• Journal of the Korea Concrete Institute
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• v.13 no.3
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• pp.195-205
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• 2001

This Paper describes a numerical method to evaluate the flexural strength of reinforced concrete members exposed to fire. An analytical method is developed for the moment-curvature relationship for the cross section which is subjected to high temperature. The method performs heat-transfer analysis for the cross sections and subsequently performs numerical analysis using the stress-strain relationships of concrete and reinforcing steel in various heat conditions. The results of the numerical studies are ; 1) the residual flexural strength exposing at high temperature is affected by the heating time, the depth of concrete cover and reinforcement ratio, 2) the residual flexural strength after exposed at high temperature is recovered of its original strength at minimum ratio of reinforcement, while members having half of maximum ratio and maximum ratio of reinforcement do not recover its original strength, 3) furthermore, the concrete may reach its maximum capacity before reinforcement yields in reinforced concrete members having maximum ratio of reinforcement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.103-111
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• 2011

This paper estimated the structural behavior of recycled aggregate concrete confined with spiral reinforcement. The main test parameter was designed to be the type of aggregates and the steel ratio of spirals. A total of 18 specimens were cast and tested in this study. All the specimens had a diameter of 150mm and a height of 300mm. The specimens can be divided into two groups, based on the type of coarse aggregate used. The ratio of spiral reinforcement was varied from 0 % to 1.75%. To measure the axial and lateral deformations of the specimens, a total of six linear variation displacement transducers (LVDTs) were installed at each specimen. Furthermore strain gauges were also attached to the steel spirals to obtain the strain of spiral reinforcements. From the experimental results, the structural performance of recycled aggregate concrete specimens confined by steel spirals was similar to that of natural aggregate concrete specimens regardless of the ratio of spiral reinforcement.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.2
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• pp.175-182
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• 2020

The application of epoxy coated reinforcements is increased as a means to prevent a corrosion of reinforcements embedded in reinforced concrete structures, However, epoxy coating may reduce the bond capacity between concrete and reinforcement, which results a longer development length and lap splice length. This paper aims to the possibility of modification in lap splice length from reduction of basic development length which was confirmed using a direct pull out test. Total 36 beam specimens were tested to compare the lap splice properties of normal and epoxy coated reinforcements with beam-end test for various lap lengths and diameters of reinforcements. According to the results on failure modes, deformations, and crack widths of this experiments, the modification factor of 1.2 should be used, though the direct bond capacity is assured through direct pull out test.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.102-109
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• 2003

The grouted splice steeve has been applied widely due to its superior construction efficiency, such as the unnecessity of post concrete and the large allowable limit to the arrangement of reinforcing bars. However, studies on grout-filled splice steeve still have not been sufficiently peformed. The purpose of this study is to investigate the confining effect of mortar grouted splice sleeve on reinforcing bar, known to strengthen the bond capacity between grout mortar and reinforcing bar. To accomplish this objective, totally 6 full-sized specimens were made and tested under monotonic loading. Each specimens were equipped with strain gauges at the 12 location of sleeve and reinforcing bar. The experimental variables adopted in this study are embedment length and size of reinforcing bars. Following conclusions are obtained; 1) Under ultimate strength condition, the confining pressure of grouted splice sleeve calculated from measured tangential and axial strain of the sleeve is over $200{\sim}300kgf/{cm}^2$ at any location of sleeve and improved with reduction in embedment length of reinforcing bar. 2) Untrauer and Henry's equation which describe bond strength of mortar as a function of its compressive strength and confining pressure, predicted the measured bond capacity of this test within the 5% limits.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.298-304
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• 2017

The corrosion of reinforcements embedded in concrete causes some durability problems in reinforced and prestressed concrete structures. The epoxy coated reinforcements are one of the effective and reliable methods to prevent corrosion of reinforcements. However, it has been known that the epoxy coating reduces the bond capacity of reinforcement to concrete. This paper investigates the bond behaviors of epoxy coated reinforcements experimentally using direct pull-out test. Bond behaviors of epoxy coated bars for various reinforcement diameters of 10, 19 and 29mm and thicknesses of cover concrete of 1, 2, 3, and $4.5c/d_b$ (ratio of cover to bar diameter) are examined. Total 66 specimens were manufactured and tested according to the RILEM standard method. As the diameters of the epoxy coated reinforcements increase, the difference of bond strength between epoxy coated reinforcements and uncoated bars also increases. Epoxy coated bars showed more than 85% bond performance compared to those of uncoated bars. A new formular for estimating basic development length of epoxy coated reinforcement based on equilibrium equation is proposed using this experimental result.

• Korean Journal of Construction Engineering and Management
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• v.13 no.1
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• pp.106-117
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• 2012

The proportion of rebar factory manufacturing which has been settled down in Korea recently seems to increase because of their strength such as high decreasing rate of rebar loss and manufacturing accuracy and the external factors such as an increase of downtown projects and a decrease of skilled workers. However, factory manufacturing using straight rebars causes a certain amount of rebar loss and an environmental problem including $CO_2$ emissions. To solve these problems, Bar in coil (BIC) has been introduced; however its application is very rare because it has not been produced so far in Korea and manufacturing machines of BIC are very expensive. Also, although BIC's application is expected to expand due to its strengths, few analysis of its application has been conducted. Therefore in this study, analysis of the BIC's characteristics and the influence to the rebar manufacturing industry are conducted for the advancement of rebar work as a basic research. To achieve this, inquiry on the present condition of rebar manufacturing industry in Korea is implemented. Then, the validation of BIC's applications by aspects of industry and the analysis of stakeholders' economical profit and loss are conducted.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.271-278
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• 2019

The corrosion of reinforcements embedded in concrete causes severe deterioration in reinforced concrete structures. As a countermeasure, epoxy coated reinforcements are used to prevent corrosion of reinforcements. When epoxy coated bars are used, the resistance of corrosion is excellent, but epoxy coating on the bars have a disadvantage of reduction in bond capacity comparing to that of normal bars. Therefore, it is necessary to confirm the bond performance of epoxy coated reinforcements through experimental and analytical methods. Bond behaviors of epoxy coated bars for various diameters of 13 and 19mm and thicknesses of cover concrete of 3 types(ratio of cover to bar diameter) are examined. As the diameters of the epoxy coated bars increase, the difference of bond strength between epoxy coated and uncoated bars also increases and damage patterns showed pull out failure. In addition, finite element analysis was performed based on the bond-slip relationship obtained by direct pullout test and compared with the flexural test results. It is considered that flexural member test is more useful than pullout test for simulating the behavior of actual structure.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.4
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• pp.305-313
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• 2000

To determine detection capabilities of locating steel bars and delamination inside concrete, commercially available nondestructive testing (NDT) equipments have been tested. The equipments include two radar systems and two electromagnetic method systems. The inclusions are a 19 mm diameter steel bar and 50 mm thick delamination embedded at different cover depths from the surface of concrete specimens. For the steel bar, attempts were made to determine the size of the bars by changing the diameter of the bars. A sample result of measuring horizontal spacing between doubly reinforced bars is presented in this paper. Experimental results on various measurement cases are discussed. Application of numerical modeling technique for the simulation of radar measurements and improved output display of radar measurements are also presented.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.3-4
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• 2009

This study predicts the structural behavior of RC beams using high strength shear reinforcement and evaluates current design codes restricting the strength of shear reinforcement steel. Under the present design codes, the yield strength of shear reinforcement steel is restricted to 400MPa. In case that use high yield strength reinforcement steel, could incure heavily crack and deflection at the members of structure, and have not verified ductility capacity, fatigue resisting capacity, shear and torsion resisting capacity, anchoring capacity and seismic capacity. To this end, we evaluate structural behavior of reinforced concrete beams using high strength shear reinforcement.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.5
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• pp.475-485
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• 2009

In this paper a two-step algorithm is proposed to efficiently generate rebar elements from 3D CAD data in the context of CAD/CAE data transfer. The first step is an algorithm to identify various type rebar objects and their attributes by analyzing 3D CAD data in STEP format, which is one of the international data standards. The second algorithmic step is a procedure to generate one-dimensional rebar elements from the object data made through the first step for finite element analysis or other CAE tasks. Successful rebar element data generation from real 3D CAD data for a reinforced concrete structure shows the efficacy of the proposed algorithm.