• Computers and Concrete
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• 제20권1호
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• pp.111-118
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• 2017

The present study established prediction models based on multiple nonlinear regressions (MNLRs) and backpropagation neural networks (BPNs) for the expansion of cement mortar caused by oxidization slag that was used as a replacement of the aggregate. The data used for the models were obtained from actual laboratory tests on specimens that were produced with water/cement ratios of 0.485 or 1.5, within which 0%, 10%, 20%, 30%, 40%, or 50% of the cement had been replaced by oxidization slag from electric-arc furnaces; the samples underwent high-temperature curing at either $80^{\circ}C$ or $100^{\circ}C$ for 1-4 days. The varied mixing ratios, curing conditions, and water/cement ratios were all used as input parameters for the expansion prediction models, which were subsequently evaluated based on their performance levels. Models of both the MNLR and BPN groups exhibited $R^2$ values greater than 0.8, indicating the effectiveness of both models. However, the BPN models were found to be the most accurate models.

• Steel and Composite Structures
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• 제37권1호
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• pp.1-14
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• 2020

Composite beams with corrugated steel webs represent a new innovative system which has emerged in the past decade for medium span in the construction technology. The use of composite beams with corrugated steel webs results in a range of benefits, including flexible spaces and reduced foundation costs in the construction technology. The thin corrugated web affords a significant weight reduction of these beams, compared with hot-rolled or welded ones. In the current research, an optimal designed I-girder beam with corrugated web has been proposed to improve the structural performance of continuous composite girder under bending moment. The experimental program has been conducted for six simply supported composite beams with different loading conditions. The tested specimens are designed by using one of the stochastic techniques called hunting search algorithm. In the optimization process, besides the thickness of concrete slab and studs, corrugated web properties are considered as design variables. The design constraints are respectively implemented from Eurocode 3, BS-8110 and DIN 18-800 Teil-1. The last part of the study focuses on performing a numerical study on composite beams by utilizing finite element analysis and the bending behavior of steel girders with corrugated webs experimentally and numerically verified the results. A nonlinear analysis was carried out using the finite element software ANSYS on the composite beams which were modelled using the elements ten-node high order quadrilateral type.

• Advances in concrete construction
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• 제8권4호
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• pp.311-320
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• 2019

In this study, the effect of cellulose nanocrystals (CNCs) on the fire resistance properties of fiber-reinforced cement composites was investigated. The main variables were CNCs content (0.4, 0.8 and 1.2vol.% compared with cement), steel fiber ratio, and exposure temperature (100, 200, 400, 600 and 800℃). The fire resistance properties, i.e., residual compressive strength, flexural strength, and porosity, were evaluated in relation with the exposure temperature of the specimens. The CNCs suspensions were prepared to composited dispersion method of magnetic stirring and ultra-sonication. CNCs are effective for increasing the compressive strength at high temperatures but CNCs do not seem to have a significant effect on flexural reinforcement. Porosity test result showed CNCs reduce the non-hydration area inside the cement and promote hydration.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
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• pp.67-68
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• 2017

This paper discusses the application of civil structure use reinforcing fiber mixed with concrete to be used as protection layer of waterproofing material and root resistant layer installed in below-grade parking lot upper slab of residential building. A performance evaluation under the prescribed method outlined in KS F 4938 was used for this new material. The testing results showed that the fiber reinforcement can be used to strengthen the protection for the waterproofing material. Also, plants that were planted in June 2016 have not yet penetrated the specimens used for root resistance testing. The domestic root resistance performance testing usually covers the period of 2 years, thus further observation to make any conclusion about the root resistance property is required.

• 한국구조물진단유지관리공학회 논문집
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• 제8권4호
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• pp.115-122
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• 2004

본 연구에서는 강화보드, 익스팬디드 메탈 그리고, 탄소섬유그리드의 세 가지 보강재와 덮개 콘크리트 대용의 세라믹메탈재를 사용하여 RC보의 인장측을 보강한 경우에 그 보강효과를 파악하기 위한 구조실험을 수행하였다. 구조실험을 통하여 RC보 구조물에서 세라믹메탈재의 부착성능을 평가하였고, 각 보강방법에 대한 강성 증가 효과와 항복 후의 연성 증진 효과를 파악하였다. 그리고, 각 시험체의 실험 결과에 대한 비교를 통하여 더 나은 보강효과를 발휘할 수 있는 방안을 제시하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제8권4호
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• pp.265-273
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• 2004

압축강도 실험결과, 고막패각 혼입량 15%와 20% 시험체가 무혼입 시험체보다 증가하는 것으로 나타났다. 시험체의 연성능력은 일반 잔골재를 사용한 시험체가 가장 높았으며, 고막패각의 혼입량이 많을수록 연성능력은 낮게 나타났고, 고막패각 혼입량이 많을수록 낮은 하중에서 초기균열이 발생하여 하중의 증가로 인하여 부재의 처짐 속도가 빨라지는 것으로 나타났다. 이는 고막패각의 혼입량에 따라 부착력이 부족하여, 이후 항복내력이 상대적으로 증가하지 못한 것으로 판단된다

• 복합신소재구조학회 논문집
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• 제2권1호
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• pp.23-29
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• 2011

본 연구에서는 CFRP쉬트로 보강된 원형 CFT기둥의 압축거동을 관찰하고 설계식을 제안하였다. 원형 CFT기둥의 CFRP쉬트의 보강효과를 관찰하기 위해 10개의 실험체를 제작하여 중심축하중 실험을 수행하였다. 실험변수로는 CFRP쉬트 보강겹수와 직경-두께비(D/t)이다. 실험결과 원형CFT기둥에 CFRP쉬트 보강을 통해 압축내력을 증가시킨 것으로 나타났다. 끝으로 ACI 440code를 응용하여 CFRP 보강된 원형 CFT기둥의 압축내력을 예측하기 위한 설계식을 제안한다. 제안식을 분석한 결과 실험결과와 비교적 일치한 것으로 나타났다.

• 한국강구조학회 논문집
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• 제19권1호
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• pp.53-65
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• 2007

새로운 형식의 기둥인 내부 구속 중공 콘크리트 충전 튜브 기둥(내부 구속 중공 CFT 기둥, ICH CFT column ; Internally Confined Hollow CFT Column)의 내진 성능 평가 실험을 수행하였다. 준정적 실험을 통하여 2가지 종류의 ICH CFT 기둥과 일반 중실 RC 기둥의 내진 성능을 비교 평가 하였다. 각각의 기둥 시험체에 대해 최대 하중과 변위의 관계를 측정하였으며, 이를 바탕으로 연성도, 소산에너지, 등가 감쇠비, 손상 지수가 계산되었다. 실험 결과 ICH CFT 기둥은 중실 RC 기둥에 비해 약 2배의 모멘트에 저항을 하였으며, 에너지의 흡수와 소산에서도 1.5배 정도의 성능을 보여주어, ICH CFT 기둥이 일반 중실 RC 기둥보다 더 뛰어난 성능을 가짐을 보여주었다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2003년도 학술.기술논문발표회
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• pp.35-38
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• 2003

The purpose of this study is to investigate the manufacture of light weight concrete panel using the artificial light-weight aggregate as a part of the substitution of foamed styrene and polyurethane because of narrow allocable temperature Bone in use. The experimental parameter of this study is 40, 60 and 8$0^{\circ}C$ of curing temperature at 100% relative humidity and the type of admixture such as cement, 6mm glass fiber and St/BA emulsion. Testing item is compressive and flexural strength and strength of specimen cured at standard condition is compared to that of specimen cured at 40, 60 and 8$0^{\circ}C$ of curing temperature at 100% relative humidity. As a result or this, it was revealed that the maximum or strength is developed in 6$0^{\circ}C$ or cure temperature at 100% relative humidity in case of the most of the specimen. Specimens modified by St/BA emulsion show the highest development of strength dependent on the curing tmeperature. So, it seems to be effective that evaporation curing method shoud be considered to curing the specimen as the panel core.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.107-108
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• 2018

In this study, we applied the fiber sheet made by the stitch bonding method, which is a structure in which transverse yarns and double yarns are crossed by applying the principle of sewing knitting without the use of adhesive, The tensile strength of the reinforced concrete structure was investigated. As a result of the tensile strength test of each specimen, the specimen to which the fiber sheet produced by the stitch bonding method was applied exhibited the highest tensile strength among the three types of specimens, and the fiber sheet produced by the needle punching method exhibited the lowest strength. In addition, the stitch - bonded fiber sheet showed a difference of strength of 0.1N / mm for both length and double - sided strength difference.