• Polymer(Korea)
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• v.26 no.3
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• pp.335-343
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• 2002

Blend resin (PET/PETG 70/30 blend) of poly (ethylene terephthalate) (PET) and poly (ethylene terephthalate glycol) (PETG) of weight percent 70/30 was prepared by a twin-screw extruder. Undrawn films of the blend and pure PETG were made by melt-press in hot press. Drawn films were made by capillary rheometer. Crystallinity, shrinkage, thermal, dynamic mechanical, and mechanical properties of these blends and PETG drawn films were investigated by wide angle X-ray diffractometer, dry oven, DSC thermal analyzer, and tensile tester. The crystallinity and density of these films increased with increasing draw ratio and draw rate but decreased with increasing draw temperature. The crystallinity and density of the blend films were higher than those of PETG films. The tensile strength and tensile modulus of these drawn alms increased with increasing draw ratio and draw rate but decreased with increasing draw temperature. The tensile strength and tensile modulus of blend films were higher than those of PETG films. Shrinkage of PETG md blend films decreased with draw ratio and draw rate. Shrinkage of undrawn blend film was 600% higher than that of pure PET film.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.551-558
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• 2011

The effect of the maximum aggregate size and substitution rate of natural sand on the mechanical properties of concrete is evaluated using 15 lightweight aggregate concrete mixes. For mechanical properties of concrete, compressive strength increase with respect to age, tensile resistance, elastic modulus, rupture modulus, and stress-strain relationship were measured. The experimental data were compared with the design equations specified in ACI 318-08, EC2, and/or CEB-FIP code provisions and empirical equations proposed by Slate et al., Yang et al., and Wang et al. The test results showed that compressive strength of lightweight concrete decreased with increase in maximum aggregate size and amount of lightweight fine aggregates. The parameters to predict the compressive strength development could be empirically formulated as a function of specific gravity of coarse aggregates and substitution rate of natural sand. The measured rupture modulus and tensile strength of concrete were commonly less than the prediction values obtained from code provisions or empirical equations, which can be attributed to the tensile resistance of lightweight aggregate concrete being significantly affected by its density as well as compressive strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.197-200
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• 2008

An analytical model for predicting the shear strength of prestressed concrete beams was developed, applying the previously proposed strain-based shear strength model. In flexure-compression member without shear reinforcement, compression zone of intact concrete primarily resist to the shear force rather than tension zone. The shear capacity of concrete at the compression zone was defined based on the material failure criteria. The shear capacity of the compression zone was evaluated along the inclined failure surface considering interaction with the normal stress. Since the distribution of normal stress varies due to the flexural deformation of member, the shear capacity was defined as a function of the flexural deformation. Finally, the shear strength was determined at the intersection of the shear capacity curve and the shear demand curve. As a result of the comparisons to prior test data, the proposed model accurately predicted the shear strength of specimens.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5600-5607
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• 2015

This study investigated experimentally the tensile behavior of polyetylene fiber-reinforced cementless composite. Four types of polyetylene fiber-reinforced cementless composite were designed. The water to binder ratio was 0.30-0.38, and the amount of polyetylene fiber was 1.75 vol%. A series of experiments including uniaxial tension, density, and compression tests were performed to evaluate the performance of the composites. From the test results, it was exhibited that the composite has superior tensile performance such as high tensile strength and tensile strain capacity compared with other types of composites.

• Journal of Korean Society of Steel Construction
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• v.17 no.2 s.75
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• pp.207-216
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• 2005

The maximum strength of the stainless steel square and the circular hollow section columns, which are cold-formed and TIG welded, is experimented on and analyzed. The paper presents centrally compressed experiments, including stub column tests and coupon tests, on stainless steel pipe columns. A total of 24 stainless steel pipe column experiments are conducted, using the slenderness ratios ($L_k/r$ = 20, 30, 40, 50, 60, 70) as parameters. The experimental results were compared with the design standard curves, AIK-LSD and AISC-LRFD, AIJ-LSD, SIJ-ASD curves, and multiple column curves.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.638-644
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• 2002

The stress-strain relationship of polymer concrete flexural member was evaluated using C-shaped polyester concrete specimen, the compressive strength of which is 1400 kgf/$\textrm{cm}^2$. Eccentric compression test was performed to estimate the parameters, ${\alpha}$, ${\beta}$1, ${\gamma}$ for equivalent rectangular stress block. The ultimate moment strength ware obtained from the bending test on reinforced polymer concrete beams which were prepared with S different tensile steel ratios with a shear span ratio of 4.0. These values were compared with theoretical ultimate moment strengths, which were obtained using the parameters ${\alpha}$=0.61 and ${\beta}$1=0.73 from stress-stain curves of C-shaped specimens. The results showed that, when tensile steel ratio was over 0.50 $\rho$b, the experimentally obtained moment strengths were well matched with theoretically calculated values. In order to develop accurate criteria for polymer concrete flexural members, however, many other expermental studies for parameter determination are necessary using C-shaped specimens which have various compressive strengths and different sizes.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.1
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• pp.42-45
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• 2014

Even though to discard the waste FRP (Fiber-Reinforced Plastic) is urgent and problematic, the way to do it has not been efficient. In our project team the FRP have been splitted into some layers which have different physical properties; mat and roving layers. Among those, the roving layer woven like a basket by bundles of glass fibers has been cut into reusable fibers called 'F-fiber'. F-fiber is 1 mm or 3 mm in width and 3 cm in length. It is used in fiber-reinforced concrete (FRC) with 0.5%, 0.7%, 1.0%, or 1.5% of volume ratio. Produced FRC was tested in compressive, tensile, and bending stress in contrast to the without-fiber (standard) concrete and 0.1% polypropylene reinforced concrete (PP-FRC). The tensile and bending stresses are more or less those of PP-FRC. The compressive stress, however, is similar (with 3 mm F-fiber) to or lower (with 1 mm F-fiber) than that of standard concrete. Conclusively the usage of the waste FRC in concrete is advised to be limited to the one where the compressive stress is not much critical.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1334-1340
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• 2004

Existing of angle assembly and angle beam joint examination with steel pole and steel beam of assembly existing anglerather then excellent enumerate, joint of beanding moment examination and economical existing show, in the futher, angle beam rather then steel I beam with all change.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.52-59
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• 2014

This study examines the compressive strength, elastic modulus and splitting tensile strength of geopolymer concrete in order to evaluate its mechanical characteristics according to the admixing of fly ash and blast furnace slag. Moreover, identical tests are also conducted considering the amount of powder, the mixing ratio of alkali activator and the mixing ratio of silica fume for further comparative analysis considering various variables. The comparison with the formulae specified in Korean and overseas codes reveal that a mixing ratio of 18% is adequate for the alkali activator and that a replacement ratio of 5% by silica fume is recommended for silica fume. The elastic modulus of the geopolymer concrete appears to increase slightly with the increase of the compressive strength per variable and age and to be smaller than the values predicted by the formulae specified in Korean and overseas codes. In addition, the examination of the stress-strain curves shows that the geopolymer concrete exhibits ductile behavior compared to the conventional OPC. In view of the splitting tensile strength, high strength is observed for a powder content of $400kg/m^3$ and a replacement ratio of 18% by silica fume. The resulting ratio of the compressive strength to the splitting tensile strength is seen to range between 8.7 and 10.2%.

• The Journal of Engineering Geology
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• v.26 no.4
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• pp.593-600
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• 2016

To understand the mechanical properties of rock masses and intact rock in Korea, data from 4,280 in situ and laboratory tests from 107 tunnels on general national roads were analyzed. The mechanical properties (unit weight, cohesion, friction angle, modulus of deformation, Young's modulus, Poisson's ratio, uniaxial compressive strength, tensile strength, coefficient of permeability, and specific gravity) were analyzed by rock types and strength of rock in each rock type. The results of analysis, the mean specific gravity was highest in gneiss. The coefficient of permeability and Poisson's ratio show the highest mean values in granite and metamorphic rock, respectively. In addition, the unit weight, cohesion and friction angle in sedimentary rock, modulus of deformation, Young's modulus, uniaxial compressive strength and tensile strength in volcanic rock have the highest mean values. The values for each mechanical property showed wide ranges by the heterogeneity and anisotropy of rock masses in spite of detailed analysis by rock type and classification of rocks according to the strength.