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再生骨材를 사용한 철근 콘크리트 보의 휨 및 剪斷擧動 特性
구봉근,나재웅,신재인,이재범,주봉철 한국자원리싸이클링학회 2001 資源 리싸이클링 Vol.10 No.1
본 연구에서는 여러 가지 건설 부산물 중에서 단순히 폐기되거나 매립에 의존하고 있는 폐콘크리트를 대상으로 건설공사에 재이용하기 위한 기술 즉, 폐콘크리트의 콘크리트용 골재(재생골재)로서의 재이용과 콘크리트 구조용 재료로써의 재사용을 위한 기술적인 방향을 제시하고 실험적 자료를 구축하고자 하였다 실험결과, 안전을 고려하여 재생골재 대체율은 30%이하, 최대철근비를 균형 철근비의 70%이하, 깊은 보의 기준은 전단 스팬비 2.0이하로 보는 것이 타당하고, 계수전단강도의 예측에는 Zsutty식을 사용하는 것이 합리적이라고 판단된다. We can reuse the portion of simple reclamation and the construction by-products. Until now, we have discarded concrete by simply throwing away or dumping in underground. Therefore, we attempted to propose the technical directions for the reuse of waste concrete as the recycled concrete aggregates and concrete structural materials. As a testing result, It is reasonable that standards are substitution of recycled aggregates under 30%, maximum steel ratio, under 70% of balanced steel ratio, under shear span ratio 0.2 for deep beam criteria for safety and Zsutty's equation is reasonable for estimation of factored shear strength
구봉근,강종수 충북대학교 건설기술연구소 1988 建設技術論文集 Vol.6 No.2
After completion of river diversion, foundation treatment and construction of temporay works including construction road, aggregate plant, batching, water supply, power, cooling, transporting and placing systems for concrete works, concrete placing works can be carried out using these facilities. 'This paper mainly covers construction method of concrete placing for gravity dams excluding all temporary works. Total quality control of concrete materials including aggregate, cement and admixtures and for all the processes of mixing, hatching, transporting, placing and curing as well as strict observing of specifications for minor works of expansion joints, construction joints and etc. is very important for the successful construction of structurally and qualitably stable concrete gravity dams. This study was carried out to study reasonable construction method of concrete gravity dams through analyzing developed methods and expriences in the fields of the above.
구봉근,김창운,류택은,이재범,류연종,이현석 충북대학교 산업과학기술연구소 2002 산업과학기술연구 논문집 Vol.16 No.1
This study was performed to investigate the strength characterstics of steel fiber reinforced recycled aggregate concrete. Test specimens were prepared with compressive, split tensile, flexural specimens and tested by ultimate strength. A superplasticizer and fly-ash were added to the mix to improve performance of recycled concrete. Test-variables are substitution of recycled aggregate(0, 30, 50%), steel fiber length(0, 30, 50, 60mm), steel fiber content(0, 0.5, 1.0, 1.5%). Test-specimen were classified by test-variables. The experimental results on the various engineering properties of steel fiber reinforced recycled aggregate concrete using waste concrete are summarized as follows. It was found that the compressive and split tensile strength were proportionally affected by quantities of recycled aggregate substitutions, but flexural strength wasn't. The maximum compressive strength was 392 kgf/㎠( series 4 : R30 L30 V1.0 A20 ), the maximun split tensile strength was 40 kgf/㎠( series 7 : R30 L30 V1.5 A20) and the maximum flexural strength was 62 kgf/㎠( series 7 : R30 L30 V1.5 A20 ).
슬래그 미분말과 석회석 미분말을 혼입한 콘크리트의 내구성에 관한 연구
구봉근,박주원 충북대학교 건설기술연구소 2003 建設技術論文集 Vol.22 No.2
This study is to investigate the durability of concrete containing slag powder and limestone powder. In order to study the effect of slag powder and limestone powder, all mixtures were prepared at a fixed water/cement ratio, slump, and entrained air quantity. The water-cement ratio was 50%, and added AE agent, water reducing agent titer as agent. When concrete containing slag powder is at a mixing rate of 40%, durability was the highest. But drying shrinkage is less than in standard concrete in general, and was the lowest at20%. When concrete containing limestone powder is at a mixing rate of 10% in all experiments, the most suitable result appeared. When cement and two admixtures are mixed together, the same result appeared. Therefore, in the case where mix slag powder is 40% and limestone powder is 10%, we can say that it gives the best concrete durability.
구봉근,라재웅,이재범,류연종,이현석 충북대학교 건설기술연구소 2003 建設技術論文集 Vol.22 No.2
As concrete is prevented from shrinking freely, tensile stresses develop which frequently result in cracking. Cracks in reinforced concrete structures reduce overall durability by allowing the penetration of water and aggressive agents, thereby accelerating the deterioration of the reinforcing steel. Highway pavement, bridge decks, and industrial floors are especially susceptible to this type of deterioration since these structures exhibit high rates of shrinkage and are frequently exposed to aggressive environmental conditions. The objectives of this investigation included the implement of experimental procedures for assessing shrinkage cracking behavior on recycled aggregate concrete, the selection of replacement rate and mix composition on recycled aggregate concrete. Specifically, the influence of a shrinkage reducing admixture(SRA) and recycled aggregate concrete was investigated. The shrinkage reducing admixture substantially reduces free, shrinkage and restrained shrinkage cracking while providing similar mechanical properties. Restrained shrinkage experiments were developed and shrinkage cracking was shown to be size dependent and recycled aggregate replacement rate. A mechanical properties experiment approach was developed to predict the behavior of a variety of recycled aggregate concrete specimens. This experimentally approach was used to successfully explain experimental results from a variety of mixture compositions and recycled aggregate concrete. This experiment was used to demonstrate the influence of material and structural properties on the potential for cracking.
하중일- 저항계수 설계법에 의한 철근콘크리트 구조물 최적설계
구봉근,강종수,김우식,김태봉 한국콘크리트학회 1990 콘크리트학회지 Vol.2 No.2
In this study, an optimization design of reinforced concrete structures is performed by using the structural optimization techniques based on the LRFD criteria. The target reliability index is estimated by the optimal reliability index considering the expected cost which is taken as a sum of the structural cost and the expected costs due to failure of the structure. The load and resistance factors calculated by using level I reliability theory with the target reliability index are compared for each load combination (D+L, D+L+w). The results of this study show that the resistance factors are ${\phi}_{M}$=0.90, ${\phi}_{V}$==0.70, ${\phi}_{C}$==0.65 and the load factors are 1.20D + 1.70L, 1.07L + 0.07L + 1.10W. The optimization techinques used to this study are S.L.P. The optimization design based on the LRFD criteria is more economical and rational than other criteria.