• 한국철도학회논문집
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• 제19권3호
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• pp.341-350
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• 2016

철도교량 구간의 콘크리트 궤도는 교량 상부구조의 움직임에 효과적으로 대응할 수 있도록 설계되어야 한다. 이를 위해 일반적으로 전단키로 명명되는 전단키를 교면 보호 콘크리트층(PCL) 위에 일정 간격으로 설치하여 그 위에 궤도 슬래브를 타설함으로써 궤도와 교량 상부구조의 상대 변위에 의해 발생하는 전단력을 전달하도록 설계하고 있다. 이 연구에서는 전단키의 전단 거동을 예측하기 위해 타설 경계면을 고려한 비선형 구조 해석 방법을 제시하였다. 제시된 해석 방법은 콘크리트 면에서의 마찰력과 철근의 다월 거동을 고려함으로써 전단키 타설 경계면(시공이음부)에서의 전단력-전단 미끌림 거동을 예측할 수 있으며, 해석 결과 4개의 시험체에 대한 실험 결과를 잘 예측하는 것으로 나타났다.

• Steel and Composite Structures
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• 제27권1호
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• pp.75-87
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• 2018

This paper presents a new method to compute the shear strength of composited structural B-C-W members. These B-C-W members, defined as concrete-filled steel box beams, columns and shear walls, consist of a slender rectangular steel plate box filled with concrete and inserted steel plates connecting the two long-side steel plates. These structural elements are intended to be used in structural members of super-tall buildings and nuclear safety-related structures. The concrete confined by the steel plate acts to be in a multi-axial stressed state: therefore, its shear strength was calculated on the basis of a concrete's failure criterion model. The shear strength of the steel plates on the long sides of the structural element was computed using the von Mises plastic strength theory without taking into account the buckling of the steel plate. The spacing and strength of the inserted plates to induce plate yielding before buckling was determined using elastic plate theory. Therefore, a predictive method to compute the shear strength of composited structural B-C-W members without considering the shear span ratio was obtained. A coefficient considering the influence of the shear span ratio was introduced into the formula to compute the anti-lateral bearing capacity of composited structural B-C-W members. Comparisons were made between the numerical results and the test results along with this method to predict the anti-lateral bearing capacity of concrete-filled steel box walls. Nonlinear static analysis of concrete-filled steel box walls was also conducted by using ABAQUS and the results agreed well with the experimental data.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.919-922
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• 2008

본 연구는 최근 국내 공동주택 지하주차장 등에 설치하는 지연 조인트에 적용할 콘크리트의 수축저감을 위한 연구로서, 팽창재와 3가지의 수축저감제를 단독 또는 병용하여 혼입할 경우 콘크리트의 물리적 특성 및 수축 특성에 대해 검토하기 위해 수행되었다. 실험 결과, 팽창재는 굳지않은 콘크리트의 유동성에 큰 영향을 미치지 않으나, 수축저감제의 경우콘크리트의 유동성을 증진시켜 고성능 감수제의 혼입량을 0.05$\sim$0.1% 정도 감소시킬 수 있다. 또한 팽창재를 혼입할 경우 경화 콘크리트의 압축, 인장 및 휨강도는 다소 증가하는 경향을 보였지만, 수축저감제를 단독 또는 팽창재와 병용 혼입한 경우에는 압축, 인장 및 휨강도가 다소 감소하는 경향을 보였다. 건조수축에 의한 길이변화율 측정결과, 수축저감제 중 SRA3을 2.0% 혼입한 경우 길이변화율 감소 효과가 가장 우수하였으며, 팽창재를 단독으로 사용하거나 팽창재와 SRA1, 2, 3을 병용 혼입한 경우에는 비슷한 감소 효과를 보였다.

• 한국구조물진단유지관리공학회 논문집
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• 제20권5호
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• pp.1-8
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• 2016

본 연구에서는 산업부산물인 TDFA를 혼입한 콘크리트에 대하여 초기재령의 공학적 특성을 분석하였다. 물-결합재비 0.5, FA 치환율 20%인 콘크리트를 대상으로 TDFA를 3~12%치환하여 경화 전 및 경화 후의 특성을 분석하였다. TDFA 혼입율 6% 이후의 배합에서는 작업성이 현저하게 감소하였고 공기량 확보가 어려웠으며, 이로 인해 감수제 및 공기연행제를 추가하여 작업성을 개선시켰다. TDFA 혼입율 6~12%까지는 콘크리트의 강도에 큰 영향은 없었으며, 탄산화저항성 및 염해저항성에서는 FA 20% 치환 배합보다 우수한 성능을 나타내었다. 그러나 공기량이 부족한 TDFA 혼입율 6%배합에서는 동결융해 저항성이 크게 감소하였다. 공기량 및 작업성이 확보된다면 FA를 12%수준까지 TDFA로 치환해도 공학적인 성능을 확보할 수 있을 것으로 판단된다.

• Composite Materials and Engineering
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• 제3권3호
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• pp.201-220
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• 2021

In this study, potential of three machine learning techniques i.e., M5P, Support vector machines and Gaussian processes were evaluated to find the best algorithm for the prediction of flexural strength of concrete mix with steel fibre. The study comprises the comparison of results obtained from above-said techniques for given dataset. The dataset consists of 124 observations from past research studies and this dataset is randomly divided into two subsets namely training and testing datasets with (70-30)% proportion by weight. Cement, fine aggregates, coarse aggregates, water, super plasticizer/ high-range water reducer, steel fibre, fibre length and curing days were taken as input parameters whereas flexural strength of the concrete mix was taken as the output parameter. Performance of the techniques was checked by statistic evaluation parameters. Results show that the Gaussian process technique works better than other techniques with its minimum error bandwidth. Statistical analysis shows that the Gaussian process predicts better results with higher coefficient of correlation value (0.9138) and minimum mean absolute error (1.2954) and Root mean square error value (1.9672). Sensitivity analysis proves that steel fibre is the significant parameter among other parameters to predict the flexural strength of concrete mix. According to the shape of the fibre, the mixed type performs better for this data than the hooked shape of the steel fibre, which has a higher CC of 0.9649, which shows that the shape of fibers do effect the flexural strength of the concrete. However, the intricacy of the mixed fibres needs further investigations. For future mixes, the most favorable range for the increase in flexural strength of concrete mix found to be (1-3)%.

• 대한수학회보
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• 제20권2호
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• pp.99-103
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• 1983

Internal heat generation is one of the insidious conditions affecting the quality of an industrial product after it is cast, coated, molded, forged or laminated. Frequently, the product is pressed into service before the exothermic chemical reactions in the generic material has been completed. The heat liberated from this continuing chemical reaction or the residual deformation from the rheological activities in the materials must be adequately removed or prevented, or the product may be discolored, warped, weakened or even "ignited" spontaneously. Numerous instances of premature structural failures, product-recalls, and/or system-malfunctions have been recorded in recent history. The Coulee Dam was poured with pre-chilled concrete just to negate this freakish encore. It is well-known that concrete (a non-isotropic conducting medium), for instance, takes 28 days to develop its full strength. During this period of curing it is conceivable that the processes of internal heat generation, heat conduction and heat dissipation take place simultaneously inside the medium.he medium.

• 국제초고층학회논문집
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• 제5권3호
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• pp.213-220
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• 2016

The "China Zun" tower in Beijing will rise to 528 meters in height and will be the tallest building in Beijing once built. Inspired by an ancient Chinese vessel, the "Zun", the plan dimensions reduce gradually from the bottom of the tower to the waist and then expand again as it rises to form an aesthetically beautiful and unique geometry. To satisfy the structural requirement for seismic and wind resistance, the structure is a dual system composed of a perimeter mega structure made of composite mega columns, mega braces, and belt trusses, and a reinforced-concrete core with steel plate-embedded walls. Advanced parametric design technology is applied to find the most efficient outer-perimeter structure system. The seismic design basically follows a mixed empirical and performance-based methodology that was verified by a shaking table test and other specimen lab tests. The tower is now half-way through its construction.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.415-418
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• 2005

Nowadays the three major commercially available of organic chemical admixtures are modified lignosulfonates(LS), sulfonated naphthalene-formaldehyde resins (SNF) and sulfonated melamine-formaldehye (SMF). In this study, various sulfonated melamine-formaldehyde (SMF) superplasticizers were synthesized via four synthetic steps. Hydroxymethylation (Step 1), Sulfonation (Step 2), Polymerization (Step 3) and Neutralization and Stabilization (Step 4). In this synthesis of SMF, reaction conditions such as the mole ratio of melamine to formaldehyde and the amount of acid catalyst were changed. After application of SMF superplasticizer to cement paste and mortar, the physical properties including workability, slump loss, compressive strength were compared.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.207-212
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• 1993

When constructing highly precise production plants, for example, super LSI plants or semiconductor plants, it is important to take the necessary control countermeasures into consideration to obtain the working microvibration environment, which is directly related to product precision. Working environment of a clean room means vibration-free and there are only ultra-miro vibration which human cannot sense. In order to provide an place having a vibration-free working environment with only ultra-micro vibration it is necessary to posses a great number of vibration isolation technlogies, wide-ranging and abundant survey and teat data, and a high level of knowledge enabling comprehensive judgments to be made. In this study, experimental modal analysis is used to analyze the dynamic characteristics of double floor for vibration-proofing near apparatus which generate vibration. It is concluded that the double floor system with rubber pad inserted between floor panel and pedestal is good for vibration proof.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1205-1210
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• 2000

In this research we made the mean cement particle size 4 $\mu\textrm{m}$ which can penetrate even minor cracks based on the theory of J.K. Michel who reported particles can penetrate the crack of width up to 3 times of maximum particle size. The cement slurries were produced by adding super plasticizer. The slurries were tested with slurry characterization methods and its rheological properties were characterized. The early hydrated phenomena of ultra fine cement were observed by SEM, XRD and DSC during 24 hours. Mechanical properties of hardened slurry with JIS molds were also tested in 3, 7 and 28 days. The cracked specimens which were repaired with slurries produced various conditions were tested after 3, 7 and 28 days curing in the air and adhesion properties were characterized.