• Structural Engineering and Mechanics
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• v.86 no.3
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• pp.385-397
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• 2023

This study presents an experiment and analysis to compare the seismic behavior of full-scale reinforced concrete beam-column joint strengthened by prestressed steel strips, externally bonded steel plate, and CFRP sheets. For experimental investigation, five specimens, including one joint without any retrofitting, one joint retrofitted by externally bonded steel plate, one joint retrofitted by CFRP sheets, and two joints retrofitted by prestressed steel strips, were tested under cyclic-reserve loading. The failure mode, strain response, shear deformation, hysteresis behavior, energy dissipation capacity, stiffness degradation and damage indexes of all specimens were analyzed according to experimental study. It was found that prestressed steel strips, steel plate and CFRP sheets improved shear resistance, energy dissipation capacity, stiffness degradation behavior and reduced the shear deformation of the joint core area, as well as changed the failure pattern of the specimen, which led to the failure mode changed from the combination of flexural failure of beams and shear failure of joints core to the flexural failure of beams. In addition, the beam-column joint retrofitted by steel plate exhibited a high bearing capacity, energy consumption capacity and low damage index compared with the joint strengthened by prestressed steel strip, and the prestressed steel strips reinforced joint showed a high strength, energy dissipation capacity and low shear deformation, stirrups strains and damage index compared to the CFRP reinforced joint, which indicated that the frame joints strengthened with steel plate exhibited the most excellent seismic behavior, followed by the prestressed steel strips.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.369-376
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• 2003

One of the most complex reinforcement location in the precast building frame is the beam-column joint in a prefabricated construction. It is generally resulted from the vortical bars of column, anchorage bars of beam, and bars of hoop. Particularly the hooked anchorage bars of beam are confronted with hoop and main column bars. The headed reinforcement is considered to place them easily and to reduce the anchorage length in a precast construction. Reversed cyclic loading tests are performed on four beam-column specimens to evaluate the strength and behavior of beam to column and column to column connections. The result of test shows that the headed reinforcement has a similar performance than that of hooked reinforcement in a precast specimen with strong column and weak beam joints. The splice column joints which are used frequently in the domestic fields also show reliable behaviors in those tests with strong column and weak beam joints.

• Journal of Korean Society of Steel Construction
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• v.20 no.3
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• pp.365-375
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• 2008

The main objective of this paper is to study the behaviour of yLRC composite columns at elevated temperatures by experimental test. The effects of load ratios, cross-section size and fire protection for the yLRC columns were investigate d by the test and compared using the heat transfer analysis perfo rmed based on the finite element program ANSYS 10.0 using the ISO834 standard fire curve, following the main guidelines proposed by the EC4 Part 1.2. As heat transfer is the movement of heat by conduction, convection, and radiation, and as temperature inside an object varies by position and time, time. As the steel's thermal conductivity is higher than that of concrete, steel loses its strength rapidly in a high-temperature situation such as a fire. Fire resistance performance of the yLRC composite column under fire conditions was evaluated througheat transfer analysis for parametric study.

• Magazine of the Korea Concrete Institute
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• v.3 no.3
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• pp.101-110
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• 1991

Results of an experimental study on the manufacture, the mechanical properties and watertightness of pitch - based carbon fiber reinforced fly ash. cement composites are presented in this paper. The carbon fiber reinforced fly ash. cement composites using early strength cement silica powder and a small amount of stylene butadiene rubber latex are prepared with carbon fiber, foaming agents and mixing conditions. As a result, the mechanical and physical properties such as compressive , tensile and flexural strengths, watertightness and drying shrinkage of lightweight carbon fiber reinforced fly ash cement composites are Improved by using a samll amount of stylene butadiene rubber latex. Also, the manufacturing pnx:ess technology of carbon fiber reinforced fly ash . cement composItes is developed. The development and applications of precast products of lightweight carbon fiber remforced cement composites are expected in the near future.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.3
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• pp.219-224
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• 2013

In this study, the inorganic insulating material was fabricated with quartzite, ordinary portland cement(OPC), lime and anhydrous gypsum. After characteristic analysis of slurry, the optimum mixing ratio was derived with different $CaO/SiO_2$ mole ratio. Based on derived mixing ratio, the inorganic insulating material was fabricated at different water content and hydrothermal synthesis conditions. Specific gravity was $0.26g/cm^3$, compressive strength was 0.4 MPa, and thermal conductivity was 0.064 W/mK. This properties were enhanced performance of conventional ALC (Autoclaved Lightweight Concrete). And it can replace organic insulation with harmless inorganic insulation through continues research and development.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.86-93
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• 2020

Shotcrete concrete is generally used in the form of ready-mixed concrete products using type I ordinary portland cement(hereinafter referred to as OPC) and about 5% of accelerator mixed separately in the field. In this study, we tested the effect of addition of slag powder(SP) and limestone powder(LSP) on a penetration resistance, compressive strength of binder for shotcrete using calcium aluminate type accerlerator. And we analysed hydrates and pore structure effects on mortar performance. In the future, it is expected to be useful for manufacturing optimized composite cement as a binder for shotcrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.917-920
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• 2008

ECC is a special kind of high performance cementititous composite which exhibits typically more than 2% tensile strain capacity by bridging microcracks at a crack section. Therefore, micromechanics should be adopted to obtain multiple cracking and strain hardening behavior. This paper propose a linear elastic analysis method to simulate the multiple cracking and strain hardening behavior of ECC. In an analysis, the stress-crack opening relation modified considering the orientation of fibers and the number of effective fibers is adopted. Furthermore, to account for uncertainty of materials and interface between materials, the randomness is assigned to the tensile strength(${\sigma}_{fci}$), elastic modulus($E_{ci}$), peak bridging stress(${\sigma}_{Bi}$) and crack opening at peak bridging stress(${\delta}_{Bi}$), initial stress at a crack section due to chemical bonding, (${\sigma}_{0i}$), and crack spacing(${\alpha}_cX_d$). Test results shows the number of cracking and stiffness of cracked section are important parameters and strain hardening behavior and maximum strain capacity can be simulated using the proposed method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.78-85
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• 2020

Shotcrete concrete is generally used in the form of ready-mixed concrete products using type I ordinary portland cement(hereinafter referred to as OPC) and about 5% of accelerator mixed separately in the field. In this study, we tested the effect of OPC fineness and SO₃ content on a penetration resistance, compressive strength of binder for shotcrete using calcium aluminate type accerlerator. And we analysed hydrates and pore structure effects on mortar performance. In the future, it is expected to be useful for manufacturing optimized OPC as a binder for shotcrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.6
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• pp.201-212
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• 2007

This study presents experimental results of Steel-PSC mixed structural system having front-rear plate connection between Steel and Prestressed Concrete. Two kinds of Steel-PSC mixed structural system of 5.4m length were tested to evaluate flexural behaviors under four point loading, and 4 kinds of specimens with and without prestressing force at R & L type connection were tested to observe the shear behavior. Based on the test results of load-deflection curves and failure modes of specimens, it is found that the proposed L shape connection with front-rear plate connection between Steel and Prestressed Concrete has higher strength and stiffness. From the study, Steel-PSC mixed structural system with L shaped connection has a better structural performance in connection part.

• Journal of the Korea Institute of Building Construction
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• v.18 no.2
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• pp.125-132
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• 2018

In this study, a direct tensile test was planned to identify the tensile performance of UHPC, and the irregularity of cracks, which is a problem of the direct tensile test, was complemented through the introduction of notches at the center of a specimen. In this regard, a number of specimens divided by batch to reduce the deviation of direct tensile test values were fabricated to present reference data with respect to highly reliable direct tensile strength values. In addition, the mechanical properties and reliability of the specimens were examined under the curing conditions of the specified design strength of 120MPa for the steel fiber reinforced concrete with 1.5% fiber volume fraction, which is most suitable for the field application. As a result, the deviation of averages by batch between compressive strength and direct tensile strength did not show a large difference, and all cracks occurred within 20mm in the direct tensile test. At the 95% confidence interval of the direct tensile strength, the range was considerably small in the mean and the standard deviation, and there was no significant difference depending on the curing conditions. The results confirmed that a stable direct tensile test was performed, and highly reliable results were obtained through the fabrication of specimens by batch and test progress.