• Advances in concrete construction
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• v.14 no.2
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• pp.79-92
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• 2022

The amount and configuration of transverse reinforcement are known as critical parameters that significantly affect the lateral confinement of concrete, the ductility capacity, and the plastic hinge length of RC columns. Based on test results, this study investigated the effect of the three variables on structural indexes such as neutral axis depth, lateral expansion of concrete, and ductility capacity. Five reinforced concrete column specimens were tested under cyclic flexure and shear while simultaneously subjected to a constant axial load. The columns were reinforced by two types of reinforcing steel: rectangular hoops and spiral type reinforcing bars. The variables in the test program were the shape, diameter, and yield strength of transverse reinforcement. The interactive influence of the amount of transverse reinforcement on the structural indexes was evaluated. Test results showed that when amounts of transverse reinforcement were similar, and yield strength of transverse reinforcement was 600 MPa or less, the neutral axis depth of a column with spiral type reinforcing bars was reduced by 28% compared with that of a column reinforced by existing rectangular hoops at peak strength. While the diagonal elements of spiral-type reinforcing bars significantly contributed to the lateral confinement of concrete, the strain of diagonal elements decreased with increases of their yield strength. It was confirmed that shapes of transverse reinforcement significantly affected the lateral confinement of concrete adjacent to plastic hinges. Transverse reinforcement with a yield strength exceeding 600 MPa, however, increased the neutral axis depth of normal-strength concrete columns at peak strength, resulting in reductions in ductility and energy dissipation capacity.

• Design & Manufacturing
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• v.17 no.3
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• pp.28-33
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• 2023

The conventional FRP (Fiber Reinforced Plastic) manufacturing process used thermoset resins for ease of molding but faced the issue of non-recyclability. To address these shortcomings, a new process utilizing thermal plastic resin was developed. However, due to the high viscosity of thermal plastic resin, problems such as fiber deformation and a reduced fiber volume fraction occurred during the high-temperature, high-pressure process. In this study, to overcome the limitations of the conventional process, fiber-reinforced composite materials were manufactured through in-situ polymerization using PLA (Poly L-Lactide) resin in the VA-RTM (Vacuum Assistance Resin Transfer Molding) process. The fiber volume of the produced specimens was calculated, and resin impregnation and porosity were confirmed through optical microscopy. Additionally, molecular weight analysis using GPC (Gel Permission Chromatography) demonstrated improvements over the conventional process and emphasized the essential requirement of temperature control.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.220-227
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• 2002

This study introduces the fragility analysis method for the safety evaluation of reinforced concrete pier subject to earthquake. Damage probability is calculated instead of the failure probability from definition of the damage state in the fragility curve. Not only the damage model determined by the response of structure subject to earthquake, but also the plastic-damage model which can represent the local damage is applied to fragility analysis. The evaluation method of damage state by damage variable in global structure is defined by this procedure. This study introduces the fragility analysis method considering the features of nonlinear time history behavior of reinforced concrete element and the plastic behavior of materials. At last, This study gives one of the approach method for seismic margin evaluation with the result of fragility analysis to design seismic load.

• Computers and Concrete
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• v.8 no.6
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• pp.631-645
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• 2011

The capacity design rule for beam-column joints, as adopted by the EC8, forces the formation of the plastic hinges to be developed in beams rather than in columns. This is achieved by deriving the design moments of the columns of a joint from equilibrium conditions, assuming that plastic hinges with their possible overstrengths have been developed in the adjacent beams of the joint. In this equilibrium the parameters (dimensions, material properties, axial forces etc) are, in general, random variables. Hence, the capacity design is associated with a probability of non-compliance (probability of failure). In the present study the probability of non-compliance of the capacity design rule of joints is being calculated by assuming the basic variables as random variables. Parameters affecting this probability are examined and a modification of the capacity design rule for beam-column joints is proposed, in order to achieve uniformity of the safety level.

• Computers and Concrete
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• v.7 no.4
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• pp.303-315
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• 2010

In this paper, we present a new finite Timoshenko beam element with a model for ultimate load computation of reinforced concrete frames. The proposed model combines the descriptions of the diffuse plastic failure in the beam-column followed by the creation of plastic hinges due to the failure or collapse of the concrete and or the re-bars. A modified multi-scale analysis is performed in order to identify the parameters for stress-resultant-based macro model, which is used to described the behavior of the Timoshenko beam element. The micro-scale is described by using the multi-fiber elements with embedded strain discontinuities in mode 1, which would typically be triggered by bending failure mode. A special attention is paid to the influence of the axial force on the bending moment - rotation response, especially for the columns behavior computation.

• Structural Engineering and Mechanics
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• v.48 no.5
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• pp.587-613
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• 2013

A 3-node 3D co-rotational beam element using vectorial rotational variables is employed to consider the geometric nonlinearity in 3D space. To account for shape versatility and reinforced concrete cross-sections, fibre model has been derived and conducted. Numerical integration over the cross-section is performed, considering both normal and shear stresses. In addition, the derivations associated with material nonlinearity are given in terms of elasto-plastic incremental stress-strain relationship for both steel and concrete. Steel reinforcement is treated as elasto-plastic material with Von Mises yield criterion. Compressive concrete behaviour is described by Modified Kent and Park model, while tensile stiffening effect is taken into account as well. Through several numerical examples, it is shown that the proposed 3D co-rotational beam element with fibre model can be used to simulate steel and reinforced concrete framed structures with satisfactory accuracy and efficiency.

• Computers and Concrete
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• v.5 no.6
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• pp.525-544
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• 2008

In this research, the self-centering effect in precast and prestressed reinforced concrete structures was investigated experimentally. The reinforced concrete beams and columns were precast and connected by post-tensioning tendons passing through the center of the beams as well as the panel zone of the connections. Three beam-to-interior-column connections were constructed to investigate parameters such as beam to column interfaces (steel on steel or plastic on plastic), energy dissipating devices (unbonded buckling restrained steel bars or steel angles) and the spacing of hoops in the panel zone. In addition to the self-centering effect, the shear strength in the panel zone of interior column connections was experimentally and theoretically evaluated, since the panel zone designed by current code provisions may not be conservative enough to resist the panel shear increased by the post-tensioning force.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.147-151
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• 2001

This study was performed to evaluate the internal and external factors affecting external strength of the 3-layer polymer composite pipes made of polymer mortar and fiber-glass reinforced plastic. Twenty four sandwich type 3-layer polymer composite pipes were made of polymer mortar and fiber-glass reinforced plastic by centrifugal method. The objective of this study was to evaluate the effects the of polymer mortar thickness for and core fiber-glass contents per unit area on external strength of 3-layer polymer composite pipes. For the more economical and practical design of 3-layer polymer composite pipe, further study should be done for the various polymer mortar, fiber-glass and different ratio of the inside/outside FRP thickness.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.3
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• pp.63-67
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• 1994

A main property for fiber reinforced thermoplastic composite material in compression molding is the flow of fibers. This flow is so effective a long direction of acting force that this study examined for the inclined angel of 30$^{\circ}$, 45$^{\circ}$ and 6$^{\circ}$. Below the near softing temperature of plastic, the fiber has been fractured at a point so that the fiber strength is smaller then the local hydrostatic stress in the mold. It has been found that the position of fracture is changing accrding to the incling angle. In case of the above softing temperature, the larger the inclined is, the farther the flow of fiber move. Also the plastic flow has been progresed with the cicular are type.

• Interaction and multiscale mechanics
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• v.2 no.3
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• pp.235-261
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• 2009

This study illustrates the differences between the elasto-plastic cap model and Lade's model with Cosserat rotation through the analyses of two large-scale geosynthetic-reinforced soil (GRS) retaining wall tests that were brought to failure using a monotonically increasing surcharge pressure. The finite element analyses with Lade's model were able to reasonably simulate the large-scale plane strain laboratory tests. On average, the finite element analyses gave reasonably good agreement with the experimental results in terms of global performances and shear band occurrences. In contrast, the cap model was not able to simulate the development of shear banding in the tests. In both test simulations the cap model predicted failure loads that were substantially less than the measured ones.