• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.49-52
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• 2008

The tensile and bond performance of GFRP rebar are different from those of conventional steel reinforcement. It requires some studies on concrete members reinforced with GFRP reinforcing bars to apply it to concrete structures. GFRP has some advantages such as high specific strength, low weight, non-corrosive nature, and disadvantage of larger deflection due to the lower modulus of elasticity than that of steel. Bridge deck is a preferred structure to apply FRP rebars due to the increase of flexural capacity by arching action. This paper focuses on the behavior of concrete bridge deck reinforced with newly developed GFRP rebar. A total of three real size bridge deck specimens were made and tested. Main variable was reinforcement ratio of GFRP rebar. Static test was performed with the load of DB-24 level until failure. Test results were compared and analyzed with ultimate load, deflection behavior.

• Magazine of the Korea Concrete Institute
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• v.6 no.2
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• pp.138-147
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• 1994

The compressive strength of horizontal joints in precast concrete large panel structures depends on parameters such as grout and panel strength, detail of joint, joint moment, width of grout column, and etc. 44 specimens were tested to investigate the effects of parameters that influence the compressive strength of horizontal joints. The design formula specified in Korean Cock for compression horizontal joints must be reviewed, because it was based on the test results of the joint types not used in Korea. In this study comparing the test results, there fore, the validity of the design formulas was evaluated and a suitable formula was proposed to predict the ultimate strengths of compression horizontal joints. The increase of ultimate strengths was not observed, even if confined the horizontal displacement of slabs and reinforced the wall edge, when the grout strength is lower than panel strength. From the comparison of test results and those by the proposed formula, it was shown that proposed formula was suitable to predict the ultimate compressive strength of horizontal joints.

• Journal of Korean Society of Steel Construction
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• v.22 no.6
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• pp.523-532
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• 2010

Concrete-filled square steel tube (CFT) columns have inherently high fire resistance and load-bearing capacity. Nevertheless, it is sometimes necessary to improve their fire resistance using external fire protection. This paper presents the experimental results of the temperature distribution of CFT columns with fire protection. A fire load test was carried out by exposing small-scale specimens to heat in an electric furnace that was especially built for testing loaded columns. The temperature distribution of CFT columns under constant axial loads was determined, as were its significant parameters, such as the types of fire protection and thickness, the thickness of the square CFT, and the fire duration times. The results of this study showed the temperature distribution of each specimen of the electric furnace and the temperature distribution properties of concrete and steel. In addition, the axial displacement and local buckling behavior of CFT columns based on temperature changes was observed.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.791-797
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• 2011

This paper presents the test results of 12 direct tensile specimens to investigate the effect of cover thickness on the tension stiffening behavior in axially loaded reinforced concrete tensile members. Six concrete cover thickness ratios are selected as a main experimental parameter. The results showed that, as cover thickness became thinner, more extensive split cracking along the reinforcement occurred and transverse crack spacing became smaller, making the effective tensile stiffness of thin specimens at the stabilized cracking stage to be much smaller than that of thick specimens. This observation is not implemented in the current design provisions, in which the significant reduction of tension stiffening effect can be achieved by applying thinner cover thickness. Based on the present results, a modified tension stiffening factor is proposed to account for the effect of the cover thickness.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.857-860
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• 2000

An experimental study on the behavior of Steel Fiber Reinforced Concrete Columns under eccentric compression are presented. Forth-one columns were tested; the variables were column type, eccentricity of load, fiber contents, and longitudinal reinforcement ratio. The column size was $250\times160$ mm in cross section with an effective length of 1150 mm. Eccentricity of load was varied in the range from 1/6 to 1/2 times the column depth. This paper is to provides a framework for basic understanding of the steel fiber concrete columns.

• Journal of Korean Society of Steel Construction
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• v.27 no.6
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• pp.525-536
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• 2015

An experimental study was performed to investigate the axial-flexural load-carrying capacity of concrete-encased and-filled steel tube (CEFT) columns. To restrain local buckling of longitudinal bars and to prevent premature failure of the thin concrete encasement, the use of U-cross ties was proposed. Five eccentrically loaded columns were tested by monotonic compression. The test parameters were axial-load eccentricity, spacing of ties, and the use of concrete encasement. Although early cracking occurred in the thin concrete encasement, the maximum axial loads of the CEFT specimens generally agreed with the strengths predicted considering the full contribution of the concrete encasement. Further, due to the effect of the circular steel tube, the CEFT columns exhibited significant ductility. The applicability of current design codes to the CEFT columns was evaluated in terms of axial-flexural strength and flexural stiffness.

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.209-216
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• 2007

This study reports on the structural characteristics of slab-column connections using fiber-reinforced ultra-high-strength concrete (UHSC). Compression tests were performed on two slab-column and four isolated column specimens. In the column load tests, slab loads were also applied on the slab-column specimens so that the actual confinement condition at the slab-column joint was considered. The main parameter investigated was the "puddling" of fiber-reinforced UHSC. This paper also investigates the effects of some parameters, such as confinement of slab concrete, steel fibers, and concrete strength of the joint, related to the ability of the slab-column specimens and isolated column specimens without the surrounding slab to transmit axial loads from the UHSC columns through slab-column connections. Furthermore, the ACI Code (2005) and the CSA Standard (2004) are compared to the experimental results. The beneficial effects of the puddling of fiber-reinforced UHSC on the transmission of column loads through slab-column connections are demonstrated.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.71-80
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• 2013

Fire-resistant (FR) test data for a square concrete-filled steel tube (CFT) columns consisting of high-strength steel (fy>650MPa) and high strength concrete (fck>100MPa) under axial loads are insufficient. The FR behavior of square high-strength CFT members was investigated experimentally for two specimens having ${\Box}-400{\times}400{\times}15{\times}3,000mm$ with two axial load cases (5,000kN and 2,500kN). The results show that the FR performance of the high-strength CFT was rapidly decreased at earlier time (much earlier at high axial load) than expected due to high strength concrete spalling and cracks. In addition, a fiber element analysis (FEA) model was proposed and used to simulate the fiber behaviour of the columns. For steel and concrete, the mechanical and thermal properties recommended in EN 1994-1-2 are adopted. Test results were compared to those of numerical analyses considering a combination of temperature and axial compression. The numerical model can reasonably predict the time-axial deformation relationship.

• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.323-332
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• 2008

The behavior of eccentrically loaded steel column base plates is investigated experimentally and analytically. A total of 8 test specimens are fabricated and tested. The effects of eccentricity and thickness of baseplate on the behavior of base plates are investigated. Analytical study is performed using the Finite Element Analysis Program ANSYS 8.1 to investigate distribution of bearing pressure. The results from to the distribution of bending strain of the base plate. However, the distribution of the bearing pressure obtained from the analysis is different from that assumed in the current design method. The results from the analysis show that the bearing pressures of the baseplate are concentrated under the compressively stressed column flange, as the eccentricity is increased. Also the results from the analysis are different from the results of design using the existing design method and the design method according to the AISC-Steel Design Guide.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.317-326
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• 2011

Today there is a growing range of applications for Concrete-Filled Steel Tube (CFT) member because of its superior performance. Ductility estimation test of concrete-filled seismic resistant steel tubular columns, subjected to axial and cyclic lateral load, was carried out in this study. Seismic resistant steel tubes are manufactured using SN400B plates by a two-seam welding at center of the column width for cold press-formed shape plates of two pieces. A total of eight specimens were manufactured and tested with the parameters of width-thickness ratio of steel tubular column, axial load ratio, and loading conditions to act axial and cyclic lateral load two dynamic actuators were used. From test results, flexural strength, deformation capacity, energy dissipation capacity, and ductility behavior of columns were analyzed.