• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.449-457
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• 2023

In this study, the structural limit for concrete was experimentally determined against corrosion of steel. The structural limit was taken as (1) the deformation of concrete at yielding, (2) the maximum pull-out strength and (3) the pull-out strength at the level for uncorroded specimen. Corrosion of steel was accelerated by extracting charges from steel surface to govern degree of steel corrosion. As a result, an increase in the steel diameter resulted in an increase in the corrosion degree to reach the concrete deformation at yielding. Again, an increase in the steel diameter resulted in an increase in the extracted charge to meet the maximum and uncorroded-equivalent level for the bond strength. However, the mass loss was marginally affected by the steel size, reflecting that these parameters could be used to alert the structural limit.

• The Korean Journal of Malacology
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• v.27 no.2
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• pp.99-105
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• 2011

This study was conducted to compare the species composition of sessile organisms on the artificial substrates of PVC submerged at different time intervals and duration in Jangmok Bay, Geoje Island, southern coast of Korea. Three PVC plates were submerged at one month interval from March to October and retrieved in November, 2007. A mussel, Mytilus galloprovincialis exclusively occupied the artificial substrates submerged from March to April and occurred as a dominant species to July. An ascidian, Styela plicata occurred as a dominant sessile species from May to August. Balanus amphtrite, Bugula sp., and hydrozoans occurred as dominant species on the plates submerged from July to September. There was a mis-match between the peak time of settlement and dominance of sessile organisms due to the interspecies competitions when the PVC plates were retrieved in November. There was no clear relationship between submerged duration and the abundance of sessile organisms due to the different settlement period. M. galloprovincialis seemed to be a strong competitor which could exclude the previous recruiters of macroalgae by overgrowth and occupy the substrate surface and maintain its high population density by preventing the settlement of other species until late autumn. These results suggested that the composition of sessile organisms in vacant hard substrates could be determined by the combined effects of supply-timing of larvae and post-settlement competitions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.92-103
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• 2015

Development of new concrete bridge deck system with FRP plank using as a permanent formwork and the main tensile reinforcement recently has been actively conducted. Concurrent use as a reinforcing material and a permanent formwork, it is possible to reduce the construction time and construction costs than the usual concrete slab. In this study, an experiment was carried out for the bond stress between cast-in-place concrete and the type of FRP plank using as a permanent formwork. The interfacial fracture energy that can be one of the most important parameters were evaluated for adhesion performance and bond stress to know the characteristics of the failure mechanism of the adhesion surface. Interfacial fracture energy of normal concrete is 0.24kN/m of GF11 case, in the case of GF21, 0.43kN/m appears, in the case of CF11 and GF31, 0.44kN/m and 0.46kN/m respectively it appeared. In case of RFCON, 0.52kN/m appears from GF12, the CF12 and GF22, 0.51kN/m and 0.36kN/m appeared each case.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6A
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• pp.457-464
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• 2011

An experimental study was performed to evaluate the possibility of using stiff type PolyUrea(PU) on RC slab as a strengthening material. Stiff type PU(STPU) was sprayed on the bottom surface of the slab specimens, which were then attached with CFRP or GFRP sheets. Also the evaluation of the bond capacity, the single most influential parameter on strengthening of RC structures, was carried out the flexural capacity evaluation test results showed that the load carrying capacity of the PU specimen was greater and less than the unstrengthened and FRP sheet attached specimens, respectively. The STPU specimens showed a ductile flexural behavior in the plastic displacement range. With respect to bond capacity, the bond strength of all of the specimen exceeded the code required bond strength of 1.5 MPa. Also, the STPU sprayed specimen without using epoxy resin did not peel off when the tensile grip was applied for testing. The stability of the PU bond failure indicate a good bond strength of PU when applied to concrete.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.127-137
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• 1999

In the previous study in relation to the current study, a test program for the verification of the proposed design equation was carried with fourteen prestressed concrete beams with unbonded tendons. Experimental results were compared with the computed results by the proposed design equations. The previous design equations are ACI code, AASHTO LRFD code, the analysis equation with the strain compatibility, Harajli/Kanj' design equation, Chakrabarti' design equation. As a result of comparative studies, it turned out that the proposed design equation could predict the ultimate tendon stress with comparatively high accuracy.

• Magazine of the Korea Concrete Institute
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• v.7 no.6
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• pp.197-208
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• 1995

The prestressed concrete continuous members with unbonded tendons were investigated while comparing the experimental data with the analytical results. The comparison was carried out with the program TAPS which can take into account the unbonded tendon effects. The subjects that were interested included the load-deflection response, the design equations for the tendon stress at failure, the effects of bonded reinforcements, the effects of span-depth ratio, the effects of loading type. In this paper, contiriuous prestressed concrete members with unbonded ten dons were investigated. Of twelve tests with continuous members, six were two-span beams and six were three span one-way slats. Analytical results were compared favorably with experimental data and disclosed that the tendon stress at flexural failure is the function of the amount of bonded reinforcements, the loading types and patterns, and the tendon profile.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.382-388
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• 2017

In this study, a basic study was carried out on the external strengthening method of public buildings. A steel damper is installed outside the specimen with a rocking wall and connected to the frame. Two specimens were fabricated, and the non-reinforced specimens utilized the existing results. As a result of evaluating the envelope curve, strength, stiffness and energy dissipation capacity, it was evaluated that the strength enhancement of the RW_P specimen externally reinforced plate damper was evaluated to be excellent. In addition, RW_S specimens with external S type damper shows a gentle envelop curve after maximum load, and it can be confirmed that the damper properly dissipates the seismic energy.

• Annual Conference on Human and Language Technology
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• 2001.10d
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• pp.123-129
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• 2001

지금까지 한국어 품사 부착을 위해 다양한 모델이 제안되었고 95% 이상의 높은 정확도를 보여주고 있다. 그러나 4-5%의 오류는 실제 응용 분야에서 많은 문제를 야기시킬 수 있다. 이러한 오류를 최소화하기 위해서는 오류를 분석하고 이를 수정할 수 있는 규칙들을 학습하여 재사용하는 방범이 효과적이다. 오류 수정 규칙을 학습하기 위한 기존의 방법들은 수동학습 방법과 자동 학습 방법으로 나눌 수 있다 수동 학습 방법은 많은 비용이 요구되는 단점이 있다. 자동 학습 방법의 경우 모두 변형규칙 기반 접근 방법을 사용하였는데 어휘 정보를 고려할 경우 탐색 공간과 규칙 적용 시간이 매우 크다는 단점이 있다. 따라서 본 논문에서는 초기 모델에 대한 오류 수정 규칙을 효율적으로 학습하기 위한 새로운 방법으로 결정 트리 학습 방법을 확장한 통계적 결정 그래프 학습 방법을 제안한다. 제안된 방법으로 두 가지 실험을 수행하였다. 초기 모델의 정확도가 높고 말뭉치의 크기가 작은 첫 번째 실험의 경우 초기 모델의 정확도 95.48%를 97.37%까지 향상시킬 수 있었다. 초기 모델의 정확도가 낮고 말뭉치 크기가 큰 두 번째 실험의 경우 초기 모델의 정확도 87.22%를 95.59%로 향상시켰다. 또한 실험을 통해 결정 트리 학습 방법에 비해 통계적 결정 그래프 학습 방법이 더욱 효과적임을 알 수 있었다.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.35-36
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• 2010

This research investigated the bond characteristic by lap splice experimental which has change relative area on rib variation of reinforcing bar. As a result has similar load-deflection curve with existing experiment, Maximum yield strength and displacement is increase.

• 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.