• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.169-170
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• 2011

In the connection of green frame, the bottom rebar of the precast concrete beam needs joint or anchorage to ensure structural integrity. However, given the characteristics of composite precast concrete joint, enough length over which rebar can be anchored or lap-spliced is not secured. In addition, due to issues with constructability, cost or quality, it is difficult to apply welding or mechanical connection techniques. Therefore, this study analyze the requirement for a bolt-type rebar coupler as a solution for the coupling issue between the lower rebars of green frame beam. The requirement for bolt-type rebar coupler proposed herein will provide basic data for development studies of the rebar coupler.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.142-143
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• 2022

In order to achieve structural performance such as rebar clear spacing in the reinforced concrete structure construction, coupler splicing joints are becoming common. To confirm the performance of rebar splicing joints, quality verification is being carried out through coupler specimen tests. However, it can be said that the required performance is reached only when the actual construction in the field is constructed under the same conditions as the coupler splicing joint specimen. Therefore, the problems and solutions of the coupler splicing joint construction of the actual field was investigated in this study.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.40-51
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• 2015

In reinforced concrete structure, rebar connection method should be considered because of its structural role to resist the tensile stress and its structural load transmission with concrete in the concrete structure. Lapped splice and mechanical sleeve type connector have been traditionally used to connect rebar in the concrete structures. In this study, to examine the mechanical and failure behaviors of rebar bar connected by taper type coupler in the concrete member depending on connection type and condition, tensile tests of steel rebar with taper type coupler and flexible loading tests of concrete beams were conducted. Its tensile strength and flexible strength of the rebar connected by taper type coupler were compared and evaluated by mechanical behaviors of rebar. From this study, steel rebar connected by taper type coupler showed it has similar mechanical performance comparing with unconnected rebar, thus taper type coupler can be used in the rebar fabrication of reinforced concrete structure.

• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.531-542
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• 2022

As buildings become taller, the strength of structural materials must increase and the amount of rebar reinforcement also increases while the application of an appropriate rebar splice method in the construction process become one of the essential factors. In this research, the current status of quality check for rebar coupler is identified by an expert questionnaire and an appropriate quality check method is proposed through a quality test on specimens similar to actual on-site construction. In the test results, it was revealed that, among the quality check methods for rebar coupler joints, the coupler tightening method and face to face degree of between upper and lower rebar did not affect the strength the specimen. Therefore, it is considered to be an appropriate way to check the coupler quality check to check whether the threads are completely assembled during on-site construction through manufacture the number of threads of rebar and coupler with a margin beyond the calculated thread number.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.319-320
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• 2023

In a reinforced concrete structure, coupler construction is easier to install than jointing or welding reinforcing bars, so it is possible to work by one person. When constructing a reinforcing bar coupler, the coupler construction method must be different for each member that receives a large tensile force or a member that receives a small tensile strength. Various coupler products are used in the global construction market, and the quality, performance, and cost of reinforcing bar joints vary from product to product. This study compares and analyzes the quality and cost of representative rebar couplers according to the requirements using the quality house of QFD-HOQ. The case study presents a quality and cost improvements strategy through QFD-HOQ analysis of rebar couplers.

• Journal of the Korea Institute of Building Construction
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• v.14 no.1
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• pp.87-93
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• 2014

A tightened coupler with two way-threading is suggested to overcome the previous one-way threaded coupler. The experiment and a mock-up test were conducted to analyze the constructability of the suggested coupler. The aim of the mock-up test was to assemble the suggested coupler in horizontal rebar of mat footing and vertical rebar of semi-fabricated column bars. The method using the suggested coupler in semi-fabricated column bars is developed by analyzing the problem of fabricated column bars using the one-way threaded coupler. The result of the mock-up test showed that the time required to assemble the suggested coupler in the horizontal bars is shorter than it is for the one-way threaded coupler. In addition, the method using the suggested coupler in semi-fabricated column bars has advantages such as lower working loads, supporting safe work and strongly tightening the rebar. From these results, it is revealed that the suggested coupler is adequate to use in rebar work in terms of cost, quality and time.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.14-15
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• 2013

Green Frame is precast concrete column-beam structure. There are three types on column connection. The coupler type which is one of the three, need to be improved because of unstability caused by pre-installation of column before casting the slab, and quality deterioration caused by lack of workspace. Therefore, in this study, new coupler connection type with thread rebar is suggested. The result of this study shall be used for the efficiency analysis of the new coupler connection.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.90-98
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• 2018

Recently, various reinforced concrete joints have been used in reinforced concrete structures. Therefore, it is important to grasp the tensile properties of the spliced rebar. In this study, uniaxial tensile tests were conducted on Grade 60 D22(#7), D29(#9), and two kinds of couplers manufactured according to ASTM A615 standard for evaluating ductility of coupler joints. The strain was measured using an image processing method more accurate and capable of measuring at various points freely. As the result of uniaxial tensile test, it was possible to calculate the stress-strain relationship and the longitudinal strain distribution according to the stress stages and it was founded that the average strain becomes lower as more occupying the coupler joint portions in the same gauge length. In addition, the empirical equations are proposed to account for the effect of the length of the coupler on the ultimate strain and the rupture strain.

• The Journal of Korea Robotics Society
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• v.16 no.3
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• pp.207-215
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• 2021

There is a risk of serious injury to workers who work at height in pier construction process. By using auto climbing formwork system that does not need to dismantle and reinstall formworks, it is possible to improve work efficiency and safety of workers. However, auto climbing formwork system still requires workers to work on a pier for rebar connection works and so on. In order to eliminate works by workers on the pier, robot manipulators with special end effectors are proposed. Through analysis of works on the pier, three specialized end effectors which are a gripper, a rebar coupler press, and a concrete vibrator, are suggested. Also, new pier construction scenario by the suggested system is confirmed using 3d modeling. It is expected that the proposed system and method enables pier construction without workers on piers. It will increase safety and efficiency of pier construction.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.11a
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• pp.37-41
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• 2002

Lap splice is used in building construction up to recently. As buildings become higher and larger, the use of high tensile bar is increasing due to increasing in the use of high compression concrete. However the using of high tensile bar in lap splice causes eccentricity and difficulty in placing of concrete inside the form, therefore not allowing enough intervening material. Various mechanical connection are being developed but the coupler of today needs either a secondary intervening material or secondary processing that consumes much time. Therefore a coupler, needing neither a secondary intervening material nor secondary processing, was made in this study which lead to following results. (1) Breaking occurred in all experimented rebar. (2) Acquirement of tension exceeding the standard requirement. (3) Acquirement of elongation percentage within the standard requirement.