• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.138-145
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• 2017

The purpose of this study is to establish a reasonable analytical method for the estimation of overall behavior characteristic from cracking to yielding of rebar and crushing of concrete and seismic performance of reinforced concrete shear wall with high-strength reinforcing bar. A total of 8 specimens of reinforced concrete walls which have constant aspect ratio and a variety of variables such as reinforcement ratio, reinforcement yielding strength, reinforcement details, concrete design strength, section shape and whether lateral restraint hoop were selected and the analysis was performed by using a non-linear finite element analysis program (RCAHEST) applying the proposed constitutive equation by the authors. The mean and coefficient of variation for maximum load from the experiment and analysis results was predicted 1.04 and 8%. The mean and coefficient of variation for displacement corresponding maximum load from the experiment and analysis results was predicted 1.17 and 19% respectively. The analytical results were predicted relatively well the fracture mode and the overall behavior until fracture for all specimens. These results are expected to be used as basic data for application of high-strength reinforcing bar to design codes in the future.

• Journal of the Society of Disaster Information
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• v.11 no.4
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• pp.520-526
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• 2015

Reinforcing bar splices are inevitable in reinforced concrete structure. In these days, there are three main types of splices used in reinforced concrete construction site - lapped splice, mechanical splice and welded splice. Low cost, practicality in construction site, less time consuming and high performance make gas pressure welding become a favorable splice method. However, reinforcing bar splice experiences thermal loading history during the welding procedure. This may lead to the presence of residual stress in the vicinity of the splice which affects the fatigue life of the reinforcing bar. Therefore, residual stress analysis and tensile test of the gas pressure welded splice are carried out in order to verify the load bearing capacity of the gas pressure welded splice. The reinforcing bar used in this work is SD400, which is manufactured in accordance with KS D 3504. The results show that the residual stresses in welded splice is relatively small, thus not affecting the performance of the reinforcing bar. Moreover, the strength of the gas pressure welded splice is high enough for the development of yielding in the bar. As such, the reinforcing bar with gas pressure welded splice has enough capacity to behave as continuous bar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.4
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• pp.79-88
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• 2012

The purpose of this study is to evaluate the stiffness of the mechanical sleeve reinforcement splices filling high-strength mortar under monotonic loading. For this objective, we analyzed and compared the previous test data of 189 actual-sized mortar-filled sleeve bar splices specimens, including the reinforcing bar splices prepared and tested by the author. The paper results indicated that the minimum values of compressive strength of mortar($f_g$) multiplied by the ratio of reinforcement development length to bar diameter(L/d) were suggested for holding the stiffness of the mortar-filled sleeve reinforcement splices required in AIJ code.

• Journal of Industrial Technology
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• v.17
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• pp.145-151
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• 1997

This paper presents evaluation results of the tensile behavior of reinforced high strength concrete. The effects of different sizes of reinforcing bar, ranging from D22 to D29, on the formation of cracks was investigated. Two different strength concretes, $270kg/cm^2$ and $550kg/cm^2$, were used in the specimens to investigate the influence if concrete strength on tension stiffening. In the present investigation a method was developed to obtain reliable load-deformation behavior in tension. The experimental results show that (1)high-strength concrete members exhibited larger amounts of tension stiffening than the companion normal-strength concrete members, (2) as the bar diameter increases, the beneficial influence of high-strength concrete on tension stiffening is reduced.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.453-456
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• 2008

Fiber composite is high anticorrosive, high strength and low weight ratio of strength(1/4 of reinforcing bar) so that strengthens concrete structures without increase of additional weight. But fiber composite has a brittle character which increases to the maximum stress point lineally and is suddenly destroyed. Hybrid fiber composite is developed to overcome weakness of fiber composite. The hybrid fiber composite is manufactured by bar type and consists of 9:1 volume ratio(glass : carbon). In this study the result indicates that it is purposed to find out reinforcing characteristics of hybrid fiber composite fixed with impact anchor.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.120-127
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• 2016

Due to the enlargement and high-rise of reinforced concrete structure, the application of high functional material is required. However, high-strength bar is recently introduced to the country and the material is insufficient to measure the variation of quantity of rebar quantitatively when using high-strength bar. For these reasons, this study is to provide useful data in cost decision making when applying high-strength bar at a stage of architectural project planning. For residence-commerce complex buildings, we set up six types of conditions such as in case of using only rebar, in case of using only high-strength bar, in case of using rebar mixed with high-strength bar and so on. With the standard of study model 1 that applies only SD400 regardless of rebar diameter, the analyzed result of rebar variation and the cost change of construction in other study model is as follows. When the rebar amount and cost in study model I was 100%, each ratio was 88.3% and 90.5% in study model II, 80.2% and 83.4% in study model III, 91.9% and 93.5% in study model IV, 88.9% and 87.7% in study model V and 82.4% and 85.5% in study model VI. Therefore, in case of rebar amount and construction cost, study model III was evaluated as the best that was applied only SD600.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.438-441
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• 2004

This paper presents the results of the experimental study on the performances of reinforced concrete beams rehabilitated by external unbonded high tension steel-bar. Design variables for the experiment in this study includes the position of anchorage zone of the high tension steel bar, the anchorage length of the reinforcing steel bar and the types of the shear strengthening measures. 5 specimens were tested with one point monotonically increased loads and structural performances such as strength capacities, ductility capacities and failure modes were analysed. It is found that the structural performance of the rehabilitated beams are strongly depended on the location of anchorage zone of the high tension steel-bars. In the case that anchorage zone is located near the critical shear zone, it is observed that the rehabilitated beam is failed in brittle failure mode and the additional shear strengthening is necessitated. But if anchorage zone is properly located or additional shear strengthening device is provided properly, it is also observed that the strength capacity of the rehabilitated beams could be increased more than $200\%$ by the proposed method.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.270-273
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• 2006

Bond between reinforcing bar and the surrounding concrete is made up of three components. There are chemical adesion, friction, and mechanical interaction between the rib of the bar and the surrounding concrete. bond of deformed bars depends primarily on the beraing of rib deformation anainst the surrounding concrete. The final objective of the study is to enhance structural stability, and workability thorough increasing the bond strength between deformed bar and surrounding concrete. The results of this study will be used to shorten bond and development length by $20{\sim}30$ percent and it will facilitate to use of high strength and high-relative rib area bars.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.129-136
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• 1999

For the prediction of concrete-steel bond ability in reinforced concrete, many countries establish specifications for the pullout test. But these methods hardly to consider many parameters such as strength, shape, diameter and location of steel, concrete restrict condition by loading plate, strength of concrete and cover depth etc, and it is difficult to solve concentration and disturbance of stress. The purpose of this study is to propose a New Ring Test method which can be rational quantity evaluations of bond splitting mechanism. For this purpose, pullout test was carried out to assess the effect of several variables on bond splitting properties between reinforcing bar and concrete. Key variables are concrete compressive strength, concrete cover, bar diameter and rib spacing. Failure mode was examined and maximum bond stress-slip relationships were presented to show the effect of above variables. As the result, it appropriately expressed general characteristics of bond splitting mechanism, and it proved capability for standard test method.

• Steel and Composite Structures
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• v.48 no.2
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• pp.131-143
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• 2023

The CFRP bar was used to achieve more ductile and durable headed-stud shear connectors in composite components. Three series of push-out tests were firstly conducted, including specimens reinforced with pure steel fibers, steel and CFRP bars. The distributed stress was measured by the commercial PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) optical fiber sensor with high spatial resolution. A series of numerical analyses using non-linear FE models were also made to study the shear force transfer mechanism and crack response based on the test results. Test results show that the CFRP bar increases the shear strength and stiffness of the large diameter headed-stud shear connection, and it has equivalent reinforcing effects on the stud shear capacity as the commonly used steel bar. The embedded CFRP bar can also largely improve the shear force transfer mechanism and decrease the tensile stress in the transverse direction. The parametric study shows that low content steel fibers could delay the crack initiation of slab around the large diameter stud, and the CFRP bar with normal elastic modulus and the standard reinforcement ratio has good resistance to splitting crack growth in headed stud shear connectors.