• Journal of the Korea Concrete Institute
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• v.19 no.5
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• pp.595-602
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• 2007

Recently, concrete structures with carbon fiber reinforced polymer (CFRP) reinforcements have been commonly used for the bridge and building construction. In this paper, pier caps were strengthened by prestressed near surface mounted CFRP. To verify the effectiveness of the strengthening method, 7 pier cap specimens were fabricated. One specimen was designed for control, two for external prestressing steel strands, two for CFRP plates, and two for CFRP bars. Experimental variables consist of type of reinforcement materials and prestressing levels. The results of laboratory have shown that the ultimate load capacities of prestressed near surface mounted CFRP specimens were about $20{\sim}33%$ greater than that of a control specimen. Also, ultimate load capacities of prestressed near surface mounted CFRP specimens were similar to those of external prestressing specimens with steel strands.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.121-125
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• 2018

This paper presents the assessment of 7-wire strand monitoring using acoustic emission technique for bridges. 7-wire strand is widely used construction materials to provide additional tensile force to bridges. PSC (PreStressed Concrete) bridge and cable-stayed bridge are representatives for such cases. However, as the bridge aging progresses recently, corrosion problems of strand are emerging. For this reason, various NDT (Non-Destructive Test) methods for cable inspection are being studied and applied to the field. One of the NDT methods, acoustic emission technique, is known as an effective technique to detect cable damage and breakage. In this study, to evaluate the applicability of acoustic emission technique to bridges, acoustic emission signals according to damage of the strand were acquired and analyzed by tensile test. Moreover, The optimal AE sensor type was selected for field application. As a result, it is considered that the acoustic emission technique will be able to detect corrosion breakage and signs of rupture.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.15-26
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• 2010

Quasi-static tests were conducted to evaluate structural performance of precast piers prestressed by bonded prestressing steels. Combinations of prestressing bars and normal reinforcing bars, embedded steel tubes and prestressing strands were used as continuous steels crossing the joints of a precast pier. Main design parameters were steel ratio, magnitude of prestress force, and section details. Flexural strength and energy dissipation capacity of precast columns with higher steel ratio showed better performance due to continuous steels after opening of the joints. Precast piers with embedded members showed stable behavior after reaching maximum loads resulting in higher displacement ductility and energy dissipation capacity increased as the introduced prestress increased. Self-centering behavior at early stages and stress increase of confining reinforcements were observed from highly prestressed columns. Combination of prestressing steels and normal reinforcing bars should be used in design to prevent rapid strength degradation after reaching the maximum load.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.143-153
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• 2006

The paper presents the results of a study on improvement in flexure capacities of continuous prestressed steel I-girder with section increasement at internal supports. After tensioning, the field experiment on prestressed steel I-girder has been performed in the various aspects of prestressed I-girder introducing section increasement at internal supports, tendon profile.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.357-360
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• 2008

This study was performed to estimate the workability and the static behavior for Bi Prestressed Concrete Girder(Bicon girder) which could introduce effectively prestressed forces into concrete girders. A bicon girder is manufactured by means of introducing pure bending moment that prestress simultaneously the compressive member(steel bar) and the tensile member(steel tendon). Static test was executed for 20m railway bridge girder specimen and evaluated whether pure bending moment was introduced or not, and the behaviors after cracking, and at the ultimate load. Test results showed that a bicon girder had the enough safety in the introduction of pure moment, the serviceability, and the ultimate behavior.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.395-401
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• 2022

In this study, the transfer length of strand was measured for three types of HCS member(H200, H320, and H400) manufactured by the pretension method. Strain gauges were attached in longitudinal direction at regular intervals on the sides of the HCS members, and the strain was measured during the cutting process of HCS. The stain at the cutting point was zero, and gradually increases in the central direction of the member, converging to a constant value after passing the transfer length. In the case of H200 members in which the strands were arranged one by one, the transfer lengths were formed within the range of the design equation (up to 762 mm). The transfer length of the H320 member and the H400 member, in which three strands were arranged, was higher than the design range (850 mm or more).

• Journal of the Korean Geotechnical Society
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• v.26 no.7
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• pp.117-133
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• 2010

A hybrid system of soil-nailing and compression anchor is proposed in this paper; the system is composed of an anchor bar (installed at the tip) with two PC strands and a steel bar. After drilling a hole, installing proposed hybrid systems, and filling the hole with grouting material, prestress is applied to the anchor bar to restrict the deformation at the head and/or to prevent shallow slope failures. However, since the elongation rate of PC strand is much larger than that of steel bar, yield at the steel bar will occur much earlier than at the PC strand. It means that the yield load of the hybrid system will be overestimated if we simply add yield loads of the two - anchor bar and PC strands. It might be needed to try to match the yielding time of the two materials by applying the prestress to the anchor bar. It means that the main purpose of applying prestress to the anchor bar should be two-fold: to restrict the deformation at the nail head; and more importantly, to maximize the design load of the hybrid system by utilizing load transfer mechanism that transfers the prestress applied at the tip to the head through anchor bar. In order to study the load transfer mechanism in a systematic way, in-situ pullout tests were performed with the following conditions: soil-nailing only; hybrid system with the variation of prestress stresses from 0 kN to 196 kN. It was found that the prestress applied to the anchor system will induce the compressive stress to the steel bar; it will result in decrease in the slope of load-displacement curve of the steel bar. Then, the elongation at which the steel bar will reach yield stress might become similar to that of PC strands. By taking advantage of prestress to match elongations at yield, the pullout design load of the hybrid system can be increased up to twice that of the soil-nailing system.

• Journal of the Korea Concrete Institute
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• v.17 no.2 s.86
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• pp.229-236
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• 2005

To cope with increasing requirements of cost reduction, labor saving, and rapid construction, the purpose of this study is to investigate the structural behavior of PSC monolithic and spliced girders. Three tests were conducted on reduced-scale girder specimens having same type. This paper presents the result of experimental studies on the load-deflection behavior in which different joint and amount of tendon as major variables were investigated. The first one used a monolithic girder was arranged with three tendons. The second one used a spliced girder was joined with three tendons after producing five segments. And the third girder was produced in same conditions with the second girder and arranged with additional tendons. The experimental results show the difference of behavior between monolithic and spliced girders.

• Computational Structural Engineering
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• v.17 no.1
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• pp.39-42
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• 2004

콘크리트 구조물에 대한 보강공법은 1950년도에 개발된 강판보강공법을 위시로 하여 강연선에 의한 외부프리스트레싱 공법으로 발전하고 있으며, 약 10년전부터는 신소재인 FRP(Fiber Reinforced Polymer)에 의한 보강공법이 본격적으로 개발되어 실용화되고 있다. 강판보강공법은 에폭시 등의 접착제를 이용하여 콘크리트 인장측에 강판을 접착함으로써 강도 및 강성을 증가시키는 공법으로 강판을 보강재로 이용함으로써 공법에 대한 인지도가 높은 장점이 있는 반면, 재료의 가공 및 취급이 어려우며 중량이 커 자중이 증가되는 단점이 있다. 또한, 강재의 부식위험이 상존하고 있어 이에 대한 세심한 배려 및 주기적인 유지관리를 필요로 한다.(중략)

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.4
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• pp.18-29
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• 2013

A new precast concrete (PC) beam and column connection system using non-prestressed wire strands was recently developed. The system is composed of one unit of two-storied PC-column and PC-beams with U-shaped ends. The connection part of the column and beams is reinforced by deformed bars and non-prestressed wire strands in combination for the improvement of workability. Structural performance of this system was verified by several experimental studies. The purpose of this study is developing a design concept of the beam reinforced by deformed bars and non-prestressed wire strands in combination, in terms of the cross-sectional analysis, based on the preceded experiment. A minimum and maximum reinforcement ratio and the calculation formula for the strength of flexural member reinforced by reinforcements having different yield strengths are derived based on KBC2009. Under consideration existing research results for the application of high strength reinforcement bars, the design yield strength of the non-prestressed wire strand is suggested. An example for the cross section design, satisfying the serviceability requirements, demonstrates the applicability of the design concept developed in the study.