• Journal of Korean Orthopaedic Sports Medicine
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• v.3 no.1
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• pp.66-72
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• 2004

Purpose: To evaluate the compensatory mechanism in vivo and develop the treatment guide by performing the comprehensive functional tests of the posterior cruciate ligament (PCL) deficient subjects. Material and Methods: 10 PCL deficient subjects and 10 healthy control group were evaluated. Performed functional tests were range of motion, posterior drawer test, Telos, 30$^{\circ}$ flexion wt-bearing view, KT-1000 arthrometer, gait analysis, EMG test and isokinetic tests. Results: Physical, KT-1000, Telos posterior tests showed significant differences, but 300 full weight bearing lateral view, muscle strength test revealed no difference between two groups. Less knee flexion at initial contact and reduced maximum valgus moment were observed in PCL deficient group. In vertical drop landing, PCL group had increased plantar flexion angle at initial contact. Conclusion: Compensatory mechanisms such as reduced unstable components and absorbing the maximal load of the joint were occurred after PCL insufficiency, which result in good clinical and functional outcomes. Further investigations would be needed to understand the functional adaptations of PCL deficient subjects.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.5
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• pp.335-342
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• 2013

Since the seriousness of environmental pollution came to the fore recently, various efforts have been made globally for the reduction of the environmental load. In particular, in the field of construction, an industry responsible for a considerable amount of pollution, studies have been actively conducted to reduce $CO_2$ emissions and energy consumption. However, most conventional research about pollution as it relates to construction is focused on the maintenance stages where $CO_2$ emissions are the greatest. Research related to the design stage is in its infancy, as it has only been conducted thus far on steel buildings and RC buildings. In fact, in order to achieve environmentally friendly construction considering the Life Cycle Assessment(LCA), the building design should be derived to reduce the $CO_2$ emissions from the early building design stage, and structural engineers should be able to suggest a design plan considering its environmental friendliness. In this study, optimal structural design method for steel reinforced concrete(SRC) columns considering $CO_2$ emissions is presented. The trends of $CO_2$ emissions in SRC columns according to the variations of steel shapes, concrete strengths and loads are investigated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.270-276
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• 2019

According to the International Maritime Organization (IMO) 2020 Regulation, ships operating outside designated emission control areas (ECA) have to use low-sulfur oil with a sulfur content of 0.5% or less by January 2020. To minimize the consumption of high-priced low-sulfur oil, it is urgent to introduce efficient energy-saving devices (ESD), and contra-rotating propeller (CRP) systems are well known to be the most effective one. The shafting system that drives a CRP is composed of an inner shaft and an outer one and has a mutually influential system that is much more complex and heavier than a general shafting system. An initial design was carried out to install a CRP system for the first time in Korea. The purpose of this study is to verify whether the journal bearing meets the classification's design criteria through a bearing reaction force analysis for the classification's approval of the initial design. It is ideal for the thrust of the propeller to act on the center of the shaft, but thrust eccentricity occurs due to the uneven wake caused by the stern shape. Load conditions were applied while considering thrust eccentricity to perform the shaft analysis, and the results were compared with the classification's criteria.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.67-76
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• 2020

This paper reports an experimental study to evaluate the flexural behavior of concrete beams reinforced using Fe based shape memory alloy (Fe-SMA) bars. For the experiment, a concrete beam of 200mm×300mm×2,200mm was produced, and a 4% pre-strained Fe-SMA bar was used as a tensile reinforcement. As experimental variables, type of tensile reinforcement (SD400, Fe-SMA), reinforcement ratio (0.2, 0.39, 0.59, 0.78), activation of Fe-SMA (activation, non-activation), and joint method of Fe-SMA bar (Continuous, welding, coupler) were considered. The electric resistance heating method was used to activate the Fe-SMA bar, and a current of 5A/㎟ was supplied until the specimen reached 160℃. After the upward displacement of the specimen due to the camber effect was stabilized, a three-point flexural loading experiment was performed using an actuator of 2,000 kN capacity. As a result of the experiment, it was found that the upward displacement occurred due to the camber effect as the Fe-SMA bar was activated. The specimen that activated the Fe-SMA bar had an initial crack at a higher load than the specimen that did not activate it. However, as with general prestressed concrete, the effect of the prestress by Fe-SMA activation on the ultimate state of the beam was insignificant.

• Journal of the Korean Geotechnical Society
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• v.22 no.1
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• pp.35-44
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• 2006

In general typically granular soils contain a certain amount of fines. It is also widely recognized that foundation soils under working loads show highly non-linear behavior from very early stages of loading. In the present study, a series of laboratory tests with sands of different silt contents are conducted and methods to assess strength and stiffiness characteristics are proposed. Modified hyperbolic stress-strain model is used to analyze non-linearity of silty sands in terms of non-linear Degradation parameters f and g as a function of silt contents and Relative density Dr. Stress-strain curves were obtained from a series of triaxial tests on sands containing different amounts of silt. Initial shear modulus, which is used to normalize Degradation modulus of silty sands, was determined from resonant column test results. From the laboratory test results, it was observed that, as the Relative density increases, values of f decrease and those of g increase. In addition, it was found that values of f and g increase and decrease respectively as a Skeleton void ratio $(e_{sk})$ increases.

• Korean Journal of Materials Research
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• v.3 no.1
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• pp.84-94
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• 1993

This paper deals with the fatigue properties of chopped strand glass mat/polyester composite to understand the effect of water absorption on fatigue behavior of GFRP. The fatigue crack in the both no water and a water absorption materials initiated at the initial of cycle. Thereafter, it was divided with two regions that one decreased with the crack extension and the other increased with the crack extension. The absorption of distilled water degrades the bond strength between fiber and matrix, there, by the tendency of fiber pull-out is increased in perpendicular to crack growth deirection and the debonding of fibers increased to the place which is parallel to crack growth direction. Therefore, the reduction of fatigue strength was caused by these factors.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.25-34
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• 2013

The purpose of the this paper is experimentally to investigate flexural behavior of slabs with suspending the deck plate. The main experimental parameters are the depth and thickness of the deck plate, slab span, rebar and support conditions. Total number of six specimens were tested and manufactured in slabs under vertical load. Based on the results of the test, the flexural behavior for slabs is determined according to the vertical deformation of the slabs, regardless of the main experimental parameters. Bending rebar reinforcement in the rib cross-section specimens can be evaluated significantly higher initial stiffness, crack stiffness and flexural strength. Result of the comparison of the theory value appeared to be fairly well matched to average 1.05.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.199-206
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• 2005

In many other countries framed structures with inadequate lateral strength and stiffness have been strengthened by providing reinforced concrete infilled wall. There is a general agreement among researchers those infilled walls have 3-5times greater lateral strength compared with bare frame. The main objective of this research is to investigate the behavior and strength of reinforced concrete frames infilled with concrete block and cast-in-place reinforced concrete panels used for strengthening the structure against seismic action. For this purpose three 1/3 scale, one-bay, one-story reinforced concrete infilled frames were tested under reversed cyclic loading simulating the seismic effect. The results indicate that infilled walls increase both strength and stiffness significantly under lateral loads. Especially Strength capacity and initial stiffness of CIP infilled wall increased 3.8 times and 6.6 times higher than lightly reinforced concrete frame.

• Journal of the Korean GEO-environmental Society
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• v.8 no.2
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• pp.29-39
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• 2007

In this study, the centrifugal tests were fulfilled to analyze the displacement characteristics caused by the embankment construction on soft ground. Embankment of height, undrained shear strength and with or without geotextile were selected to evaluate the displacement characteristics of soft ground by embankment. As a result, the replacement section without geotextile showed the parabola shape. The replacement section with geotextile showed the trapezoidal shape which represents the uniform settlements. The replacement angle is increasing nearly lineally with increasing the height of embankment and G-level. The position, where the maximum horizontal displacement occurred, was between $0.24H_0$ and $0.35H_0$ and was at $0.3H_0$ on the average. In the case of with and without geotextile, the relationship between the maximum settlement of ground(S) and maximum horizontal displacement(${\delta}_m$) was ${\delta}_m$ = 0.60S, ${\delta}_m$ = 0.54S, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.3
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• pp.347-353
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• 2012

Recently, multi-functionalization (as in smart phones) has been in demand, and the connectors connecting the electrical signals of each board in a cellular phone have become key components. The miniaturization of these connectors is required to achieve a finer pitch design and enhance the electrical signal transfer capacity. However, the miniaturization of connectors reduces the structural safety, and a finer pitch design may cause contact problems under external impact. In this paper, a preliminary design for miniaturized, finer-pitch connectors is suggested for a product with 50 pins and a thickness of 0.2 mm. The assembly process of the FPCB (Flexible Printed Circuit Board) and connector was simulated to ensure the holding force between the two components and avoid overstressing. The design optimization process was performed with the Taguchi method. Fatigue analysis was also conducted to predict the fatigue life of the terminal, and the theoretical and experimental results were compared.