• Nuclear Engineering and Technology
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• 제47권6호
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• pp.756-765
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• 2015

Background: Fibers have been used in cement mixture to improve its toughness, ductility, and tensile strength, and to enhance the cracking and deformation characteristics of concrete structural members. The addition of fibers into conventional reinforced concrete can enhance the structural and functional performances of safety-related concrete structures in nuclear power plants. Methods: The effects of steel and polyamide fibers on the shear resisting capacity of a prestressed concrete containment vessel (PCCV) were investigated in this study. For a comparative evaluation between the shear performances of structural walls constructed with conventional concrete, steel fiber reinforced concrete, and polyamide fiber reinforced concrete, cyclic tests for wall specimens were conducted and hysteretic models were derived. Results: The shear resisting capacity of a PCCV constructed with fiber reinforced concrete can be improved considerably. When steel fiber reinforced concrete contains hooked steel fibers in a volume fraction of 1.0%, the maximum lateral displacement of a PCCV can be improved by > 50%, in comparison with that of a conventional PCCV. When polyamide fiber reinforced concrete contains polyamide fibers in a volume fraction of 1.5%, the maximum lateral displacement of a PCCV can be enhanced by ~40%. In particular, the energy dissipation capacity in a fiber reinforced PCCV can be enhanced by > 200%. Conclusion: The addition of fibers into conventional concrete increases the ductility and energy dissipation of wall structures significantly. Fibers can be effectively used to improve the structural performance of a PCCV subjected to strong ground motions. Steel fibers are more effective in enhancing the shear performance of a PCCV than polyamide fibers.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.388-399
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• 2003

Light losses in optical fibers are investigated by a fiber optic OTDR (Optical Time Domain Reflectometry) sensor system to develop fiber optic probes for structural strain measurement. The sensing fibers are manufactured 3 kinds of fibers: one is single mode fiber, and second is multimode fiber, and the third is low-cladding-index fiber. Fiber bending tests are performed to determine the strain sensitivity according to the strain of gage length of optical fibers. In the result of this experiments, the strain sensitivity of the single mode fiber was shown the highest value than others. The fiber optic strain probe was manufactured to verify the feasibility of the structural strain measurement. In this test, the fiber optic strain probe of the OTDR sensor could be easily made by the single mode fiber.

• Advances in concrete construction
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• 제11권1호
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• pp.45-58
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• 2021

Experimental investigation has been conducted to study the effect of using Micro/Nano Silica in presence of steel fibers on improving the static response of reinforced concrete beams. Twenty-one mixtures were prepared with micro silica (MS), Nano silica (NS) and steel fibers (SFs) at different percentages. Cement was replaced by 10% and 15% of Micro silica and 1%, 2% and 3% of Nano silica in the presence of steel fibers at different volume fractions 0%, 1%, and 2%. 258 concrete samples, (126 cubes, 63 cylinders, 63 prisms, and six R.C beams), were investigated experimentally in two stages. The first stage was to investigate the mechanical properties of the prepared mixtures. The second stage was to study the static behavior of R.C beams, using the designed concrete mixtures, under a four-point flexural test. The results showed that replacing cement by (10% MS and 1% NS) produces the optimum mix with a significant improvement in the mechanical properties and the response of R.C beams under static loads. In addition, incorporating steel fibers at different volume fractions have a considerable effect on the flexural toughness of concrete mixes.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.335-340
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• 2001

Recently in abroad, structural synthetic fiber developed, has been studied extensively as a substitute for steel fiber due to its properties such as corrosion-resistance, low density, good pumping, and in-place safety, etc. In this study, we conducted pull-out test, for seven different geometries of structural synthetic fibers and obtained optimum geometry for structural synthetic fiber which fully utilizes matrix anchoring without revealing fiber fracturing. According to pull-out test results, it was found that crimped type structural synthetic fiber give significant improvement in the interface toughness(roll-out enemy) and pull-out load.

• Smart Structures and Systems
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• 제5권2호
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• pp.139-152
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• 2009

Globally, civil infrastructures are deteriorating at an alarming rate caused by overuse, overloading, aging, damage or failure due to natural or man-made hazards. With such a vast network of deteriorating infrastructure, there is a growing interest in continuous monitoring technologies. In order to provide a true distributed sensor and control system for civil structures, we are developing a Structural Nervous System that mimics key attributes of a human nervous system. This nervous system is made up of building blocks that are designed based on mechanoreceptors as a fundamentally new approach for the development of a structural health monitoring and diagnostic system that utilizes the recently developed piezo-fibers capable of sensing and actuation. In particular, our research has been focused on producing a sensory nervous system for civil structures by using piezo-fibers as sensory receptors, nerve fibers, neuronal pools, and spinocervical tract to the nodal and central processing units. This paper presents up to date results of our research, including the design and analysis of the structural nervous system.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.311-318
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• 1995

Increases in strength and ductilities of steel fiber reinforced concrete(SFRC) under direct tension and compression result in improvements of flexural behavior of reinforced steel fibrous concrete beam(RSFCB) Use of hooked steel fibers in stead of round steel fibers enhances futher the structural porperties of a beam due to their greater mechanical bond resistance compared to that of round steel fibers. Flexural strength, initial stiffness ductility and failure mechani는 of RSFCB are dependent upon material and structural parameters and among which are the volume fraction of fibers, reinforcement ratio, and casting depth of SFRC in a beam section. The flexural behavior of RSFCB's are examined experimentally in this study and some conclusions are made regarding those effects of main material and structural parameters on the overall behavior of RSFCB.

• Carbon letters
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• 제9권2호
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• pp.127-130
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• 2008

This study aims to find a correlation between XRD and Raman result of the activated carbon fibers as a function of its activation degrees. La of the isotropic carbon fiber prepared by oxidation in carbon dioxide gas have been observed using laser Raman spectroscopy. The basic structural parameters of the fibers were evaluated by XRD as well, and compared with Raman result. The La of the carbon fibers were measured to be 25.5 ${\AA}$ from Raman analysis and 23.6 ${\AA}$ from XRD analysis. La of the ACFs were 23.6 ${\AA}$ and 20.4 ${\AA}$, respectively, representing less ordered through activation process. It seems that the $I_D/I_G$ of Raman spectra were related to crystallite size(La). Raman spectroscopy has demonstrated its unique ability to detect structural changes during the activation of the fibers. There was good correlation between the La value obtained from Raman and XRD.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.445-450
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• 2006

It is proposed that the electromechanical relation of the conductive materials with high electrical resistance may be used to estimate the current stress of prestressing tendons. To choose the best conductive material to this end, we studied the electromechanical relations of carbon fibers and metalic heat wires experimentally. It is found that the relation of carbon fibers can be modelled by a parabolic(or hyperbolic) function in the early stage of deformation. However because the relation is not consistent when it is unloaded and reload, carbon fibers are not suitable for this purpose. Metallic heat wires show a consistent linear relation during loading and unloading in the elastic deformation and are suitable for this purpose. To estimate the electromechanics relation of metallic wires, we developed a simple formula based on the rigid plasticity. We propose a new kind of prestressing tendons whose stress can be monitored.

• Animal cells and systems
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• 제7권1호
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• pp.35-41
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• 2003

The principal fibers used in constructing the cocoon in the garden spider, Argiope aurantia, are large-diameter fibers developed from tubuliform glands and small-diameter fibers presumed to be spun by the aciniform silk glands. Scanning electron micrographs of the large-diameter fibers on both surfaces of the cocoon clearly reveal their fine structural differences. While the silk fibers on the inner surface have smooth and homogeneous appearances, each fiber on the outer surface represents a multicomponent internal structure. Examination of each fibers using transmission electron microscope also provides additional evidence that the multicomponent fibers contain numerous electron lucent fibrils embedded in an amorphous electron dense matrix. It has been also revealed that two types of secretory granules presumed to be the precursors of tubuliform fibers are closely related to the production of distinct coloration in luminal contents - brownish and yellowish components. Moreover, these electron-dense granules, possibly precursor of fibrillar component, and electron-lucent granules, possibly precursor of matrix component, are densely packed and remain close to each other without fusion. It is critical evidence that the individual tubuliform fiber is not only heterogeneous and multicomponent but also takes place in a variety at manners throughout the length of the gland.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.373-378
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• 2003

The cement-based composites have relatively low tensile strength and toughness. The fiber addition is one of the most important ways of increasing the toughness of concrete. The steel fibers have been used conventionally in the shotcrete of tunnel lining. Recently, the structural synthetic fibers were developed and used frequently in some actual tunnel shotcreting in foreign countries. Now types of synthetic fibers have been developed in this study. The purpose of this study is to explore the strength and toughness characteristic of the concrete reinforced with synthetic fibers developed in this study. The result were compared with those of steel fiber reinforced concrete. It is seen that the performance of synthetic fiber reinforced concrete is good as much as that of steel fiber reinforced concrete, while the synthetic fibers have advantages in corrsion resistance and economy.