• Steel and Composite Structures
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• v.24 no.2
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• pp.177-189
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• 2017

Hybrid-fiber reinforced concrete (HFRC) may provide much higher tensile and flexural strengths, tensile ductility, and flexural toughness than normal concrete (NC). HFRC slab has outstanding advantages for use as a composite bridge potential deck slab owing to higher tensile strength, ductility and crack resistance. However, there is little information on shear connector associated with HFRC slabs. To investigate the mechanical behavior of the stud shear connectors embedded in HFRC slab, 14 push-out tests (five batches) in HFRC and NC were conducted. It was found that the stud shear connector embedded in HFRC had a better ductility, higher stiffness and a slightly larger shear bearing capacity than those in NC. The experimentally obtained ultimate resistances of the stud shear connectors were also compared against the equations provided by GB50017 2003, ACI 318-112011, AISC 2011, AASHTO LRFD 2010, PCI 2004, and EN 1994-1-1 (2004), and an empirical equation to predict the ultimate shear connector resistance considering the effect of the HFRC slabs was proposed and validated by the experimental data. Curve fitting was performed to find fitting parameters for all tested specimens and idealized load-slip models were obtained for the specimens with HFRC slabs.

• Structural Engineering and Mechanics
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• v.80 no.5
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• pp.595-608
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• 2021

To investigate the mechanical behavior of large stud shear connector embedded in hybrid fiber-reinforced concrete (HFRC), a refined 3D nonlinear finite element (FE) model incorporating the constitutive model of HFRC was developed using ANSYS. Firstly, the test results conducted by the authors (He et al. 2017) were used to validate FE model of push out tests. Secondly, a total of 27 specimens were analyzed with various parameters including fiber volume fractions of HFRC, diameter of studs and HFRC strength. Finally, an empirical equation considering the contribution of steel fiber (SF) and polypropylene fiber (PF) was recommended to estimate the ultimate capacity of large stud shear connector embedded in HFRC.

• Steel and Composite Structures
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• v.49 no.2
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• pp.197-213
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• 2023

To investigate the static properties of large high strength bolt shear connector in hybrid fiber-reinforced concrete (HFRC) and normal concrete (NC), eight push-out test specimens with single/double nut and HFRC/NC slabs were designed and push-out tests were conducted. A fine 3D nonlinear finite element (FE) model including HFRC constitutive model was established by using ANSYS 18.0, and the test results were used to verify FE models of the push-out test specimens. Then a total of 13 FE models were analyzed with various parameters including fiber volume fractions of HFRC, bolt diameter and thickness of steel flange. Finally, the empirical equations considering the contribution of polypropylene fiber (PF) and steel fiber (SF) obtained from the regression of the test results and FE analysis were recommended to evaluate the load-slip curve and ultimate capacity of the large high strength bolt shear connector embedded in HFRC/NC.

• Structural Engineering and Mechanics
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• v.83 no.1
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• pp.109-121
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• 2022

Twelve push-out test specimens were conducted with various parameters to study the static and fatigue performance of a new through-bolt shear connector transferring the shear forces of interface between prefabricated hybrid fiber reinforced concrete (HFRC) slabs and steel girders. It was found that the fibers could improve the fatigue life, capacity and initial stiffness of through-bolt shear connector. While the bolt-hole clearance reduced, the initial stiffness, capacity and slippage of through-bolt shear connector increased. After the steel-concrete interface properties were improved, the initial stiffness increased, and the capacity and slippage reduced. Base on the test results, the equation of the load-slip curve and capacity of through-bolt shear connector with prefabricated HFRC slab were obtained by the regression of test results, and the allowable range of shear force under fatigue load was recommended, which could provide the reference in the design of through-bolt shear connector with prefabricated HFRC slabs.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.4
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• pp.29-35
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• 2013

The objective of the current study is to evaluate the effects depending on the types of reinforcing fibers being influential in view of mechanical properties and impact resistance of hybrid fiber reinforced concrete (HFRC) for applications to precast concrete structure. Hybrid fibers applied therefor were three types such as PP/MSF (polypropylene fiber+macro synthetic fiber), PVA/MAF (polyvinyl alcohol fiber+MSF) and JUTE/MSF (natural jute fiber+MSF), where the volume fraction of PP, PVA and natural jute was applied with 0.2 %, respectively, while based on 0.05 % volume fraction of MSF. The HFRC was tested for slump, compressive strength, flexural strength and impact resistance. The test result demonstrated that mixture of such hybrid fibers improve compressive strength, flexural strength and impact resistance of concrete. Moreover, it was found that HFRCs to which hydrophilic fibers, i.e. PVA/MSF and JUTE/MSF, were mixed show more improved features that HFRC to which non-hydrophilic fiber, i.e. PP/MSF was mixed. Meanwhile, the finding that PVA/MSF HFRC exhibited better performance than JUTE/MSF HFRC was attributed from the former having higher aspect ratio than that of the latter.

• Journal of Nutrition and Health
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• v.48 no.5
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• pp.381-389
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• 2015

Purpose: The objective of this study was to investigate the effects of a high fructose and fat diet on bone growth and maturation in growing female rats. Methods: Three-week-old female SD rats were randomly assigned to four experimental groups; the control group (CON: fed control diet based on AIN-93G, n = 8); the high-fructose diet group (HFrc: fed control diet with 30% fructose, n = 8); the high-fat diet group (Hfat: fed control diet with 45 kcal% fat, n = 8); and the high-fat diet plus high fructose group (HFrc + HFat: fed diets 45 kcal% fat with 30% fructose, n = 8). Each group was assigned their respective diets for the remaining eight weeks. Bone-related parameters (bone mineral density (BMD) and structural parameters, osteocalcin (OC), deoxypyridinoline (DPD)) and morphologic changes of kidney were analyzed at the end of the experiment. Results: Final body weights and weight gain were higher in the HFat and HFrc + HFat groups and showed higher tendency in the HFrc group compared with those of the CON group (p < 0.05); however, no significant difference in caloric intake was observed among the four experimental groups. The serum OC levels of the HFrc and HFrc + HFat groups were lower than those of the CON and HFat groups (p < 0.05). Urinary levels of DPD did not differ among the experimental groups. BV/TV and Tb.N of trabecular bone were higher in the HFrc + HFat group and showed a higher tendency in the HFrc group than those of the CON and HFat groups (p < 0.05). Tb.Pf of trabecular bone were lower in the HFrc + HFat group than those in the CON and HFat groups (p < 0.05). However, no difference in trabecular BMD was observed among the experimental groups. Cortical bone volume was higher in the HFat and HFrc + HFat groups than in the CON and HFrc groups (p < 0.05). No morphology change in kidney was observed among the experimental groups. Conclusion: Our study suggests that 8 weeks of high-fructose and high fat intake could improve the bone quality (Structural parameters) of trabecular and cortical bone of tibia in growing female rats.

• Advances in concrete construction
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• v.8 no.1
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• pp.21-31
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• 2019

The rich recipe of ultra high performance concrete (UHPC) offers the higher mechanical, durability and dense microstructure property. The variable like cement/sand ratio, amount of supplementary cementitious material, water/binder ratio, amount of fiber etc. alters the UHPC hardened properties to any extent. Therefore, to understand the effects of these variables on the performance of UHPC, inevitably a stage-wise development is required. In the present experimental study, the effect of sand/cement ratio, the addition of finer material (fly ash and quartz powder) and, hybrid fiber on the fresh, compressive and microstructural property of UHPC is evaluated. The experiment is conducted in three phases; the first phase evaluates the flow value and strength attainment of ingredients, the second phase evaluates the efficiency of finer materials (fly ash and quartz powder) to develop the UHPC and the third phase evaluate the effect of hybrid fiber on the flow value and strength of ultra high performance hybrid fiber reinforced concrete (UHP-HFRC). It has been seen that the addition of fly ash improves the flow value and compressive strength of UHPC as compared to quartz powder. Further, the usage of hybrid fiber in fly ash contained matrix decreases the flow value and improves the strength of the UHP-HFRC matrix. The dense interface between matrix and fiber and, a higher amount of calcium silicate hydrate (CSH) in fly ash contained UHP-HFRC is revealed by SEM and XRD respectively. The dense interface (bond between the fiber and the UHPC matrix) and the higher CSH formation are the reason for the improvement in the compressive strength of fly ash based UHP-HFRC. The differential thermal analysis (DTA/TGA) shows the similar type of mass loss pattern, however, the amount of mass loss differs in fly ash and quartz powder contained UHP-HFRC.

• Earthquakes and Structures
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• v.23 no.5
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• pp.463-472
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• 2022

Reinforced concrete (RC) beam column joints (BCJ) have mostly exhibited poor seismic performance during several past earthquakes, typically due to the poor-quality concrete or lack of reinforcement detailing typical of pre-code design practice. The present study is motivated towards numerical simulation and seismic fragility assessment of one such RC-BCJ. The BCJ is loaded to failure and strengthened using Ultra High Performance-Hybrid Fiber Reinforced Concrete (UHP-HFRC) jacketing. The strengthening is performed for four different BCJ specimens, each representing an intermediate damage state before collapse. viz., slight, moderate, severe, and collapse. From the numerical simulation of all the BCJ specimens, an attempt is made to correlate different modelling and design parameters of the BC joint with respect to the damage states. In addition, seismic fragility analysis of the original as well as the retrofitted damaged BCJ specimens show the relative enhancement achieved in each case.

• Structural Engineering and Mechanics
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• v.66 no.5
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• pp.631-636
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• 2018

This study aims to investigate the flexural behaviour of glass fibre reinforced polymer (GFRP) laminated hybrid fibre reinforced concrete (HFRC) beams. The flexural and ductility performance of GFRP laminated HFRC beams having different proportions of polyolefin and steel fibres with 1.0% of total volume fraction were investigated. The parameters of this investigation included: load and deflection at first crack, yield, and ultimate stages, ductility and crack width. A total of seven beams of $150{\times}250mm$ in cross-section were tested in the laboratory over an effective span of 2800 mm. One reinforced concrete (RC) beam without any internal or external GFRP was taken as the reference beam. Of the remaining six beams, one beam was strengthened with GFRP, one beam with 100% steel fibres was strengthened with GFRP and four beams, each with different volume proportions of polyolefin and steel fibres (20:80, 30:70, 40:60, 50:50) were strengthened with GFRP. All the above beams were tested until failure. The experimental results show that a fibre volume proportion of 40:60 (polyolefin-steel) has significantly improved the overall performance of the tested beams.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.340-343
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• 2004

The cement-based composites have been used for construction industry because of their economy, suitability for architecture and structure function, fire resistance, low fee of repair, easiness for acquisition. but the limited strain capacity of these makes them tension-weak, brittle, and considerable notch-sensitive. As one of solution, FRC(fiber reinforced concrete) have been investigated for regulating weakness of the cement-based composites. In these day different fiber types are proposed for better performance such as HFRC(hybrid fiber reinforced concrete). This study shows experimental results to search the ultimate strength, the ultimate mean strain, and the tension toughness of HFRC. The tension toughness is proportional to the amount of steel fiber and carbon fiber. In this experimental program we kept the total of steel fiber and carbon fiber as $1.0\%,\;1.5\%$, respectively.