of 'computer-model' RC slabs having different material and geometric properties. Equations derived from these results constitute the primary database of an intelligent computer-aided-design (CAD) system developed for accurate and fast information retrieval on arbitrary slabs. The system is capable of generating a secondary database through systems of interpolation and can be used for design assistance purposes.

• 한국압력기기공학회 논문집
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• 제19권2호
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• pp.117-129
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• 2023

Hydrogen embrittlement of a pipe is an important factor in hydrogen transport. To characterize hydrogen embrittlement, tensile and fracture toughness tests should be conducted. However, in the case of hydrogen-embrittled materials, it is difficult to perform tests in hydrogen environment, particularly at low temperatures. It would be useful to develop a methodology to predict the fracture toughness of hydrogen-embrittled materials at low temperatures using more efficient tests. In this study, the fracture toughness of API X52 steels in hydrogen at low temperatures is predicted from numerical simulation using coupled finite element (FE) damage analyses with FE diffusion analysis, calibrated by analyzing small punch test data.

• 한국항공우주학회지
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• 제36권12호
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• pp.1229-1235
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• 2008

비상위치송신기(ELT)는 무수한 조난시의 응급구조에 큰 역할을 해왔다. 비행사, 항해사 그리고 지상 사용자들은 세상 어디에서든지 비상시에 조난신호를 위성에 송신이 가능한 장치를 갖추고 있는 것이다. 이 논문에서는 비상위치송신기의 본체를 낙하충격에 대하여 MSC/Dytran을 이용하여 해석하였다. 그리고 그 결과를 Karas' Example 이론 결과에 비교하였다. 또한, 추락생존성 시험에 대해 MSC/Nastran을 이용해 해석하였다. 비상위치송신기의 충격조건하에 과도응답해석을 하였다.

• Computers and Concrete
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• 제21권4호
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• pp.399-406
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• 2018

The present study focuses on the performance of basalt fiber reinforced concrete (BFRC) lining in tunnel situated in sandstone rock when subjected to internal blast loading. The blast analysis of the lined tunnel is carried out using the three-dimensional (3-D) nonlinear finite element (FE) method. The stress-strain response of the sandstone rock is simulated using a crushable plasticity model which can simulate the brittle behavior of rock and that of BFRC lining is analyzed using a damaged plasticity model for concrete capturing damage response. The strain rate dependent material properties of BFRC are collected from the literature and that of rock are taken from the authors' previous work using split Hopkinson pressure bar (SHPB). The constitutive model performance is validated through the FE simulation of SHPB test and the comparison of simulation results with the experimental data. Further, blast loading in the tunnel is simulated for 10 kg and 50 kg Trinitrotoluene (TNT) charge weights using the equivalent pressure-time curves obtained through hydrocode simulations. The analysis results are studied for the stress and displacement response of rock and tunnel lining. Blast performance of BFRC lining is compared with that of plain concrete (PC) and steel fiber reinforced concrete (SFRC) lining materials. It is observed that the BFRC lining exhibits almost 65% lesser displacement as compared to PC and 30% lesser displacement as compared to SFRC tunnel linings.