• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.47-56
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• 2006

The repeated loading responses of four shear-critical reinforced concrete beams with two different shear span-to-depth ratios, were studied. One series of beams was reinforced using pairs of bundled stirrups with $90^{\circ}$ standard hooks, haying free end extensions of $6d_b$. The companion beams contained shear reinforcement made with larger diameter headed bars anchored with 50mm diameter circular heads. A single headed bar had the same area as a pair of bundled stirrups and hence the two series were comparable. The test results indicate that beams containing headed bar stirrups have a superior performance to companion beams containing bundled standard stirrups with improved ductility, larger energy absorption and enhanced post-peak load carrying capability. Due to splitting of the concrete cover and local crushing, the hooks of the standard stirrups opened resulting in loss of anchorage. In contrast, the headed bar stirrups did not lose their anchorage and hence were able to develop strain hardening and also served to delay buckling of the flexural compression steel. Excellent load-deflection predictions were obtained by reducing the tension stiffening to account for repeated load effects.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.80-81
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• 2014

Generally significant reinforcement is used for nuclear power plant structures and may cause potential problems when concrete is poured. In particular pouring concrete into structural member joint area is more difficult than other areas since the joint area is very congested due to hooked bars, embedded plates, and other reinforcements. The purpose of this study is to solve the problem by applying high-strength(ASTM A615 Gr. 75/80) bars. In addition large-sized(#14 & #18) headed deformed bar could be used as alternative of standard hooked bars to relieve the congestion to some extent. In order to apply headed deformed bars to nuclear power plant structures effectively, the large-sized diameter bars and the high-strength bars shall be used as thick as clear cover thickness 1". Therefore, test results were obtained by taking bar size, yield strength, and clear cover thickness as variables.

• Journal of Korean Association for Spatial Structures
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• v.9 no.2
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• pp.45-52
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• 2009

This paper experimentally evaluates the strength characteristics of precast column-R.C. foundation anchor joint subjected to the cyclic horizontal load. The study presents differences in accurate stress transfer path and destruction mechanism between the concrete structural body applying the precast column-R.C. foundation anchor joint and the concrete structural body applying the steel joint. the result from width load experiment on reinforcing steel under the cyclic horizontal load provides the necessary minimum insertion length to construct the precast column-R.C. foundation anchor joint. This study also presents the accurate stress transfer path and destruction mechanism on the anchor joint th meet the customer's requirements, comparing stress transfer path and destruction mechanism provided by the experiment and those provided by the product manual. Eventually, this study presents all the necessary fundamental data to provide the construction design with accurate number of reinforcing steel, diameter of the steel, fixation length of the steel, etc. to build the optimum precast concrete column.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.6
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• pp.169-180
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• 2007

Among several splicing system of reinforcing bar, the grout-filled splice sleeve system has been applied widely. However, as the splice sleeve for high strength rebar as SD500 is not yet made in korea, the development of splice sleeve for high strength reinforcing bar are required as soon as possible. It is the purpose of this study to develop the steel pipe sleeve for high strength rebar as SD500 and estimate its structural performance by monotonic loading test. The experimental variables adopted in this study are the development length of rebars, types of sleeve etc. The results of this study showed that the developed steel pipe splice sleeve system for high strength reinforcing bar as SD500 retained the structural performance required in domestic, ACI and AIJ criteria. And it is considered that the study result presented in this paper can be helpful in developing reasonable design method of steel pipe splice sleeve system for high strength reinforcing bar as SD500.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.53-61
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• 2013

A new deformation of reinforcing bar in coils was proposed to improve a machinability of straightening process, which has crescent-shaped transverse ribs with an inclination angle of 50 degrees, a crest width of $0.15d_b$, and a flank inclination of 55 degrees. The proposed deformation can increase contact area between a surface of re-bar and a groove of a roller during a straightening process and, therefore, it might reduce a damage of ribs, improve a final straightness, and enhance an efficiency of the straightening process. Splice tests were conducted to evaluate bond strengths of three types of re-bar in coils including the proposed re-bar, of which the inclination angles of transverse ribs were 50, 60, and 90 degrees, respectively. Test results show that the re-bars in coils have higher bond strengths than predicted strengths by equations of Orangun et al., ACI 408, and KCI by at least 10%. Correlation coefficients of bond strengths between a straight bar and re-bars in coils are 0.94 and more. Consequently, equations of the KCI code for determining development and splice lengths can be applied to the tested re-bars in coils.

• Korean Journal of Construction Engineering and Management
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• v.24 no.5
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• pp.52-62
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• 2023

The objective of this study is to propose an automated algorithm for precise cutting length of slab rebar complying with regulations such as anchorage length, standard hooks, and lapping length. This algorithm aims to improve the traditional manual quantity take-off process typically outsourced by external contractors. By providing accurate rebar quantity data at BBS(Bar Bending Schedule) level from the bidding phase, uncertainty in quantity take-off can be eliminated and reliance on out-sourcing reduced. In addition, the algorithm allows for early determination of precise quantities, enabling construction firms to preapre competitive and optimized bids, leading to increased profit margins during contract negotiations. The proposed algorithm not only streamlines redundant tasks across various processes, including estimating, budgeting, and BBS generation but also offers flexibility in handling post-contract structural drawing changes. In particular, the proposed algorithm, when combined with BIM, can solve the technical problems of using BIM in the early phases of construction, and the algorithm's formulas and shape codes that built as REVIT-based family files, can help saving time and manpower.

• Journal of the Korean Geotechnical Society
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• v.33 no.12
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• pp.107-113
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• 2017

Shear Connector should be used to fix the PHC pile with extension wall in order to utilize PHC-W retaining wall as permanent wall. The pullout behaviours on shear connectors anchored into PHC-W pile were observed as two modes. The first type behaviour showed that after reaching the maximum pullout resistance, the anchorage was broken and shear connector was pulled out abruptly. The second type behaviour showed that even after arriving the maximum pullout resistance, the anchorage was not destroyed and there was a progressive increase in pullout displacement. The maximum pullout resistance of the steel anchor shear connector is larger than that of deformed bar shear connector. The larger the diameter and the longer the embedment length of shear connector, the higher the maximum pullout resistance would be. The pullout displacements corresponding to the maximum pullout resistance of the shear connector showed various ranges regardless of the materials, the diameters and the anchoring lengths. A-D20 shear connectors showed a pull-out displacement of about 8~10 mm. A-D16, D-D19 and D-D16 shear connectors exhibited a pulling displacement of about 14~20 mm, but a pulling displacement of about 6~10 mm when the anchoring lengths were 50 and 80 mm.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.2
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• pp.51-58
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• 2022

Flat plate slab is cost-efficient structural system widely used in high rise building, apartment and parking garages. But flat plate-column connections are so weak against punching shear failure that it may cause collapse of overall structure. In this study, spiral type shear reinforcement which increases the shear strength and ductility of the plate-column connection and has good workability was proposed. And experimental test was performed to verify the punching shear capacity of spiral type shear reinforcement. The current code does not accurately estimate the punching shear strength of slab-column connection with shear reinforcement because slab is so slender that punching failure may occurred before shear reinforcement reached yield stress. Therefore modified equation of ACI code for punching shear strength was proposed base on finite element analysis using LUSAS program, and data analysis from CEB-FIP database.

• Magazine of the Korea Concrete Institute
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• v.5 no.4
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• pp.167-178
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• 1993

The objective of this paper is to look into the possibility of the detailed and practical optimum design of rt:inforced concrete beam using methods oi discrete mathematical programming. In this discrete optimum formulation, the design variables are the overall depth, width and effective depth of members, and area of longitudinal reinforcement. In addition, the details such as the amount of web reinforcement and cutoff points of longitudinal reinforcement are also considered as variables. Total cost has been used as the objective function. The constraints include the code requirments such as flexural strength, shear strength, ductility, serviceability, concrete cover. spacing, web reinforcement, and development length and cutoff points of longitudinal renforcement. An optimization algorithm is presented for effective optimum design of R.C. beam with discrete de sign variables. First, the continuous variable optimization can be achieved by Feasible Direction Method. Using the results obtained from the continuous variable optimization, a branch and bound method is used to obtained the discrete design values. The proposed algorithm is applied to test problem for reliability, and the results are compared with those of graphical method and rounded-up method. And a simply supported R.C. beam and a two-span continuous R.C. beam are presented as numerical examples for effectiveness and applicability. It is considered that the presented algorithm can be effectively applied to the discrete optimum design of R.C. beams.

• Magazine of the Korea Concrete Institute
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• v.10 no.5
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• pp.151-158
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• 1998

최근 들어 구조물을 보강하는 방법으로 강판 또는 섬유쉬트를 외부에 부착시키는 공법이 많이 사용되고 있다. 섬유쉬트 중에서 가장 널리 사용되는 것은 탄소섬유쉬트이지만, 성능면에서 뒤지지 않고 가격면에서는 오히려 유리한 아라미드섬유쉬트에 관한 연구는 전무한 실정이다. 본 연구에서는 아라미드섬유쉬트로 휨보강한 RC보의 파괴양상 및 강도성능, 변형성능을조사하고, 여섯 개의 보강변수에 대한 보강효과를 조사하였다. 인장철근비, 보강길이, 보강겹수, 앵커볼트 정착 유무가 각각 다른 16개의 실험체와 밑면 마감처리 및 부재손상 여부가 다른 2개의 실험체, 그리고 이들 보강 실험체의 비교 근거가 되는 비보강 실험체 2개를 실험하여 그 특성을 연구하였다. 실험결과, 보강성능과 파괴양상에 가장 큰 영향을 미치는 변수는 보강길이로 나타났다. 보강겹수도 어느 정도의 영향을 미치는 것으로 나타났으나 그외 다른 변수들의 영향은 미비한 것으로 판단된다.