• Journal of Ocean Engineering and Technology
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• v.19 no.1 s.62
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• pp.20-25
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• 2005

The authors performed the underwater explosion analysis for the liquified oxygen tank - a kind of fuel tank of a mid-size submarine, and tried to verify the structural safety for this structure. First, the authors reviewed the theory and application of underwater explosion analysis, using a Structure-Fluid Interaction technique and its finite element modeling scheme. Next, the authors modeled the explosive and sea water as fluid elements, the LOX tank as structural elements, and the interface between the two regions as the ALE scheme. The effect on shock pressure and impulse of fluid mesh size and shape are also investigated. Upon analysis, it was found that the shock pressure due to explosion propagated into the water region, and hit the structure region. The plastic deformation and the equivalent stress were apparent at the web frame and the shock mount of LOX structure, but these values were acceptable for the design criteria.

• Journal of the Korean Solar Energy Society
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• v.33 no.4
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• pp.70-79
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• 2013

These day cities experience serious climatic changes due to environmental load caused by disturbance in the circulation systems of water resources and energy. As technological improvement to respond to various climatic changes and disasters are also requested in the field of construction, inter-disciplinary studies linked to the establishment of sustainable environmental control and energy systems is required in a consilient perspective. This study aims to infer correlations in the impact of environmental changes caused by rooftop greening system on the photovoltaic power generation efficiency through computer simulation in an integrated perspective. By doing so, it seeks to provide basic study for developing a photovoltaic system integrated with building revegetation that is sustainable in environmental and resource aspects. A simulation showed that, in the case of sunshine hours in June, the green surface indicated temperature lowering effects of $9.19^{\circ}C$ on average compared to the non-green surface and temperature was $9.81^{\circ}C$ lower. Due to such greening effects, at the highest sunlight timepoint in June, Pmpp improved 119W and heat loss rate dropped 7.8%.

• Structural Engineering and Mechanics
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• v.69 no.6
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• pp.667-676
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• 2019

Minimizing the stress concentration around hypotrochoid hole in finite metallic plates under in-plane loading is an important consideration in engineering design. In the analysis of finite metallic plate, the effective factors on stress distribution around holes include curvature radius of the corner of the hole, hole orientation, plate's aspect ratio, and hole size. This paper aims to investigate the impact of these factors on stress analysis of finite metallic plate with central hypotrochoid hole. To obtain the lowest value of stress around a hypotrochoid hole, a swarm intelligence optimization method named ant lion optimizer is used. In this study, with the hypothesis of plane stress circumstances, analytical solution of Muskhelishvili's complex variable method and conformal mapping is employed. The plate is taken into account to be finite, isotropic and linearly elastic. By applying suitable boundary conditions and least square boundary collocation technique, undefined coefficients of stress function are found. The results revealed that by choosing the above-mentioned factor correctly, the lowest value of stress would be obtained around the hole allowing to an increment in load-bearing capacity of the structure.

• Steel and Composite Structures
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• v.29 no.6
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• pp.689-701
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• 2018

Corrosion of steel reinforcement is a principal cause of deterioration of RC columns. Making these corrosion-damaged columns conform to new safety regulations and functions is a tremendous technological challenge. This study presented an experimental investigation on steel-concrete jacketed corrosion-damaged RC columns. The influences of steel jacket thickness and concrete strength on the enhancement performance of the strengthened specimens were investigated. The results showed that the use of steel-concrete jacketing is efficient since the stub strengthened columns behaved in a more ductile manner. Moreover, the ultimate strength of the corrosion-damaged RC columns is increased by an average of 5.3 times, and the ductility is also significantly improved by the strengthening method. The bearing capacity of the strengthening columns increases with the steel tube thickness increasing, and the strengthening concrete strength has a positive impact on both bearing capacity, whereas a negative influence on the ductility. Subsequently, a numerical model was developed to predict the behavior of the retrofitted columns. The model takes into account corrosion-damage of steel rebar and confining enhancement supplied by the steel tube. Comparative results with the experimental results indicated that the developed numerical model is an effective simulation. Based on extensive verified numerical studies, a design equation was proposed and found to predict well the ultimate eccentric strength of the strengthened columns.

• Steel and Composite Structures
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• v.42 no.4
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• pp.447-458
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• 2022

Cold-formed steel (CFS) sections are thin-walled, therefore, more susceptible to different types of geometric imperfections. Global type of geometric imperfections has a significant impact on the load-carrying capacity of flexural members. This paper reports an experimental study that discusses the influence of global imperfections on the flexural response of CFS built-up I-beams composed of two lipped channels, with simply supported ends, under four-point loading. Global imperfections of magnitude over eight times the maximum permissible ones were induced in the specimens, leading to their distress. Using various simple stiffening schemes, the capacity and stiffness of the distressed specimens were improvised. The performance comparisons were made based on the maximum loads resisted, flexural stiffnesses offered, and failure modes experienced by the specimens. As experimental data on such distressed specimens are currently lacking in the literature, the test results of the present study will provide the necessary data needed by future researchers to numerically extend this study further, which will help in the development of necessary design guidelines for the same. The stiffening schemes significantly improved the structural efficiency of distressed specimens in terms of strength and stiffness, by over 60%. As a result, an effective and time-saving solution to such realistic structural engineering problems is given.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.21 no.4
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• pp.503-516
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• 2023

A transfer cask serves as the container for transporting and handling canisters loaded with spent nuclear fuels from light water reactors. This study focuses on a cylindrical transfer cask, standing at 5,300 mm with an external diameter of 2,170 mm, featuring impact limiters on the top and bottom sides. The base of the cask body has an openable/closable lid for loading canisters with storage modules. The transfer cask houses a canister containing spent nuclear fuels from lightweight reactors, serving as the confinement boundary while the cask itself lacks the confinement structure. The objective of this study was to conduct a structural analysis evaluation of the transfer cask, currently under development in Korea, ensuring its safety. This evaluation encompasses analyses of loads under normal, off-normal, and accident conditions, adhering to NUREG-2215. Structural integrity was assessed by comparing combined results for each load against stress limits. The results confirm that the transfer cask meets stress limits across normal, off-normal, and accident conditions, establishing its structural safety.

• Structural Engineering and Mechanics
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• v.88 no.5
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• pp.501-519
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• 2023

This paper introduces a new hybrid structural connection joint that combines shear walls with section steel beams, fundamentally resolving the construction complexity issue of requiring pre-embedded connectors in the connection between shear walls and steel beams. Initially, a quasi-static loading scheme with load-deformation dual control was employed to conduct low-cycle repeated loading experiments on five new connection joints. Data was acquired using displacement and strain gauges to compare the energy dissipation coefficients of each specimen. The destruction process of the new connection joints was meticulously observed and recorded, delineating it into three stages. Hysteresis curves and skeleton curves of the joint specimens were plotted based on experimental results, summarizing the energy dissipation performance of the joints. It's noteworthy that the addition of shear walls led to an approximate 17% increase in the energy dissipation coefficient. The energy dissipation coefficients of dog-bone-shaped connection joints with shear walls and cover plates reached 2.043 and 2.059, respectively, exhibiting the most comprehensive hysteresis curves. Additionally, the impact of laminated steel plates covering composite concrete floors on the stiffness of semi-rigid joint ends under excessive stretching should not be disregarded. A comparison with finite element analysis results yielded an error of merely 2.2%, offering substantial evidence for the wide-ranging application prospects of this innovative joint in seismic performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.11
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• pp.891-899
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• 2013

This paper suggests a test and evaluation procedure of conformal load-bearing antenna structure(CLAS) for high speed military jet application. A log periodic patch type antenna was designed for multi-band communication and navigation antenna. Carbon/Glass fiber reinforced polymer was used as a structure supporting aerodynamic loads and honeycomb layer was used to improve antenna performance. Multi-layers were stacked and cured in a hot temperature oven. Gain, VSWR and polarization pattern of CLAS were measured using anechoic chamber within 0.15~2.0 GHz frequency range. Tension, shear, fatigue and impact load test were performed to evaluate structural strength of CLAS. Antenna performance test after every structural strength test was conducted to check the effect of structural test to antenna performance. After the application of new test and evaluation procedure to validate a new CLAS, a design improvement was found.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.54-63
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• 2018

In this study, the stability and economic feasibility of a MSE (Mechanically stability earth) wall with a pre-cast concrete pacing panel was investigated for a standard section of highway. Based on the design criteria, the MSE walls of the panel type were designed considering the load conditions of the highway, such as the dead load of the concrete pavement, traffic load, and impact load of the barrier. The length of the ribbed metal strip was arranged at 0.9H according to the height of the MSE walls. Because the length of the reinforcement was set to 0.9H according to the height of the MSE wall, the external stability governed by the shape of the reinforced soil was not affected by the height increase. The factor of safety (FOS) for the bearing capacity was decreased drastically due to the increase in self-weight according to the height of the MSE wall. As a result of examining the internal stability according to the cohesive gravity method, the FOS of pullout was increased and the FOS of fracture was decreased. As the height of the MSEW wall increases, the horizontal earth pressure acting as an active force and the vertical earth pressure acting as a resistance force are increased together, so that the FOS of the pullout is increased. Because the long-term allowable tensile force of the ribbed metal strip is constant, the FOS of the fracture is decreased by only an increase in the horizontal earth pressure according to the height. The panel type MSE wall was more economical than the block type at all heights. Compared to the concrete retaining wall, it has excellent economic efficiency at a height of 5.0 m or more.

• Science of Emotion and Sensibility
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• v.13 no.1
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• pp.21-32
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• 2010

This study investigated the effects of contiguity and reading mode on cognitive load factors measured by Galvanic Skin Response(GSR). In this study two experimental conditions were imposed to participants to measure cognitive load with the high contiguity picture and low contiguity picture. Thirty-four college students participated to this experiment(experiment group=17, control group=17), and spilt-plot factorial design was applied to control individual difference in galvanic skin response. Tasks of this experiment were reading and summary. The dependent variables were skin conductance response, and perceived difficulty. The independent variables were the degree of contiguity of visual material(high contiguity vs. low contiguity). The major result of this study was identification of a significant difference of GSR with low contiguity condition. Indeed it was identified that more complex reading condition required more cognitive loads. This finding supported that different cognitive process might require different amounts of cognitive loads. For the further research, this study discussed the validity of applying physiological signals to assess cognitive loads and relationships the associated affective reactions.