• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.727-734
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• 2007

The influence of the differences in the physical and mechanical properties between fiber-reinforced polymer (FRP) and conventional steel, concentrated reinforcement in the immediate column region, as well as using steel fiber-reinforced concrete (SFRC) in the slab near the column faces, on the punching behavior of two-way slabs were investigated. The punching shear capacity, stiffness, ductility, strain distribution, and crack control were investigated. Concentrating of the slab reinforcement and the use of SFRC in the slab enhanced the punching behavior of the slabs reinforced with glass fiber-reinforced polymer (GFRP) bars. In addition the test results of the slabs with concentrated reinforcement were compared with various code equations and the predictions proposed in the literature specifically for FRP-reinforced slabs. An appropriate method for determining the reinforcement ratio of slabs with a banded distribution was also investigated to allow predictions to properly reflect the benefit of the slab reinforcement concentration.

• Journal of the Korean Society of Safety
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• v.29 no.6
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• pp.9-14
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• 2014

Recently many efforts and researches have been done to cope with industrial facilities that require a low energy machines due to the gradual depletion of the natural resources. The fiber-reinforced composite materials in general have good properties and have the proper mechanical properties according to the change of the ply sequences and fiber distribution types. However, in the fiber-reinforced composite material, there are several problems, including fiber breaking, peeling, layer lamination, fiber cracking that can not be seen from the metallic material. Particularly, the fracture and delamination are likely to be affected by the thickness of the stacking laminates when the bi-material laminated structure is subjected to a load of the mixed mode. In this study, we investigated the effect of the thickness ratio of the difference in the CFRP/GFRP bi-material laminate composites by measuring the cracking behavior and the AE characteristics in a mixed mode loading, which may be generated in the actual structure. The results show that the thickness of the CFRP becomes more thick, the mode I energy release rate becomes a larger, and also the influence of mode I is greater than that of mode II. In addition, AE amplitude which shows the level of the damage in the structure was obtained the more damage in the CFRP with the thin thickness.

• Korean Journal of Community Nutrition
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• v.15 no.1
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• pp.27-35
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• 2010

This study was done to investigate the association of blood clinical parameters and dietary intakes with serum adiponectin level. Athropometric measurement, dietary intakes, serum lipids and adiponectin levels were examined in 160 overweight and obese women. The subjects were divided into 5 groups by quintile according to serum adiponectin level. Weight, BMI, waist circumferences and waist/hip ratio of the highest quintile group were significantly lower than those of the lowest quintile group. Serum lipid analysis showed a significant higher level of TG, LDL-cholesterol, LDL/HDL ratio, AI, and serum hs-CRP in the lowest quintile group. Similarly, correlation data also showed that serum adiponectin level was positively correlated with serum HDL-cholesterol level (p < 0.01) and was negatively correlated with BMI (p < 0.01), waist circumferences (p < 0.01), waist/hip ratio (p<0.01), systolic (p < 0.01) and diastolic blood pressure (p < 0.05), TG (p < 0.01), LDL-cholesterol (p < 0.05), LDL/HDL ratio (p < 0.05), AI (p < 0.01), Homa-IR (p < 0.01), hs-CRP (p < 0.05) and leptin (p < 0.05). Dietary intake data showed that protein intake was significantly lower in the highest quintile group compared to the lower quintile groups while intakes of vitamin C was significantly higher in highest quintile group after adjustment by BMI, waist and energy intake, In addition, the highest quintile group had higher fiber intakes than the lower quintile groups. These results might suggest that a diet high in fiber and vitamin C and low in protein for obese patients would better be recommended to improve adiponectin level. However, further research is needed to elucidate the association of dietary intakes or dietary patterns and serum adiponectin level.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.579-584
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• 2001

The reinforced concrete(RC) beam is developed cracks because the compression strength of concrete is strong but the tensile strength is weak. The structural strength and stiffness is decreased by reduction of tension resistance capacity of concrete due to the developed cracks. Using the fiber reinforced concrete that is increased the flexural strength and tensile strength at tensile part can enhance the strength and stiffness of concrete structure and decrease the tensile flexural cracks and deflection. Therefore, The reinforced concrete used the fiber reinforced concrete at tensile part ensure the safety and serviceability of the concrete structures. In this study, analytical model of a dual concrete beam that is composed of the normal strength concrete at compression part and the high tensile strength concrete at tensile part is developed by using the equilibrium condition of forces and compatibility condition of strains and is parted into elastic analytical model and ultimate analytical model. Three group of test beam that is formed of one reinforced concrete beam and two dual concrete beams for each steel reinforcement ratio is tested to examine the flexural behavior of dual concrete beams. The comparative study of total nine test beams is shown that the ultimate load of a dual concrete beams relative to the reinforced concrete beams have an increase in approximately 30%. In addition, the initial flexural rigidity, as used here, refer to the slope of load-deflection curves in elastic state is increased and the deflection is decreased.

• Structural Engineering and Mechanics
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• v.61 no.6
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• pp.711-719
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• 2017

This study investigates the effects of reinforcing bar diameter and cover depth on the shrinkage behavior of restrained ultra-high-performance fiber-reinforced concrete (UHPFRC) slabs. For this, twelve large-sized UHPFRC slabs with three different rebar diameters ($d_b=9.5$, 15.9, and 22.2 mm) and four different cover depths (h=5, 10, 20, and 30 mm) were fabricated. In addition, a large-sized UHPFRC slab without steel rebar was fabricated for evaluating degree of restraint. Test results revealed that the uses of steel rebar with a large diameter, leading to a larger reinforcement ratio, and a low cover depth are unfavorable regarding the restrained shrinkage performance of UHPFRC slabs, since a larger rebar diameter and a lower cover depth result in a higher degree of restraint. The shrinkage strain near the exposed surface was high because of water evaporation. However, below a depth of 18 mm, the shrinkage strain was seldom influenced by the cover depth; this was because of the very dense microstructure of UHPFRC. Finally, owing to their superior tensile strength, all UHPFRC slabs with steel rebars tested in this study showed no shrinkage cracks until 30 days.

• Advances in concrete construction
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• v.6 no.1
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• pp.29-45
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• 2018

This paper investigates the effect of inclusion of glass fibers on mechanical and fracture properties of binary blend geopolymer concrete produced by using fly ash and ground granulated blast furnace slag. To study the effect of glass fibers, the mix design parameters like binder content, alkaline solution/binder ratio, sodium hydroxide concentration and aggregate grading were kept constant. Four different volume fractions (0.1%, 0.2%, 0.3% and 0.4%) and two different lengths (6 mm, 13 mm) of glass fibers were considered in the present study. Three different notch-depth ratios (0.1, 0.2, and 0.3) were considered for determining the fracture properties. The test results indicated that the addition of glass fibers improved the flexural strength, split tensile strength, fracture energy, critical stress intensity factor and critical crack mouth opening displacement of geopolymer concrete. 13 mm fibers are found to be more effective than 6 mm fibers and the optimum dosage of glass fibers was found to be 0.3% (by volume of concrete). The study shows the enormous potential of glass fiber reinforced geopolymer concrete in structural applications.

• Structural Engineering and Mechanics
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• v.27 no.2
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• pp.223-241
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• 2007

Seven full-scale exterior beam-column joints were produced and tested under reversible cyclic loads to determine. Two of these seven specimens were produced using ordinary reinforced concrete (RC). Steel Fiber Reinforced Concrete (SFRC) was placed in three different regions of the beams of the rest five specimens to determine the extent of the region where SFRC is the most effective. The extent of the region of SFRC was kept constant at the columns of all five specimens. Three of these five specimens which had one stirrup in the joint, were tested to evaluate the effect of the stirrup on the behavior of the beam-column joint together with SFRC. In production of the specimens with SFRC, all special requirements of the Turkish Earthquake Code related to the spacing of hoops were disregarded. Previous researches reported in the literature indicate that the fiber type, the volume content, and the aspect ratio of steel fibers affect the behavior of beam-column joints produced with SFRC. The results of the present investigation show that the behavior of exterior beam-column joints depends on the extent of the region where SFRC is used and the usage of stirrup in the joint, in addition to the parameters listed in the literature.

• Journal of the Korean Society of Clothing and Textiles
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• v.38 no.3
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• pp.372-385
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• 2014

Lignin is an abundant natural polymer in the biosphere and second only to cellulose; however, it is under-utilized and considered a waste. In this study, lignin was fabricated into nanofibers via electrospinning. The critical parameters that affected the electrospinnability and morphology of the resulting fibers were examined with the aim to utilize lignin as a resource for a new textile material. Poly(vinyl alcohol) (PVA) was added as a carrier polymer to facilitate the fiber formation of lignin, and the electrospun fibers were deposited on polyester (PET) nonwoven substrate. Eleven lignin/PVA hybrid solutions with a different lignin to PVA mass ratio were prepared and then electrospun to find an optimum concentration. Lignin nano-fibers were electrospun under a variety of conditions such as various feed rates, needle gauges, electric voltage, and tip-to-collector distances in order to find an optimum spinning condition. We found that the optimum concentration for electrospinning was a 5wt% PVA precursor solution upon the addition of lignin with the mass ratio of PVA:lignin=1:5.6. The viscosity of the lignin/PVA hybrid solution was determined as an important parameter that affected the electrospinning process; in addition, the interrelation between the viscosity of hybrid solution and the electrospinnability was examined. The solution viscosity increased with lignin loading, but exhibited a shear thinning behavior beyond a certain concentration that resulted in needle clogging. A steep increase in viscosity was also noted when the electrospun system started to form fibers. Consequently, the viscosity range to produce bead-free lignin nanofibers was revealed. The energy dispersive X-ray analysis confirmed that lignin remained after being transformed into nanofibers. The results indicate the possibility of developing a new fiber material that utilizes biomass with resulting fibers that can be applied to various applications such as filtration to wound dressing.

• Asian-Australasian Journal of Animal Sciences
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• v.5 no.3
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• pp.487-494
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• 1992

This experiment was conducted to study the effect of addition of Lucerne juice (LJ) obtained by mechanical extraction of freshly harvested crop on the nutritive value of rice straw silage. Rice straw (RS) was ensiled with intact, NaOH or $NH_3$ treated LJ at 3:7 ratio on fresh weight basis (LJ RS, LJ NaOH RS and LJ $NH_3$ RS, respectively). Each alkali was mixed with fresh juice at a level of 4% of rice straw dry matter just before ensiling. Rice straw ensiled with water was prepared as the control (W RS). In the digestion trial, goats were allocated in a $4{\times}4$ Latin-square design and fed the diet containing three parts of RS silage and one part of wheat bran (DM basis). For the goats receiving the control silage, urea was supplemented at feeding time so as to adjust the nitrogen intake except for goats on LJ $NH_3$ RS silage. Crude protein content of RS silage was increased from 5.2 to 9.1% (DM basis) by the addition of intact LJ and to about 24% by $NH_3$ treated LJ. The control W RS silage contained only trace amount of lactic acid and was dominated by acetic and butyric acid. The addition of intact LJ reduced butyric acid content and $NH_3-N/TN$ of the silage whereas the addition of alkalized LJ increased those values and shifted to a butyrate type fermentation. Nutrient digestibilities and nitrogen balance of goats were almost the same when they were fed W RS and LJ RS silage indicating the addition of intact LJ did not improve the nutritive value. The addition of alkalized LJ significantly increased the fiber digestibilities of RS silage and $NH_3$ treatment was more effective than NaOH treatment. Postprandial ruminal $NH_3-N$ and blood urea nitrogen (BUN) concentrations were decreased by feeding LJ NaOH RS silage suggesting ruminal protein synthesis was enhanced along with the increase of energy supply for supply for rumen microbes by the alkali treatment. The advantageous fiber digestibilities of LJ $NH_3$ RS silage compared with those of LJ NaOH RS silage might be attributable to a sufficient nitrogen supply for microbial fiber digestion in the rumen.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.3 s.55
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• pp.119-126
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• 2009

This study investigated the fire resistance of RC columns applying Fiber addition method, Fire board attaching method, and Fire proof sparying method. The results were summarized as following. The test showed that increase of fiber content, as expected, decreased the fluidity of fresh concrete, but for the types of fiber, the specimens containing nylon(NY) was favorable. The incline of fiber content also affected on the air content of concrete, which the specimens adding polypropylene(PP) fiber was the lowest, followed by a less decrease in polyvinyl alchhol(PVA) and then NY respectively. For the compressive strength at 28days, it was over 50MPa and showed slight increasing tendency by rising fiber contents. After the fire test completed, control concrete exhibited the severe demage, while the specimens containing more than 0.05vol.% of PP and NY was able to protect from spalling. In the case of splay, the partly spalling occurred at the all finishing material, however the RC columns were protected from spalling. For the methods attached with boards, all RC columns were protected except the dry attaching method. The reduced weight ratio was favorable because it was below 8 % except for plain concrete.