• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.639-644
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• 2000

Prestressing steels are susceptible to corrosion, which is considered the major reason in the deterioration of prestressed concrete structures. To solve this problem, many research have been made to utilize new type of tendons. FRP tendons have many advantages compared to steel tendons. However, FRP tendons have some disadvantages, such as no plastic behavior. This study focused on the flexural behavior of prestresssed concrete beams which is fabricated by post-tensioning method with CFRP (Carbon Fiber Reinforced Plastic) tendons. Th results drawn from the study, prestressed concrete beams with CFRP tendons have higher flexural cracking load, flexural yielding load, and flexural fracture load. While displacement at the fracture stage is lower compared to prestressed concrete beams with steel tendon. Excessive steel reinforcement lead lower ductility index. So, appropriate reinforcement guideline is needed. Further more, prestressed concrete beams with CFRP tendons can have sufficient ductility index when ruptured by crushing of concrete or used unbonded tendon. Therefore, the best design method for prestressed concrete beams with CFRP tendons is over-reinforcement, and use of unbonded tendon.

• 한국구조물진단유지관리공학회 논문집
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• 제4권1호
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• pp.139-145
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• 2000

In this experimental program specimens. designed by the test variables, such as percentage of steel fiber incorporated, were constructed and tested to evaluate the flexural performance of reinforced steel fiber concrete beams. Based on the test results reported in this study, the following conclusions are made. Comparing with the load-displacement relationship of standard specimen, specimen over 0.5% of steel fiber incorporated, could be improved significantly flexural performance, such as capacity, ductility, and crack pattern. As increasing in quantity of steel fiber incorporated(0.5%~2.0%), the flexural strength of each specimen was shown the enhancement of 13%~40% in comparision with the standard specimen BSS.

• 콘크리트학회논문집
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• 제13권6호
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• pp.553-560
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• 2001

철근콘크리트 휨부재의 비탄성해석 및 설계를 위해서는 연성능력의 평가가 필요하며, 이를 위해서는 모멘트-곡률 관계가 정의되어야 한다. 따라서, 본 연구에서는 모멘트 곡률관계를 가정하여 철근콘크리트 휨부재의 연성능력을 해석적 방법으로 구하고, 실험결과와 비교한 결과, 실험값과 해석값은 거의 일치하였으므로 가정한 모멘트-곡률관계는 적합한 것으로 판명 되었다. 또한, 연성률은 곡률연성, 회전연성, 변위연성을 비교하였으며, 철근콘크리트 휨부재의 연성능력에 주로 영향을 미치는 요소는 인장철근, 압축철근 및 휨보강근으로 보고, 실험값과 해석값을 다양하게 분석한 결과 ($\rho$$_{s}$ ＋ $\rho$')/$\rho$의 항으로 연성능력을 나타냄이 적절한 것으로 나타났다.

• 한국지진공학회논문집
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• 제10권3호
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• pp.113-123
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• 2006

콘크리트 부재의 내진설계에 있어 강도와 더불어 변형 능력은 중요한 요소이다. 연결보는 전단 지배 부재임에도 항복 이후 소성 변형을 요구하는 부재인데 본 연구에서는 연결보의 변형 능력에 대한 실험을 통해 변형 모형을 제시하였다. 일반적인 배근 형태를 가진 철근 콘크리트 연결보를 대상으로 단조하중실험을 수행하였다. 경간-깊이비, 휨 철근비, 전단 철근비를 변수로 하여 연결보의 거동을 평가하였다. 전단 지배 부재인 연결보는 아치작용과 트러스 작용으로 전단력에 대해 저항하는데 실험 결과를 통해 전단력을 두 작용의 구분과 항복 강도 발현 이후 소성 변형에 따른 두 작용의 구성비 변화에 대해 분석하였다. 실험결과에 기초한 전단 철근과 휨 철근의 변형률 분포 모형을 이용하여 휨 철근의 응력 상태를 산정하였다. 휨 철근의 부착-미끄러짐에 의해 결정되는 균열폭을 고려하는 연결보의 변형 모형을 제시하였다. 항복 상태는 휨 철근의 항복 시점으로 정의하였고, 극한 상태는 변형 증가에 따른 스트럿의 압축 강도 저하에 의해 결정되었다. 이 변형 모형은 변위기초설계에 활용될 수 있을 것으로 기대된다.

• 대한토목학회논문집
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• 제28권6D호
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• pp.905-913
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• 2008

최근 고속전철의 자갈도상에 대한 대안으로 콘크리트 슬래브궤도가 도입되어 고속전철 신규노선에 시공되고 있다. 콘크리트 슬래브궤도는 자갈도상에 비해 내구성, 유지관리 측면에서의 경제성, 열차운행의 안정성 등의 측면에서 우위에 있지만, 우수 및 지하수로 인한 노반강성의 저하, 연약한 원지반의 침하 등으로 인한 슬래브궤도의 처짐은 열차안정성에 치명적인 결함이 된다. 본 연구에서는 슬래브궤도의 처짐 지표로서 슬래브궤도의 휨강성을 설정하고, 슬래브궤도의 휨강성을 2차원 영상으로 표현할 수 있는 FRACTAL (Flexural-Rigidity Assessment of Concrete Tracks by Antisymmetric Lamb Waves) 기법이라는 비파괴 탄성파 기법을 제안하였다. 이론적 근거 확보를 위하여 콘크리트 슬래브궤도에서의 탄성파 시험을 수치해석적으로 모사하여 영향인자 연구를 수행하였고, FRACTAL 기법의 적용성 평가를 위하여 실제 고속전철 슬래브궤도에 적용하여 보았다. 그리고 FRACTAL 시험측선과 동일 측선에서 Impulse-Response 기법과 인접지반에서 전기비저항시험을 수행하여, FRACTAL 기법의 신뢰성을 검증하였다.

• Computational Structural Engineering : An International Journal
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• 제1권2호
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• pp.117-130
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• 2001

Investigations of low-rice unbounded reinforced concrete shear walls with or without openings are performed with comparison of analytical and experimental results. Theoretical analysis is based on nonlinear finite element algorithm, which incorporates concrete failure criterion and nonlinear constitutive relationships. Studios focus on the effects of height-to-length ratio of shear walls, opening ratio, horizontal and vertical reinforcement radios, and diagonal reinforcement. Analytical solutions conform well with experimental results. Equations for cracking, yielding and ultimate loads with corresponding lateral displacements are derived by regression using analytical results and experimental data. Also, failure modes of low-rise unbounded shear walls are theoretically investigated. An explanation of change in failure mode is ascertained by comparing analytical results and ACI code equations. Shear-flexural failure can be obtained with additional flexural reinforcement to increase a wall's capacity. This concept leads to a design method of reducing flexural reinforcement in low-rise bounded solid shear wall's. Avoidance of shear failure as well as less reinforcement congestion leer these walls is expected.

• 한국세라믹학회지
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• 제35권9호
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• pp.923-932
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• 1998

Al2O3/Al composites were produced by displacement reaction method which was carried out by imm-ersing the sintered silica preform which was prepared form fused silica powder in molten aluminu. an ac-tivation energy of 94kJ/mole was calculated from Al-SiO2 reaction data in 1000-130$0^{\circ}C$ temperature range With increase of reaction temperature the alumina particle in the Al2O3/Al composites produced with pur metal Al showed grain growth and the growth of alumina particle in Al2O3/Al composite produced by using of Mg contained Al alloy was inhibited. The flexural strength of Al2O3/Al composites produced at 100$0^{\circ}C$ showed the highest value as 393 MPa. Flexural strength of the composite fabricated at 85$0^{\circ}C$ showed higher deviation than that of the composite produced at above 100$0^{\circ}C$ Low flexural strength of the composite fa-bricated at 120$0^{\circ}C$ due to the growth of pore and alumina particle size. The hardness of composites de-pended on alumina content in Al2O3/Al composite decreased with increasing of aluminium content in case the same alumina content and increased with increasing of silicon content in composite.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.93-96
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• 2005

Since the columns with flexure-shear failure have lower ductility than those with flexural failure, shear capacity curve models shall be applied as well as flexural capacity curve in order to determine ultimate displacement for seismic design or performance evaluation. In this paper, a modified shear capacity curve model is proposed and compared with the other models such as the CALTRANS model, Aschheim et al.'s model, and Priestley et al.'s model. Four shear capacity curve models are applied to the 4 full scale circular bridge column test results and the accuracy of each model is discussed. It may not be fully adequate to drive a final decision from the application to the limited number of test results, however the proposed model provides the better prediction of failure mode and ultimate displacement than the other models for the selected column test results.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.186-189
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• 2006

Since the columns with flexure-shear failure have lower ductility than those with flexural failure, shear capacity curve models shall be applied as well as flexural capacity curve in order to determine ultimate displacement for seismic design or performance evaluation. In this paper, a proposed modified shear capacity curve model is compared with the other models such as the CALTRANS model, Aschheim et al.'s model, and Priestley et al.'s model. Four shear capacity curve models are applied to the 4 full scale and 7 small scale circular bridge column test results and the accuracy of each model is discussed. It may not be fully adequate to drive a final decision from the application to the limited number of test results, however the proposed model provides the better prediction of failure mode and ultimate displacement than the other models for the selected column test results.

• Structural Engineering and Mechanics
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• 제18권4호
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• pp.493-516
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• 2004

This paper addresses the behavior and strength of structural walls with a concrete compressive strength exceeding 69 MPa. This information also enhances the current database for improvement of design recommendations. The objectives of this investigation are to study the effect of axial-load ratio on seismic behavior of high-strength concrete flexural walls. An analysis has been carried out in order to assess the contribution of deformation components, i.e., flexural, diagonal shear, and sliding shear on total displacement. The results from the analysis are then utilized to evaluate the prevailing inelastic deformation mode in each of wall. Moment-curvature characteristics, ductility and damage index are quantified and discussed in relation with axial stress levels. Experimental results show that axial-load ratio have a significant effect on the flexural strength, failure mode, deformation characteristics and ductility of high-strength concrete structural walls.