• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.11-12
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• 2015

Green Frame is a Rahmen structure made of composite precast concrete members. According to the concrete design code, a lower rebar of precast concrete girder, should be extended to the inner precast concrete column. However, such extension of lower rebar may sharply reduce its constructability. To satisfy the criteria, the connection and anchorage of beam rebar should be taken into consideration, yet it is difficult to use lapping as it is not easy to ensure enough space when Green Frame method is adopted. To solve this, a new method of lower rebar connection and anchorage was developed, and this study is intended to review economic feasibility prior to applying the method developed onto sites. The study result can be used as basic data for selection of the optimal joint and anchorage method for lower rebar of the green frame construction.

• Composites Research
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• v.34 no.4
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• pp.241-248
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• 2021

As the electric vehicle market grows, there is an issue of light weight vehicles to increase battery efficiency. Therefore, it is going to replace the battery module cover that protects the battery module of electric vehicles with high strength/high heat-resistant polymer composite material which has lighter weight from existing aluminum materials. It also aims to respond to the early electric vehicle market where technology changes quickly by combining 3D printing technology that is advantageous for small production of multiple varieties without restrictions on complex shapes. Based on the composite material mechanics, the critical length of glass fibers in short glass fiber (GF)/polycarbonate (PC) composite materials manufactured through extruder was derived as 453.87 ㎛, and the side feeding method was adopted to improve the residual fiber length from 365.87 ㎛ and to increase a dispersibility. Thus, the optimal properties of tensile strength 135 MPa and Young's modulus 7.8 MPa were implemented as GF/PC composite materials containing 30 wt% of GF. In addition, the filament extrusion conditions (temperature, extrusion speed) were optimized to meet the commercial filament specification of 1.75 mm thickness and 0.05 mm standard deviation. Through manufactured filaments, 3D printing process conditions (temperature, printing speed) were optimized by multi-optimization that minimize porosity, maximize tensile strength, and printing speed to increase the productivity. Through this procedure, tensile strength and elastic modulus were improved 11%, 56% respectively. Also, by post-processing, tensile strength and Young's modulus were improved 5%, 18% respectively. Lastly, using the FEA (finite element analysis) technique, the structure of the battery module cover was optimized to meet the mechanical shock test criteria of the electric vehicle battery module cover (ISO-12405), and it is satisfied the battery cover mechanical shock test while achieving 37% lighter weight compared to aluminum battery module cover. Based on this research, it is expected that 3D printing technology of polymer composite materials can be used in various fields in the future.

• KIEAE Journal
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• v.7 no.6
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• pp.113-118
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• 2007

The composite beam adopted in the study was designed to reduce the floor height as well as to embed the top flange of steel frame into the slab that will enable to avoid applying the fire-resistant coating and to unify the joint method with a steel frame-type. As the steel frame and bottom concrete of the beam is pre-fabricated at the factory it could reduce the overall schedule at the jobsite. Applying such composite beam system to the work is expected to provide the efficient and enhanced performance, given the current tendency of the building construction that tends to be getting higher, larger and dense. The study focused on combining the composite beam with various column systems in a bid to propose the details thereof. A desirable composite girder can be adopted depending on site conditions through the evaluation of various beam and jointing approaches. Among the column systems applied to the study are steel column, SRC column, RC-PC column and RC column. The ways of combining with the columns addressed in the study were categorized into the rigid joint, pin joint, steel frame joint and bracket type joint. Besides, the instruction for site fabrication of beam-column was added in an effort to help set up the site fabrication procedures.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.181-185
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• 2003

The composite structural system with reinforced concrete column and steel beam has some advantages in the structural efficiency by complementing the shortcomings between the two systems. The system, however, has also a lot of problems in earthquake-proof capacity and construction process because it is wet method of construction. So, this paper proposed PCS(Precast Concrete Column and Steel Beam) structural system with dry method of construction. Purpose of this study is to enhance merit and control failure mechanism by installing Dog-Bone on H-beam.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.48-49
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• 2014

Green Frame is a column-beam system that uses composite precast concrete members. Previous studies have proven this system to be not only structurally safe, constructible, and economically feasible, but also environmentally-friendly. If the computerized program is used to estimate the quantity, the result of it shall be calculated much easily, quickly and exactly than manual estimation, because precast concrete members of Green Frame has standard size and connection method between it. Therefore, this study suggest quantity survey concept for column-beam structure comprised of composite precast concrete members. Hereafter, the quantity survey of Green Frame shall be much quickly and accurate, if the system would be made based on the result of this study.

• Steel and Composite Structures
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• v.37 no.1
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• pp.27-35
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• 2020

This study examines the wave propagation of the functionally graded polymer composite (FG-PC) nanoplates reinforced with graphene nanoplatelets (GNPs) resting on elastic foundations in the framework of the nonlocal strain gradient theory incorporating both stiffness hardening and softening mechanisms of nanostructures. To this end, the material properties are based on the Halpin-Tsai model, and the expressions for the classical and higher-order stresses and strains are consistently derived employing the second-order shear deformation theory. The equations of motion are then consistently derived using Hamilton's principle of variation. These governing equations are solved with the help of Trial function method. Extensive numerical discussions are conducted for wave propagation of the nanoplates and the influences of different parameters, such as the nonlocal parameter, strain gradient parameter, weight fraction of GNPs, uniform and non-uniform distributions of GNPs, elastic foundation parameters as well as wave number.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.287-292
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• 1999

The conducting composites were prepared by solution blending of polyaniline (PANI) as a conducting polymer and polycarbonate (PC) as a matrix in chloroform. Also the composites film was prepared by solution casting method. The PANI was protonated with alkylbenzenesulfonic acids, such as camphorsulfonic acid (CSA) or dodecylbenzenesulfonic acid (DBSA). The electrical conductivity of composites prepared by solution casting was enhanced compared with that of compression molding. The electrical conductivity, tensile strength and morphology were observed as a function of the amount of protonating agent as well as PANI complex content. In general, as the PANI complex content was increased, the electrical conductivity increased. In the case of the composite film containing 25 wt % of PANI complex doped with DBSA, the electrical conductivity exhibited 3.18 S/cm.

• Journal of the Korean Electrochemical Society
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• v.13 no.4
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• pp.235-239
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• 2010

The $Li_4Ti_5O_{12}$/CNT composite is prepared by ultrasound associated sol-gel method. The prepared composite is characterized by SEM, TEM, XRD and TG analysis, and their electrochemical behaviors are investigated by cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge test in 1M $LiBF_4$/PC electrolyte. From the results, it is identified that the $Li_4Ti_5O_{12}$ nanoparticles coated on CNT surface have regular size with around 10~30 nm and spinel-framework structure. At the current rate of 20C, the discharge capacities of $Li_4Ti_5O_{12}$/CNT composites with CNT contents of 15, 30 and 50 wt% are 57, 63 and $48mAhg^{-1}$, respectively, which have similar value. The improved electrochemical behavior of the $Li_4Ti_5O_{12}$/CNT composite electrode is attributed to the addition of CNT with electronic conductivity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.56-66
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• 2015

This study aims at developing a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were performed on one unreinforced beam-column specimen and two reinforced specimens with U-type precast wall panels. Seismic resistant test of anchored and welded steel plate connections manifested an average of 2.8 times increase in the maximum loading (average 591.8 kN) in comparison to unreinforced beam-column specimen. The maximum drift ratios were also shown between 1.4% and 2.7%. An analytical study was performed while assuming the RC column on the right side and the vertical element of the reinforced PC panel to behave in completely composite manner and the RC column on the left side and PC panel to behave in completely non-composite manner when loading was exerted from upper right end of RC frame of specimen to its left side. It was found with the assumptions that the overall flexural behavior in principle agreed with the experimental result.

• Journal of the Korea Institute of Building Construction
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• v.10 no.2
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• pp.89-96
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• 2010

This study was based on an experiment that examines the manufacture and performance of fiber-reinforced cement composite panels. The conclusions were drawn after testing the mechanical properties and durability characteristics of fiber-reinforced mortar, and the mechanical properties and fire resistance of ECC fire resistant column panels. It was found that the fluidity of CEL fiber was lower than that of PVA and NY fiber. The amount of air increased slightly as the combination of fibers caused the number of fine pores to increase. It was found that the mechanical performance and deformability of high strength concrete could be improved through the confinement effect of ECC fire resistant column panels. Through continuous studies on the manufacturing and field construction methods of fire resistant column panels, a new PC method that eliminates weakness in the existing processes may be developed for skyscrapers.