• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.67-76
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• 2011

The use of glass-fiber-reinforced polymer (GFRP) bars in reinforced concrete (RC) structures has emerged as an alternative to traditional RC due to the corrosion of steel in aggressive environments. Although the number of analytical and experimental studies on RC beams with GFRP reinforcement has increased in recent decades, it is still lower than the number of such studies related to steel RC structures. This paper presents the experimental moment deflection relations of GFRP reinforced beam which are spliced. Test variables were different reinforcement ratio and cover thickness of GFRP rebars. Seven concrete beams reinforced with steel GFRP re-Bars were tested. All the specimens had a span of 4000mm, provided with 12.7mm nominal diameter steel and GFRP rebars. All test specimens were tested under 2-point loads so that the spliced region be subject to constant moment. The experimental results show that the ultimate moment capacity of beam increasing of the reinforcement ratio. Failure mode of these specimens was sensitively vary according to the reinforcement ratio. The change of beam effective depth, which was caused by cover thickness variation, controlled the maximum strength and deflection because of cover spalling in tension face.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.83-91
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• 2015

With varying conditions of concrete surface, induced chloride contents are changed and this is a key parameter for steel corrosion and service life in RC (Reinforced Concrete) structures. Many surface enhancement techniques using impregnation have been developed, however the evaluation techniques for chloride behavior through doubly layered media and time-dependent diffusion are rarely proposed. This paper presents an analysis technique considering double-layer concrete and time-dependent diffusion behavior, and the results are compared with those from the previous test results through reverse analysis. The chloride profiles from the surface-impregnated concrete exposed to atmospheric, tidal, submerged zone for 2 years are adopted. Furthermore surface chloride contents and diffusion coefficients are obtained, and are compared with those from Life365. Through consideration of time effect, the relative error decreases from 0.28 to 0.20 in atmospheric, 0.29 to 0.11 in tidal, and 0.54 to 0.40 in submerged zone, respectively, which shows more reasonable results. Utilizing the diffusion coefficients from Life365, relative errors increases and it needs deeper penetration depth (e) and lower diffusion coefficient ratio ($D_1/D_2$) due to higher diffusion coefficient.

• Composites Research
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• v.21 no.6
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• pp.8-14
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• 2008

Lighting system of road is an essential structure used for the safety of pedestrians and vehicles. Most of the lighting pole is made with steel which is vulnerable under corrosive environment. To overcome such corrosion problems, stainless steel and iron steel are used, but they are usually manufactured by hand which is not efficient. Due to their high strength and stiffness, when there is car collision with the lighting pole structure the safety of driver may not be ensured. Hence, the development of new-type lighting pole system which is easy to adjust the right on the road, lengthen the service life, and reduce the maintenance, is necessary. Lighting pole made with aluminum alloy is high in strength per unit weight, is strong against corrosive environment, and is easy to construct due to flexibility and right weight. But, because the strength and stiffness of the material is lower than that of steel, the structural safety and serviceability of the system can be a problem. To mitigate the structural problem associated with conventional lighting pole system, experimental investigation is conducted on the conventional lighting pole and rib reinforced aluminum alloy lighting pole, respectively. By comparison of results, it was found that the rib reinforced Mg-Si aluminum alloy lighting pole is efficiently applicable to the lighting pole system of road.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.691-697
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• 2008

Coating the high tension bolted frictional joint has been generally allowed for anti-corrosion purpose. However in case of painting on paying surface of the high tension bolt, the influence on a slip strength of the joint depending on precision of painting has remained controversial. The study thus was intended to identify the slip behavior on high tension bolted frictional joint when applying ceramic painting, which has been currently developed. A slip test was conducted on a high tension bolted frictional joint specimen on which ceramic painting has been applied and a slip load and slip coefficient were measured. Based on result, the safety and usability of ceramic painting-applied high tension bolted frictional joint was evaluated. As a result, a difference to some extent by specimen in terms of load-displacement when a slip occurred was observed but an average slip coefficient appeared to have exceeded 0.4, which is the design frictional coefficient set forth in the specification. To secure the safety and usability of ceramic painting-applied high tension bolted frictional joint, it's necessary to establish the standard for painting as well as to revise the relevant specification.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.04a
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• pp.9-10
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• 2000

An important business-field of world-wide steel-industry is the coating of thin metal-sheets with zinc, zinc-aluminum and aluminum based materials. These products mostly go into automotive industry. in particular for the car-body. into building and construction industry as well as household appliances. Due to mass-production, the processing is done in large continuously operating plants where the mostly cold-rolled metal-strip as the substrate is handled in coils up to 40 tons unwind before and rolled up again after passing the processing plant which includes cleaning, annealing, hot-dip galvanizing / aluminizing and chemical treatment. In the liquid Zn, Zn-AI, AI-Zn and AI-Si bathes a combined action of corrosion and wear under high temperature and high stress onto the transfer components (rolls) accounts for major economic losses. Most critical here are the bearing systems of these rolls operating in the liquid system. Rolls in liquid system can not be avoided as they are needed to transfer the steel-strip into and out of the crucible. Since several years, ceramic roller bearings are tested here [1.2], however, in particular due to uncontrollable Slag-impurities within the hot bath [3], slide bearings are still expected to be of a higher potential [4]. The today's state of the art is the application of slide bearings based on Stellite\ulcorneragainst Stellite which is in general a 50-60 wt% Co-matrix with incorporated Cr- and W-carbides and other composites. Indeed Stellite is used as the bearing-material as of it's chemical properties (does not go into solution), the physical properties in particular with poor lubricating properties are not satisfying at all. To increase the Sliding behavior in the bearing system, about 0.15-0.2 wt% of lead has been added into the hot-bath in the past. Due to environmental regulations. this had to be reduced dramatically_ This together with the heavily increasing production rates expressed by increased velocity of the substrate-steel-band up to 200 m/min and increased tractate power up to 10 tons in modern plants. leads to life times of the bearings of a few up to several days only. To improve this situation. the Mechanical Alloying (MA) TeChnique [5.6.7.8] is used to prOduce advanced Stellite-based bearing materials. A lubricating phase is introduced into Stellite-powder-material by MA, the composite-powder-particles are coated by High Energy Milling (HEM) in order to produce bearing-bushes of approximately 12 kg by Sintering, Liquid Phase Sintering (LPS) and Hot Isostatic Pressing (HIP). The chemical and physical behavior of samples as well as the bearing systems in the hot galvanizing / aluminizing plant are discussed. DependenCies like lubricant material and composite, LPS-binder and composite, particle shape and PM-route with respect to achievable density. (temperature--) shock-reSistibility and corrosive-wear behavior will be described. The materials are characterized by particle size analysis (laser diffraction), scanning electron microscopy and X-ray diffraction. corrosive-wear behavior is determined using a special cylinder-in-bush apparatus (CIBA) as well as field-test in real production condition. Part I of this work describes the initial testing phase where different sample materials are produced, characterized, consolidated and tested in the CIBA under a common AI-Zn-system. The results are discussed and the material-system for the large components to be produced for the field test in real production condition is decided. Outlook: Part II of this work will describe the field test in a hot-dip-galvanizing/aluminizing plant of the mechanically alloyed bearing bushes under aluminum-rich liquid metal. Alter testing, the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed. Part III of this project will describe a second initial testing phase where the won results of part 1+11 will be transferred to the AI-Si system. Part IV of this project will describe the field test in a hot-dip-aluminizing plant of the mechanically alloyed bearing bushes under aluminum liquid metal. After testing. the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.481-490
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• 2012

Evaluation of chloride penetration is very important, because induced chloride ion causes corrosion in embedded steel. Diffusion coefficient obtained from rapid chloride penetration test is currently used, however this method cannot provide a correct prediction of chloride content since it shows only ion migration velocity in electrical field. Apparent diffusion coefficient of chloride ion based on simple Fick's Law can provide a total chloride penetration magnitude to engineers. This study proposes an analysis technique to predict chloride penetration using apparent diffusion coefficient of chloride ion from neural network (NN) algorithm and time-dependent diffusion phenomena. For this work, thirty mix proportions with the related diffusion coefficients are studied. The components of mix proportions such as w/b ratio, unit content of cement, slag, fly ash, silica fume, and fine/coarse aggregate are selected as neurons, then learning for apparent diffusion coefficient is trained. Considering time-dependent diffusion coefficient based on Fick's Law, the technique for chloride penetration analysis is proposed. The applicability of the technique is verified through test results from short, long term submerged test, and field investigations. The proposed technique can be improved through NN learning-training based on the acquisition of various mix proportions and the related diffusion coefficients of chloride ion.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3562-3569
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• 2013

The performance of concrete structure decreases with change in time and the external environment. In order to reinforce the structure, the research about new material development and application of newly developed materials are widely conducted. In the case of composite FRP, it received good attention in the academia due to its high intensity-weight ratio, excellent corrosion resistency as well as good workability. When applying at the construction field, however, the utilization of FRP did not increase as much due to lack of reliability and design standard. Current study investigated the material characteristics during the temperature change at high temperature and the structural behavior from restraint effect for GFRP reinforcing materials. Two experimental variables were set in this study: GFRP reinforcements due to tensile properties of temperature and restraint compression effects. Three concrete specimen were selected for each set temperatures. For this reason, as a variable to experiment with the effects confined compression concrete members value and tensile properties with temperature reinforcement GFRP, experiment produced three pieces each for each set temperature, the concrete specimen, which is confined in the GFRP was selected each I did. For the temperature change during the experiment, the concrete specimen were mounted in order to expose to experimental high temperature for certain period of time. For compression performance evaluation, reinforcement effect from horizontal constraint of the fiber were measured using an Universal Material Testing Machine (UTM). Finally, this study revealed that the binding characteristics of GFRP materials from temperature change decreased. Also, this study showed that the maximum compression intensity decreased as the temperature increased up to $150^{\circ}C$ in the constraints ability of the GFRP reinforcements during the horizontal constraint of concrete.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.135-144
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• 2011

Recently, researches about fiber reinforced polymer (FRP) which has excellent durability, corrosion resistance, and tensile strength as a substitution material to steel tendon have been actively pursued. This study is performed to examine FRP tendon used prestressed beam's safety under service load. The specimen was a prestressed concrete beam with internal bonded FRP tendon. In order to compare the member fatigue capacity, a control specimen of a prestressed concrete beam with ordinary steel tendon was tested. A fatigue load was applied at a load range of 60%, 70%, and 80% of the 40% ultimate load, which was obtained though a static test. The fatigue load was applied as a 1~3 Hz sine wave with 4 point loading setup. Fatigue load with maximum 1 million cycles was applied. The specimen applied with a load ranging between 40~60% did not show a fatigue failure until 1 million cycles. However, it was found that horizontal cracks in the direction of tendons were found and bond force between the tendon and concrete was degraded as the load cycles increased. This fatigue study showed that the prestressed concrete beam using FRP tendon was safe under a fatigue load within a service load range. Fatigue strength of the specimen with FRP and steel tendon after 1 million cycles was 69.2% and 59.8% of the prestressed concrete beam's static strength, respectively.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.7 no.1
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• pp.63-72
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• 2009

Recently the importance and interest for the microbes has been increased because several important results for the effects of microbes on the radioactive waste disposal have been published continuously. In this study, research status and major results on the various roles and effects of microbes in the radioactive waste disposal have been investigated. We investigated and summarized the roles and major results of microbes in a multi-barrier system consisting of an engineered barrier and a natural barrier which is considered in radioactive waste disposal systems. For the engineered barrier, we discussed about the effects of microbes on the corrosion of a waste container and investigated the survival possibility and roles of microbes in a compacted bentonite buffer. For the natural barrier, the roles of microbes present in groundwaters and rocks were discussed and summarized with major results from natural analogue studies. Furthermore, we investigated and summarized the roles and various interactions processes of microbes and their effects on the radionuclide migration and retardation including recent research status. Therefore, it is expected that the effects and roles of microbes on the radioactive waste disposal can be rigorously evaluated if further researches are carried out for a long-term behavior of the disposal system in the deep geological environments and for the effects of microbes on the radionuclide migration through geological media.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.1
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• pp.69-74
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• 2015

With difficulties during the cleaning of reflow flux residues due to the decrease of the part size and interconnection pitch in the advanced electronic devices, the need for the no-clean solder paste is increasing. In this study, an epoxy curable solder paste was made with SAC305 solder powder and the curable flux of which the main ingredient is epoxy resin and its reflow solderability, flux residue corrosivity and solder joint mechanical properties was investigated with comparison to the commercial rosin type solder paste. The fillet shape of the cured product around the reflowed solder joint revealed that the curing reaction occurred following the fluxing reaction and solder joint formation. The copper plate solderability test result also revealed that the wettability of the epoxy curable solder paste was comparable to those of the commercial rosin type solder pastes. In the highly accelerated temperature and humidity test, the cured product residue of the curable solder paste showed no corrosion of copper plate. From FT-IR analysis, it was considered to be resulted from the formation of tight bond through epoxy curing reaction. Ball shear, ball pull and die shear tests revealed that the adhesive bonding was formed with the solder surface and the increase of die shear strength of about 15~40% was achieved. It was considered that the epoxy curable solder paste could contribute to the improvement of the package reliability as well as the removal of the flux residue cleaning process.