• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.271-274
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• 2003

국내 해안지역의 표층에는 두께 약 5~60m의 연약한 해성 충적 점성토층이 형성되어 있어 상부에 구조물을 축조할 경우 목적에 부합되게 다양한 말뚝시공에 의한 연약지반 개량공법을 적용하고 있는 실정이다 따라서 매우 연약한 지반특성을 나타내는 경우에는 설계에서 정해진 단면이상으로 콘크리트 재료가 지반 중으로 투입되어 콘크리트 재료의 손실이 많이 발생하여 합리적인 시공을 수행하여도 비경제적인 공사가 될 우려가 크다. (중략)

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.795-805
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• 1994

This paper presents the analytical results for the prediction of elastical local buckling stress of fiber reinforced plastic (orthotropic) structural shapes manufactured from pultrusion process. In the derivation, existing Bleich's approach which was originally derived for the isotropic structural shapes was extended and non-dimensionalized parameters which can simplify the numerical calculations were adopted. Analytical results were compared with reported closed-form solutions and experimental results. It is graphically shown that the results can be used effectively to predict the local buckling stress of pultruded fiber reinforced plastic structural shapes. Numerical results were presented graphically to estimate the local buckling stress of various cross-sectional dimensions and lengths of columns. In addition, limits of width to thickness ratio of flange and web of pultruded structural shapes were suggested in which material failure or overall buckling occurs prior to local buckling.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.4
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• pp.78-85
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• 2023

In this study, synthetic fibers were applied to reduce shrinkage cracks that may occur in mortar produced by 3D printer. We used a biopolymer in powder form made from cactus stem (CS) as an admixture. The material properties of 3D printed mortar were experimentally evaluated. Replacing methylcellulose(MC) with 10% CS increases compressive strength by 9.84-23.92% regardless of the casting method. In addition, regardless of the casting method, shrinkage change, freeze-thaw resistance, and crack resistance are more effective than Plain. Incorporation of CS increases the polysaccharide macromolecular structure and improves durability. Mortars reinforced with synthetic fibers do not affect compressive strength and freeze-thaw. It is also effective for shrink deformation and crack resistance. Incorporating CS and fibers from 3D-printed mortar was found to be effective for durability and crack resistance.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.92-92
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• 2012

나노필라멘트 섬유는 직편물 등으로 구조/용도 다양화 가능하다. 나노필라멘트 섬유는 소재특유의 닦음성, 흡착성, 고밀도 특성 등을 활용하여 직편물의 형태로 다양한 용도 개발이 가능하며, 나노기술을 접목시킨 새로운 기능성과 고성능 섬유 소재 개발을 통한 자동차 분야의 개발 트랜드인 고급화, 경량화, 고성능화 추진을 위해 연료전지, 신슐레이터, 고성능 필터, 시트나 도어트림, 헤드라인과 같은 인테리어류와 전자 분야의 제조원가 절감, 공정 단순화를 위해 프린터 토너, 하드디스크 연마제, 다용도 No Dust Cleaner 등의 개발, 의료/바이오 분야의 혈액필터, 수술용 보호제, 창상억제제(유착 방지막), 항균마스크, 의료용 약물전달 시스템 및 환경 분야의 정수/공기 정화 시스템, 건축 토목용 보강제, 고(高)인성 콘크리트, 폐수처리용 슬러리 담체(Matrix) 등 다양한 분야로 용도 개발이 가능하다. 본 연구는 나노필라멘트의 다양한 분야로의 용도 개발 적용의 기초연구로서, 부직포 상으로 얻어지는 나노섬유 제조기술의 단점인 직경의 불균일, 물리적 특성의 한계와 필라멘트가 아닌 단섬유로 인해 발생하는 용도 및 상품 개발에의 제한성을 개선하기 위하여 연속적으로 필라멘트를 생산가능한 해도형 복합방사 방법을 도입하여 개발한 장섬유 필라멘트 형태의 해도형 나노 섬유 소재를 활용하는 것으로 방사된 SDY 형태의 나노필라멘트 섬유를 제직상에서의 작업성 용이 및 직물의 벌키성 증대와 Crimp성을 향상 시켜 터치감 및 후가공에 용이할 수 있도록 DTY를 제조함에 있어 기존 일반 POY사에서의 DTY공정과는 달리 소재의 특성 즉, 해도사의 해성분 및 도성분의 후공정을 감안하여 최적의 Crimp는 발현하되 단면의 형상을 유지할 수 있는 다양한 사가공 조건을 설정 하고 이에 따라 가공사를 생산하여 공정조건에 따른 가공사의 물성 및 수축특성을 비교 분석 하여 염색 및 후가공시 소재의 물성 및 수축특성이 미치는 영향성을 살펴보고자 하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6A
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• pp.457-464
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• 2011

An experimental study was performed to evaluate the possibility of using stiff type PolyUrea(PU) on RC slab as a strengthening material. Stiff type PU(STPU) was sprayed on the bottom surface of the slab specimens, which were then attached with CFRP or GFRP sheets. Also the evaluation of the bond capacity, the single most influential parameter on strengthening of RC structures, was carried out the flexural capacity evaluation test results showed that the load carrying capacity of the PU specimen was greater and less than the unstrengthened and FRP sheet attached specimens, respectively. The STPU specimens showed a ductile flexural behavior in the plastic displacement range. With respect to bond capacity, the bond strength of all of the specimen exceeded the code required bond strength of 1.5 MPa. Also, the STPU sprayed specimen without using epoxy resin did not peel off when the tensile grip was applied for testing. The stability of the PU bond failure indicate a good bond strength of PU when applied to concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.2
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• pp.51-59
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• 2019

There is increasingly more research focusing on the application of FRP reinforcing bars as an alternative material for steel reinforcing bars, but most such research look at short term behavior of FRP reinforced structures. In this study, the microscopic analysis and tensile behavior of Basalt and Glass FRP bars under freezing-thawing and alkaline conditions were experimentally evaluated. After 100 cycles of the freezing and thawing, the tensile strength and elastic modulus of FRP bars decreased by about 5%. In the case of microstructure of FRP bars during the initial 20 days, no significant damages of FRP bar sections were found under $20^{\circ}C$ alkaline solution; however, the specimens immersed in $60^{\circ}C$ alkaline solution were found to experience resin dissolution, fiber damage and the separation of the resin-fiber interface. In the alkaline environment, the strength decrease of about 10% occurred in the environment at $20^{\circ}C$ for 100 days, but the tensile strength of FRPs exposed for 500 days decreased by 50%. At temperature of $40^{\circ}C$ and $60^{\circ}C$, an abrupt decrease in the strength was observed at 50 and 100 days. Especially, the tensile strength decrease of Basalt fiber Reinforced Polymer bars showed more severe degradation due to the damage caused by dissolution of resin matrix and fiber swelling in alkaline solution. Therefore, in order to improve the long-term performance of the surface braided FRPr reinforcing bars, surface treatment is required to ensure alkali resistance.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.65-76
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• 2011

This paper presents the results of a numerical investigation on the long-term behavior of geosynthetic reinforced soil abutment. The investigation was carried out aiming at identifying the governing mechanisms of the long-term deformation of geosynthetic-reinforced soil abutment subjected to sustained loads during service life. A numerical modeling strategy was first established using the Singh-Mitchell creep model and the power law model, respectively, for the backfill and the geosyntehtic reinforcement. A parametric study on the creep properties of the backfill and the geosynthetic reinforcement was then conducted. The results indicated that a geosynthetic reinforced soil structure backfilled with marginal soil may exhibit substantial long-term deformation due to the creep effects caused by both the backfill soil and the geosynthetic reinforcement, the magnitude of which depends largely on the creep properties. This paper highlights the importance of considering the creep effect on load supporting geosynthetic reinforced soil structures when the long-term serviceability requirement is of prime importance.

• Journal of the Korean Geosynthetics Society
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• v.6 no.1
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• pp.9-16
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• 2007

Geotextile is one of the most useful and effective polymer material in civil construction works and the main function of geotextile is separation, reinforcement, filtering and drainage. Recently, because of the shortage of natural rock, traditional forms of river and coastal structures have become very expensive to build and maintain. Therefore, the materials used in hydraulic and coastal structures are changing from the traditional rubble and concrete systems to the cheaper materials and systems. One of these alternatives employs geotextile tube technology in the construction of coastal and shore protection structures, such as embankment, see dyke, groins, jetties, detached breakwaters and so on. Geotextile tube technology has changed from being an alternative construction technique and, in fact, has advanced to become the most effective solution of choice. This paper presents case history of sea dyke filter construction using geotextile tube mattress and also, various issues related to the tube mattress design and construction technology.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.83-90
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• 2024

This study investigates the 3D printing characteristics of strain hardening cement composites (SHCC) reinforced by PVA fibers. Three SHCC mixtures with diverse fiber volume fractions (1.0% for F1.0 mixture, 1.5% for F1.5 mixture, and 1.8% for F1.8 mixture) were designed. Except for the F1.0 mixture, all mixtures met the necessary conditions for multiple micro-cracking, with higher fiber volume fractions more readily satisfying these conditions. The flow values of three SHCC mixtures were within the 3D printable range of 120~160 mm, exhibiting decreased flow values with increasing the fiber volume fractions. Observation of the printed SHCC surfaces indicated that the F1.0 mixture had a Level-3 (good) rating, while F1.5 and F1.8 were rated as Level-2 (average). Higher fiber volume fractions resulted in poorer surface quality, thus, further research needs to be performed for modulating SHCC mixture suitable for 3D printing. The uniaxial tension behavior showed that the F1.0 mixture failed at lower strain, whereas F1.5 and F1.8 exhibited higher strain performance with multiple micro-cracks occurring.

• Journal of the Korean Geotechnical Society
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• v.15 no.5
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• pp.171-191
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• 1999

The final aim of this research is to systematize the reinforced-earth wall system using the geosynthetic composite reinforcement in the weathered granite backfill soils having relatively large amount of fines. As a staged endeavour to accomplish this purpose, laboratory pull-out tests and finite element modeling are carried out in the present study focusing on the analyses of friction characteristics associated with interaction behaviors of the geosynthetic composite reinforcement composed of geogrid with a superior function in tensile resistance and geotextile with sufficient drainage effects. In addition, drainage effects of the geotextile below geogrid are examined based on the analysis of finite difference numerical modeling. From the present investigation, it is concluded that the geosynthetic composite reinforcement in the weathered granite backfills may possibly be used to achieve effects on both a reduction of deformations and an increase of the tensile resistance, together with drainage effects resulting from the geotextile.