• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.365-373
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• 2008

Fiber Reinforced Polymer, FRP has a light weight, a high tensile strength based on design, non-electronic, non-magnetic, and rust-resistant feature, etc and many researches are being conducted recently on FRP in the construction area. Among them, GFRP (Glass Fiber Reinforced Polymer) is excellent in price competitiveness and is widely being used. However, since GFRP has a relative low modulus of elasticity and causes excessive deflection, the section must be large to be used as a structural component and an investigative review must be carried out in design to set the limit for deflection by the use load. Therefore, in order to solve the mentioned technical problems, this study suggested a section of a module form such that application of a large-scale section is possible. Also, to secure the low rigidity of FRP, this study developed a new FRP+ concrete composite girder form that confined the concrete. To identify the structural movement of the developed FRP+ concrete composite girder, shear strength test was carried out.

• Composites Research
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• v.29 no.6
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• pp.328-335
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• 2016

The purpose of this study is to develop fiber reinforced cement matrix composite (ECC) produced with limestone powder in order to achieve high ductility of the composite, and to evaluate flexural performance of structural members made with ECC. Four kinds of mixture proportions were determined on the basis of the micromechanics and a steady state cracking theory considering the matrix fracture toughness and fiber-matrix interfacial characteristics. The mechanical properties of ECC, represented by strain-hardening behavior in uniaxial tension, were investigated. Also, strength property of the composite was experimentally evaluated. Two structural members made with ECC were produced and tested. Test results were compared with those of conventional concrete structural members. Increased limestone powder contents of ECC provides higher ductility of the composites while generally resulting in a lower strength property. ECC structural members exhibited higher flexural ductility, higher flexural load-carrying capacity and tighter crack width compared to conventional structural members.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.35-43
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• 2012

In general, load carrying capacity, one of the load & resistance capacities in bridges, has more margins than the load carrying capacity evaluated with theoretical methods, unless there are severe damages, defects or material deterioration phenomena that can have a great impact on the behavior of bridges. However, errors have been already included in the current processes of loading tests and structural analysis for measuring load carrying capacity, thus devaluing the reliability of response adjustment factor. Therefore, this study found out the problems of existing electric resistance strain and displacement sensors in sensor suite to solve the problems with sensors and the errors in the appropriateness of structural analysis model, thereby leading to the changes into an optical fiber smart sensor with excellent performance. Besides, the study attempted to ensure the accuracy of response adjustment factor by selecting the optimal models through the interpretation of various structural analysis models.

• Korean Journal of Human Ecology
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• v.18 no.1
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• pp.137-143
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• 2009

The purpose of this study is to examine the evaluation of texture image and preference according to the structural characteristics of silk fabric, and to analyze the effects of texture image and sensibility on the preference. 53 female subjects evaluated fabric image and sensibility of 17 specimens of white silk fabrics sold on the market with semantic differential scale. The data were analyzed through factor analysis, Pearson correlational coefficient and t-test using SPSS win 13.0. For the evaluation, structural characteristics such as fiber contents, weave type, weight and thickness were analyzed. Factor analysis showed that sensibilities were classified into 3 categories; 'surface property', 'weight', 'flexibility'. Fabric images were classified into 2 categories; 'elegance' and 'naturalness'. Statistically significant differences of structural characteristics on the texture image were observed. Weave type affected 'surface property' and fiber contents affected' flexibility'. Weight and weave type affected' elegance', too. The significant factors affecting preference were fabric image of 'elegance' and structural characteristics of 'weave type'. The results of this study showed that the most preferred silk fabric is smooth and soft satin weaved fabric with texture image of 'elegance'.

• Structural Engineering and Mechanics
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• v.20 no.5
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• pp.589-608
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• 2005

There is a growing need for the development and implementation of new methods for the rapid and cost-effective rehabilitation of deteriorating steel structural components to offset the drawbacks related to welding and/or bolting in the field. Carbon fiber reinforced polymer (CFRP) composites provide a potential alternative as externally bonded patches for strengthening and repair of metallic structural members for building and bridge systems. This paper describes results of an investigation of tensile and fatigue response of steel/CFRP joints simulating scenarios of strengthening and crack-patching. It is shown that appropriately designed schemes, even when fabricated with levels of inaccuracy as could be expected in the field, can provide significant strain relief and load transfer capability. A simplified elasto-plastic closed form solution for stress analysis is presented, and validated experimentally. It is shown that the bond development length remains constant in the linear range, whereas it increases as the adhesive is deformed plastically. Fatigue resistance is shown to be at least comparable with the requirements for welded cover plates without attendant decreases in stiffness and strength.

• Journal of the Korea Concrete Institute
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• v.26 no.6
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• pp.771-778
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• 2014

This paper concerns the flexural behavior of hybrid steel fiber-reinforced ultra high performance concrete (UHPC) beams. It presents experimental research results of hybrid steel fiber-reinforced UHPC with steel fiber content of 1.5% by volume and steel reinforcement ratio of less than 0.02. This study aims at providing realistic information about UHPC beams in bending in order to establish a reasonable prediction model for flexural resistance in structural code in the future. The experimental results show that hybrid steel fiber-reinforced UHPC is in favor of cracking resistance and ductility of beams. The ductility indices range through 9.2 to 15.2, which means high ductility of UHPC. Also, the flexural capacity of beam which contains stirrups in pure bending zone is similar to that of beam which does not contain stirrups in pure bending zone. This result represents that the flexural capacity is not affected by the presence of stirrups whose spacing is 150 mm in bending zone.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.5
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• pp.25-34
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• 2012

It has been well known that concrete structures exposed to acid and sulfate environments such as sewer etc. show significant decrease in their durability due to chemical attack. Such deleterious acid and sulfate attacks lead to expansion and cracking in concrete, and thus, eventually result in damage to cement mortar by forming expansive hydration products due to the reaction between cement hydration products and acid and sulfate ions. In this study, the effect of fly ash and blast furnace slag on the bond performances of structural synthetic fiber in latex modified cement mortar under sulfate environments. Fly ash and blast furnace slag contents ranging from 0 % to 20 % are used in the mix proportions. The latex modified cement mortar specimens were immersed in fresh water, 8 % sodium sulfate ($Na_2SO_4$) solutions for 28 and 50 days, respectively. Pullout tests are conducted to measure the bond performance of structural synthetic fiber from latex modified cement mortar after sulfate environments exposure. Test results are found that the incorporation of fly ash and blast furnace slag can effectively enhance the PVA fiber-latex modified cement mortar interfacial bond properties (bond behavior, bond strength and interface toughness) after sulfate environments exposure. The microstructural observation confirms the findings on the interface bond mechanism drawn from the fiber pullout test results under sulfate environments.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.152-163
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• 2019

In this paper, effect of steel fiber inclusion, compressive strength of matrix, shear reinforcement and shear span to depth ratio on the flexural behavior of UHPFRC(Ultra High Performance Fiber Reinforced Concrete) were investigated with test of 10-UHPFRC beam specimens. All test specimens were subjected to the flexural static loading. It was shown that steel fiber significantly improve the shear strength of UHPFRC beams. 2% volume fraction of steel fiber change the mode of failure from shear failure to flexural failure and delayed the failure of compressive strut with comparatively short shear span to depth ratio. UHPFRC beams without steel fiber had a 45-degree crack angle and fiber reinforced one had lower crack angle. Shear reinforcement contribution on shear strength of beams can be calculated by 45-degree truss model with acceptable conservatism. Using test results, French and Korean UHPFRC design recommendations were evaluated. French recommendation have shown conservative results on flexural behavior but Korean recommendation have shown overestimation for flexural strength. Both recommendations have shown the conservatism on the flexural ductility and shear strength either.

• International Journal of Highway Engineering
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• v.19 no.5
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• pp.43-48
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• 2017

PURPOSES : The purpose of this study is to verify the effects of fiber grid reinforcement on the thickness reduction of asphalt pavement. Test sections were constructed on the national highway to evaluate the structural capacity of asphalt pavement with the reinforced fiber grid and normal asphalt pavement. METHODS : Falling Weight Deflectometer (FWD) tests were performed to measure the structural capacity of test sections. The loads of the FWD test are 4.1 ton, 8.0 ton, 10.0 ton, and loaded twice, respectively. The test sections consist of a reference asphalt pavement section, an asphalt pavement section reduced with a 5-cm base layer thickness, and a fiber grid reinforced asphalt pavement section reduced with a 5-cm base layer thickness. In addition, strain data was collected using strain gauges installed in the test sections. RESULTS : The results of the FWD tests showed that the deflections of the pavement section reinforced with the fiber grid was reduced by about 14% compared with that of the reference asphalt pavement section. The strain at the bottom of the asphalt surface layer of the pavement section reduced to a 5-cm base thickness and reinforced with a fiber grid was similar to that at the bottom of the asphalt layer of the reference asphalt pavement. CONCLUSIONS : The results of the FWD and strain tests showed the possibility of the pavement thickness reduction by reinforcement with a fiber grid.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.106-113
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• 2013

One of feasible non-destructivity test methods for evaluation of concrete permeability is the measurement of surface resistivity. But the application to steel fiber-reinforced concrete has been limited because mis-evaluation could be caused by the steel fibers in concrete. In this study, the effect of fiber distribution on surface electrical resistivity of steel fiber-reinforced concrete was investigated through experimental program. Resistivity was measured three times on four surfaces in three rectangular and circular specimens with 0.5%, 1% and 1.5% steel fibers by volume and compared each other. The results obtained from circular specimens were consistent compared to those from rectangular specimens. And the results demonstrated that the effect of fiber distribution on surface resistivity was not significant compared to that of mixing ratio of steel fibers. In conclusion, this non-destructive testing method using measurement of surface resistivity could be used for SFRC within 0.5% steel fibers by volume.