• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.99-104
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• 2002

In this paper the influence or specimen length on flexural compressive strength and parameter or equivalent rectangular stress block of polymer concrete was evaluated. For this purpose, a series of C-shaped specimens subjected to eccentric compression were tested using four different length-to-depth ratios(from 1.0, 2.0, 3.0 and 4.0) of specimens with compressive strength of 1,020kgf/cm$^2$. Results indicate that for the region of h/c$\leq$3.0 the reduction in equivalent rectangular stress block depth and flexural compressive strength with increase of length-to-depth ratios was apparent but for the region of h/c$\geq$3.0 they were nearly constant. It means that for the region of h/c$\geq$3.0 effect of specimen length on equivalent rectangular stress block depth and flexural compressive strength was negligible. It was also founded that the effect of specimen length on v, a coefficient of strength, that was from 0.84 to 0.86 regardless of h/c was petty. Finally, predictive equation is, suggested by using modified law of effect of specimen length and results.

• 대한토목학회논문집
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• 제30권2A호
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• pp.185-191
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• 2010

콘크리트 구조물의 사용성과 내구성 저하의 원인이 되는 균열은 응력의 크기, 응력구배 및 기타 구조적 재료적 원인 등에 의하여 발생하기 때문에 콘크리트의 균열강도를 정확히 예측하기는 매우 어렵다. 특히 판구조의 경우 기존의 일축휨강도에 의한 균열평가가 실제 구조물의 균열강도와 상이할 수 있다. 본 연구에서는 이축휨인장강도 평가에 적합한 시험체 제원을 적용하여 일축과 이축휨강도 특성을 비교, 평가하였다. 실험결과 골재의 크기 및 실험체 크기의 증가에 따라 일축 및 이축휨강도 모두 강도가 저하되는 것으로 나타났다. 일축휨강도에 비하여 이축휨강도가 일축휨강도의 39.5~99.2%로서 전반적으로 낮은 강도를 갖는 것으로 평가되었으며, 특히 20 mm 골재를 사용한 경우에는 76%정도로 고찰되었다.

• 한국해양공학회지
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• 제19권4호
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• pp.28-34
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• 2005

In the study application of volcanic scoria concrete to artificial reefs is investigated. Volcanic scoria is a natural volcanic product that shows light weight, mil/i-porous, and far-infrared irradiation characteristics. The properties of volcanic scoria concrete using Jeju scoria aggregate are evaluated by conducting a comprehensive series of tests on strength and void ratio. It is concluded that the volcanic scoria concrete has the sufficient strength of 4MPa-13MPa and adequate void ratio of $12\%-35\%$ to be accepted as artificial reef concrete. The field experiments are performed through observation by scuba diver's at the Seogwipo coast. Porous specimen and plane concrete specimen are prepared for comparison purposes. Seasonal changes of soft coral on the two series of test specimens were have been observed from Apr. 9, 2004 to Mar. 18, 2005. The soft coral is well grown on the porous specimen however there are no significant changes on the conventional plain concrete specimen. Thus it is concluded that the volcanic scoria concrete is highly suitable as artificial reef concrete.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술.기술논문발표회
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• pp.55-58
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• 2002

This study is to analyze the influence of correction factor and specimen thickness on the fundamental properties of porous concrete. Results of this study were shown as follows; 1) As correction factor decrease, compaction time according to correction factor and specimen thickness decrease. Also, though correction factor is same, as specimen thickness increase, compaction time increase. So It mutt be considered that the influence of compaction time according to correction factor and specimen thickness. 2) As correction factor decrease, difference of measured thickness and designed thickness according to correction factor and specimen thickness decrease. Also, correction factor of aggregate of 10~l5mm is smaller than that of 5~l0mm. So It must be considered that the influence of correction factor according to size of aggregate.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.457-460
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• 2008

본 연구에서는 폴리프로필렌섬유와 강섬유 혼입에 따른 고강도 기둥 콘크리트의 내화특성을 평가하였으며 내화특성 평가를 위하여 ISO-834 곡선을 적용하여 내화실험을 실시하였다. 실험결과 섬유보강재를 혼입하지 않은 기둥 시험체의 경우 폭렬이 심하게 발생하였으며 높은 내부온도를 나타났다. 폴리프로필렌섬유를 혼입한 고강도 콘크리트 기둥 시험체의 경우 폭렬이 발생하지 않았으며 내부온도 결과에 있어서도 섬유보강재를 혼입하지 않은 경우보다 낮게 나타났다. 폴리프로필렌섬유와 강섬유를 혼입한 기둥 공시체의 경우 폭렬이 발생하지 않았으며 가장 낮은 내부온도를 나타내 가장 우수한 내화성능을 나타냈다.

• Structural Engineering and Mechanics
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• 제23권1호
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• pp.43-61
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• 2006

An investigation of the effectiveness of the interface treatment when column concrete jacketing is performed is presented. Alternative methods of interface connection were used in order to investigate the performance of strengthened concrete columns. These connecting techniques involved roughening the surface of the original column, embedding steel dowels into the original column and a combination of these two techniques. The experimental program included three strengthened specimens, one original specimen (unstrengthened) and one as-built specimen (monolithic). The specimens represented half height full-scale old Greek Code (1950's) designed ground floor columns of a typical concrete frame building. The jackets of the strengthened specimens were constructed with shotcrete. All specimens were subjected to displacement controlled earthquake simulation loading. The seismic performance of the strengthened specimens is compared to both the original and the monolithic specimens. The comparison was performed in terms of strength, stiffness and hysteretic response. The results demonstrate the effectiveness of the strengthening methods and indicate that the proper construction of a jacket can improve the behaviour of the specimens up to a level comparable to monolithic behaviour. It was found that different methods of interface treatment could influence the failure mechanism and the crack patterns of the specimens. It was also found that the specimen that combined roughening with dowel placement performed the best and all strengthened columns were better at dissipating energy than the monolithic specimen.

• Steel and Composite Structures
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• 제18권5호
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• pp.1129-1144
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• 2015

Based on the experiment, this paper focuses on studying flexural behavior of splicing concrete-filled glass fiber reinforced polymer (GFRP) tubular composite members connected with steel bars. The test results indicated the confinement effects of GFRP tubes on the concrete core in compression zone began to produce, when the load reached about $50%P_u$ ($P_u$-ultimate load), but the confinement effects in tensile zone was unobvious. In addition, the failure modes of composite members were influenced by the steel ratio of the joint. For splicing unreinforced composite members, the steel ratio more than 1.96% could satisfy the splicing requirements and the steel ratio 2.94% was ideal comparatively. For splicing reinforced specimen, the bearing capacity of specimen with 3.92% steel ratio was higher 21.4% than specimen with 2.94% steel ratio and the latter was higher 21.2% than the contrast non-splicing specimen, which indicated that the steel ratio more than 2.94% could satisfy the splicing requirements and both splicing ways used in the experiment were feasible. So, the optimal steel ratio 2.94% was suggested economically. The experimental results also indicated that the carrying capacity and ductility of splicing concrete-filled GFRP tubular composite members could be improved by setting internal longitudinal rebars.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.137-140
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• 2006

In this study, a seismic performance of reinforced concrete columns strengthened by a sprayed fiber reinforced polymer (SFRP) is investigated. For this purpose, six column specimens approximately scaled into 2/3, are designed and tested under a constant axial load, 10% of the nominal axial strength of column, and pseudo-static reversed cyclic lateral loading system. Four specimens are strengthened by Sprayed FRP using different combinations of short fibers (carbon or glass fiber) and resins (epoxy or vinyl esther). For comparison, the test investigated in this study also includes a specimen strengthened using carbon fiber reinforced polymer (CFRP), and also a control specimen without strengthening. The results revealed that specimens strengthened using SFRP showed a improved structure behavior, compared to control specimen, in terms of strength, ductility, lateral drift capacity, and energy-absorbtion capacity. In addition, compared to the specimen strengthened using CFRP, Sprayed FRP-strengthened specimens reasonably showed a equivalent seismic performance.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.653-660
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• 1998

Bond strength of reinforcing bar to high-performance concrete using belite cement is explored using beam end test specimen. The key parameters for the bond test are slump of concrete, top bar effect, and strength of concrete in addition to concrete covers. Specimen failed in the typical brittle bond failure splitting the concrete cover as the wedging action. The test results show that the specimens with belire cement concrete show higher bond strength than those with portland cement concrete. Bond strength of the top bar is less than bond strength of bottom bar, but the top bar factor satisfies the modification factor for top reinforcement. The results also show that the bond strength is function of the square root of concrete compressive strength and cover thickness. The recently developed high-strength and high-slump concrete with belite cement performs well in terms of bond strength to reinforcing steel.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.489-494
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• 2002

The basic Physical properties, Slump, Slump Flow, Air content, Bleeding, and Settlement of concrete was investigated to test Characteristic of Setting and to evaluate the relation between Model Specimen and Heat of Hydration for construction under Low Temperature (CFT). The objective of this study is to take the partial core after the cementation of Model Specimen, test the compression intensity and analyze the relation to Test Piece.