• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.665-668
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• 2011

철근콘크리트 구조물은 타설 후 시간이 경과함에 따라 물리적인 요인과 화학적인 요인으로 인하여 열화가 발생한다. 열화를 고려한 구조해석에서 모든 열화 관련 변수를 고려하는 것은 비효율적이다. 따라서 구조물의 거동과 밀접한 관련이 있는 중요열화변수를 정의하는 것이 필요하다. 본 연구에서는 철근콘크리트 전단벽의 경년열화 해석시 중요변수를 고려하기 위하여 민감도해석을 수행하였다. 해석결과에 의하면 재료의 경화와 관련한 변수들이 열화와 관련한 변수들보다 지진응답이 민감하게 나타났다. 해석모델의 낮은 철근비로 인하여 콘크리트의 탈락에 의한 지진응답의 변화보다 철근의 단면손실에 의한 지진응답의 변화가 크게 나타났다. 만약 원전과 같이 철근비가 높은 전단벽에서는 철근의 단면손실도 지진응답에 대한 중요변수가 될 수 있을 것으로 사료된다.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.5
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• pp.45-54
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• 2011

This paper presents a nonlinear finite element analysis procedure for the performance assessment of deteriorated reinforced concrete bridge columns. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), was used to analyze these reinforced concrete structures. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. Advanced deteriorated material models are developed to predict behaviors of deteriorated reinforced concrete bridge columns. The proposed numerical method for the performance of damaged reinforced concrete bridge columns is verified by comparison with reliable experimental results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.766-769
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• 2010

본 논문은 콘크리트 구조물 중 원전구조물에서 열화요인에 따른 미세구조적 변화에 대해서 평가하였다. 이는 원전구조물의 경우 열화현상이 발생하게 되면 일반 구조물에 비해 심각한 영향을 초래하기 때문에 기존의 열화 평가 방법에 의존하기 보다는 미세구조적 관점에서 콘크리트의 열화를 재평가해야 한다. 그에 일환으로 열화 요인 중 동결 융해와 황산염에 대한 미세구조 평가를 실시하였다. 동결융해의 경우, 미세구조적 관점에서의 미세공극의 양이 증가하는 것을 확인하였으나 그 증가 폭이 크지 않음을 알 수 있었으며, 물리적 실험에서도 그 변화가 매우 작음을 확인할 수 있다. 그리고 황산염에서는 초지 침지 구간에서는 플라이 애쉬를 사용한 원전 콘크리트 배합이 콘크리트에 더 유리하게 작용함을 알 수 있다.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2022.10a
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• pp.301-302
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• 2022

최근 들어 염해, 콘크리트의 탄산화, 동결융해 등의 열화요인 의하여 발생할 수 있는 콘크리트의 내구성에 대한 다양한 연구가 진행되고 있는데, 이러한 열화요인은 독립적이 아닌 복합열화의 형태로 작용하게 되는데, 열화현상을 저감하는 한 방편으로 플라이애쉬와 같은 혼화재를 사용하디도 한다. 플라이애쉬는 유동성 증진을 통한 내구성의 향상과, 수화열 저감을 통한 균열감소 및 장기강도 증진 등의 효과가 있으며, 시멘트를 대체함으로써 경제적인 효과를 유발하는 장점도 가지고 있다. 그러나 플라이애쉬는 품질편차가 크고, 경우에 따라서 미연탄소분에 의한 AE제 흡착 등으로 인한 콘크리트의 내구성 및 강도를 저하시킬 수 있는 요소를 내포하고 있으므로 사용 시 주의가 필요하다. 본 연구에서는 열화를 저감하고, 내구성을 갖는 고강도 콘크리트를 제조하기 위하여 다양한 배합비의 플라이애쉬 혼입 콘크리트를 실험한 후 그 결과를 분석·고찰함으로써 내구성 콘크리트의 제작 시 혼화재로서의 적용성 및 타당성을 검증하고자 하며, 플라이애쉬를 내구성 재료로 그 활용을 극대화하고, 다양한 플라이애쉬의 사용량과 물/결합재비(W/B)에 대하여 내구성이 높은 고강도 콘크리트 제조방법을 범용화하며, 그 품질을 평가하는 것을 목적으로 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.623-631
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• 2018

In this study, the degree of deterioration of concrete was investigated in the laboratory under conditions of carbonation and freeze-thaw cycling, which are the major causes of the deterioration of its performance. In this test, the carbonated concrete was subjected to combined freeze-thaw deterioration tests for up to 300 cycles, and its dynamic elastic modulus and compressive strength were measured. The evaluation of the effect of the water-binder ratio on normal concrete subjected to combined carbonization and freezing-thawing showed that its resistibility against such combined deterioration decreased more rapidly in the concrete with a water-binder ratio of 55 % compared with that having a water-binder ratio of 35 %. In the case where the concrete was blended with a mineral admixture consisting of fly ash and blast furnace slag at the same water-binder ratio, it showed an increase of its resistibility against combined deterioration.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.4
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• pp.391-398
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• 2011

After a concrete is poured, reinforced concrete structures were distressed by physical and chemical factor over time. It is in need to define important variables related to structural behavior for effectively conducting seismic analysis of structures with age-related degradation. In this study, a sensibility analysis using the first-order second moment method was performed to analyze an important variables for the reinforced concrete shear wall with age-related degradation. Because the seismic capacity of aging structures without a concrete hardening effect can be underestimated, the sensibility of analysis variables was analyzed according to the concrete hardening. Important variables for RC shear wall with age-related degradation was presented by using the tornado diagram.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.359-366
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• 2007

Recently, analysis researches on durability are focused on chloride attack and carbonation due to increased social and engineering significance. Generally, chloride penetration and carbonation occur simultaneously except for in submerged condition and chloride behavior in carbonated concrete is evaluated to be different from that in normal concrete. Furthermore, if unavoidable crack occurs in concrete, it influences not only single attack but also coupled deterioration more severely. This is a study on analysis technique with system dynamics for chloride penetration in concrete structures exposed to coupled chloride attack and carbonation through chloride diffusion, permeation, and carbonation reaction. For the purpose, a modeling for chloride behavior considering diffusion and permeation is performed through previous models for early-aged concrete such as MCHHM (multi component hydration heat model) and MPSFM (micro pore structure formation). Then model for combined deterioration is developed considering changed characteristics such as pore distribution, saturation and dissociation of bound chloride content under carbonation. The developed model is verified through comparison with previous experimental data. Additionally, simulation for combined deterioration in cracked concrete is carried out through utilizing previously developed models for chloride penetration and carbonation in cracked concrete. From the simulated results, CCTZ (chloride-carbonation transition zone) for evaluating combined deterioration is proposed. It is numerically verified that concrete with slag has better resistance to combined deterioration than concrete with OPC in sound and cracked concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.495-496
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• 2009

The restorative materials for deteriorated concrete are estimated by various kinds of strength, carbonation, and at same time, by various deteriorate factors and others. So, it's properties must have maintained many functional properties. In this study, to improvement of durability of restorative materials, we take restorative materials with insulation performance, for deterioration by temperature exchange as deterioration factor.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.91-96
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• 1993

본 연구의 목적은 콘크리트의 열화손상을 주는 요인 중 특히 수분의 공급이 충분한 동결융해작용에 대한 영향인자에 대한 실험적 연구이다. 콘크리트의 열화에 영향을 주는 여러 영향인자 중에서 주로 공기량 및 물-시멘트비를 다루었다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.22-32
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• 2014

Durability is one of the most important and attractive subjects in concrete research field because not only durability of concrete is reduced by various degradation factors but also its reduction adversely influences the structural performance and service life of concrete structure. For this reason, a considerable amount of papers associated with concrete durability have been published and those researches were mainly focused on the changes of intrinsic properties of concrete due to chemicophysical degradations. However, the relationship between durability of concrete and structural behavior of concrete member has not been well established yet. In this study, calcium leaching degradation, a cause of concrete strength reduction, was dealt with. The experiments of compressive and flexural behavior of degraded concrete member were performed to evaluate the characteristics of structural behavior according to degradation level. Finally, the results from the experiments were compared with those obtained from nonlinear FEM analysis. The results from this study clearly showed that leaching degradation leads to decrease in compressive strength and compressive behavior evolves from brittle to ductile failure pattern during the degradation process. Load capacity and flexible rigidity of the degraded RC member decreased when the degradation level increased, in compressive zone. Additionally, it was found that the values from nonlinear FEM analysis, CDP model in ABAQUS, coincided well with the experimental results.