• 한국전산구조공학회논문집
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• 제36권6호
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• pp.399-405
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• 2023

본 연구에서는 철근콘크리트 모멘트골조의 보-힌지 붕괴 기구를 유도하기 위한 유전자알고리즘 기반의 최적내진설계기법을 제시한다. 제안하는 기법은 두 가지의 목적함수을 사용한다. 첫 번째는 구조물의 비용을 최소화하는 것이고, 두 번째는 구조물의 에너지소산능력을 최대화하는 것이다. 제약조건은 기둥과 보의 강도조건, 기둥-보 휨강도비 최소 조건, 기둥의 소성힌지 발생 방지조건 등이 사용된다. 부재의 강도 평가를 위해 선형정적해석이 수행되고, 에너지소산능력과 소성힌지 발생여부를 평가하기 위해 비선형정적해석이 수행된다. 제안하는 기법은 4층 예제 구조물에 적용되었으며, 보-힌지 붕괴 기구를 유도하는 설계안이 얻어지는 것을 확인하였다. 획득된 설계안의 기둥-보 휨강도비를 분석한 결과, 그 값은 기존 내진 기준에서 제시하는 값보다 큰 것으로 나타났다. 보-힌지 붕괴 모드를 유도하기 위해서는 보다 더 강화된 전략이 필요하다.

• 한국전산구조공학회논문집
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• 제29권3호
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• pp.253-260
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• 2016

본 연구에서는 철골모멘트골조의 보-힌지 붕괴모드를 유도하는 최적 내진설계기법을 제안한다. 이는 유전자알고리즘을 사용하며, 기둥의 소성힌지 발생을 억제하는 제약조건을 설정하여 보-힌지 붕괴모드를 유도한다. 제안하는 기법은 구조물량를 최소화하고 에너지소산능력을 최대화하는 목적함수를 사용한다. 제안하는 기법은 9층 철골모멘트골조 예제 적용을 통해 검증한다. 예제 적용을 통해 철골모멘트골조의 보-힌지 붕괴모드를 유도하기 위해 요구되는 기둥-보 강도비를 평가한다. 패널존에 대한 3가지 모델링 기법을 각각 적용하여 모델링 조건에 따른 휨강도비 영향이 추가적으로 검토된다.

• 한국도로학회논문집
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• 제18권1호
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• pp.43-55
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• 2016

PURPOSES : This study aims to develop a repair material that can enhance pavement performance, inducing rapid traffic opening through early strength development and fast setting time by utilizing MgO-based patching materials for repairing road pavements. METHODS : To consider the applicability of MgO-based patching materials for repairing domestic road pavements, first, strength development and setting time of the materials were evaluated, based on MgO to $KH_2PO_4$ ratio, water to binder ratio, and addition ratio of retarder (Borax), by which the optimal mixture ratio of the developed material was obtained. To validate the performance of the developed material as a repair material, the strength(compressive strength and bonding strength) and durability (freezing, thawing, and chloride ion penetration resistance) was checked through testing, and its applicability was evaluated. RESULTS : The results showed that when an MgO-based patching material was used, the condensation time was reduced by 80%, and the compressive strength was enhanced by approximately 300%, as compared to existing cement-based repair materials. In addition, it was observed that the strength (compressive strength and bonding strength) and durability (freezing and thawing, and chloride ion penetration resistance) showed an excellent performance that satisfied the regulations. CONCLUSIONS : The results imply that an emergent repair/restoration could be covered by a rapid-hardening cement to meet the traffic limitation (i.e. the traffic restriction is only several hours for repair treatment). Furthermore, MgO-based patching materials can improve bonding strength and durability compared to existing repair materials.

• Advances in concrete construction
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• 제7권4호
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• pp.277-288
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• 2019

The formulation of self-compacting concretes (SCC) and the study of their properties at the laboratory level were currently well mastered. The aim of this work is to characterize SCC under hot climatic conditions and their effects on the properties of fresh and hardened SCC. Particularly, the effect of the initial wet curing time on the mechanical behavior such as the compressive strength and the durability of the SCCs (acid and sulfate attack) as well as the microstructure of SCCs mixtures. In this study, we used two types of cement, Portland cement and slag cement, three water/binder (W/B) ratio (0.32, 0.38 and 0.44) and five curing modes. The obtained results shows that the compressive strength is strongly influenced by the curing methods, 7-days of curing in the water and then followed by a maturing in a hot climate was the optimal duration for the development of a better compressive strength, regardless of the type of binder and the W/B ratio.

• Computers and Concrete
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• 제28권6호
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• pp.585-603
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• 2021

The validation based on the experimental data demonstrates that the concrete strength under triaxial compression (TC) is overestimated by Lubliner-Oller strength criterion (SC) but underestimated by Lubliner-Lee SC in ABAQUS. Moreover, the discontinuous derivatives of failure criterion exists near the unexpected breakpoints. Both resulted from the piecewise linear meridians of the original Lubliner SC with constants γ. Following the screen for the available failure criteria to determine the model parameter γ of Lubliner SC, Menétrey-Willam SC (MWSC) is considered the most promising option with a reasonable aspect ratio Kc but no other strength values required and only two new model parameters introduced. The failure surface of the new Lubliner SC based on MWSC (Lubliner-MWSC) is smooth and has no breakpoints along the hydrostatic pressure (HP) axis. Finally, predicted results of Lubliner-MWSC are compared with other concrete failure criteria and experimental data. It turns out that the Lubliner-MWSC can represent the concrete failure behavior, and MWSC is the optimal choice to improve the applicability of the concrete damaged plasticity model (CDPM) under TC in ABAQUS.

• KIEAE Journal
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• 제13권6호
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• pp.137-143
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• 2013

The purpose of this study is to suggest optimum micro-filler experiment method to select the optimal particle size of earth for using in earth construction works and test this suggestion through compressive strength measurement. According to the results of selecting the method to choose the optimum micro-filler mixing of earth and sand, three-stage filling(plate tamping) showed relatively high results and so was estimated to be the proper filling method. According to the results of optimum micro-filler experiment of earth and sand by the maximal sizes of sand, between 80% and 90% showed the highest result values. The larger the maximum size of sand was, the lower the addition ratio of sand was in optimum micro-filler mixing. According to the results of compressive strength experiment by the particle sizes of earth and sand, 90% in the addition ratio of sand showed the highest results, and so tended to be similar to the results of unit volume weight experiment.

• 한국지반환경공학회 논문집
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• 제20권5호
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• pp.47-55
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• 2019

본 연구에서는 토양의 종류에 따라 친환경고화재인 E.S.B.(Eco Soil Binder)를 사용하여 혼합토의 강도특성과 활용목적에 따른 흙 포장의 기초자료를 제공하고자 한다. 연구에 사용된 토양은 우리나라 주변에서 흔히 채취되는 화강풍화토로 토질분류법에 의한 SW, SP, SC로 구분된다. 일축압축강도 시험을 위한 공시체는 지름 50mm, 높이 100mm의 크기로 혼합토 중량대비 E.S.B.의 혼합비율을 5%, 10%, 15%, 20%, 25%, 30%로 변화시키고 각 조건에 따라 다짐도를 90%, 100%를 적용하고 재령기간 3, 7, 28일에 따른 일축압축강도 특성을 분석하였다. 또한 흙 포장 기준강도와 일축압축강도의 강도비를 산정하여 최적의 E.S.B.혼합비율을 결정하고 ACI209R의 추정식을 활용한 일축압축강도의 현장 적용성을 평가하였다.

• 한국지반신소재학회논문집
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• 제22권4호
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• pp.35-42
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• 2023

본 연구에서는 유기오염물의 흡수가 가능한 차수재의 반응재료에 대하여 지중 매입 재료로서의 적용성을 평가하기 위해 오염물의 접촉에 의한 강도 특성 변화를 평가하였으며, 강도 평가는 일축압축시험 결과를 이용하였다. 시험 결과, 오염물 종류에 따른 반응재료의 강도는 물 > TCE > TPH의 순서로 확인되었다. 그러나 폴리노보넨의 구성비가 12% 이하에서는 TPH의 강도가 TCE에 비하여 크게 나타났다. 물로 접촉된 반응재료는 폴리노보넨의 구성비가 작을수록 강도가 지속적으로 감소하였지만, TCE 및 TPH와 접촉된 반응재료의 강도는 폴리노보넨의 구성비가 30%에서 21%까지 작아질수록 증가하다가 이후에는 감소하였다. 즉, 지중에서 발생되는 응력 조건에 따라 오염물의 접촉에 의한 강도를 고려하여 반응재료의 최적 구성비가 적용되어야 한다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.450-453
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• 2004

The present study is a basic experiment on the estimation of the compression strength of high strength concrete, aiming at estimating the compression strength of mass test pieces of high strength concrete by giving the temperature hysteresis of the mass test pieces to managerial test pieces. Thus, this study made concrete test pieces in an optimal mix ratio for each strength level, and also created adiabatic curing tank and managerial test pieces. Then it carried out comparative analysis in relation to core strength and suggested equipment and a technique that can control the strength of high strength concrete mass more conveniently and accurately.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.229-232
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• 1999

This study provided the engineering properties of the recycled aggregate concrete with fly-ash and silica-fume. There are considered recycled aggregate substitution ratio, and fly-ash silica-fume mix ratio as the experimental variable. From the experimental result, we could know that the recycled aggregate concrete mixed silica-fume is superior on the compressive strength but, is poor on the construction property than fly-ash. The optimal mix ratio of the fly-ash and silica-fume is 10% in all.