• Magazine of the Korea Concrete Institute
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• v.7 no.5
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• pp.133-144
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• 1995

This study investigated to the properties of structural behaviors through a series of experiment with the key parameter, such as diameter-to-thickness(D/t) ratio, selenderness ratio of steel t~ube and strength of concrete under loading condition simple confined concrete by steel tube as a fundmental study on adaptability with structural members in high-rise building. The obtained results are sumnarised as follow. (1) The fracture mode of confined concrete was presented digonal tension fracture in the direction of $45^{\circ}$ with compression failure at the end of specimen in stub column, but the fracture mode of long column was assumed an aspect of bending fracture transversely. (2) The deformation capacity and ductility effect was increased by confine steel tube for concrete. (3) 'The emprical formula to predict the ultimate capacity of confined concrete by steel tube and concrete filled steel tube column using restraint of concrete considered D / t ratio, selenderness ratio of steel tube anti strength of' concrete were proposed.

• Magazine of the Korea Concrete Institute
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• v.6 no.4
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• pp.161-168
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• 1994

Half-P.C. slab system is the composite structural system which utilizes precast concrete for lower portion and cast in situ concrete for upper portion slab. When the composite slab using Half P.C. slab is deformed by flexural moment, horizontal shear happened at the interface between Half P.C. slab and topping concrete. To resist horizontal shear strength a scratch method has tried. To determine ultimate interface shear strength, shear stress, and shear coefficient, high and normal strength concrete are used for topping concrete. Major variables are compressive strength of topping concrete with or without shear reinforcement, quantitative roughness of the P.C. :surface and tie or untie of the stud with welded deformed wire fabric in the P.C. member. The Icross sectional area on joints is 3,200 $cm^2$ in all specimens. Test results showed that shear stress increased, as the depth of the quantitative roughness increased. The horizontal shear strength could be resisted with safe by the quantitative roughness without shear tie. A shear coefficient determinant equation is proposed such that K = 0.025918 + 0.0068894$\cdot$R – 0.000182354${\cdot}R^2$

• Journal of the Korea Institute of Building Construction
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• v.9 no.4
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• pp.131-137
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• 2009

The rate of recycling of waste concrete, which represents the majority of construction-related waste, is increasing. However, a general recognition of the inferior qualify of recycled aggregates and their lower grade of compressive strength, bending strength, shear strength, frost resistance and ductility make the application of recycled aggregates to structures insufficient. Therefore, this study conducted material and member experiments by adding steel fiber for the purpose of improving the properties of recycled aggregate concrete. To synthesize the experimental results, it was found that specimens with a 30% steel fiber admixture had levels of compressive strength, tensile strength and frost resistance that were equivalent to or higher than the standard specimen, and that concrete that had a 30% replacement of recycled aggregates with steel fiber was suitable for application to actual structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.189-196
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• 2018

Degraded shear performance of reinforced concrete members with recycled coarse aggregate (RCA) compared to flexural strength is a problem. To address this, steel fibers can be used as concrete reinforcement material. In this study, the strength and deformation characteristics of SFRC beams using RCA were to be determined by shear tests. Major experimental variables include the volume fraction of steel fiber (0, 0.5%, 1%), the replacement rate of RCA (0%, 100%), and the shear span ratio (a/d = 1, 2). As a result of the experiment, the shear strength of the specimen increased as the rate of mixing steel fiber increased. For specimens with RCA and 1% steel fiber, the maximum shear strengths increased by 1.77 - 6.25% compared to specimens with normal coarse aggregate (NCA). On the other hand, at 0-0.5% steel fiber, the shear strengths of RCA specimens were reduced by 24.2% to 49.2% compared to NCA specimens. This indicates that reinforcement with 1% volume fraction of steel fiber greatly contributes to preventing shear strength reduction due to the use of RCA.

• Journal of the Korea Institute of Building Construction
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• v.10 no.6
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• pp.67-75
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• 2010

In this paper, by using steel fiber, polypropylene fiber and these two hybrid fibers, the fire resistance performance and explosive properties of High Strength Concrete (HSC) with specified compressive strength of 40MPa are discussed. The paper also examines the bending resistance of the beam and the shearing resistance properties of non-reinforced HSC beam. This research helps to clarify the fire resistance of fiber HSC and its anti-explosion methods. The test results show that crack generation, explosion and carbonization can be effectively restrained when HSC is mixed with hybrid fibers under high temperature; furthermore, the maximum internal force and ductility are increased and the initial cracking can be restrained in the mechanical test.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.182-189
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• 2021

VPS(Void Plywood Slab System, VPS) has optimized the shape of the hollow material. In addition, it has a function to prevent the floating of the hollow material and the separation due to the working load. In this study, the punching shear capacity of flat plate was performed using Void Plywood Slab System with form work panel proposed in the previous study. As a result of the test, the strength of the VSPS specimen in which the hollow material was placed beyond 2.0 times the column width from the loading point was reduced by 9.4% compared to the reference specimen. However, the strength value was about 1.57 times higher than the design value suggested by KBC 2016. It was found that there was no change in stiffness compared to the reference specimen until shear failure occurred in the VSPS specimen in which the hollow material was placed. It can be seen that this experiment is being destroyed by shear as the flexural reinforcing bars are sufficiently reinforced.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.873-880
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• 2006

PSC composite bridge with precast decks which was designed by the proposed horizontal shear equation was fabricated. Fatigue test was performed to evaluate the endurance of shear connection and the behavior of PSC composite bridge. After all the fatigue loading were applied, no crack and no residual slip were occurred. The flexural stiffness of PSC composite bridge was maintained the initial value, and demage of shear connection was not occurred. To verify the applicability of horizontal shear equation and shear connection detail and to evaluate the strength of PSC composite bridges, static test was also executed. PSC composite bridges with precast decks had 2.08 safety factor which was the ratio of crack to serviceability load and showed ductile behavior after ultimate load. Test results showed that the proposed design equation of the shear connection gave reasonable horizontal shear connection design. Fast and easy construction would be achieved using the suggested precast system.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.73-80
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• 2022

In this study, details of NRC beam-column connections were developed in which beam and columns pre-assembled in factories using steel angles were bolted on site. The developed joint details are NRC-J type and NRC-JD type. NRC-J type is a method of tensile joining with TS bolts to the side and lower surfaces of the side plate of the NRC column and the end plate of the NRC beam. NRC-JD type has a rigid joint with high-strength bolts between the NRC beam and the side of the NRC column for shear, and with lap splices of reinforcing bar penetrating the joint and the beam main reinforcement for bending. For the seismic performance evaluation of the joint, three specimens were tested: an NRC-J specimen and NRC-JD specimen with NRC beam-column joint details, and an RC-J specimen with RC beam-column joint detail. As a result of the repeated lateral load test, the final failure mode of all specimens was the bending fracture of the beam at the beam-column interface. Compared to the RC-J specimen, the maximum strength of the specimen by the positive force was 10.1% and 29.6% higher in the NRC-J specimen and the NRC-JD specimen, respectively. Both NRC joint details were evaluated to secure ductility of 0.03 rad or more, the minimum total inter-story displacement angle required for the composite intermediate moment frame according to the KDS standard (KDS 41 31 00). At the slope by relative storey displacemet of 5.7%, the NRC-J specimen and the NRC-JD specimen had about 34.8% and 61.1% greater cumulative energy dissipation capacity than the RC specimen. The experimental strength of the NRC beam-column connection was evaluated to be 30% to 53% greater than the theoretical strength according to the KDS standard formula, and the standard formula evaluated the joint performance as a safety side.

• Journal of Korean Society of Steel Construction
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• v.29 no.6
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• pp.411-422
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• 2017

In this study, to investigate the seismic performance of beam-column joints using concrete-encased and -filled circular steel tube(CEFT) columns, two types of tests were performed: (1) column - flange tension test and (2) beam - column joint cyclic load test. In column - flange tension test, test parameters were concrete encasement and connection details: flange width and strengthening rebar. Five specimens were tested to investigate the load-carrying capacity and the failure mode. Test results showed that increase of flange width from 200mm to 350mm result in increase of connection strength and stiffness by 61% and 56%, respectively. Structural performances were further improved with addition of tensile rebars by 35% and 92%, respectively. In cyclic loading test, three exterior beam-column joints were prepared. Test parameters were strengthening details including additional tensile rebars, thickened steel tube, and vertical plate connection. In all joint specimens, flexural yielding of beam was occurred with limited damages in the connection regions. In particular, flexural capacity of beam-column joint was increased due to additional load transfer through tube - beam web connection. Also, connection details such as increase of tube thickness and using vertical plate connection were effective in improving the resistance of panel zone.

• Journal of Korean Society of Steel Construction
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• v.22 no.2
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• pp.151-160
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• 2010

The number of cases of collapsed plastic greenhouses in farmlands has increased due to the heavy local snowfall caused by extraordinary atmospheric phenomena. Consequently, the economic losses of farmers have also increased. However the government policy in relation to damage pretension is insufficient and collapse case is repeated every year. The main reason for frame collapse is that the moment capacity of a steel pipe is not sufficient to resist a heavy snowload. In this study, experiments were conducted on the current frame system of a greenhouse with a tension tie. The frame consisted of two sections(${\phi}25.4{\times}1.5$, ${\phi}31.8{\times}1.5$), and its span length was 6.5 m. A temporary tension tie using a steel wire and a fabric rope was connected to the two joints, to which a curved beam and a straight column were connected. The pretension force was applied at the tension tie, and a vertical force simulating snowfall was applied until failure. The fabric rope frame increased the load-carrying capacity by 10-45% compared to the normal frame without a tension tie, and the steel wire frame increased the load-carrying capacity by 58-73% compared to the normal frame without a tension tie. Steel wire was found to be more effective as far as strength is concerned, but its connection details and pretension application are more difficult and complicated than those of the fabric rope. The test results thus show that the fabric rope is more preferable.