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Young Soo Yoon - One of the best experts on this subject based on the ideXlab platform.

  • effect of fiber orientation on the rate dependent Flexural Behavior of ultra high performance fiber reinforced concrete
    Composite Structures, 2016
    Co-Authors: Doo-yeol Yoo, Nemkumar Banthia, Su-tae Kang, Young Soo Yoon
    Abstract:

    Abstract This study aims to investigate the effect of fiber orientation on the Flexural Behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) under quasi-static and impact loadings. Two placement methods and two specimen sizes were considered to provide different fiber orientations, and image analysis was carried out to quantitatively evaluate the fiber orientation. Quasi-static Flexural tests were performed according to ASTM standard, while impact tests were performed with two different potential energies (0.48 and 1.13 kJ) using a drop-weight impact test machine. Test results indicated that under quasi-static loading conditions, higher Flexural strength, normalized deflection capacity, and toughness were obtained in the beams that contained better fiber orientation in the direction of the tensile load compared to those with poor fiber orientation; however, no obvious difference in the first-cracking properties was observed with respect to the fiber orientation. Under impact loading conditions, the Flexural strength and energy absorption capacity were both increased with better fiber orientation, and a greater increase in the Flexural strength with strain-rate was obtained in the beams with better fiber orientation at an identical potential energy (relative to their counterparts with poorer orientation). Therefore, providing good fiber orientation can be an effective way to improve the impact resistance of UHPFRC beams.

  • Flexural Behavior of ultra high performance fiber reinforced concrete beams reinforced with gfrp and steel rebars
    Engineering Structures, 2016
    Co-Authors: Nemkumar Banthia, Young Soo Yoon
    Abstract:

    Abstract This study describes the Flexural Behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams reinforced with glass fiber-reinforced polymer (GFRP) rebars and hybrid reinforcements (steel + GFRP rebars). Three GFRP bar-reinforced beams and four hybrid reinforced beams with different reinforcement ratios were fabricated and tested. Owing to the strain-hardening characteristics of UHPFRC, all test beams exhibited very stiff load–deflection Behavior after the formation of cracks and satisfied the service crack width criteria of CAN/CSA S806. In addition, deformability factors higher than the lower limit of CAN/CSA-S6 were obtained for all test beams. The increase in the reinforcement ratio of GFRP rebars resulted in the improvement of their Flexural performances, including post-cracking stiffness, load carrying capacity, and ductility (or deformability). The use of hybrid reinforcements by replacing a part of a GFRP rebar with a steel rebar contributed to a higher post-cracking stiffness before steel yielding, but led to lower deformability. Based on a sectional analysis, both AFGC/SETRA and JSCE recommendations were appropriate for predicting the moment–curvature response of UHPFRC beams with GFRP rebars and hybrid reinforcements: the average ratios of the maximum moments obtained from experiments and numerical analyses were found to be 1.12 and 0.94, respectively.

  • Flexural Behavior of ultra high performance fiber reinforced concrete beams reinforced with gfrp and steel rebars
    Engineering Structures, 2016
    Co-Authors: Nemkumar Banthia, Young Soo Yoon
    Abstract:

    Abstract This study describes the Flexural Behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams reinforced with glass fiber-reinforced polymer (GFRP) rebars and hybrid reinforcements (steel + GFRP rebars). Three GFRP bar-reinforced beams and four hybrid reinforced beams with different reinforcement ratios were fabricated and tested. Owing to the strain-hardening characteristics of UHPFRC, all test beams exhibited very stiff load–deflection Behavior after the formation of cracks and satisfied the service crack width criteria of CAN/CSA S806. In addition, deformability factors higher than the lower limit of CAN/CSA-S6 were obtained for all test beams. The increase in the reinforcement ratio of GFRP rebars resulted in the improvement of their Flexural performances, including post-cracking stiffness, load carrying capacity, and ductility (or deformability). The use of hybrid reinforcements by replacing a part of a GFRP rebar with a steel rebar contributed to a higher post-cracking stiffness before steel yielding, but led to lower deformability. Based on a sectional analysis, both AFGC/SETRA and JSCE recommendations were appropriate for predicting the moment–curvature response of UHPFRC beams with GFRP rebars and hybrid reinforcements: the average ratios of the maximum moments obtained from experiments and numerical analyses were found to be 1.12 and 0.94, respectively.

  • biaxial Flexural Behavior of ultra high performance fiber reinforced concrete with different fiber lengths and placement methods
    Cement & Concrete Composites, 2015
    Co-Authors: Doo-yeol Yoo, Su-tae Kang, Young Soo Yoon
    Abstract:

    Abstract This study investigates the effects of fiber length and placement method on the biaxial Flexural Behavior and fiber distribution characteristics of ultra-high-performance fiber-reinforced concrete (UHPFRC). A number of UHPFRC panels including three different fiber lengths were fabricated using two different placement methods, and an image analysis was performed to quantitatively evaluate the fiber distribution characteristics such as fiber orientation, fiber dispersion, and number of fibers per unit area. The biaxial Flexural performances including load carrying capacity, energy absorption capacity, and cracking Behavior were found to be improved with the increase in fiber length up to 19.5 mm. The biaxial Flexural performances were also influenced by the placement method; the specimens with concrete placed at the center (maximum moment region) showed better Flexural performances than those with concrete placed at the corner. These observations were confirmed by the image analysis results, which showed poorer fiber orientation and fewer fibers across the crack surfaces at the maximum moment region for the specimens with concrete placed at the corner, compared with their counterparts.

Nemkumar Banthia - One of the best experts on this subject based on the ideXlab platform.

  • Flexural Behavior of geopolymer composites reinforced with steel and polypropylene macro fibers
    Cement & Concrete Composites, 2017
    Co-Authors: Aamer Bhutta, Paulo H R Borges, Cristina Zanotti, Mohammed Farooq, Nemkumar Banthia
    Abstract:

    Abstract Like ordinary Portland cement concrete, the matrix brittleness in geopolymer composites can be reduced by introducing appropriate fiber reinforcement. Several studies on fiber reinforced geopolymer composites are available, however there is still a gap to understand and optimize their performance. This paper presents the Flexural Behavior of fly ash-based geopolymer composites reinforced with different types of macro steel and polypropylene fibers with higher aspect ratio. Three types (length-deformed, end-deformed and straight) of steel fibers and another type of length-deformed polypropylene fiber with optimum fiber volume fraction of 0.5% are studied. The effects of different geometries of the fibers, curing regimes (ambient cured and heat cured at 60 °C for 24 h) and concentration of NaOH activator (10 M and 12 M) on the first peak strength, modulus of rupture and toughness of the geopolymer composites are investigated. The quantitative effect of fiber geometry on geopolymer composite performance was also analyzed through a fiber deformation ratio. The compressive strength, splitting tensile strength and Flexural toughness are significantly improved with macro fibers reinforcement and heat curing. The results also show that heat curing increases the first peak load of all fiber-reinforced geopolymers composites. End-deformed steel fibers exhibit the most ductile Flexural response compared to other steel fibers in both heat and ambient-cured fiber reinforced geopolymer composites.

  • effect of fiber orientation on the rate dependent Flexural Behavior of ultra high performance fiber reinforced concrete
    Composite Structures, 2016
    Co-Authors: Doo-yeol Yoo, Nemkumar Banthia, Su-tae Kang, Young Soo Yoon
    Abstract:

    Abstract This study aims to investigate the effect of fiber orientation on the Flexural Behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) under quasi-static and impact loadings. Two placement methods and two specimen sizes were considered to provide different fiber orientations, and image analysis was carried out to quantitatively evaluate the fiber orientation. Quasi-static Flexural tests were performed according to ASTM standard, while impact tests were performed with two different potential energies (0.48 and 1.13 kJ) using a drop-weight impact test machine. Test results indicated that under quasi-static loading conditions, higher Flexural strength, normalized deflection capacity, and toughness were obtained in the beams that contained better fiber orientation in the direction of the tensile load compared to those with poor fiber orientation; however, no obvious difference in the first-cracking properties was observed with respect to the fiber orientation. Under impact loading conditions, the Flexural strength and energy absorption capacity were both increased with better fiber orientation, and a greater increase in the Flexural strength with strain-rate was obtained in the beams with better fiber orientation at an identical potential energy (relative to their counterparts with poorer orientation). Therefore, providing good fiber orientation can be an effective way to improve the impact resistance of UHPFRC beams.

  • Flexural Behavior of ultra high performance fiber reinforced concrete beams reinforced with gfrp and steel rebars
    Engineering Structures, 2016
    Co-Authors: Nemkumar Banthia, Young Soo Yoon
    Abstract:

    Abstract This study describes the Flexural Behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams reinforced with glass fiber-reinforced polymer (GFRP) rebars and hybrid reinforcements (steel + GFRP rebars). Three GFRP bar-reinforced beams and four hybrid reinforced beams with different reinforcement ratios were fabricated and tested. Owing to the strain-hardening characteristics of UHPFRC, all test beams exhibited very stiff load–deflection Behavior after the formation of cracks and satisfied the service crack width criteria of CAN/CSA S806. In addition, deformability factors higher than the lower limit of CAN/CSA-S6 were obtained for all test beams. The increase in the reinforcement ratio of GFRP rebars resulted in the improvement of their Flexural performances, including post-cracking stiffness, load carrying capacity, and ductility (or deformability). The use of hybrid reinforcements by replacing a part of a GFRP rebar with a steel rebar contributed to a higher post-cracking stiffness before steel yielding, but led to lower deformability. Based on a sectional analysis, both AFGC/SETRA and JSCE recommendations were appropriate for predicting the moment–curvature response of UHPFRC beams with GFRP rebars and hybrid reinforcements: the average ratios of the maximum moments obtained from experiments and numerical analyses were found to be 1.12 and 0.94, respectively.

  • Flexural Behavior of ultra high performance fiber reinforced concrete beams reinforced with gfrp and steel rebars
    Engineering Structures, 2016
    Co-Authors: Nemkumar Banthia, Young Soo Yoon
    Abstract:

    Abstract This study describes the Flexural Behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams reinforced with glass fiber-reinforced polymer (GFRP) rebars and hybrid reinforcements (steel + GFRP rebars). Three GFRP bar-reinforced beams and four hybrid reinforced beams with different reinforcement ratios were fabricated and tested. Owing to the strain-hardening characteristics of UHPFRC, all test beams exhibited very stiff load–deflection Behavior after the formation of cracks and satisfied the service crack width criteria of CAN/CSA S806. In addition, deformability factors higher than the lower limit of CAN/CSA-S6 were obtained for all test beams. The increase in the reinforcement ratio of GFRP rebars resulted in the improvement of their Flexural performances, including post-cracking stiffness, load carrying capacity, and ductility (or deformability). The use of hybrid reinforcements by replacing a part of a GFRP rebar with a steel rebar contributed to a higher post-cracking stiffness before steel yielding, but led to lower deformability. Based on a sectional analysis, both AFGC/SETRA and JSCE recommendations were appropriate for predicting the moment–curvature response of UHPFRC beams with GFRP rebars and hybrid reinforcements: the average ratios of the maximum moments obtained from experiments and numerical analyses were found to be 1.12 and 0.94, respectively.

Doo-yeol Yoo - One of the best experts on this subject based on the ideXlab platform.

  • Effects of Hooked-End Steel Fiber Geometry and Volume Fraction on the Flexural Behavior of Concrete Pedestrian Decks
    MDPI AG, 2019
    Co-Authors: Seung-jung Lee, Doo-yeol Yoo, Do-young Moon
    Abstract:

    This study investigates the effects of hooked-end fiber geometry and volume fraction on the Flexural Behavior of concrete pedestrian decks. To achieve this, three different fiber geometries, i.e., three-dimensional (3D), four-dimensional (4D), and five-dimensional (5D), and volume fractions of 0.37%, 0.6%, and 1.0% were considered. Test results indicate that a higher number of hook ends can more effectively enhance the Flexural strength and Flexural strength margin at all volume fractions than a lower number, so that the order of effectiveness of hooked-end fibers on the Flexural strength parameters was as follows: 5D > 4D > 3D. To satisfy the ductility index of 0.39, the amounts of 3D, 4D, and 5D hooked steel fibers should be in the range of 0.98%‒1.10%. Moreover, at a fiber volume fraction of 1.0%, only multiple cracking Behaviors were observed, and the numerical results indicated that the volume fraction should be equal to 1.0% to guarantee a deflection-hardening response of pedestrian decks, regardless of the hooked-end fiber geometry. Consequently, a 1.0% by volume of hooked-end steel fiber is recommended to replace the minimum longitudinal steel rebars and guarantee a ductile Flexural Behavior with multiple cracks for pedestrian decks made of high-strength concrete

  • effect of fiber orientation on the rate dependent Flexural Behavior of ultra high performance fiber reinforced concrete
    Composite Structures, 2016
    Co-Authors: Doo-yeol Yoo, Nemkumar Banthia, Su-tae Kang, Young Soo Yoon
    Abstract:

    Abstract This study aims to investigate the effect of fiber orientation on the Flexural Behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) under quasi-static and impact loadings. Two placement methods and two specimen sizes were considered to provide different fiber orientations, and image analysis was carried out to quantitatively evaluate the fiber orientation. Quasi-static Flexural tests were performed according to ASTM standard, while impact tests were performed with two different potential energies (0.48 and 1.13 kJ) using a drop-weight impact test machine. Test results indicated that under quasi-static loading conditions, higher Flexural strength, normalized deflection capacity, and toughness were obtained in the beams that contained better fiber orientation in the direction of the tensile load compared to those with poor fiber orientation; however, no obvious difference in the first-cracking properties was observed with respect to the fiber orientation. Under impact loading conditions, the Flexural strength and energy absorption capacity were both increased with better fiber orientation, and a greater increase in the Flexural strength with strain-rate was obtained in the beams with better fiber orientation at an identical potential energy (relative to their counterparts with poorer orientation). Therefore, providing good fiber orientation can be an effective way to improve the impact resistance of UHPFRC beams.

  • biaxial Flexural Behavior of ultra high performance fiber reinforced concrete with different fiber lengths and placement methods
    Cement & Concrete Composites, 2015
    Co-Authors: Doo-yeol Yoo, Su-tae Kang, Young Soo Yoon
    Abstract:

    Abstract This study investigates the effects of fiber length and placement method on the biaxial Flexural Behavior and fiber distribution characteristics of ultra-high-performance fiber-reinforced concrete (UHPFRC). A number of UHPFRC panels including three different fiber lengths were fabricated using two different placement methods, and an image analysis was performed to quantitatively evaluate the fiber distribution characteristics such as fiber orientation, fiber dispersion, and number of fibers per unit area. The biaxial Flexural performances including load carrying capacity, energy absorption capacity, and cracking Behavior were found to be improved with the increase in fiber length up to 19.5 mm. The biaxial Flexural performances were also influenced by the placement method; the specimens with concrete placed at the center (maximum moment region) showed better Flexural performances than those with concrete placed at the corner. These observations were confirmed by the image analysis results, which showed poorer fiber orientation and fewer fibers across the crack surfaces at the maximum moment region for the specimens with concrete placed at the corner, compared with their counterparts.

Su-tae Kang - One of the best experts on this subject based on the ideXlab platform.

  • effect of fiber orientation on the rate dependent Flexural Behavior of ultra high performance fiber reinforced concrete
    Composite Structures, 2016
    Co-Authors: Doo-yeol Yoo, Nemkumar Banthia, Su-tae Kang, Young Soo Yoon
    Abstract:

    Abstract This study aims to investigate the effect of fiber orientation on the Flexural Behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) under quasi-static and impact loadings. Two placement methods and two specimen sizes were considered to provide different fiber orientations, and image analysis was carried out to quantitatively evaluate the fiber orientation. Quasi-static Flexural tests were performed according to ASTM standard, while impact tests were performed with two different potential energies (0.48 and 1.13 kJ) using a drop-weight impact test machine. Test results indicated that under quasi-static loading conditions, higher Flexural strength, normalized deflection capacity, and toughness were obtained in the beams that contained better fiber orientation in the direction of the tensile load compared to those with poor fiber orientation; however, no obvious difference in the first-cracking properties was observed with respect to the fiber orientation. Under impact loading conditions, the Flexural strength and energy absorption capacity were both increased with better fiber orientation, and a greater increase in the Flexural strength with strain-rate was obtained in the beams with better fiber orientation at an identical potential energy (relative to their counterparts with poorer orientation). Therefore, providing good fiber orientation can be an effective way to improve the impact resistance of UHPFRC beams.

  • biaxial Flexural Behavior of ultra high performance fiber reinforced concrete with different fiber lengths and placement methods
    Cement & Concrete Composites, 2015
    Co-Authors: Doo-yeol Yoo, Su-tae Kang, Young Soo Yoon
    Abstract:

    Abstract This study investigates the effects of fiber length and placement method on the biaxial Flexural Behavior and fiber distribution characteristics of ultra-high-performance fiber-reinforced concrete (UHPFRC). A number of UHPFRC panels including three different fiber lengths were fabricated using two different placement methods, and an image analysis was performed to quantitatively evaluate the fiber distribution characteristics such as fiber orientation, fiber dispersion, and number of fibers per unit area. The biaxial Flexural performances including load carrying capacity, energy absorption capacity, and cracking Behavior were found to be improved with the increase in fiber length up to 19.5 mm. The biaxial Flexural performances were also influenced by the placement method; the specimens with concrete placed at the center (maximum moment region) showed better Flexural performances than those with concrete placed at the corner. These observations were confirmed by the image analysis results, which showed poorer fiber orientation and fewer fibers across the crack surfaces at the maximum moment region for the specimens with concrete placed at the corner, compared with their counterparts.

  • Investigation on the Flexural Behavior of UHPCC considering the effect of fiber orientation distribution
    Construction and Building Materials, 2012
    Co-Authors: Su-tae Kang, Jin-keun Kim
    Abstract:

    Abstract This study aims to investigate the effect of fiber orientation distribution on the Flexural Behavior of ultra high performance cementitious composites (UHPCC) and to propose an analytical approach which enables to predict the Flexural Behavior considering probabilistic fiber orientation distribution. A three-point bending test with the notched beams was carried out and the fiber orientation distribution was quantitatively estimated by the help of image analysis process. The measured fiber orientation distributions for two different Flexural performances confirmed that the fiber orientation distribution has a strong impact on the deflection hardening Behavior in bending. Finite element analyses were performed to predict Flexural Behavior of UHPCC considering the difference in fiber bridging Behavior depending on the fiber orientation distribution. The analytical results were in good agreement with the experimental results.

Claudia P Ostertag - One of the best experts on this subject based on the ideXlab platform.

  • Flexural Behavior and durability properties of high performance hybrid fiber reinforced concrete
    Construction and Building Materials, 2018
    Co-Authors: Susanto Teng, Vahid Afroughsabet, Claudia P Ostertag
    Abstract:

    Abstract The aim of the present study is to investigate the Flexural Behavior and durability properties of high performance hybrid-fiber-reinforced concrete. In the fiber-reinforced concrete (FRC) mixes, silica fume (SF) and ground granulated blast-furnace slag (GGBS) were used as mineral admixtures at the proportions of 10% and 30% of the cement by weight, respectively. Double hooked-end (DHE) steel fibers, single hooked-end (HE) steel fibers, and polyvinyl alcohol (PVA) fibers were mixed in different proportions in the concrete to develop hybrid FRC. The total combined volume fractions of the fibers were 0%, 0.6%, and 1.2%. Various tests to obtain compressive strengths, Flexural Behavior, rapid chloride migration coefficients, and electrical resistivity were carried out. The results indicate that mineral admixtures and particularly silica fume have significant influence on durability properties of concrete. A very high durable concrete can be achieved by simultaneous addition of SF and GGBS in concrete. The results also show that the incorporation of fibers notably improved the mechanical strengths of the concrete. The post-cracking Flexural resistance and toughness of the FRC can be effectively increased through the addition of 1.2% DHE steel fibers. It was observed that the substitution of DHE steel fibers with HE steel fibers or PVA fibers led to a reduction in Flexural performance of hybrid FRC. It was also observed that the chloride diffusivity of FRC was higher, while the electrical resistivity of FRC was lower than those of similar mixes but without fibers.