• 대한토목학회논문집
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• 제28권2A호
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• pp.187-196
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• 2008

이 연구에서는 단순 트러스 모델을 이용한 철근콘크리트 바닥판의 펀칭전단강도 평가방안을 제안하였다. 철근콘크리트 바닥판의 펀칭전단 해석의 본질적인 어려움을 극복하기 위해 집중하중이 작용하는 바닥판을 펀칭전단 파괴 형태에 기초하여 펀칭콘과 나머지 부분의 소구조체로 구분하였다. 펀칭콘의 강도는 이상화한 트러스의 경사압축부재의 강성도로써 유도되었다. 수평변위를 제어하고 있는 롤러지점의 수평방향 스프링 부재의 강성도는 펀칭콘 내에 포함된 철근에 의하여 결정되었다. 3차원 구조물의 2차원화에 따른 오차와 해석과정에 포함되지 않은 나머지 소구조체의 강성도 등에 기인하는 불확실성들을 포함하기 위하여 경사압축재의 초기각은 실험결과들에 대해 주인장 철근비를 변수로 수행된 회귀분석을 통하여 구하였다. 단순 트러스 모델로부터 구한 펀칭전단강도는 실험결과와의 비교에서 신뢰성이 높은 것으로 나타났다. 단순 트러스 모델의 스냅스로우(snap-through)좌굴해석으로부터 구한 펀칭전단강도는 철근콘크리트 바닥판의 펀칭전단강도의 검토에 유용하게 사용될 수 있을 것이다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.167-172
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• 2002

Nonlinear analysis of the reinforced concrete beam subjected to torsion is presented. Seventeen equations involving seventeen variables are derived from the equilibrium equation, compatibility equation, and the material constitutive laws to solve the torsion problem. Newton method was used to solve the nonlinear simultaneous equations and efficient algorithms are proposed. Present model covers the behavior of reinforced concrete beam under pure torsion from service load range to ultimate stage. Tensile resistance of concrete after cracking is appropriately considered. The softened concrete truss model and the average stress-strain relations of concrete and steel are used. To verify the validity of Present model, the nominal torsional moment strengths according to ACI-99 code and the ultimate torsional moment by present model are compared to experimental torsional strengths of 55 test specimens found in literature. The ultimate torsional moment strengths by the present model show good results.

• Structural Engineering and Mechanics
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• 제61권5호
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• pp.605-615
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• 2017

Shear failure of reinforced concrete (RC) beams is a major concern for structural engineers. It has been shown through various studies that the shear strength and ductility of RC beams can be improved by adding steel fibers to the concrete. An accurate model predicting the shear strength of steel fiber reinforced concrete (SFRC) beams will help SFRC to become widely used. An artificial neural network (ANN) model consisting of an input layer, a hidden layer of six neurons and an output layer was developed to predict the shear strength of SFRC slender beams without stirrups, where the input parameters are concrete compressive strength, tensile reinforcement ratio, shear span-to-depth ratio, effective depth, volume fraction of fibers, aspect ratio of fibers and fiber bond factor, and the output is an estimate of shear strength. It is shown that the model is superior to fourteen equations proposed by various researchers in predicting the shear strength of SFRC beams considered in this study and it is verified through a parametric study that the model has a good generalization capability.

• 한국구조물진단유지관리공학회 논문집
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• 제6권2호
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• pp.157-165
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• 2002

Nonlinear analysis of the reinforced concrete beam subjected to torsion is presented. Seventeen equations involving seventeen variables are derived from the equilibrium equation, compatibility equation, and the material constitutive laws to solve the torsion problem. Newton method was used to solve the nonlinear simultaneous equations and efficient algorithms are proposed. Present model covers the behavior of reinforced concrete beam under pure torsion from service load range to ultimate stage. Tensile resistance of concrete after cracking is appropriately considered. The softened concrete truss model and the average stress-strain relations of concrete and steel are used. To verify the validity of present model, the nominal torsional moment strengths according to ACI-99 code and the ultimate torsional moment by present model are compared to experimental torsional strengths of 55 test specimens found in literature. The ultimate torsional moment strengths by the present model show good results.

• Earthquakes and Structures
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• 제25권3호
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• pp.177-186
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• 2023

Reinforced concrete frames with a masonry infill panel is a structural typology frequently used worldwide. In seismic cases, the interaction between the masonry infill and the RC frames constitutes one of the most complex subjects in earthquake engineering. In this work, an enhancement of an existing numerical model is proposed to improve the estimation of lateral strength and stiffness of masonry-infilled frame structures and predict their probable failure modes. The proposed improvement is based on attributing corrective coefficients to the shear strength of each diagonal shear spring of the macro element, which simulates the masonry infill. The improved numerical model is validated by comparing the results with those of the original numerical model and with experimental results available in the literature. The enhanced macro element model can be used as a powerful, accessible tool for assessing the capacity and stiffness of masonry-infilled frame structures and predicting their probable failure modes.

• Computers and Concrete
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• 제2권3호
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• pp.215-238
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• 2005

This work is based on a nonlinear finite-element model with proven capacity for yielding realistic predictions of the response of reinforced-concrete structures under static monotonically-increasing loading. In it, the material description relies essentially on the two key properties of triaxiality and brittleness and, thus, is simpler than those of most other material models in use. In this article, the finite-element program is successfully used in investigating the behaviour of a series of RC walls under static cyclic loading. This type of loading offers a more strenuous test of the validity of the proposed program since cracks continuously form and close during each load cycle. Such a test is considered to be essential before attempting to use the program for the analysis of concrete structures under seismic excitation in order to ensure that the solution procedure adopted is numerically stable and can accurately predict the behaviour of RC structures under such earthquake-loading conditions. This is achieved through a comparative study between the numerical predictions obtained presently from the program and available experimental data.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.113-116
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• 2005

In this study, in order to. investigate the effectiveness af tuned liquid damper (TLD) for the seismic performance enhancement af the existing reinforced concrete (RC) apartment structure which is nat seismically designed, shaking table test was conducted for the small scale five stary RC structure with TLD. TLD model was constructed to. have the frequency tuned to. the first modal frequency af the structure, $2\%$ mass ratio. af the first modal mass, and 0.08 liquid depth ratio. White noise with $0.2\~5Hz$ frequency bandwidth tests were performed using the shaking table at Korea Institute af Machinery and Materials, and the displacement and absolute acceleration af each floor were measured. Test results indicate that mare than $30\%$ seismic responses reduction can be achieved using TLD for RC structure under white noise.

• 천문학회보
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• 제42권2호
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• pp.77.4-78
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• 2017

The presence of double red clump (RC; metal-rich counterpart of horizontal-branch) in high latitude field of the Milky Way (MW) bulge is widely interpreted as evidence for an X-shaped structure originated from the bar instability. However, Lee et al. (2015) recently suggested an alternative model, according to which the double RC is metal-rich manifestation of multiple stellar population phenomenon observed in globular clusters (GCs). Here we show that stars in bright RC are enhanced in CN compared to those in faint RC from our low-resolution spectroscopy. CN traces N, and N-rich stars are also enhanced in Na and He in GCs. Since GCs are the only environment that produce second generation stars with enhanced N, Na, & He, this is a direct evidence that stars in the classical bulge component of the MW were mostly provided by proto-GCs.

• Architectural research
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• 제20권1호
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• pp.9-16
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• 2018

Nonlinear analysis of reinforced concrete (RC) structures is performed by using isogeometric Reissner-Mindlin (RM) shell element. The elasto-plastic constitutive model is employed to express the nonlinear behavior of concrete material and the equivalent smeared steel layer is introduced to represent steel reinforcement. The arc-length control method is used to produce the entire load-displacement path of RC structures. Finally, three benchmark tests are carried out to verify the performance of the present shell element. From isogeometric analysis, the present results show a good agreement with experimental results and it is provided as future benchmark test solutions.

• Structural Engineering and Mechanics
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• 제12권3호
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• pp.297-312
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• 2001

The accurate finite element (FE) simulation of reinforced concrete (RC) slabs, having different boundary conditions and subjected to uniformly distributed loading, has led to the use of the developed FE models for generating results of ultimate loads from predictions of 'computer-model' RC slabs having different material and geometric properties. Equations derived from these results constitute the primary database of an intelligent computer-aided-design (CAD) system developed for accurate and fast information retrieval on arbitrary slabs. The system is capable of generating a secondary database through systems of interpolation and can be used for design assistance purposes.