• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.3
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• pp.79-87
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• 2011

Deep corrugated steel plate structure has more compressive force and flexibility in bending behavior than short span structure. Asymmetric earth pressure distribution has occurred during construction. Ultimate strength and moment in domestic area, having superior ability at bending strain has been examined in this study. Based on the result of the study preceded, performance of Deep corrugated steel plate specimen has been evaluated by comparing increase of strength according to the increase of reinforcement content in bolt connections and failure mode of specimen.

• Smart Structures and Systems
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• v.5 no.4
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• pp.443-455
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• 2009

The use of fiber reinforced polymer (FRP) reinforcement in concrete structures has been on the rise due to its advantages over conventional steel reinforcement such as corrosion. Reinforcing steel corrosion has been the primary cause of deterioration of reinforced concrete (RC) structures, resulting in tremendous annual repair costs. One application of FRP reinforcement to be further explored is its use in RC frames. Nonetheless, due to FRP's inherently elastic behavior, FRP-reinforced (FRP-RC) members exhibit low ductility and energy dissipation as well as different damage mechanisms. Furthermore, current design standards for FRP-RC structures do not address seismic design in which the beam-column joint is a key issue. During an earthquake, the safety of beam-column joints is essential to the whole structure integrity. Thus, research is needed to gain better understanding of the behavior of FRP-RC structures and their damage mechanisms under seismic loading. In this study, two full-scale beam-column joint specimens reinforced with steel and GFRP configurations were tested under quasi-static loading. The control steel-reinforced specimen was detailed according to current design code provisions. The GFRP-RC specimen was detailed in a similar scheme. The damage in the two specimens is characterized to compare their performance under simulated seismic loading.

• Earthquakes and Structures
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• v.13 no.5
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• pp.473-484
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• 2017

The objective of this paper is to report on a study of the use of unstiffened thin steel plate shear walls (SPSWs) for the seismic performance improvement of reinforced concrete frames with deficient lateral rigidity. The behaviour of reinforced concrete frames during seismic activities was rehabilitated with an alternative and occupant-friendly retrofitting scheme. The study involved tests of eight 1/3 scale, one bay, two storey test specimens under cyclic quasi-static lateral loadings. The first specimen, tested in previous test program, was a reference specimen, and in seven other specimens, steel infill plates were used to replace the conventional infill brick or the concrete panels. The identification of the load-deformation characteristics, the determination of the level of improvement in the overall strength, and the elastic post-buckling stiffness were the main issues investigated during the quasi-static test program. With the introduction of the SPSWs, it was observed that the strength, stiffness and energy absorption capacities were significantly improved. It was also observed that the experimental hysteresis curves were stable, and the composite systems showed excellent energy dissipation capacities due to the formation of a diagonal tension field action along with a diagonal compression buckling of the infill plates.

• Journal of Korea Foundry Society
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• v.28 no.3
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• pp.119-123
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• 2008

Wear test on two die steels for aluminum die casting was carried out by dipping and rotating the specimens into the molten aluminum maintained $680^{\circ}C{\sim}780^{\circ}C$. The rotating speed of the specimen was $4.5rpm{\sim}20.0rpm$. Diffusion layer was formed between the die steel and molten aluminum, and became thicker with dipping time. Wear rate was not proportional with the thickness of the diffusion layer, but was closely related to the density of the diffusion layer. Wear rate was little affected by the kind of die steel and by the microstructure such as martensite, tempered martensite, and pearlite. Specimen with nitrided surface showed good wear resistance, and its wear rate was decreased with increase in the thickness of nitrided layer. While whole surface was worn in heat treated specimens, wear of nitrided specimens was proceeded by pitting partially.

• Steel and Composite Structures
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• v.38 no.3
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• pp.241-255
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• 2021

In order to study the interfacial bond-slip behavior of steel reinforced recycled concrete (SRRC) under cyclic loading, thirteen specimens were designed and tested under cyclic loading and one under monotonic loading. The test results indicated that the average bond strength of SRRC decreased with the increasing replacement ratio of recycled concrete, whereas the bond strength increased with an increase in the concrete cover thickness, the volumetric stirrup ratio, and the strength of recycled concrete. The ultimate bond strength of the cyclically-loaded specimen was significantly (41%) lower than that of the companion monotonically-loaded specimen. The cyclic phenomena also showed that SRRC specimens went through the nonslip phase, initial slip phase, failure phase, bond strength degradation phase and residual phase, with all specimens exhibiting basically the same shape of the bond-slip curve. Additionally, the paper presents the equations that were developed to calculate the characteristic bond strength of SRRC, which were verified based on experimental results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.139-141
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• 2009

This study analyzed the effect of the microstructure and alloying element on hydrogen-induced delayed fracture properties for the Energy Saving Wire (ESW) developed recently. Specimens were produced with a diameter 6.5mm post to the deformation (0, 10, 20 and 30%), followed by injecting the hydrogen. The experimental results by using GAS chromatography showed that the more hydrogen was emitted for high-carbon steel (0.45%C steel and 0.35%C steel) than low-carbon steel(0.2%C-Cr steel and 0.2%C-Cr-Mo steel). And, 0.45%C steel, 0.35%C steel and 0.2%C-Cr-Mo steel exhibited the crack for 30% deformed specimen. The hydrogen emitted was analyzed with the amount, the spheroidization, and the size of the carbides.

• Korean Journal of Materials Research
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• v.24 no.10
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• pp.550-555
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• 2014

The present study deals with the effects of tempering treatment on the microstructure and mechanical properties of Cu-bearing high-strength steels. Three kinds of steel specimens with different levels of Cu content were fabricated by controlled rolling and accelerated cooling, ; some of these steel specimen were tempered at temperatures ranging from $350^{\circ}C$ to $650^{\circ}C$ for 30 min. Hardness, tensile, and Charpy impact tests were conducted in order to investigate the relationship of microstructure and mechanical properties. The hardness of the Cu-added specimens is much higher than that of Cu-free specimen, presumably due to the enhanced solid solution hardening and precipitation hardening, result from the formation of very-fine Cu precipitates. Tensile test results indicated that the yield strength increased and then slightly decreased, while the tensile strength gradually decreased with increasing tempering temperature. On the other hand, the energy absorbed at room and lower temperatures remarkably increased after tempering at $350^{\circ}C$; and after this, the energy absorbed then did not change much. Suitable tempering treatment remarkably improved both the strength and the impact toughness. In the 1.5 Cu steel specimen tempered at $550^{\circ}C$, the yield strength reached 1.2 GPa and the absorbed energy at $-20^{\circ}C$ showed a level above 200 J, which was the best combination of high strength and good toughness.

• Journal of Korean Society of Steel Construction
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• v.23 no.1
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• pp.125-135
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• 2011

To obtain a lower story height with a long span and better fire resistance, a new composite floor system using GFRP (glass-fiber-reinforced plastics) was proposed. This floor system consists of asymmetric steel with a web opening, a hollow core ball, concrete, and GFRP. To evaluate the flexural performance of the new composite floor system, an experiment was conducted. The test parameters were the presence of GFRP, the void ratio in relation to the hollow core balls, and the web opening. The test results showed that the resistance and stiffness of the specimen with GFRP were 10% higher than those of the reference specimen, and that fully composite action was accomplished up to the yielding point. After the attainment of the yield strength, the ductility of the specimen was reduced due to the stress concentration around the web openings. The slip between the concrete and steel beam, however, was small. Thus, in the design of the proposed new floor systems, it is desirable that the calculated resistance be reduced by 15%, for safety.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.255-264
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• 2015

Steel plate concrete (SC) structure has been developed as a new structural type. Rational damping value shall be determined for the seismic design of SC structure. This study evaluated damping ratio of SC structure through experiments. For the study, a SC shear wall specimen was constructed and dynamically tested on the shaking table. Acceleration time history responses measured from testing were converted to the transfer functions and analyzed by using experimental modal analysis technique. The structural damping ratio of the specimen was identified as 4% to critical. Considering the shaking table test was performed at the excitation level corresponding to the low stress level of the specimen, 4% could be suggested as a structural damping for design of SC structure for operating basis earthquake.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.809-815
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• 2011

An experimental investigations on the bond-slip properties of the steel and Glass Fiber Reinforced Polymer(GFRP) bars in engineered cementitious composite (ECC) with Polyvinyl Alcohol (PVA) fibers are presented. Total of 8 beam specimens prepared according to the Rilem procedures with 2% of PVA and PE fiber volume percentage and steel and GFRP reinforcements significantly changed the failure mechanism and slightly improved bond strength. The main objective of the tests was to evaluate the load versus displacement and load versus slip behaviors and the bond strength for the following parameters: concrete type (normal and fiber concrete) and bar diameter (10 and 13 mm). The study results showed that ordinary concrete and ECC specimens showed similar behavior for steel reinforced specimen. However, GFRP reinforced specimen showed different behavior that the steel specimen. The code analytical results showed more accuracy compared to the experimental results as expected in conservative code provisions. Based on the obtained results, it is safe to conclude that the new parameters need to be adopted to ensure safe usage of ECC for construction applications.