• International Journal of Concrete Structures and Materials
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• v.7 no.1
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• pp.35-50
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• 2013

Rapid and effective repair methods are desired to enable quick reopening of damaged bridges after an earthquake occurs, especially for those bridges that are critical for emergency response and other essential functions. This paper presents results of tests conducted as a proof-of-concept in the effectiveness of a proposed method using externally bonded carbon fiber reinforced polymer (CFRP) composites to rapidly repair severely damaged RC columns with different damage conditions. The experimental work included five large-scale severely damaged square RC columns with the same geometry and material properties but with different damage conditions due to different loading combinations of bending, shear, and torsion in the previous tests. Over a three-day period, each column was repaired and retested under the same loading combination as the corresponding original column. Quickset repair mortar was used to replace the removed loose concrete. Without any treatment to damaged reinforcing bars, longitudinal and transverse CFRP sheets were externally bonded to the prepared surface to restore the column strength. Measured data were analyzed to investigate the performance of the repaired columns compared to the corresponding original column responses. It was concluded that the technique can be successful for severely damaged columns with damage to the concrete and transverse reinforcement. For severely damaged columns with damaged longitudinal reinforcement, the technique was found to be successful if the damaged longitudinal reinforcement is able to provide tensile resistance, or if the damage is located at a section where longitudinal CFRP strength can be developed.

• Composites Research
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• v.27 no.2
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• pp.77-81
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• 2014

In this study, it was performed damage assessment and repair of small scale aircraft adopted on composite. This aircraft adopted the sandwich structure to skin of wing. This study aims to investigate the residual strength of sandwich composites with nomex honeycomb core and carbon fiber face sheets after the open hole damage by the experimental investigation. The 4-point bending tests were used to find the bending strength, and the open hole was applied to introduce the simulated damage on the specimen. The bending strength test results after open hole were compared with the results of no damaged specimen test. In addition, The damaged composite structure was repaired using external patch repair method after removing damaged area. After that, this study presents comparison results of the experimental investigation between the damaged and the repaired specimen. It was found that the bending strength of repaired specimen was recovered up to 95% of undamaged specimen.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3
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• pp.388-393
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• 2013

Carbon fiber reinforced plastic (CFRP) has many desirable qualities, including being lightweight and very strong. These characteristics have led to its use in applications ranging from small consumer products to vehicles. Circular and square CFRP members were fabricated using 8ply unidirectional prepreg sheets stacked at different angles ($[+15^{\circ}/-15^{\circ}]_4$, $[+45^{\circ}/-45^{\circ}]_4$ and $[90]_8$, where $0^{\circ}$ coincides with the axis of the member). Based on the collapse characteristics of a CFRP circular member, the collapse characteristics and energy absorption capability were analyzed. Impact collapse tests were carried out for each section member. In this study, the impact energies at crossheads speeds of 5.52 m/s, 5.14 m/s and 4.57 m/s were 611.52 J, 529.2 J and 419.44 J (circular member) 2.16 m/s, 1.85 m/s and 1.67 m/s are 372.4 J, 274.4 J and 223.44 J (square member). The purpose is to experimentally examine the absorption behavior and evaluation the strength in relation to changes in the stacking configuration when the CFRP circular members with different stacking configurations were exposed to various impact velocities. In addition, the dynamic characteristics were considered.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.2
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• pp.146-151
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• 2014

Objectives: Chrysotile is mineralogically distinct from amphiboles, displaying a notably different chemical structure. The thin sheets that form chrysotile fiber lead to the ability of the lung/macrophage system to decompose the chrysotile fibers. This study was performed in order to compare the physicochemical characteristics of Korean asbestos with those of Canadian amphiboles. Materials: An acid solubility test for each test substance was done to compare pH 4.5 and pH 1.2 distilled water. Asbestos fibers which had been placed in acid solutions for five days, five weeks and weeks were analyzed with a transmission electron microscope equipped with an energy dispersive X-ray spectrometer (TEM-EDS). Results: The composition element (Mg) of Korean chrysotile, Korean anthophyllite and Canadian amosite significantly decreased from 5 days and also decreased significantly after 5 weeks and 10 weeks. Only the composition (Mg) of Canadian crocidolite did not change under any conditions. From 5 days, the Mg of Korean chrysotile, Korean anthophyllite and Canadian amosite were significantly lower than before the acid treatment, but there were no changes over time or by the pH of the acid solutions. Particularly after 10 weeks, the composition (Mg) of Korean chrysotile in the pH 1.2 acid solution showed a rapid reduction of 15.86%. Conclusions: Korean chrysotile was very weak in an acid environment, beginning to show significant changes after 5 days. The Mg component rapidly decreased after 10 weeks in the pH 1.2 acid solution.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.180-189
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• 2002

The objective of this experimental research is to assess the seismic performance of circular RC bridge pier specimens retrofitted with fibers which were designed as a prototype of Hagal bridge in the city of Suwon, Korea. Pseudo dynamic test has been done for four(4) test specimens which were nonseismically or seismically designed by the related provisions of the Korea roadway bridge design specification, and four nonseisemic test specimens retrofitted with fibers in the plastic hinge region. Glass and carbon fiber sheets were used for the seismic capacity enhancement of circular test specimens. Important test parameters were confinement steel ratio, load pattern, and retrofitting. The seismic behavior has been analyzed through the displacement ductility, energy analysis, and capacity spectrum. Approximate 7.7 ∼8.7 displacement ductility was observed for nonseismic test specimens retrofitted with fibers subjected to Korea Highway Cooperation artificial earthquake motions. It is concluded that these retrofitted test specimens could have sufficient seismic capacity in the region of moderate seismic zone.

• Membrane Journal
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• v.28 no.4
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• pp.271-278
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• 2018

In this study, the carbon electrodes using activated carbon fibers (ACFs) were prepared for the capacitive deionization process. The Polyvinylidene fluoride (PVDF) was used as the binder and the mixed ACFs with proper solvent was cast on the commercial graphite sheets to prepare the carbon electrodes. At this moment, the different particle sizes of ACFs were applied and the mixing ratio of solvent, PVDF and ACFs, 80 : 2 : 18 and 80 : 5 : 15, were used for the electrode preparation. Then their salt removal efficiencies were characterized under the various operating conditions, adsorption potential and time, desorption potential and time, concentration of feed NaCl solution and flow rate as well. Typically, the salt removal efficiency of 53.6% were obtained at the particle size below $32{\mu}m$, mixing ratio 80 : 2 : 18, adsorption 1.2 V and 3 min, desorption -0.1V and 1 min, and 15 mL/min flow rate of NaCl 100 mg/L.

• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.787-793
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• 1996

In this paper, to investigate the effect of the offset ink formulation on deinking of Korean old newspaper, the samples printed with five different types of offset ink were aged naturally for 10, 30, 90, 180 days, and then yield, brightness, fiber length, physical properties(tensile, tear, burst index) were evaluated according to aging time. As the aging time increased, the yield and brightness of respective samples decreased. Particially, as the addition amounts of linseed oil increased, those of samples decreased. Therefore, linseed oil is thought to reduce the deinkability of ink. Also, containing rosin-modified phenolic resin and gilsonite seem to reduce brightness of samples according aging time. In physical properties, tensile index and burst index were roughly decreased, but tear index was increased according to aging time. However, the three indexes of the sample containing only linseed oil as the vehicle component were considerably reduced in comparison with those of other samples, as once crosslinked a strong bond between the ink and fibers was produced and made it difficult to defibrate in producing sheets.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.327-341
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• 2017

Openings in slabs are usually required for many different applications such as aeriation ducts and air conditioning. Opening in concrete slabs due to cutouts significantly decrease the member stiffness. There are different techniques to strengthen slabs with opening cutouts. This study presents experimental and numerical investigations on the use of Carbon Fiber Reinforced Polymers (CFRP) as strengthening material to strengthen and restore the load carrying capacity of R.C. slabs after having cutout in the hogging moment region. The experimental program consisted of testing five (oneway spanning R.C. flat slabs) with overhang. All slabs were prismatic, rectangular in cross-section and nominally 2000 mm long, 1000 mm width, and 100 mm thickness with a clear span (distance between supports) of 1200 mm and the overhang length is 700 mm. All slabs were loaded up to 30 kN (45% of ultimate load for reference slab, before yielding of the longitudinal reinforcement), then the load was kept constant during cutting concrete and steel bars (producing cut out). After that operation, slabs were loaded till failure. An analytical study using finite element analysis (FEA) is performed using the commercial software ANSYS. The FEA has been validated and calibrated using the experimental results. The FE model was found to be in a good agreement with the experimental results. The investigated key parameters were slab aspect ratio for the opening ratios of [1:1, 2:1], CFRP layers and the laminates widths, positions for cutouts and the CFRP configurations around cutouts.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.29-32
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• 2008

The renewal of existing buildings rather than new construction has increased due to it's cost effective characteristics. Remodeling is also an environmentally-friendly approach that reduces the amount of waste in construction site. Remodeling can sometimes include partial destruction of the structural members of a building. In addition it is important that the buildings under going remodeling retrofitted to make themselves stable and meet up with the future demands for better structural performance. The objective of this paper is to present the test results and structural behavior of RC walls that are perforated and to introduce effective retrofitting methods by evaluating efficacy of passive retrofit and active retrofit. Passive retrofit and Active retrofit using carbon fiber sheets, steel plates and wire that are widely used for strengthening the main members of existing buildings. The test results showed that the failed specimens had shear fractures and that two different types of retrofit method had different effects on the strengths of each specimen.

• Korean Journal of Plant Resources
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• v.24 no.4
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• pp.419-429
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• 2011

This study was carried out to classify the regional folk plants in Gyeongsangnam-do. According to the survey results from 293 survey sheets of 60 residents at 52 places of 17 counties and cities from March to October, 2009, the folk plants in Gyeongsangnam-do consisted of a total 182 taxa; 73 families, 157 genera, 168 species, 2 subspecies, 11 varieties, and 1 form. The use by its usage was: 129 taxa; edible, 41 taxa; medicinal, 3 taxa; dye, 2 taxa; aroma, 2 taxa; spice, 2 taxa; ornamental, 6 taxa; fiber, 2 taxa; oil, 25 taxa; others, respectively, so the edible use was the highest. The most useful part was the leaf, followed by all parts, fruit and root.