• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.732-742
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• 1985

Measurements of mean velocity and turbulence characteristics are obtained with a linearized constant temperature hot-wire anemometer in a two-dimensional turbulent jet discharging parallel to a flate. Wall static pressure distribution is also measure. The Reynolds number based on the jet nozzle width (D) is about 42,000 and the step height is 2.5D. The reattachment length is found to be 7.5D by using both wool tuft and oil methods. Upstream of the reattachment point, there exist double coherent structures and mean velocity, Reynolds stresses and triple product profiles are asymmetric about jet center line due to the influence of streamline curvature and recirculating flow region. Near the reattachment point, wall static pressure and turbulence quantities change its shape rapidly because of the large eddies by the solid wall. Especially, turbulence intensity has a maximum value in the reattachment regin, then decreases slowly in the redeveloping wall jet ragion. Downstream of X/D=14, a single large scale eddy structure is formed. Far downstream affer the reattachment(X/D.geq.18) mean velocity profile, the decay of maximum velocity and the variation of jet half width are nearly similar to those of plane wall jet, but the Reynolds stresses are higher than those of the latter.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.1
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• pp.134-141
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• 2017

Many studies have been conducted with respect to the materials to replace the cement in order to reduce the carbon dioxide emissions during the cement production. Activated hwangtoh as cement replacement material goes through calcination process of $850^{\circ}C$. PVA fibers and GFRP bars are used in order to compensate for the cracks of activated hwangtoh concrete(AHC). This paper presents an experimental study investigating the bond characteristic of GFRP bars in PVA fiber reinforced AHC under tensile loads. Experimental results showed that average bond strength factor of specimens with and without PVA fiber was 2.27~2.48 and was not significantly affected by the ratio of PVA fiber andactivated hwangtoh. In addition, as the bond length was increased, the bond strength was reduced.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1089-1092
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• 2008

The bond behavior between concrete and reinforcement is a important requirement for reinforced concrete constructions. For practical application, it is very important to study bond behavior of reinforcing bars in recycled fine aggregate concrete. Therefore, pull-out test in order to investigate the bond behavior between recycled fine aggregate concrete and deformed bars was performed. Recycled fine aggregate concrete replacement ratios (i.e., 0% and 100%) and positions of deformed bars (i.e., vertical and horizontal position) were considered as variables in this study. Test results were compared with the bond strength requirement recommended by CEB-FIP code. Based on the test results, It was found that the bond strength between the recycled fine aggregate concrete and deformed bars were influenced by both recycled fine aggregate concrete replacement ratios and positions of deformed bars. The reduction of bonded area at the soffit of horizontal reinforcement caused by concrete bleeding was observed in H type specimen. So, Only V type and HB specimen satisfied the bond strength requirement recommended by CEB-FIP code.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2016.11a
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• pp.353-356
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• 2016

불투수성 방수아스팔트는 아스팔트 혼합물이 골재와 골재 사이를 강력하게 부착하며, 골재간의 공간을 메우고, 골재표면을 두껍게 코팅하여 골재 상호간의 강한 접착을 유지시켜주는 열가소성 폴리머를 사용한 포장공법이다. 이러한 불투수성 아스팔트는 기존의 가열식 일반아스팔트 공법에서 문제시 되고 있는 내구성 저하와 잦은 유지보수로 인한 문제점을 해결할 수 있는 공법으로 차세대 고내구성 포장공법으로 주목을 받고 있다. 본 연구는 불투수성 방수아스팔트 혼합물 개발을 위한 연구의 일환으로 상온과 영하 $10^{\circ}C$의 조건하에서 기존 아스팔트수지와 새로운 개념의 불투수성 고분자계 수지의 부착성능 비교 검토하였으며, 아스팔트혼합물의 부착성능도 실험을 통해 비교 하였다. 실험결과 불투수성 아스팔트의 부착성능이 기존 아스팔트에 비해 상온은 물론 저온에서도 뛰어난 성능을 발휘하는 것을 확인 하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.555-563
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• 2006

Recently, many bridges become not only functionally obsolete of bridge deck due to inadequate width but also structurally deficient of substructure due to erosion. In these cases, widening is almost always more economical than complete replacement, and therefore there is a need to make available the results of research and field experience pertaining to the widening of bridge substructure. But, an experimental study for the guarantee of unification between existing and new substructure with adhesive anchor is so insufficient that the development of adhesive anchor system for the unification should be settled promptly. The purpose of the present study is to explore pull out and shear characteristics of adhesive anchor system. For this purpose, several series of concrete specimens have been tested. Major test variables were the bonded length, anchor diameter and anchor slope. The pull out strength, bond stress and shear strength of adhesive faces were measured for the specimens. The present study indicates that the pull out strength increased with more bonded length and more anchor diameter, and that the bond stress decreased with more bonded length and more anchor diameter. The pull out strength and the bond stress increases with more anchor slope and it is considered that the slope of $5^{\circ}$ was more efficient. From the shear tests, it is supposed that anchor diameters more than D19 was proper to the adhesive anchor. Finally, it is expected that both experimental data in these tests and further study including mock-up tests will contribute to the establishment of the unification between existing and new substructure with adhesive anchor.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.191-198
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• 2005

This study was carried out to investigate quantitatively the relationship between the degree of rebar corrosion and the strength of reinforced concrete beams. After producing equations for the relationship between both the tensile properties of rebars and bond properties and the corrosion percentage of rebars, finite element analysis and bending tests were conducted for RC beams damaged by corrosion of tension main rebar. As a result, it was made that the strength of RC beams damaged by corrosion could be practically simulated by FEM analysis using experimentally determined material properties representing the bond and the mechanical characteristics of corroded rebars.

• Journal of the Korea Society of Computer and Information
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• v.15 no.12
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• pp.47-55
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• 2010

In this paper, we implemented a serious game system for study to accompany exercising and generating to keep on computer game side effect. The implemented serious game system was divided into the game part and the athletic part. The athletic part for whole body exercising was composed of health bicycle for lower body exercise and additional apparatus for upper body exercise, that was attached to the rear side of health bicycle and several generator was attached to the power point of athletic part. The circuit board and logic program was composed to adjust the exercise strength control, to get data and to communicate with the computer. The game part was composed to promote and educational effectiveness, the whole system emphasized on amusement side while avoided violence side. We confirmed the effect of the serious game system with the fourteen fun form which Garneau insists.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.211-217
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• 2011

Although a compression splice length does not need to be longer than a tension splice length due to end bearing effect, current design codes impose a longer compression lap splice than a tension lap splice in high strength concrete. Hence, new criteria for the compression lap splice including concrete strength effect need to be found for economical design of ultra-high strength concrete. An experimental study has been conducted using column specimens with concrete strength of 80 and 100 MPa with transverse reinforcement. The test results showed that splice strengths improved when the amount of transverse reinforcement increased. However, end bearing strength did not increase when larger amount of transverse reinforcement is provided within the spliced zone. Therefore, the splice strength enhancement was attributed to the improvement of bond. From regression analysis of 94 test results including specimens made with concrete strength of 40 and 60 MPa, a new design equation is proposed for compression lap splice in the concrete compressive strength ranging from 40 to 100 MPa with transverse reinforcement. By using the proposed equation, the incorrect design equations for lap splice lengths in tension and compression can be corrected. In addition, the equation has a reliability equivalent to those of the specified strengths of materials.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.76-85
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• 2017

In this study, to evaluate the mechanical properties of fiber-reinforced cement composites by strain rate, hydraulic rapid loading test system was developed. And compressive and tensile strength of the hooked steel fiber and polyamide fiber reinforced cement composite were evaluated. As a result, the compressive strength, strain capacity and elastic modulus were increased with increasing strain rate. The effect of compressive strength by type and volume fraction of fibers was not significant. The dynamic increase factor(DIF) of the compressive strength was higher than that of the CEB-FIP model code 2010 and showed a trend similar to that of ACI-349. The tensile strength and strain capacity were increased with increasing strain rate. The hooked steel fibers were drawn from the matrix. The tensile strength and strain capacity of hooked steel fiber reinforced cement composites were increased as the strain rate increased. The tensile strength and deformation capacity of the fiber reinforced cement composites were increased. And, hooked steel fibers were drawn from the matrix. On the other hand, because the bonding properties of polyamide fiber and matrix is large, polyamide fiber was cut-off with out pullout from matrix. The strain rate effect on the tensile properties of polyamide fiber reinforced cement composites was found to be strongly affected by the tensile strength of the fibers.

• Membrane Journal
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• v.11 no.1
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• pp.29-37
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• 2001

본 논문은 인공 진피와 조직공학용 scaffold로 이용하기 위해 다공성 membrane로서 gelatin-based sponge의 효율성을 연구하였다. 불용성의 다공성 membrane은 1-ethyl-(3-3dimethylaminopropyl)carbodiimide(EDC)로 가교하여 제조하였다. Fourier-transformed infrared (FT-IR) spectroscopy, scanning electron microscopy(SEM) 그리고 Instron analysis로 다공성 membrane의 특성을 조사하였다. 다공성 membrane은 용적당 큰 표면적을 제공하는 micro porous한 구조를 가지고 있다. Gelatin/hyaluronic acid (HA) membrane의 공경크기는 40~200$\mu\textrm{m}$이다. HA의 첨가는 다공성 membrane의 기계적 강도와 세포부착능력에 영향을 미쳤다. Gelatin/HA 다공성 membrane의 압축강도는 collagen과 비슷하며, 세포배양과 인공진피 transplantation에 있어서의 충분한 기계적 강도를 가지고 있다. Fibroblasts를 함유한 진피기질을 제조하기 위해 직경 8mm의 다공성 membran에 4$\times$10(sup)5cells/membrane의 세포밀도로 fibroblast를 배양하였다. GH91 porous membrane에서의 fibroblast 부착성은 GH55 porous membrane에서보다 우수하였다. 삼차원 구조의 gelatin/HA membrane matrix에서의 fibroblast의 배양은 생체내 조건과 유사한 생리적 환경을 제공하였다.