• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.5
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• pp.287-297
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• 2022

This paper presents experimental and analytical studies on the lateral cyclic behavior of RC columns actively confined with iron-based shape memory alloy (Fe-SMA) strips. Based on the Anexperimental study, we investigated the effectiveness of active confinement through compression testings of concrete cylinders confined by Fe SMA strips and carbon fiber-reinforced polymer (CFRP) sheets. The test results showed that the specimens confined with Fe SMA strips significantly increased the deformation capacity of the concrete, even under lower confining pressures, compared to those specimensconfined with CFRP sheets. The experimental results were used to develop finite-element models of RC columns confined with Fe SMA or CFRP in their plastic-hinge region. After validating the proposed analytical model through comparison with the results from a previous RC column test, a series of lateral cyclic load analyses were carried out for the RC columns confined with Fe SMA and CFRP. The analytical results revealed that the lateral cyclic behavior of the Fe SMA-confined column was greatly enhanced in terms of deformation and energy dissipation capacities compared with tothat of the as-built and CFRP-confined columns.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.10-22
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• 1998

In the present work the elastic-plastic FE formulations using dynamic explicit time integration schemes are used for numerical analysis of a large auto-body panel stamping processes. For analyses of more complex cases with larger and more refined meshes, the explicit method is more time effective than implicit method, and has no convergency problem and has the robust nature of contact and friction algorithms while implicit method is widely used because of excellent accuracy and reliability. The elastic-plastic scheme is more reliable and rigorous while the rigid-plastic scheme require small computation time. In finite element simulation of auto-body panel stamping processes, the roobustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry conditions. The performnce of the dynamic explicit algorithms are investigated by comparing the simulation results of formaing of complicate shaped autobody parts, such as a fuel tank and a rear hinge, with the experimental results. It has been shown that the proposed dynamic explicit elastic-plastic finite element method enables an effective computation for complicated auto-body panel stamping processes.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.275-281
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• 2001

In the sheet metal forming process, the drawbead is used to control the flow of material during the forming process. The drawbead provides proper restraining force to the material and prevents defects such as wrinkling or breakage. For these reasons, many studies for designing the effective drawbead have been conducted. In this paper, the effect of the drawbead shape will be introduced. For the analysis, the numerical method called the static-explicit finite element method was used. The finite element analysis code for this method has been developed and applied to the drawbead process problems. In result, convergence problem and computation time due to large non-linearity in the existing numerical analysis methods were no longer a critial Problem. Futhermore, this approach could treat the contact friction problem easily by applying very small time intervals. It is expected that various results from the numerical analysis will give very useful information for the design of tools in sheet metal forming process.

• The Journal of Korean Association of Computer Education
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• v.15 no.6
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• pp.75-82
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• 2012

The sensor registry system has been proposed to interpret and process semantics of sensor data independently of heterogeneous sensor networks. However, the existing sensor registry system provides the static processing method. In other words, the existing system reduces the overall performance because it executes unnecessary operations and does not consider data scope to be used. To resolve the problem of the existing sensor registry system, this paper proposes a performance enhancement model based on sensor metadata reusability and scoping. The proposed model in this paper provides a function that can decide a proper scope of sensor metadata from the sensor registry system. The proposed model improves the overall performance by providing reusability of sensor metadata. This paper also shows the advantages of the proposed model through the comparative performance evaluation.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.86-98
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• 1996

An combined implicit/explicit scheme for the analysis of sheet forming problems has been proposed in this work. In finite element simulation of sheet metal forming processes, the robustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry and boundary conditions. The implicit scheme dmploys a more reliable and rigorous scheme in considering the equilibrium at each step of deformation, while in the explict scheme the problem of convergency is elimented at thecost of solution accuracy. The explicit approach and the implicit approach have merits and demerits, respectively. In order to combine the merits of these two methods a step-wise combined implici/explicit scheme has been developed. In the present work, the rigid-plastic finite element method using bending energy augmented membraneelements(BEAM)(1) is employed for computation. Computations are carried out for some typical sheet forming examples by implicit, combined implicit/explicit schemes including deep drawing of an oil pan, front fender and fuel tank. From the comparison between the methods the advantages and disadvantages of the methods are discussed.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.21-21
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• 2022

충적하천의 하상과 제방은 흐름에 의해 쉽게 침식되는 사립자들로 구성되어 있다. 흐름이 더욱 강해지면 커다란 입자들도 움직이게 되고 더욱 커지면 결국 모든 입자들이 움직인다. 이렇게 흐름에 의해 하상과 제방을 구성하는 사립자들이 움직이기 시작하는 상태를 한계운동이라 하며, 이때의 흐름조건을 한계조건이라 한다. 한계조건은 이동상 수리학의 시작으로, 이때부터 흐름은 물과 유사의 혼합이라는 이상류가 되어 순수한 물의 흐름보다 더 복잡하게 된다. 개수로는 관수로와 달리 반드시 자유수면이 있으며, 따라서 물과 공기와의 마찰은 상대적으로 매우 작으므로 개수로의 전단응력 분포는 관수로와 달리 근본적으로 비대칭이다. 따라서 전단응력은 수로 바닥이나 측벽에서만 작용하게 된다. 한계조건은 이러한 추상적인 의미에 앞서 바닥이 침식되지 않는 하도나 수로의 설계 등에 기본적인 자료가 된다. 개수로에서 경계면의 전단응력을 힘으로 표시하는 것을 통상 소류력이라 하며, 개수로 경계면에서 전단응력의 분포도; 이른바 단면의 평균 전단응력의 개념을 도입하여 해석하고 설계기준으로 제시되고 있다. 본 연구에서는 자연하천과 유사한 조건의 건설기술연구원 하천실험센터의 급경사수로에서 연구를 진행하였으며, 기존 연구를 바탕으로 제작된 소류력 측정장치를 이용하였다. 하천의 설계나 평가에 적용되는 평균 소류력 개념은 복잡한 난류흐름에서 평가지표로써 대표하기 힘들기 때문에 유사 하천환경의 바닥에서 발생하는 소류력을 직접 측정하고자 연구를 진행하였고, 연구결과를 기존의 소류력 산정방법과 비교하였다. 본 연구에 사용된 장치는 실규모 실험을 위해 제작되었으며, 실규모 적용성 검토를 위해 실험실에서 충분한 검증실험을 거친 후 실규모 실험에 적용하였다.

• Journal of the Korean Geosynthetics Society
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• v.14 no.1
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• pp.51-58
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• 2015

The counter weight filling is a technology to accumulate soils on the side of berm with a proper width and height for improving the stability of the embankment. This study aims to assess a feasibility of the counter weight filling in the construction of pavement roads for recovery of shear failure during the construction. An effective counter weight filling section was suggested using the numerical analysis. The results showed that the effective counter weight filling section is two-fold (x2) higher than the ratio of width in counter weight filling : embankment height and one third (1/3) to the ratio of height in counter weight filling : embankment height. Also a range of effective trench crossing the counter weight filling required when a trench crossing counter weight filling is installed was suggested by supplying a proper distance between the counter weight filling section and cross-sectional trench.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.9-16
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• 2014

In recent years, the structural shock response to UNDEX (UNDerwater EXplosion) has been studied as much, or more, through numerical simulations than through testing for several reasons. Very high costs and sensitive environmental concerns have kept destructive underwater explosion testing to a minimum. Increase of simulation capabilities and sophisticated simulation tools has made numerical simulations more efficient analysis methods as well as more reliable testing aids. In this study, the main issue is the fluid-structure interaction. Here, appropriate relations between the acoustic pressure on the fluid surface and displacements on the structure surface are formed internally. The analysis was carried out using ABAQUS/Explicit and the results have been visualized in ABAQUS CAE. The shock loading history, acoustic pressure, stress of stand-off point, the velocity and strain energy time histories were presented.

• Journal of Ocean Engineering and Technology
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• v.26 no.4
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• pp.77-85
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• 2012

A study was performed on the design of a mooring line to maintain the position of a floating WEC (wave energy conversion) system. The procedure to design a mooring line is set up and the safety of the designed mooring system is evaluated using commercial software, Orcaflex. The characteristics curve for one line is analyzed to determine the properties and pretension of a mooring line. While considering the ocean environmental condition and importance of a floating WEC system, a multi-line layout is determined. A 4-point mooring system with 4 lines shows the instability in the yaw motion of the floating WEC system under a designed ocean environmental condition. The redesigned 4-point mooring system with 8 lines is found to be safe on the condition of a harsh ocean environment. The floating WEC system with the redesigned mooring system also shows stable motion in surge and pitch under operating conditions. From a parametric study on the mooring line length, the extreme value of the mooring line tension is found to be very sensitive to the pretension and length of mooring line. The results of this study can contribute to the establishment of a design procedure for mooring lines.

• Journal of KIISE
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• v.42 no.2
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• pp.255-263
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• 2015

The sensor registry system has been developed for instant use and seamless interpretation of sensor data in a heterogeneous sensor network environment. However, the existing sensor registry system cannot provide information for interpretation of the sensor data in situations in which the network is unstable. This limitation causes several problems such as sensor data loss, inaccuracy of processed results, and low service quality. A method to resolve such problems in the aspect of software is presented herein. In other words, an extended sensor registry system is proposed to enable the stable use of sensor information, even under conditions of unstable network connection, by providing sensor information with a mobile device in advance through the user path prediction. The results of experiments and evaluation are also presented. The extended sensor registry system proposed in this paper enhances the stable usability of sensor information as well as improves the quality of sensor-based services.