• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.263-266
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• 2005

Many RC structures built without seismic provisions have exhibited brittle shear failures in the beam-column joint area, and resulted in large permanent deformations and structural collapse. This paper presents the results of an experimental investigation pertaining to the use of carbon fiber-reinforced polymer(FRP) for strengthening of RC beam-column connections. The selective upgrade is obtained by choosing different combinations and locations of carbon FRP sheets to determine the effective way to improve the structural performance of joints. Experimental results demonstrate significant improvement of flexural capacity and ductility of beam-column connections originally built without seismic details.

• Advances in concrete construction
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• v.3 no.2
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• pp.113-126
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• 2015

Holed-Incrementally Prestressed Concrete (H-IPC) girders are designed using the following new design concepts. At first, web openings reduce the self-weight of the girder, and also diffuse prestressing tendon anchorages. The reduced end anchoring forces decrease the web thickness of the end sections. Additionally, precast technology help to improve the quality of concrete and to reduce the construction period at the site. For experimentally verification, two 50 m full-scale H-IPC girders are manufactured with different concrete strength of 55 MPa and 80 MPa. The safety, stiffness, ductility, serviceability and crack development of H-IPC girder are measured and compared with each other for different strengths. Both girders show enough strength to carry live load and good stiffness to satisfy the design criteria. The experimental result shows the advantages of using high strength concrete and adopting precast girder. The test data can be used as a criterion for safety control and maintenance of the H-IPC girder.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.7-13
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• 2019

Power module is getting attention from electronic industries such as solar cell, battery and electric vehicles. Transient liquid phase (TLP) boding, sintering with Ag and Cu powders and wire bonding are applied to power module packaging. Sintering is a popular process but it has some disadvantages such as high cost, complex procedures and long bonding time. Meanwhile, TLP bonding has lower bonding temperature, cost effectiveness and less porosity. However, it also needs to improve ductility of the intermetallic compounds (IMCs) at the joint. Wire boding is also an important interconnection process between semiconductor chip and metal lead for direct bonded copper (DBC). In this study, TLP bonding using Sn-based solders and wire bonding process for power electronics packaging are described.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.291-294
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• 2008

A ICH-CFT colunn(internally confined hollow-concrete filled tube column) has many advantages compare with R.C column and CFT column. For example using a hollow section, it is possible to save material and to reduce self weight of column. Also two steel tubes on both sid of concrete, inner and outter tube, can improve ductility of ICH-CFT column. But study about ICH-CFT section has done only theoretically. Thus although ICH-CFT column has many advantages, ICH-CFT column dosen't use in construction. In this thesis, through out 3-D full modeling using ABAQUS analyze the nonlinear behavaior of ICH-CFT column. And using the analysis result, review the theoretical knowledge.

• 연구논문집
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• s.22
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• pp.127-139
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• 1992

The mechnial properties such as fracture strength, ductility and fatigue strength of Cu shape memory alloy are lower than those of Ti-Ni SMA, because of their high elastic anisotropy and large grain size. And in order to improve the mechanical property of Cu SMA, some techniques such as casting method by addition of refining element, powder metallurgy and rapid solidification process have been studied on the refinement of the grain size of Cu SMA. This study was carried out to refine the grain size of CuAlNi SMA by applying the melt spinning method. According to this study, the conclusions are as follows; - grain size of the melt-spun ribbon was about $1\mum$ - there was not change in grain size, although increasing of hot pressing temperature -grain size of the hot-extruded specimen was about $30-40\mum$, it is more refiner than that of castings

• Structural Engineering and Mechanics
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• v.86 no.2
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• pp.277-290
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• 2023

A supplementary reinforced concrete wall can be used to improve the seismic behavior of a buckling restrained braced frame as a mixed system. In such a novel system, the total lateral force is resisted by the combination of the RC wall system and the BRBF. There is not enough research on the response modification factor of such a mixed system. This paper investigates the response modification factor, and such relevant factors as ductility reduction factor and over strength factor for a system consisting of reinforced concrete wall and buckling restrained braced frame. To this purpose, nonlinear incremental dynamic analysis as well as static push over analysis are used for 6- to 14-story sample structures. The results show that for mixed considered systems, the mean value of response modification factor varies approximately from 7 to 9.

• Earthquakes and Structures
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• v.22 no.5
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• pp.475-485
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• 2022

This paper presents a comparative experimental study on structural behavior of the interlocking masonry walls under in-plane cyclic loading. The main purpose of this study is to increase lateral load-bearing capacities of masonry walls by using interlocking units. The interlocking units were designed by considering failure modes of masonry walls and produced using lightweight foamed concrete. To this end, three masonry walls which are hollow, fully grouted, and reinforced were constructed with interlocking units. Also, a traditional masonry brick wall was built for comparison reasons. The walls were tested under in-plane cyclic loading. Then, structural parameters of the walls such as lateral load bearing and total energy dissipation capacities, ductility, stiffness degradation as well as failure modes obtained from the tests were compared with each other. The results have shown that the walls with the interlocking units have better structural performance than traditional masonry brick walls and they may be used in the construction of low-rise masonry structures in rural areas to improve in-plane structural performance.

• Structural Engineering and Mechanics
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• v.87 no.3
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• pp.201-210
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• 2023

This paper investigates the flexural behavior of reinforced recycled aggregates concrete (RRAC) beams after exposed to high temperatures. The experimental results from 17 specimens were present and compared with temperatures, recycled coarse aggregate (RCA) replacement percentages, and concrete strength as variables. It was found that the high temperature would not cause an observable change in the failure pattern. However, high temperature can significantly reduce the stiffness and ductility, and accelerate the damage degradation of specimens. After exposure to 600℃, the ultimate bearing capacity of the specimens decreased by 20%-30% The mechanical properties of RRAC beams after high temperatures were barely impacted by the replacement percentages. Increasing the concrete strength of RCA could effectively improve the bearing capacity and peak deflection of RRAC beams after exposed to high temperatures. Furthermore, the calculation method of the bending bearing capacity and deflection of RRAC beams was also discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.118-125
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• 2013

The synthetic fibers including Polyvinyl alcohol and Polyethylene fibers have been successfully used in the manufacture of high ductile fiber reinforced cementitious composites. Polypropylene (PP) fiber has also been used in composites, not for the purpose of achieving a high level of tensile ductility but to improve the fire resistance performance of concrete exposed to high temperatures. This paper discusses the method for enhancing the performance of composites supplemented with PP fiber. Five types of mixture proportions were designed with high volume fly ash for testing the performance of composites. Type I cement and fly ash F were used as binding materials. The water-to-binder ratio was 0.23~0.25, and the amount of PP fiber used was 2 vol%. Polystyrene bead were also used to increase the tensile ductility of composites. A series of experiments including slump, density, compression and uniaxial tension tests were performed to evaluate the performance of cementitious composites supplemented with PP fiber. From the test results, it was exhibited that the performance of composites supplemented with PP fiber can be enhanced by adopting the mechanics and statistics theory.

• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.209-216
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• 2017

One of the important considerations in structural designing the flat plate system is ensuring the resistance to punching shear caused by axial loads and the ductile ability to follow horizontal deformation under earthquake. In this study, the ECC (Engineered Cementitious Composite) has been placed in the critical section zone of punching shear at slab-column joint to improve ductility and the advanced details of shear reinforced area nearby critical section zone has been developed using stud and steel fiber. The shear performance tests were performed on the specimens with parameters of fiber type mixed with ECC, stud and steel fiber set into the shear reinforced area in which the failure pattern, joint strength, displacement and strain of the specimen were compared and analyzed. The test results showed that the strength and ductility of specimens with ECC applied to joint were better than those of RC flat plate system. Also, the shear reinforcement effect of stud and the ductility improvement of steel fiber concrete were confirmed in the shear reinforcement area.