• Journal of Korean Society of Steel Construction
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• v.22 no.5
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• pp.465-475
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• 2010

In the horizontally curved bridges, girders are subjected to the combined action of vertical bending and torsion due to their curvatures without any eccentric loads. As subjected to bending and torsion, the ultimate strength of steel/concrete composite box girders are limited by the diagonal tensile stress in the deck concrete induced by the St. Venant torsion. To determine the ultimate strength of composite box girders in bending and torsion and their interactions, this study conducted a 3-dimensional FEA and classical strength of materials investigation. Using ABAQUS, the FEA fully utilized advanced nonlinear analysis techniques simulating material/geometrical nonlinearity and post-cracking behaviors. The ultimate strength from numerical data were compared with theoretically derived values. Concurrent compressive stresses in the concrete deck improve the shear-resisting capacity of concrete, thereby resulting in an increased torsional resistance of the composite box girder in positive bending. The proposed interaction equation is very simple yet it provides a rational lower bound in determining the ultimate strength of concrete/steel composite box girders.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.40-40
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• 2011

현재 일반적으로 활용되고 있는 원통형 쉘구조로 이루어진 타워구조의 대형화가 추진되면서 제작, 운반 편의성, 단면효율성, 경제성 제고를 위해 다각형단면 기둥구조물의 활용이 대두되고 있다. 하지만 다각형 단면 기둥구조의 극한강도에 대한 자료가 충분치 않고 관련 기준이나 지침이 명확히 제시되고 있지 않은 실정이다. 본 연구에서는 원통형 쉘구조물을 다각형구조물로 대체하여 제작될 경우 축방향 압축에 대한 내하력 향상 효과를 수치해석적으로 검토해 보고자 한다. 해석모델은 지름 2m, 두께 20mm인 원형강관 프로토타입 풍력타워 구조를 참고로 하여 이에 내접하도록 결정한 6~12각형 단면 형상으로써 높이 10,000mm인 3차원 기둥모델을 구현하였고 유한요소프로그램인 ABAQUS를 이용하여 해석하였다. 각 subpanel의 중앙에 종방향 보강재를 설치하였을 때 국부좌굴에 대한 내하력 변화를 비교하기 위해 종방향보강재로 보강한 모델을 구성하여 비교 해석을 수행하였다. 종방향 보강재의 제원은 미국 SSRC 제안식을 기준으로 삼았다. 탄성좌굴해석을 통해 탄성좌굴모드 형상을, 비선형비탄성해석을 통해 최종파괴모드 및 극한강도를 얻었다. 보강 전 후의 탄성좌굴 해석 결과로부터 최소모드의 고유치 값을 비교하였다. 각 subpanel 단면 중심부에 한 개의 보강재를 설치한 경우 탄성좌굴강도가 4배 가량 증가하였다. 이로부터, 보강재(n=1) 설치에 따라 유효 폭두께비가 1/2로 감소하는 효과를 확인 할 수 있다. 비선형해석결과로부터 subpanel의 단면중심에 보강재를 설치한 경우 보강재가 위치한 곳에 고정점이 형성되어 이를 중심으로 국부 좌굴모드에 변화가 생기는 것이 확인되었다. 이러한 변화는 다각형 단면 기둥구조의 내하력 성능, 즉 국부좌굴강도에 영향을 준다. 충분한 강성을 갖는 종방향 보강재가 설치된 경우, 극한상태에서도 유효폭두께비가 줄어드는 것과 같은 강도 향상 효과를 확인할 수 있다. 이러한 사실은 각 해석결과 극한강도를 DIN code, Migita와 Fukumoto의 제안식, SSRC 설계제안식 등과의 비교를 통해 확인할 수 있었다.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.157-165
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• 1999

When the ultimate strength of a concrete flexural member is evaluated, the effect of member size is usually not considered. For various types of loading, however, the strength always decreases with the increment of member size. In this paper the size effect of a flexural compression member is investigated by experiments. For this purpose, a series of C-shaped specimens subjected to axial compressive load and bending moment was tested using three different sizes of specimens with a compressive strength of 528 kg/$cm^2$. According to test results the size effect on flexural compressive strength was apparent, and more distinct than that for uniaxial compressive strength of cylinders. Finally a model equation was derived using regression analyses with experimental data.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.31-39
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• 2013

The ultimate behavior of high-strength concrete beams is studied with respect to their strength. Thirteen beams were analyzed and the results are presented herein. The variable parameters were the concrete's compressive strength, from 57 to 184 MPa and the amount of lateral torsional reinforcement, from 0.35 to 1.49%. The ultimate torsional strengths from tests were compared with those by this proposed theory and by the ACI code. As a consequence, The ultimate torsional strengths by this proposed theory show the better results than those by the ACI code.

• Journal of the Society of Disaster Information
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• v.16 no.4
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• pp.796-805
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• 2020

Purpose: A static loading test was performed to evaluate the ultimate flexural strength of a girder in which 80MPa high-strength concrete was synthesized on the compressive flange of the I-shape steel girder. Method: This test is designed and fabricated two types of specimens with different shear-connection specifications, and evaluated their ultimate flexural behavior until reaching the extreme event limit states. In addition, the ultimate strength was evaluated by comparing the test results and the results of the strain compatibility method. Result: By confirming the displacement within 0.02mm as a result of the relative slip measurement, it was verified that the two specimens secured perfect bonding. Therefore, the difference in the shear specification does not have a great effect on the stiffness, and if the specimens are completely synthesized, there is no difference in the behavior until it reaches the extreme-event limit states. Conclusion: The girder to be tested has a working load within the elastic range and meets the usability requirements for allowable deflection. Therefore, even if a part of the casing is subjected to the tensile force at the level of cracking, the deck will first reach the compression failure due to the role of the reinforcing bar.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.3
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• pp.202-208
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• 2014

For evaluating basic structural behavior of HVFA (High Volume Fly Ash) concrete, several tests are performed considering different ratios of fly ash replacement and structural evaluation regarding compressive strength, elasticity modulus, stress-strain relationship, and bond strength is also performed. Test results show that elasticity modulus of HVFA concrete has close relationships with compressive strength and fly ash replacement ratio. The ultimate strain shows slight difference from domestic design code. On the other hand, there are no differences between general concrete and HVFA concrete for elasticity modulus and bond strength.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.81-92
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• 2013

The ultimate flexural strength of HSB I-girders, considering the effect of local bucking, was investigated through a series of nonlinear finite element analysis. The girders were selected such that the inelastic local flange buckling or the plastic yielding of compression flanges governs the flexural strength. Both homogeneous sections fabricated from HSB600 or HSB800 steel and hybrid sections with HSB800 flanges and SM570-TMC web were considered. In the FE analysis, the flanges and web were modeled using thin shell elements and initial imperfections and residual stresses were imposed on the FE model. An elasto-plastic strain hardening material was used for steels. After establishing the validity of present FE analysis by comparing FE results with test results published in the literature, the effects of initial imperfection and residual stress on the inelastic flange local buckling behavior were assessed. The ultimate flexural strengths of 60 I-girders with various compression flange slenderness were obtained by FE analysis and compared with those calculated from the KHBDC, AASHTO LRFD and Eurocode 3 provisions. Based on the comparison, the applicability of design equations in these specifications for the flexural strength of I-girder considering flange local buckling was evaluated.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.160-160
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• 2011

현대의 건설기술은 자원절약과 환경보전이라는 시대적 흐름 속에, 자원순환과 지속 가능한 친환경 건설기술 개발은 차세대 연구분야로써, 연구가 시급한 분야가 되었다. 최근에는 골재 수급불균형 문제를 해결하고 동시에 자원순환을 위한 방안으로서 건설폐기물로부터 생산된 순환골재를 콘크리트용 천연골재의 대체재로 활용하기 위한 연구개발이 이루어지고 있다. 지속가능형 건설기술을 국내 독자 기술로 확립하고 건설현장에서 발생하는 폐기물의 순환시스템을 확고하게 구축하여 순환자원에 의한 국가경쟁력 강화를 기대할 수 있다. 본 연구의 목적은 순환골재 콘크리트의 역학적 특성을 개선하기 위해 순환골재 콘크리트 공시체를 제작하여 강도 및 강성을 검증하는 것이다. 실험방법으로 순환굵은골재의 치환 비율을 0%에서 100%까지 변화시킨 공시체를 제작하고 각 공시체의 정적 극한강도 거동을 비교 분석하였다. 하중은 공시체가 파괴가 발생 할 때까지 변위제어 방식으로 재하 하였으며 이 때 공시체의 파괴거동은 설치된 계측센서들을 이용하여 계측 및 분석하였다. 실험결과 공시체의 압축강도는 순환굵은골재 치환률이 25% 미만일 경우 일반 콘크리트 압축강도의 95% 이상의 구조성능을 갖지만, 순환굵은골재 치환률이 100%인 경우, 일반콘크리트 압축강도의 85% 수준의 구조성능을 나타냈다. 강성은 FRP 부재의 순환골재 치환률에 따라 최대 14%의 강성차이를 보였다. 이를 통해 순환골재 치환률이 높을수록 순환골재 표면의 폐모르타르와 이물질의 영향으로 재료간의 부착강도가 감소되어 강도와 강성이 저하되었음을 확인하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.298-303
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• 2016

Owing to the advantages of reduced weight and wind effect, the space-framed towers that consist of vertical and horizontal members of circular hollow tubular sections have been adopted widely for various purposes. It is critical to guarantee the strengths of tubular joints where vertical and horizontal members are connected structurally to make the entire space-framed system behave as a single tower structure. In this study, a strength evaluation was conducted for T-type tubular joints subjected to the concurrent action of compression and bending. Three of the available design codes, i.e., AISC, Eurocode 3, ISO 19902 were investigated and a design equation was suggested for an ultimate strength interaction between the axial force and bending moment based on nonlinear finite element analyses by selecting the slenderness ratios at the joints as major parameters.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.23-31
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• 1992

In this study, Behavior of Eccentrically Loaded Restrained Concrete Slender Columns are investigated the continuation. The paper is : nonlinear constitutive relations of reinforced concrete columns are formulated, the multivariable nonlinear equation formulated in this study is solved by the incremental iterative method, the solution scheme is suitable for computer application, the proposed method bas been compared with the numerical examples and other research results and is shown to be in good agreement Accordingly, the objectives of this investigation are to use the method developed to conduct a parametric study of the different variable (Rotational Restraints,Ratio of End Restraints. End Eccentricity, Ratio of End Eccentricities,Lateral Restraint, Concrete Strength, Ratio of Reinforcement. Yield Point of Reinforcement) influencing the behavior and the ultimate strength for columns. Chosen values for different parameters and their variations are based on values encountered in practice and on results of other analylitical studies.