• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.339-347
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• 2002

An in-situ experiment was performed to evaluate the pullout resistance capacity of chains which is used as a reinforcement of reinforced earth wall. It was also considered that chain was combined with a bar or L-type steel angle by the transverse reinforcement member in the experiment. About 80 pullout tests were peformed with varying the lengths of chain(2.0m, 2.5m, and 3.0m), the combination of each transverse members(chain only, chain＋bar, or chain＋angle), and the vertical placement of reinforcements. In the case that uses a chain only and a chain combined with bar, the maximum displacement was about 150mm and load continuously increased to the ultimate tensile strength of chain, and then tension failure of chains occurred. But in the case of a chain combined with angle, the displacement decreased to about 100mm and so it was expected that this combination can constrain the displacement of chain. On the other hand, comparing the yielding pullout load measured in the field to that calculated by theoretical equation, it is shown that measured values are 1.2~3.0 times greater than those of calculated values according to the length of chain, normal vertical stress, and the combination of chain with transverse members. However, the difference in the increment of yielding pullout load between bar and angle is not clear but it appears almost the same increment. It is expected that chain can be safely used as reinforcements of reinforced earth wall, although a theoretical estimation of the pullout resistance capability of chain is too conservative.

• Journal of the Korean Geotechnical Society
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• v.20 no.9
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• pp.167-176
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• 2004

Underground structures will be affected by the additional surcharge loads such as traffic load et al. Terzaghi (1956) suggested the equation on the influences of surcharge loads in vertically backfilled spaces. In field, the shapes of backfill spaces are not always formed vertically. Then the Terzagi (1956) equation is not suitable to use because of boundary condition. This study suggests equation to calculate the stress in backfilled space caused by surcharge loads when the backfilled space is sloped symmetrically. The suggested equation is verified by carbon box test and numerical analysis. The experimental results show good agreement with the suggested equation but the numerical analysis result shows a little disagreement. The differences are estimated to be caused by the fact that ground made by carbon rod has become more dense and internal frction and wall friction has increased itself as surcharge load is added but that this increase can not be considered in the numerical analysis. The suggested equation shows good agreement with Terzaghi (1956) equation in case of sloped backfill ground. According to the results, it is considered that the suggested equation can be applied not only to sloped space but also to vertical space. Further investigation using full scale experiment is needed.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.6
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• pp.679-685
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• 2011

This paper presents an algorithm identifying devices that generate observed mixed signals that are collected at main power-supply line. The proposed algorithm, which is necessary for low cost electric power monitoring system at appliance-level, that is non-intrusive load monitoring system, divides incoming mixed signal into multiple time intervals, calculating difference-signals between consecutive time interval, and identifies which device is operating at the time interval by analysing the difference-signals. Since the features of one device can remain when the time interval is short enough and the features are independent and additive, well-known classification algorithms can be used to classify the difference-signals with features of N individual devices, otherwise $2^N$ features might be necessary. The proposed algorithm was verified using data mixed in a laboratory with individual devices's data collected from field. When maximum 4 devices operate or stop sequentially and when features satisfy the requirements of proposed algorithm, the proposed algorithm resulted nearly 100% success rate under the constrained test condition. In order to apply the proposed algorithm in real world, the number devices shall increase, the time interval shall be smaller and the pattern of mixture shall be more diverse. However we can expect, if features used follow guidelines of proposed algorithm, future system could have certain level of performance without the guideline.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.686-693
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• 2018

Various types of re-bar splicing methods have been developed and applied to reinforced concrete (RC) structures in the field. According to previous studies, the coupler splice is relatively superior to the lap splice in terms of cost efficiency when the diameter or strength of the re-bar is larger or higher. This study was performed to develop a filler type mechanical splice for a high-strength re-bar (SD600) in reinforced concrete structures. The deformed re-bars were inserted into a circular steel tube coupler and high-strength epoxy filler was then injected into the coupler. The splice system was completed by hardened filler in a coupler. The epoxy filler was used as the manufactured production epoxy to conduct experiments of filler type mechanical splice specimens, and to observe the failure loads and failure aspects of the specimens. For this goal, the experiment of one-way tensile test was conducted for the epoxy filler type mechanical splices specimens according to the compressive strength of epoxy, length of coupler, and diameter of re-bar. The shape of failure of the re-bar coupler splice showed that the re-bars were pulled between the lugs of the re-bars as a result of the shear fracture of the hardened epoxy. The actual failure load of the experiment specimen was approximately 2 times higher than the expected failure load of the epoxy filler, which greatly improves the failure load of the hardening epoxy filler due to the restraint of the steel coupler.

• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.13-22
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• 2008

Fourteen calibration ehamber tests were performed using one cylindrical and two tapered piles with different taper angles to investigate the changes of the bearing capacity of tapered piles with soil state and taper angle of piles. The results of calibration chamber tests show that the ultimate base resistance of tapered piles increases with increasing mean stress and relative density of soil. It also increases with increasing taper angle for medium sand, but with decreasing taper angle for dense sand. The ultimate shaft resistance of tapered piles increases as vertical and horizontal stresses, relative density and taper angle increase. Based on the results of model pile load tests, a new design method with shape factors for estimation of the bearing capacity of tapered piles is proposed considering the effect of soil state and taper angle on bearing capacity of tapered piles. In order to check the accuracy of predictions calculated using the new method, middle-scale field pile load tests were also conducted on cylindrical and tapered drilled shafts in clayey sand. Comparison of calculated values with measured ones shows that the new design method produces satisfactory predictions tor tapered piles.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.77-77
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• 2017

Titanium and its alloys offer attractive properties in a variety of applications. These are widely used for the field of biomedical implants because of its good biocompatibility and high corrosion resistance. Titanium anodizing is often used in the metal finishing of products, especially those can be used in the medical devices with dense oxide surface. Based on SAE/AMS (Society of Automotive Engineers/Aerospace Material Specification) 2488D, it has the specification for industrial titanium anodizing that have three different types of titanium anodization as following: Type I is used as a coating for elevated temperature forming; Type II is used as an anti-galling coating without additional lubrication or as a pre-treatment for improving adherence of film lubricants; Type III is used as a treatment to produce a spectrum of surface colours on titanium. In this study, we have focused on Type II anodization for the medical (dental and orthopedic) application, the anodized surface was modified with gray color under alkaline electrolyte. The surface characteristics were analyzed with Focused Ion Beam (FIB), Scanning Electron Microscopy (SEM), surface roughness, Vickers hardness, three point bending test, biocompatibility, and corrosion (potentiodynamic) test. The Ti-6Al-4V alloy was used for specimen, the anodizing procedure was conducted in alkaline solution (NaOH based, pH>13). Applied voltage was range between 20 V to 40 V until the ampere to be zero. As results, the surface characteristics of anodic oxide layer were analyzed with SEM, the dissecting layer was fabricated with FIB method prior to analyze surface. The surface roughness was measured by arithmetic mean deviation of the roughness profile (Ra). The Vickers hardness was obtained with Vickers hardness tester, indentation was repeated for 5 times on each sample, and the three point bending property was verified by yield load values. In order to determine the corrosion resistance for the corrosion rate, the potentiodynamic test was performed for each specimen. The biological safety assessment was analyzed by cytotoxic and pyrogen test. Through FIB feature of anodic surfaces, the thickness of oxide layer was 1.1 um. The surface roughness, Vickers hardness, bending yield, and corrosion resistance of the anodized specimen were shown higher value than those of non-treated specimen. Also we could verify that there was no significant issues from cytotoxicity and pyrogen test.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.87-98
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• 2004

In this study reinforcing effect of soil nailed-drilled shafts subjected to axial and lateral loads was evaluated. Special attention was given to the reinforcing effects of soil nails placed from the drilled shafts to surrounding weathered- and soft-rocks based on model tests, numerical analyses and field tests. The model tests and numerical analyses are conducted to analyze the reinforcing effect of various conditions of number, inclination, position and length. The results of 1/40 scale model tests and numerical analyses show that as the number of reinforcing level increases, the incremental effect of reinforcement tends to increase, whereas the reinforcing effect on relative position is negligible. In addition there is a reinforcing effect as the inclination angle increase up to 30 degrees. Based on the results of tensile load tests, soil nailed-drilled shaft has a considerably smaller settlement to reach the ultimate level compared with the result of un-reinforced drilled shafts. For compression tests, there is a reinforcing effect of about 200% measured.

• Geomechanics and Engineering
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• v.35 no.2
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• pp.195-208
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• 2023

The nodular diaphragm wall (NDW) is a novel type of foundation with favorable engineering characteristics, which has already been utilized in high-rise buildings and high-speed railways. Compared to traditional diaphragm walls, the NDW offers significantly improved vertical bearing capacity due to the presence of nodular parts while reducing construction time and excavation work. Despite its potential, research on the vertical bearing characteristics of NDW requires further study, and the investigation and visualization of its displacement pattern and failure mode are scant. Meanwhile, the measurement of the force component acting on the nodular parts remains challenging. In this paper, the vertical bearing characteristics of NDW are studied in detail through the indoor model test, and the displacement and failure mode of the foundation is analyzed using particle image velocimetry (PIV) technology. The principles and methods for monitoring the force acting on the nodular parts are described in detail. The research results show that the nodular part plays an essential role in the bearing capacity of the NDW, and its maximum load-bearing ratio can reach 30.92%. The existence of the bottom nodular part contributes more to the bearing capacity of the foundation compared to the middle nodular part, and the use of both middle and bottom nodular parts increases the bearing capacity of the foundation by about 9~12% compared to a single nodular part of the NDW. The increase in the number of nodular parts cannot produce a simple superposition effect on the resistance born by the nodular parts since the nodular parts have an insignificant influence on the exertion and distribution of the skin friction of NDW. The existence of the nodular part changes the displacement field of the soil around NDW and increases the displacement influence range of the foundation to a certain extent. For NDWs with three different nodal arrangements, the failure modes of the foundations appear to be local shear failures. Overall, this study provides valuable insights into the performance and behavior of NDWs, which will aid in their effective utilization and further research in the field.

• Women's Health Nursing
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• v.4 no.2
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• pp.173-186
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• 1998

In this study, both the literary survey as well as empirical research has been executed to test the validity of the scales that measure the construct of self-monitoring scale could not be classified into five factors as Snyder suggested. Many other scholars (Briggs, Cheek and Buss, 1980) suggested 3 different classifications which was accepted by Snyder and Gangestad (1986). John, Cheek and Klohnen (1996) claimed a two-factor classification. As has been discussed, factor analysis is used to prove convergent validity within the factor and discriminant validity between the factors. However, depending on the researchers, many variations in classification of the factors were found and a lack of content and discriminant validity was found in the previous research findings. It is also important to note that Snyder's self-monitoring scale, did not factor-load at over 30 for all 25 items, regardless of how many factors could be classified. According to findings of this study, the self-monitoring scale neither classified as five, three or two factors nor factor loaded as hypothesized. It is also clear that Snyder's self-monitoring scale lack convergent validity as the sub-factors of the scale fail to prove its uni-dimensionality. The A self-monitoring scale not only fail to overcome the problems of Snyder's self-monitoring scale but even lost the attractiveness of the self-monitoring scale. In this study, it was also found that the A self-monitoring scale was not classified as hypothesized in either in a two or three-factor classification. It is, of course, not desirable to use any scale that lacks convergent and discriminant validity even though it has been widely used but also has held a great deal of influence on the field of social psychology. To overcome the shortcomings of Snyder's self-monitoring scale, Lennox and Wolfe(1984) suggested 13 items. This study 1. was dedicated to test the validity and reliability of the scale, in which we found that the data presented in validity as the two factors were classified and loaded as expected. Reliability was also proven by checking Cronbach's alpha for each factor and for the total items. In addition, a confirmatory factor analysis was executed for the 13 items using LISREL 8.12 program to confirm convergent validity in a two-factor classification. The model was fitting and sound ; however, the self-monitoring scale was unfitted and not validated. Thus, it is recommended to use not the original or the abbreviated self-monitoring scale but the 13 items in future studies. It should also be noted that items 7 and 13 should be removed to obtain better uni-dimensionality for the 13 items. These items loaded at over .30, too high for the two factors in the test results of factor analysis. In addition, it is necessary to double-check the cause of two-hold loading at over .30 for the two factors. It could be a problem caused by data or by the scale itself. Therefore, additional studies should follow to better clarify this matter.

• Journal of Korean Society of Steel Construction
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• v.21 no.1
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• pp.37-44
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• 2009

A truss deck system that has replaced the slab form conventional method has become widely used in the construction of reinforced concrete structures as well as steel structures. The current commercial products, however, have some problems. The discontinuity between the lattice wires on the joint of the bottom wire induces vierendeel behavior, which increases the deflection of the system. In this research, a new truss deck system with continuous lattice wires on the level of the bottom wire was developed to reduce the system's vierendeel behavior and to improve its deformation capacity. To investigate the system's structural behavior, an experimental test and an analysis were performed. The main parameters of the test and analysis were the longitudinal shape and spacing of the lattices. To simulate the loading condition in the construction field, uniform construction loads were directly applied on the deck plates of the analysis model and the test specimens. The results of such analysis and test revealed that the longitudinal shape of the lattice wires is a major factor affecting the structural behavior of a steel wire truss deck. Thus, continuous lattice wires could result in decreased vierendeel behavior in the steel wire truss deck. It was also found that the truss deck system with lattices spaced longer than in the conventional products could be effectively used without increasing the member stresses.