• 대한토목학회논문집
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• 제36권6호
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• pp.1109-1116
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• 2016

아스팔트 콘크리트 포장의 반사균열 저항성을 평가하기 위해 다양한 방법이 적용되고 있다. 반복직접인장시험은 기존실험에 비해 저렴하고 간편하게 아스팔트 콘크리트 포장의 반사균열 저항성을 평가할 수 있는 장점이 있다. 국내에 반복직접인장시험을 도입하기 위해서는 파괴기준의 결정이 필요하다. 반복직접인장시험의 파괴횟수를 결정하기 위해 다양한 방법을 검토한 결과 초기하중의 10%일 때를 파괴시점으로 산정할 경우 10% 이내의 반복횟수 편차를 나타내었다. 아스팔트 콘크리트의 두께가 30 mm에서 50 mm로 증가할 경우 파괴횟수는 13.6배 증가하여 포장두께가 반사균열 저항성에 큰 영향을 미치는 것을 알 수 있었다. 또한 재하변형의 크기가 클수록 반사균열의 진전속도가 증가하는 것으로 나타났다. 반복직접인장시험은 포장 두께, 변형크기, 재료적 특성에 따라 반사균열저항성을 정량적으로 평가할 수 있기 때문에 포장설계시 반사균열 저항성 평가 방법으로 적용 가능한 것으로 나타났다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.275-282
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• 2001

In this paper, nonlinear analyses of RC (Reinforced Concrete) columns are conducted, and an improved criterion to estimate the design load carrying capacity of slender RC columns is proposed. To simulate the material nonlinearty including the cracking of concrete, the layer model is adopted, and the initial stress matrix is considered for the simulation of P- effect. After correlation studies with previous numerical results to verify the efficiency of the developed numerical model, many parameter studies are followed, and a regression formula which can give more exact resisting capacity of slender RC columns is introduced on the basis of the obtained numerical results.

• Steel and Composite Structures
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• 제21권5호
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• pp.981-997
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• 2016

To avoid the cracks of cast-in-place concrete in shear pockets and seams in the traditional composite beam with precast decks, this paper proposed a new type of prefabricated steel truss-concrete composite beam (ab. PSTC beam) with pre-embedded shear studs (ab. PSS connector). To study the initial cracking load of concrete deck, the development and distribution laws of the cracks, 3 PSTC beams were tested under hogging moment. And the crack behavior of the deck was compared with traditional precast composite beam, which was assembled by shear pockets and cast-in-place joints. Results show that: (i) the initial crack appears on the deck, thus avoid the appearance of the cracks in the traditional shear pockets; (ii) the crack of the seam appears later than that of the deck, which verifies the reliability of epoxy cement mortar seam, thus solves the complex structure and easily crack behavior of the traditional cast-in-place joints; (iii) the development and the distribution laws of the cracks in PSTC beam are different from the conventional composite beam. Therefore, in the deduction of crack calculation theory, all the above factors should be considered.

• Structural Engineering and Mechanics
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• 제65권1호
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• pp.1-7
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• 2018

This paper reviews the mechanical effects produced by reinforcement corrosion of prestressed concrete beams. Specifically, modifications in the bonding of the tendon to the concrete that reduce service life and load bearing capacity are studied. Experimental information gathered from previous works has been used for the theoretical analysis. Relationships between bond stress loss and reinforcement penetration in the concrete, and concrete external cracking were established. Also, it was analysed the influence that has the location of the area affected by corrosion on the loss magnitude of the initial prestress.

• 한국안전학회지
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• 제27권2호
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• pp.25-32
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• 2012

In this study, the effect of blast furnace slag on precast concrete culvert was assessed by measuring the flexural strength using to full scaled box culvert. As a result, the initial cracking load and yield load of reinforced concrete box converts are increased in comparison with those of the normal concrete box culvert, but the ultimate load is decreased slightly. It can be concluded that use of blast furnace slag induce to flexural strength in precast concrete box culvert greatly improved the serviceability.

• 한국철도학회논문집
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• 제9권6호
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• pp.778-783
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• 2006

This study investigates the ultimate behavior of reinforced concrete beams by means of practical nonlinear finite element (FE) analyses. Uniaxial constitutive models for the concrete and steel material are selected in this study. The adopted material model is integrated into the ABAQUS fiber beam elements through a user-defined material subroutine (UMAT). Within a developed nonlinear finite element framework, the FE results have been compared to experimental results reported by other researchers. It has been found that the proposed finite element model is capable of predicting the initial cracking load level, the yield load, the ultimate load, and the crack distribution with acceptable accuracy.

• 콘크리트학회논문집
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• 제25권4호
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• pp.371-379
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• 2013

이 논문에서는 100 MPa 수축보상된 초고강도 변형경화형 시멘트 복합체 및 보통 콘크리트를 사용한 인장부재의 단조 및 반복재하시 인장강성 및 균열특성을 비교 평가하였다. 재하단계별 인장부재의 전체 변형률 및 표면균열 특성은 인장부재의 양측에 설치된 두 개의 변위계와 50배율 확대 가능한 계측기에 의해 측정되었다. 시멘트 복합체의 특성에 따른 인장부재의 인장 강성 및 균열특성을 평가하기 위하여 보통 콘크리트, 수축보상 변형경화형 시멘트 복합체 및 보통 변형경화형 시멘트 복합체 등 세 종류의 시멘트 복합체가 사용되었다. 실험 결과, 초고강도 변형경화형 시멘트 복합체의 시멘트 중량의 10%를 팽창재로 대체 시 초기 수축량은 현저하게 감소되었으며 인장부재의 초기균열강도도 증가되는 경향을 보였다. 수축보상된 초고강도 변형경화형 시멘트 복합체를 사용한 인장부재는 재하 단계별로 균열이 부재길이 전면에 확산되고 균열폭이 감소되어 인장강성 특성을 개선하였다. 반복재하시 인장부재의 인장거동 특성은 단조재하시와 큰 차이를 보이지 않았다.

• 한국농공학회지
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• 제40권5호
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• pp.68-79
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• 1998

In the years, the concern about high-strength concrete which is new material has been heightened as a result of active research and development. Recently, as the building structure has been being bigger, higher, longer and more specialized, the demand of material with high-strength concrete for building has been increasing. The demand of high -strength concrete is expected to increase with expansion of usage about the complex concrete structures such as bridge structure as well as nuclear plants, underground structures, hydraulic structures and arctic area sturctures. In this research, silica-fume was used as an admixture in order to get a high-strength concrete. Water/binder ration was limited no more than 18 percent and the amount of unit cement was increased. In this study, a number of trial in concrete mix was carried out to get optimal mix design, and the target slump with $10{\pm}2cm$ was set for in-situ construction. High-strength concrete with cylinder strength of 1,200kgf/$cm^2$ in the 28-days was produced and tested. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns, fracture modes. The load versus strain and load versus deflection relations were obtained form the static test. The test results were compared with the shear strengths predicted by the equations of ACI code 318-89 and orther researchers. Based on the test results, shear strength equation of reinforced concrete beam using high strength concrete was proposed. Form an evaluation of the results of this experimental investigation, it was concluded that shear strength after diagonal tention cracking diminished with the increase in compressive strength for beams.

• 한국터널지하공간학회 논문집
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• 제16권2호
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• pp.173-180
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• 2014

세그먼트 설계시, 축력과 휨모멘트가 주로 고려되는 하중이다. 두개의 하중에서 축력이 모멘트 보다 상대적으로 매우 크기 때문에 전단면이 압축상태에 있으며, 이는 균열 폭을 줄이는 효과가 있다. 그러나 콘크리트 구조물의 사용성 검토에서 축력은 고려하지 않고 있기 때문에 설계는 사용성에 지배되고, 사용성을 만족시키기 위하여 소요 철근량을 증가시키게 된다. 본 논문에서는 축력이 세그먼트의 사용성에 미치는 영향을 시험과 단면해석을 통하여 분석하였다. 세그먼트에 대한 시험을 수행하였으며, 초기균열저항성능에 대하여 고찰하였다. 분석결과 사용성 분석에서 축력을 고려함으로서 더욱 합리적인 설계가 가능한 것을 확인할 수 있었다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.433-439
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• 2005

This paper describes a reinforced concrete crack model, which utilizes a strain decomposition technique. The strain decomposition technique enables the explicit inclusion of physical behavior across the cracked concrete surface such as aggregate interlock and dowel action rather than intuitively defining the shear retention factor. The proposed concrete crack model is integrated into the commercial finite element software ABAQUS shell elements through a user-supplied material subroutine. The FE results have been compared to experimental results reported by other researchers. The proposed bridge FE model is capable of predicting the initial cracking load level, the ultimate load capacity, and the crack pattern with good accuracy.