• Korean Journal of Construction Engineering and Management
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• v.16 no.3
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• pp.143-151
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• 2015

The Crack, occurred in the concrete structure, is a major cause of function deterioration such as strength, durability and waterproof. Therefore the need for crack reduction will continue as long as there is concrete structure. But, it is not easy to reduce or prevent crack cause of impact factor of it. There are so many factors of crack such as material, construction and maintenance environment, and structure, and these are acting in combination. So, this study derives a correlation between the cracks and members through reviewing member crack occurred. And member's attribute, related crack, is analyzed by it. It consider that the basic attribute of member is similar when its requirements are similar. Through this study, therefore, foundation of countermeasure of crack will be provided by prediction of crack shape through member's attribute.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.1-6
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• 2018

Hydro-forming technology has spread dramatically throughout automotive industry over the last 20 years. This technology has many advantages for automotive applications in terms of better structural integrity of the parts, lower cost from fewer parts, material savings, weight reduction, lower springback, improved strength, durability, and design flexibility. In this study, various simulation technologies were developed to investigate the formability of hydro-forming components. Through this technology, to establish the effective forming process for appropriate components design, the bending process, pre-forming process, die closing process, etc. were considered for good forming. This paper proposes the forming amount, section length (corresponding to the hydro-forming press capacity), and minimum curvature (curvature effect evaluation according to the hydro-forming pressure) among the considerations in the design of the hydro-forming part. In addition, a design method is proposed for hydro-forming molding by carrying out cross section analysis of a real sub-frame part for automobiles. The effects of pre-bending, axial feed, hydraulic pressure, press load, and friction among the hydro-forming process parameters were analyzed. Therefore, whether these processes are necessary factors for hydro-forming were examined.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.2
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• pp.185-191
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• 2003

This paper presents the thermal problems of steel-concrete composite structure and the basic references in placing concrete into the structure. Based on the analytical investigation, application of the composite structure has the effect of highly decreasing the temperature difference between the center section and the surface section of the structure, though its application has little influence on the decrement of the maximum temperature under the same using material and placing temperature. Meanwhile, its application causes the section decrement of a concrete structure, and in the section which the decrement ratio is relatively large, the restraint action by a old concrete structure takes place highly tensile stresses over a tensile strength. And, the stress is concentrated on sharp edges of the steel-concrete boundary. Both restraint action and stress concentration considerably decrease the reduction effect of the temperature difference. Therefore, the prediction of thermal response and the reasonable steps are required through the simulation considering the factors and the sections related to those problems.

• Journal of the Korean Geotechnical Society
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• v.30 no.11
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• pp.5-15
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• 2014

It is very important to design and construct slopes safely because damage cases are increasing due to slope failure. Recently, Limit Equilibrium Method (LEM) based programs are commonly used for slope designs. Though LEM can give factors of safety through simple calculation, it has a disadvantage that the sliding surface should be assumed in advance. On the other hand, the use of Finite Difference Method (FDM) is increasing since the factor of safety can be easily estimated by using shear strength reduction technique. Therefore the purpose of this study is to present a reasonable slope design methodology by comparing the two commonly used analysis approaches; LEM and FDM. To this end, the reinforcement effects of the two methods were compared in terms of the support pattern of soil nailing reinforced in the section where plane failure is anticipated. As a result, the reinforcement effects by nail angle and nail spacing turned out to be equal. Also it was found that the factor of safety increased in LEM, but not changed in FDM when the nail length increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1021-1026
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• 2011

Structural impact problems are becoming increasingly important for a modern defense industry, high-speed transportation, and other applications because of the weight reduction with high strength. In this study, a numerical investigation on the impact fracture behavior of aluminum plates was performed under various projectile conditions such as nose shapes, velocities, and incidence angles. In order to reduce the iterative numerical analysis, the Latin Square Method was employed. The influence factor was then determined by an FE analysis according to the conditions. The results were evaluated by means of a statistical significance interpretation using variance assessment. It was shown that the velocity and incidence angle can be the most important influence factors representing the impact absorption energy and plastic deformation, respectively.

• Journal of the Optical Society of Korea
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• v.18 no.1
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• pp.55-59
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• 2014

Sarcopenia, or reduced muscle mass and volume, is due to various factors such as senile change, neuronal degeneration, drug, malignancy, and sepsis. Sarcopenia with the aging process has been evidenced by the decline in muscle mass by 0.5 to 1% per year with 3-5% reduction in muscle strength for 10 years between the ages of 40 and 50, and a 1-2% of decline of mass every year in people aged 60-70. Therefore, early diagnosis and understanding the mechanism of sarcopenia are crucial in the prevention of muscle loss. However, it is still difficult to image changes of muscle microstructure due to a lack of techniques. In this study, we developed an animal model using denervated rats to induce a rapid atrophy in the tibialis anterior (TA) and imaged its structural changes using optical coherence tomography (OCT) along with histologic and ultrasound analyses. Ultrasound showed changes of overall muscle size. Histology revealed that the atrophic TA muscle displayed an increased size variability of muscle fiber and inflammatory changes. Three dimensional OCT imaged the changes of perimysial grid and muscle fiber structure in real time without sacrifice. These observed advantages of multimodal imaging using OCT and ultrasound would provide clinical benefits in the diagnosis of sarcopenia.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4298-4307
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• 2015

The expenses of maintenance and reinforcement for aged concrete structures are significantly on the increase as their durability and general performance has been naturally degraded. Due to this reason, interests on concrete crack reduction technology are growing but more researches are required to fulfill such fast growing demands. Particularly in the underground power facilities, it is difficult to maintain the quality of aging concrete spheres for underground power as their deterioration caused by long-term operation is on-going. In recent years, many studies have been made to overcome the issues and now it is determined that the shrinkage reducing technology which can dramatically reduce the crack at the design stage is one of the most effective solutions. In this study, the test investigated fundamental propertiesof concrete using various shrinkage reducing materials to develop low shrinkage mortar. According to results of experimental study, for mortar and concrete, glycol based material showed excellent shrinkage property and compressive strength. For the later study to generic application of the shrinkage reducing materials, performance reviews on the shrinkage reducing materials with variable factors and various materials such as changes in the amount and type of materials should be followed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.637-640
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• 2005

The mechanical properties of bellows, such as the extensibility and the strength can be changed depending on the shape. For the shipbuilding material, it is favorable that the fatigue lift is long due to the elastic property and the reduction of thermal stress in piping system. Nowadays, the domestic production and design of bellows are based on the E.J.M.A Code. Therefore, the design standard is in need because of much errors and lack of detailed analysis. In this study, it is attempted to find out the optimal shape of U-type ship's bellows that is applied to design of experiment using the finite element method. The effective factors, mountain height, length, thickness, and number of mountains and the length of joint are considered and the proper values are chosen for the simulation. The number of mountains are increased, the volume increases above the standard volume and the stress obviously increases. In addition, the effect of the thickness of bellows on the stress is very large. Both of the volume and stress are decreasing at a certain lower value region.

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.61-70
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• 2008

The control and prediction of surface settlement, gradient and ground displacement are the main factors in shallow tunnel design and construction in urban area. For deformation analysis of shallow tunnel due to excavation it is important to identify possible deformation mechanism of shear bands developing from tunnel shoulder to the ground surface. This paper investigaties quantitatively the deformation behavior of shallow tunneling by model tunnel test and strain softening analysis Incorporating the reduction of shear stiffness and strength parameters. The comparison of model tunnel test result and numerical simulation using strain softening analysis showed good agreement in crown settlement, normalized subsidence settlement and developing shear bands above tunnel shoulder. In this study, it is blown that the strain softening modeling is applicable to the nonlinear deformation analysis of shallow tunnel.

• Journal of the Korea Institute of Building Construction
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• v.23 no.4
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• pp.441-452
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• 2023

Buildings that have been long neglected can suffer severe durability reduction due to factors such as rebar rust and concrete quality deterioration resulting from exposure to outside air. Furthermore, the issues associated with these suspended buildings, including safety accidents, social crimes, and environmental pollution, are becoming increasingly serious. This study investigates the current status of these buildings in the Jeju area, identifies the problems, and examines the durability of the structure in a specific location to assess the possibility of future use. Aesthetic surveys(visual and slope inspections) as well as non-destructive tests(compressive strength tests, neutralization tests, and rebar detection tests) were conducted to assess durability. The analysis revealed that the structure maintained satisfactory durability and the building's condition was good in comparison to the years of neglect.