• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.3
• /
• pp.281-288
• /
• 2004

The hybrid composite material (Al/GFRP laminates) are applied to the fuselage and wing in a aircraft. Therefore, Al/GFRP laminates suffer from the cyclic bending moments. This study was to evaluate the effect of fiber stacking angle on the fatigue crack propagation and delamination behavior using the relationship between crack growth rate (da/dN) and stress intensity factor range (ΔK) in Al/GFRP laminates under cyclic bending moment. The variable delamination growth behavior in case of three different type of fiber orientations, i.e., [Al/O$_2$/Al], [Al/+45$_2$/Al] and [Al/90$_2$/Al] at the interface of Al layer and glass fiber layer was measured by ultrasonic C-scan images. As results of this study, It represent that the delamination shape should turns out to have more effective characteristics on the fiber stacking angle. The extension of the delamination zone in case of [Al/+45$_2$/Al] and [Al/90$_2$/Al] were not formed along the fatigue crack profile. The shape of delamination zone depend on fiber stacking angle and the variable type with the delamination contour decreased non-linearly toward the crack tip at the Al layer.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.5
• /
• pp.542-548
• /
• 2005

A fluidized bed reactor containing porous media has been known to be effective for nitrogen and organic matters removal in wastewater. The porous media which attached microbes plays important roles in simultaneous nitrification/denitrification (SND) due to coexistence of oxic, anaerobic and anoxic zone. For SND reaction, oxygen and organic substrates should be effectively diffused from wastewater into the intra-carrier zone. However, the overgrowth heterotrophic microbes at the surface of porous media may restrict from substrates diffusion. From these viewpoints, the existence and effect of heterotrophic bacteria at surface of porous media might be the key point for nitrogen removal. A porous media-membrane hybrid process was found to have improved nitrogen removal efficiency, due to stimulated denitrification as well as nitrification. Microelectrode studies revealed that although intra-media denitrification rate in a conventional fluidized bed was limited by organic carbon, this limitation was reduced in the hybrid process, resulting in the increased denitrification rate from 0.5 to $4.2\; mgNO_3-N/L/hr$.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.34 no.6
• /
• pp.275-289
• /
• 2022

New businesses such as marine leisure and floating construction have recently flourished on the coast. As a result, consideration is given to a floating structure appropriate for marine environments. In this study, we applied a damping plate to increase the stability of a hybrid floating structure that was expanded by vertical and horizontal stacking of mobile unit modules. In the numerical analysis using ANSYS AQWA, the behavioral characteristics of the floating structure were analyzed according to the length change of the damping plate. However, the wave forces acting on a floating structure are excessively calculated by the resonance of fluid surrounded by the structure in the numerical analysis using potential flow. Therefore, we used the damping zone option of the ANSYS AQWA in the frequency domain analysis.

• Nuclear Engineering and Technology
• /
• v.53 no.6
• /
• pp.1736-1746
• /
• 2021

The results of full-scale numerical experiments of a hybrid thorium-containing fuel cell facility operating in a close-to-critical state due to a controlled source of fusion neutrons are discussed in this work. The facility under study was a complex consisting of two blocks. The first block was based on the concept of a high-temperature gas-cooled thorium reactor core. The second block was an axially symmetrical extended plasma generator of additional neutrons that was placed in the near-axial zone of the facility blanket. The calculated models of the blanket and the plasma generator of D-T neutrons created within the work allowed for research of the neutronic parameters of the facility in stationary and pulse-periodic operation modes. This research will make it possible to construct a safe facility and investigate the properties of thorium fuel, which can be continuously used in the epithermal spectrum of the considered hybrid fusion-fission reactor.

• Advances in concrete construction
• /
• v.12 no.6
• /
• pp.451-459
• /
• 2021

The mechanical behaviors and chloride resistance performance of fiber reinforced cementitious composites (FRCC) with hybrid polyethylene (PE) and steel fiber (in total 2% by volume) were investigated. Based on micro-mechanics and fracture mechanics, the reason why the tensile strain capacity of FRCC changed obviously was obtained. Besides, the effects of the total surface area of fiber in FRCC on compressive strength and chloride content were clarified. It is found that the improvement of the tensile strain capacity of FRCC with hybrid fiber is attributed to the growth of strain-hardening performance index (the ratio of complementary energy to crack tip toughness). As the total surface area of fiber related with the interfacial transition zone (ITZ) between fiber and matrix increases, compressive strength decreases obviously. Since the total surface area of fiber is small, the chloride resistance performance of FRCC with hybrid PE and steel fiber is better than that of FRCC containing only PE fiber.

• Structural Engineering and Mechanics
• /
• v.82 no.1
• /
• pp.17-30
• /
• 2022

The use of composite patches for the reduction of stresses at the level of the damaged zone in aeronautical structures has experienced rapid expansion given its advantages over conventional mechanical processes (riveting, bolting, etc.). Initially, The research axes in this field were aimed at choosing suitable mechanical properties for the composite and the adhesive, then to optimize the shape of the composite patch in order to ensure good load transfer and avoid having a debonding at the level of the edges essentially for the case of a repair by single side where the bending moment is present due to the non-symmetry of the structure. Our work falls within this context; the objective is to analyze by the finite element method the fracture behavior of a damaged plate repaired by composite patch. Stress reduction at the edge is accomplished by creating a variable angle chamfer on the composite patch. The effects of the crack length, the laminate sequence and the nature of the patch as well as the use of a hybrid patch were investigated. The results show clearly that a beveled patch reduces the stress concentrations in the damaged area and even at its edges. The hybrid patch also ensures good durability of the repair by optimizing its stacking sequence and the location of the different layers according to the fibers orientations.

• Journal of Korean Association for Spatial Structures
• /
• v.23 no.1
• /
• pp.53-60
• /
• 2023

A bending experiment was conducted to verify the structural performance of the U-flange truss hybrid bean using rebars or steel pipes to reinforce the upper compression zone. As a result of evaluating the bending strength of the truss hybrid beam according to the Structural Design Standard (KDS 14 2020: 2022) by introducing the lattice member as a tensile resistance element, the following conclusions were obtained. Considering the lattice element as a tensile resistance element, the nominal bending strength was increased by 38.57 to 47.90 kN.m. As a result of reviewing the experiment as to whether the flexural member has proper ductility, it was found that it is desirable to place appropriate rebars, steel quality plans, and lateral restraints on the upper and lower parts of the hybrid beam to have sufficient ductility ratio.

• Journal of the Korean Geotechnical Society
• /
• v.15 no.4
• /
• pp.99-112
• /
• 1999

When there exists a fault zone ahead of the tunnel face and a tunnel is excavated without perceiving its existence, it will cause stress concentration in the region between the tunnel face and the fault zone because of the influence of the fault zone on the arching phenomena. Because the underground structure has many unreliable factors in the design stage, the prediction of a fault zone ahead of the tunnel face by monitoring plans during tunnel construction and the rapid establishment of appropriate support system are required for more economical and safer tunnel construction. Recent study shows that longitudinal displacement changes during excavation due to the change of rock property, and if longitudinal displacement and settlement, which are measured in the field, are considered together in displacement analysis, the prediction of change in rock mass property is possible. This study provided the method for the prediction of fault zones by analyzing the changes of L/C and (Ll-Lr)/C ratio (L= longitudinal displacement at crown, C = settlement at crown, Ll = longitudinal displacement at left sidewall, Lr = longitudinal displacement at right sidewall) and the stereographic projection of displacement vectors which were obtained from the 3-D numerical analysis of hybrid method in various initial stress conditions.

• Computers and Concrete
• /
• v.19 no.1
• /
• pp.79-85
• /
• 2017

This paper summarizes the experimental study of the shear behaviour of Hybrid Fibre Reinforced Concrete (HFRC) beams retrofitted by using externally bonded Glass Fibre Reinforced Polymer (GFRP) laminates. To attain the set-out objectives of the present investigation, steel fibre of 1% and polypropylene fibre of 0.30% was used for hybrid steel-polypropylene fibre reinforced concrete: whereas for hybrid glass-polypropylene fibre reinforced concrete, glass fibre by 0.03% and polypropylene fibre of 0.03% by volume of concrete was used. In this study, 9 numbers of beams were cast and tested into three groups (Group I, II & III). Each group containing 3 numbers of beams, out of which one serve as a control beam or a hybrid steel-polypropylene fibre reinforced concrete beam or a hybrid glass - polypropylene fibre reinforced concrete beam and the remaining two beams were preloaded until shear cracks appeared up to 75% of ultimate load and then preloaded beams (damaged beams) were retrofitted with GFRP laminates at shear zone in the form of strips, as one beam in vertical position and another beam in inclined position to restrict the shear cracks. Finally, the retrofitted beams were loaded until failure and test results were compared. The experimental tests have been conducted to investigate various parameters of structural performance, such as load carrying capacity, crack pattern and failure modes, load-deflection responses and ductility relations. The test results revealed that beams retrofitted using GFRP laminates considerably increased the load carrying capacity. In addition, it was found that beams retrofitted with inclined strip offers superior performance than vertical one. Comparing the test results, it was observed that hybrid steel-polypropylene fibre reinforced concrete beam retrofitted with GFRP laminates showed enhanced behaviour as compared to other tested beams.

• Journal of the Korea Concrete Institute
• /
• v.16 no.4 s.82
• /
• pp.451-458
• /
• 2004

This study describes the basic concept and the applicability of Hybrid Reinforcement System using conventional steel reinforcing bars and Fiber Reinforced Polymer bars. The concrete bridge decks are assumed to be supported by beams and reinforced with two layers of reinforcing bars. In concrete bridge deck using HRS, the top tensile force for negative moment zone on beam supports is assumed to be resisted by FRP reinforcing bars, and the bottom tensile force for positive moment zone in the middle of hem supports is assumed to be resisted by conventional steel reinforcing bars, respectively. The FRP reinforcing bars are non-corrosive. Thus, the steel reinforcement is as far away as possible from the top surface of the deck and protected from intrusion of corrosive agent. HRS concrete bridge deck has sufficient ductility at ultimate state as the following reasons; 1) FRP bars have lower elastic modulus and higher ultimate strain than steel re-bars have, 2) FRP bars have lower ultimate strain if provided higher reinforcement ratio, 3) ultimate strain of FRP bars can be reduced if FRP bars are unbonded. Test results showed that FRP and HRS concrete slabs are not failed by FRP bar rupture, but failed by concrete compression in the range of ordinary reinforcement ratio. Therefore, in continuous concrete bridge deck using HRS, steel reinforcing bars for positive moment yield and form plastic hinge first and compressive concrete fail in the bottom of supports or in the top of the middle of supports last. Thus, bridge deck consumes significant inelastic strain energy before its failure.