• Journal of the Korean Geotechnical Society
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• v.23 no.8
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• pp.87-95
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• 2007

This study analyzed ground settlement and ground stress depending on tunnel excavation and the ground reinforcing grouting methods for double line road tunnel through deep weathered zone. Diameter of double line road tunnel was approximately 12m and umbrella arch method and side wall reinforcing grouting were applied. The ring-cut split excavation method and CD-cut excavation method for excavation method were applied. Analyses of failure rate and vertical stress ratio show that the tunnel for which the height of the cover (H) was higher than four times the diameter, can be considered a deep tunnel. Comparisons of various excavation and ground reinforcement methods showed that CD-cut method results in lower surface and crown settlement, and lower failure rate than that obtained by Ring-cut split method. In addition, the side wall reinforcing grouting resulted in reduction of tunnel displacement and settlement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.775-785
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• 2006

This study focused on the development of surface deformations of GFRP rebars with a better bond characteristic for reinforcing concrete, and simultaneously, of GFRP rebars with more simple and economic production process. This research paper describes a development and bond performance of GFRP rebar with molded deformations, which is composed of polymer resin and milled glass fiber. To determine proper mix ration of milled fibers, material test of hardened epoxy and pullout tests of GFRP rebar with various mix ratio were conducted. The test results indicate that the new strategy of using a mixture of epoxy resin and milled fiber could be successfully applied to a surface structure of GFRP rebar to enhance bond with concrete. The bearing resistance of the ribs was further enhanced by the milled fibers at mechanical and environmental loading state.

• Advances in concrete construction
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• v.14 no.3
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• pp.153-167
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• 2022

The interaction between blast load and structures, as well as the interaction among structural members may well affect the structural response and damages. Therefore, it is necessary to analyse more realistic reinforced concrete structures in order to gain an extensive knowledge on the possible structural response under blast load effect. Among all the civilian structures, columns are considered to be the most vulnerable to terrorist threat and hence detailed investigation in the dynamic response of these structures is essential. Therefore, current research examines the effect of blast loads on the reinforced concrete columns via development of Pressure- Impulse (P-I) diagrams. In the finite element analysis, the level of damage on each of the aforementioned RC column will be assessed and the response of the RC columns when subjected to explosive loads will also be identified. Numerical models carried out using LS-DYNA were compared with experimental results. It was shown that the model yields a reliable prediction of damage on all RC columns. Validation study is conducted based on the experimental test to investigate the accuracy of finite element models to represent the behaviour of the models. The blast load application in the current research is determined based on the Lagrangian approach. To develop the designated P-I curves, damage assessment criteria are used based on the residual capacity of column. Intensive investigations are implemented to assess the effect of column dimension, concrete and steel properties and reinforcement ratio on the P-I diagram of RC columns. The produced P-I models can be applied by designers to predict the damage of new columns and to assess existing columns subjected to different blast load conditions.

• Computers and Concrete
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• v.32 no.4
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• pp.351-363
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• 2023

Reducing the self-weight of reinforced concrete structures problem is discussed in this paper by using two types of self-weight reduction, the first is by using lightweight coarse aggregate (crushed brick) and the second is by using styropor block. Experimental and Numerical studies are conducted on (LWAC) lightweight aggregate reinforced concrete slabs, having styropor blocks with various sizes of blocks and the ratio of shear span to the effective depth (a/d). The experimental part included testing eleven lightweight concrete one-way simply supported slabs, comprising three as reference slabs (solid slabs) and eight as styropor block slabs (SBS) with a total reduction in cross-sectional area of (43.3% and 49.7%) were considered. The holes were formed by placing styropor at the ineffective concrete zones in resisting the tensile stresses. The length, width, and thickness of specimen dimensions were 1.1 m, 0.6 m, and 0.12 m respectively, except one specimen had a depth of 85 mm (which has a cross-sectional area equal to styropor block slab with a weight reduction of 49.7%). Two shear spans to effective depth ratios (a/d) of (3.125) for load case (A) and (a/d) of (2) for load case (B), (two-line monotonic loads) are considered. The test results showed under loading cases A and B (using minimum shear reinforcement and the reduction in cross-sectional area of styropor block slab by 29.1%) caused an increase in strength capacity by 60.4% and 54.6 % compared to the lightweight reference slab. Also, the best percentage of reduction in cross-sectional area is found to be 49.7%. Numerically, the computer program named (ANSYS) was used to study the behavior of these reinforced concrete slabs by using the finite element method. The results show acceptable agreement with the experimental test results. The average difference between experimental and numerical results is found to be (11.06%) in ultimate strength and (5.33%) in ultimate deflection.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.1
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• pp.39-48
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• 2024

Plastic greenhouses are simple structures consisting of lightweight materials such as steel pipes and polyvinyl chloride. However, serious damage occurs due to heavy winds and typhoon every year. To prevent a collapse of structural members, the Ministry of Agriculture and Rural Development has distributed plans and specifications for disaster-resistant standards. Despite these efforts, more than 50% of greenhouses still do not satisfy the disaster-resistant standards. Among the greenhouses that do not meet these standards, 85% are single-span greenhouses proposed 20 years ago. Consequently, there is a need to evaluate the safety of wind loads for the single-span greenhouse. Unfortunately, there are no design specifications for the greenhouses under wind loads. Therefore, a Korean design standard (KDS) has been utilized. KDS is defined with reference to wind speeds occurring once every 500 years, raising concerns about potential overdesign when considering the durability of plastic greenhouses. To address this, the modified wind load, considering the durability of the plastic greenhouse, was calculated, and a safety evaluation was conducted for sigle G-type plastic greenhouse. It was observed that the moment acting on the windward surface was substantial, and there was a risk of the foundation being pulled out if the basic wind speed exceeded 32 m/s. In terms of the combination strength ratio, it was less than 1.0 only on the leeward side when the basic wind speed was 24 m/s and 26 m/s. However, in all other cases, it exceeded 1.0, indicating an unsafe condition and highlighting the necessity for reinforcement.

• Journal of the Korean Geotechnical Society
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• v.40 no.2
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• pp.41-53
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• 2024

Micropiles are small, cast-in-place piles with a diameter of 300 mm or less, primarily used to reinforce existing structures and support new constructions. As the application of these piles has expanded, extensive research has been conducted on their bearing characteristics, particularly in micropiled rafts. These studies have consistently demonstrated the positive impact of micropiles on foundation reinforcement. However, previous research often overlooked the potential variations in behavior between micropiled and conventional piled rafts based on different pile conditions. Furthermore, the influence of the cohesive characteristics of the soil layer beneath the foundation on the reinforcing effect of the micropiles has not been adequately addressed. This study, therefore, undertook 3D numerical analysis to assess the reinforcing effect of micropiles, considering both pile conditions and the cohesive characteristics of the soil layer beneath the foundation. The findings revealed that micropiles are significantly more effective in non-cohesive soil layers compared to cohesive ones, with the potential to increase the bearing capacity of the raft by up to 3.7 times.

• Steel and Composite Structures
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• v.51 no.3
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• pp.243-260
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• 2024

Thirteen self-compacting recycled concrete filled aluminium tubular (SCRCFAT) columns were tested under concentric compression loads. The effects of the replacement ratio of the recycled concrete aggregate (RCA) and steel fibre (SF) reinforcement on the structural performance of the SCRCFAT columns were studied. A control specimen (C000) was cast with normal concrete without SF to be reference for comparison. Twelve columns were cast using RCA, six columns were cast using concrete incorporating 2% SF while the rest of columns were cast without SF. Failure mode, ductility, ultimate load capacity, axial deformation, ultimate strains, stress-strain response, and stiffness of the SCRCFAT columns were studied. The results showed that, the peak load of tested SCRCFAT columns incorporating 5-100 % RCA without SF reduced by 2.33-11.28 % compared to that of C000. Conversely, the peak load of tested SCRCFAT columns incorporating 5-100% RCA in addition to 2% SF increased by 21.1-40.25%, compared to C000. Consequently, the ultimate axial deformation (Δ) of column C100 (RCA=100% and SF 0%) increased by about 118.9 % compared to C000. The addition of 2% SF to the concrete mix decreased the axial deformation of SCRCFAT columns compared to those cast with 0% SF. Moreover, the stiffness of the columns cast without SF decreased as the RCA % increased. In contrast, the columns stiffness cast with 2% SF increased by 26.28-89.7 % over that of C000. Finally, a theoretical model was proposed to predict the ultimate loads tested SCRCFAT columns and the obtained theoretical results agreed well with the experimental results.

• Journal of the Korean Geosynthetics Society
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• v.23 no.2
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• pp.29-42
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• 2024

The 2017 Pohang earthquake caused damage to quay structures due to liquefaction. Liquefaction occurs when effective stress is lost due to an increase in excess pore water pressure during an earthquake. As a result, the damage caused to the pier-type quay wall was identified and the damage caused by liquefaction was analyzed. In addition, in the case of improved ground, damage occurred due to liquefaction of the lower sand layer due to the difference in stiffness from the soft rock layer, so additional numerical analysis was performed assuming non-liquefaction ground. There are several factors that affect the increase in excess pore water pressure ratio, such as the relative density of the ground and the magnitude of the input seismic acceleration. Therefore, this study performed numerical analysis for Cases 1 to 3 by increasing the magnitude of the input acceleration, and in the case of improved ground, damage occurred due to liquefaction of the lower sand layer, so the analysis was performed assuming non-liquefaction ground. As a result, the improved ground requires additional reinforcement when there is liquefied ground below, and the horizontal displacement of the pier-type quay piles was reduced by about two times.

• Journal of Korean Medicine Rehabilitation
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• v.15 no.1
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• pp.109-126
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• 2005

Objectives : This study is to examine the influence of exorcise program to body shape and body composition of women. Exercise program is composed muscular resistance exercise and aerobic exorcise with 70min/time, 5day/week for 4weeks and designed for the reinforcement of muscular strength and the decease the decrease of obesity. Methods : The subjects of this study are 26 females who are from twenty until thirty-nine years old and are divided into two groups according to Obese Rate. normal weight group is 18 females under a BMI of 23 and overweight group is 8 females over a BMI of 23. we measured body compositon and body shape with body composition analyzer(inbody 3.0) measured body compositions are body weight, Lean body mass, base metabolic rate, body fat, %body fat, waist hip ratio, body mass index. measured 6body shade are upper arm circumference, chest circumference, waist circumference, hip circumference, thigh circumference. the measurements had been taken before exercise of each group, after 4 weeks, after 8 weeks, after 12 weeks. Body compositon and body shape of the measured data were analyzed by two-way repeated ANOVA followed by Dunnett's Post hoc test using SPSS. Differences were considered significant at p<0.05. Results and Conclusions : The weight was reduced at a significant level in overweight group after 4 weeks. Body fat percent was reduced at a significant level in normal group alter 4 weeks and overweight group after 8 weeks. Waist-hip ratio was reduced at a significant level in normal and overweight group after 4 weeks. Lean body mass and body metabolic rate were reduced but did not satisfy statistical significance. Circumference of all body parts showed an decrease after 12 weeks exercise program. Upper Arm, Chest, Waist, Hip Circumference were reduced at a significant level in overweight group after 4 weeks, but In normal group only Waist Circumference was reduced at a significant level after 4 weeks. Aerobic and Circuit weight training for 12 weeks reduced body weight and body fat percent, waist circumstance statistically significant without loss of lean body mass and body metabolic rate. Also these change was more effective in overweight group than in normal group.

• Journal of Ginseng Research
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• v.27 no.3
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• pp.110-114
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• 2003

Objective; Antistress effect of Korean red ginseng (RG) on postmenopausal women with severe climacteric syndrome (CS) were evaluated from the viewpoint of traditional KAMPO-medicine and Western medicine. Methods; All patients with CS were treated with daily oral administration of 6g RG for 30 days. Nine patients with CS were evaluated with the use of diagnostic scores for KI-deficiency (deficiency of vital energy) and OKETSU (blood stagnation) syndrome from the viewpoint of KAMPO-medicine. In the same patients with CS, peripheral blood levels of ${\beta}$-endorphin and total plasminogen activator inhibitor-1 (t-PAI-1) were measured before and after treatment with RG. In another group, 12 patients with CS, psychological test using CMI, STAI and SDS were performed from the viewpoint of Western medicine. Stress related hormones, such as ACTH, cortisol and DHEA-S in those 12 patients with CS were also measured before and after treatment with RG. Results; KI-deficiency score and OKETSU score in patients with CS were significantly (p<0.001) higher than those in patients without CS. After treatment with RG, both scores were markedly (p<0.001) decreased compared to before treatment with RG. ${\beta}$-endorphin levels in patients with CS were significantly (p<0.05) higher than those in patients without CS. Total PAI-levels in patients with CS were increased before treatment with RG. No significant difference, however, were observed between patients with and without CS. After treatment with RG, both levels of ${\beta}$-endorphin and total PAI-1 in patients with CS were significantly (p<0.001 and p<0.05, respectively) decreased compared to before treatment with RG. CMI and STAI scores in patients with CS were significantly (p<0.05) higher than those in patients without CS. SDS scores in patients with CS were also markedly (p<0.00l) higher than in those without CS. After treatment with RG, all scores decreased within normal range. DHEA-S levels in patients with CS were about a half of those without CS. Consequently, cortisol/DHEA-S (C/D) ratio was significantly(p<0.001) higher in patients with CS than in those without CS. Although the decreased DHEA-S levels were not restored to the levels in patients without CS, the C/D ratio decreased significantly (p<0.05) after treatment with RG. Conclusion; Reinforcement of vital energy and improvement of stagnant blood circulations by oral administration of RG were elucidated from the viewpoint of traditional KAMPO-medicine. From the viewpoint of Western medicine, effect of RG on postmenopsusal women with CS seemed to be brought about in part by not only an improvement of psychoneuroendocrine dysfunctions but also an amelioration of blood coagulation systems.