• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.579-584
• /
• 2001

A method is described for predicting crack with and spacing in Steel Fiber Reinforced Concrete (SFRC). The crack behavior of SFRC influenced by longitudinal reinforcement ratio, volume and type of steel fiber, strength of concrete. It can be observed from experimental results that addition of steel fiber to reinforced concrete beam reduces crack width in serviceability limit states. The proposed method predicts crack widths in cracking stage of the beam. Calculated crack widths obtained for reinforced concrete beams and different volume and type of steel fiber, strength of concrete showed good agreement with experimental results.

• Journal of the Korean Society for Railway
• /
• v.8 no.4
• /
• pp.293-298
• /
• 2005

A method is described for predicting crack with and spacing in Steel Fiber Reinforced Concrete (SFRC). The crack behavior of SFRC influenced by longitudinal reinforcement ratio, volume and type of sleet fiber, strength of concrete. It can be observed from experimental results that addition of steel fiber to reinforced concrete beam reduces crack width in serviceability limit stales. The proposed method predicts crack widths in cracking stage of the beam. Calculated crack widths obtained for reinforced concrete beams and different volume and type of steel fiber, strength of concrete showed good agreement with experimental results.

• Computers and Concrete
• /
• v.20 no.4
• /
• pp.449-459
• /
• 2017

Fresh and hardened behaviors of a new hybrid fiber (steel fiber, polyvinyl alcohol fiber and calcium carbonate whisker) reinforced cementitious composites (HyFRCC) with admixtures (fly ash, silica fume and water reducer) have been studied. Within the limitations of the equipment and testing program, it is illustrated that the rheological properties of the new HyFRCC conform to the modified Bingham model. The relations between flow spread and yield stress as well as flow rate and plastic viscosity both conform well with negative exponent correlation, justifying that slump flow and flow rate test can be applied to replace the other two as simple rheology measurement and control method in jobsite. In addition, for the new HyFRCC with fly ash and water reducer, the mathematical model between the rheological and mechanical properties conform well with the quadratic function, and these quadratic function curves are always concave upward. Based on mathematical analysis, an optimal range of rheology/ flowability can be identified to achieve ideal mechanical properties. In addition, this optimization method can be extended to PVA fiber reinforced cement-based composites.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.44 no.4
• /
• pp.123-128
• /
• 2002

This study was performed to use fiber mixed soil which has clayey soil or sandy soil with fibrillated fiber or monofilament fiber on purpose of construction materials, filling materials, and back filling materials. In addition, this study was conducted to analyze strength properties and fiber reinforcing effect with fiber mixed soil by direct-shear test. In case of fibrillated fiber mixed soil, the more quantity of fiber was in both cohesive soil and sandy soil, the larger shear stress was in respective step of normal load. The respective mixed soil at 0.5% and 0.1% mixing ratio of monofilament fiber mixed soil showed maximum shear stress. According to unconfined compression or direct-shear test, making specimen of the monofilament fiber mixed soil, it is required to be careful and stable mixing method, while it is expected that monofilament fiber mixed soil doesn't increase strength.

• Journal of Ocean Engineering and Technology
• /
• v.27 no.4
• /
• pp.45-54
• /
• 2013

In this study, various types of composite materials and adhesives that are actually used in the shipbuilding field for small ships, leisure boats, and fishing boats were applied in the hand lay-up method and vacuum infusion method to manufacture specimens. Then the tensile strength, tensile modulus, flexural strength, and flexural modulus values of these specimens were obtained. In addition, the barcol hardness and fiber content were obtained from the specimens. The results showed that the strengths of the specimens manufactured using the vacuum infusion method were higher than those manufactured using the hand lay-up method. Moreover, the barcol hardness and fiber content were also higher in those manufactured using the vacuum infusion method. The specimens manufactured using the vacuum infusion method were thinner despite their large fiber content.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.11a
• /
• pp.891-896
• /
• 2001

As composite materials, the addition of steel fiber in concrete significantly improves the engineering properties of structural members, notably shear strength and ductility, In this study, shear capacity evaluation method according to steel fiber contents was proposed from the literature surveys and member tests. For this, previously proposed five shear strength equation were examined and evaluated by maximum shear strength and shear capacity ratio. From the parametric study and regression analysis, following conclusion can be made; the maximum shear strength of steel fiber reinforced column will be estimated by relative shear capacity ratio.

• International Journal of Precision Engineering and Manufacturing
• /
• v.3 no.3
• /
• pp.37-43
• /
• 2002

Electronic speckle contouring(ESC) based on electronic speckle pattern interferometry is the optical method for measuring object shape by using fringe-projection techniques. This method has the advantages of being non-contact, non-destructive and a whole-field measurement of the surface under investigation. Fringes in ESC represent the difference in depth along the view direction between the master wavefront and the test component. The contour maps of three-dimensional diffuse objects can be obtained by small shifts of optical fiber carrying the dual-object-beams and 4-frame phase shifting. In this study we proposed the contouring method by shifting the collimated illumination beams through optical fiber in order to obtain the contour fringe patterns. And also, we performed the addition of incremental images through the geometrical analysis to obtain the contour fringe interval when we performed the incremental addition of images and experiments based on this method. We obtained both quantitative increment without decorrelation effect and qualitative improvement by reducing the noise of contour fringes.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2018.05a
• /
• pp.107-108
• /
• 2018

In this study, we applied the fiber sheet made by the stitch bonding method, which is a structure in which transverse yarns and double yarns are crossed by applying the principle of sewing knitting without the use of adhesive, The tensile strength of the reinforced concrete structure was investigated. As a result of the tensile strength test of each specimen, the specimen to which the fiber sheet produced by the stitch bonding method was applied exhibited the highest tensile strength among the three types of specimens, and the fiber sheet produced by the needle punching method exhibited the lowest strength. In addition, the stitch - bonded fiber sheet showed a difference of strength of 0.1N / mm for both length and double - sided strength difference.

• Structural Engineering and Mechanics
• /
• v.51 no.1
• /
• pp.89-110
• /
• 2014

In this study, two beam-column elements based on the Elasto-Fiber element theory for reinforced concrete (RC) element have been developed and compared with each other. The first element is based on Elasto Fiber Approach (EFA) was initially developed for steel structures and this theory was applied for RC element in there and the second element is called as Fiber & Bernoulli-Euler element approach (FBEA). In this element, Cubic Hermitian polynomials are used for obtaining stiffness matrix. The beams or columns element in both approaches are divided into a sub-element called the segment for obtaining element stiffness matrix. The internal freedoms of this segment are dynamically condensed to the external freedoms at the ends of the element by using a dynamic substructure technique. Thus, nonlinear dynamic analysis of high RC building can be obtained within short times. In addition to, external loads of the segment are assumed to be distributed along to element. Therefore, damages can be taken account of along to element and redistributions of the loading for solutions. Bossak-${\alpha}$ integration with predicted-corrected method is used for the nonlinear seismic analysis of RC frames. For numerical application, seismic damage analyses for a 4-story frame and an 8-story RC frame with soft-story are obtained to comparisons of RC element according to both approaches. Damages evaluation and propagation in the frame elements are studied and response quantities from obtained both approaches are investigated in the detail.

• Journal of Radiation Industry
• /
• v.9 no.1
• /
• pp.15-20
• /
• 2015

Carbon fiber has received much attention owing to its properties, including a large surface-to-volume ratio, chemical and thermal stability, high thermal and electrical conductivity, and high mechanical strengths. In particular, magnetic nanopowder dispersed carbon fiber has been attractive in technological applications such as the electrochemical capacitor and electromagnetic wave shielding. In this study, the nickel-oxide-nanoparticle dispersed polyacrylonitrile (PAN) fibers were prepared through an electrospinning method. Electron beam irradiation was carried out with a 2.5 MeV beam energy to stabilize the materials. The samples were then heat-treated for stabilization and carbonization. The nanofiber surface was analyzed using a field emission scanning electron microscope (FE-SEM). The crystal structures of the carbon matrix and nickel nanopowders were analysed using X-ray diffraction (XRD). In addition, the magnetic and electrical properties were analyzed using a vibrating sample magnetometer (VSM) and 4 point probe. As the irradiation dose increases, the density of the carbon fiber was increased. In addition, the electrical properties of the carbon fiber improved through electron beam irradiation. This is because the amorphous region of the carbon fiber decreases. This electron beam effect of PAN fibers containing nickel nanoparticles confirmed their potential as a high performance carbon material for various applications.