• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.291-292
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• 2010

In this study, high-strength concrete mixtures were made with blast-furnace slag of 50% and 70% replacement level to evaluate material properties including compressive strength development, adiabatic temperature rise, autogenous shrinkage and chloride-ion migration coefficient. Test results showed that the use of high percentage blast-furnace slag in high-strength concrete can reduce heat of hydration and chloride-ion migration coefficient, result in control thermal cracking and improve durability performance especially under high corrosive environment.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.644-647
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• 2011

지형 및 환경에 따라 해안 사면의 침식, 세굴을 막기 위한 효과 있는 해안구조물의 설치가 필요하다. 본 연구에서는 유체-구조 상호작용을 고려해서 유한요소해석 프로그램인 LS-DYNA를 사용하여 조파 실험모델링을 하고, 해안사석구조물과 상호작용에 의한 유체 흐름을 분석하였다. 사석의 유무와 크기, 개수 등의 변수를 조정하여 서로 다른 4가지 경우에 따른 결과를 비교 분석하였다. 또한 해안사석구조물을 구성하는 투수 콘크리트의 특성 분석을 위하여 CT 이미지를 사용하여 투수 콘크리트의 공극 분포를 관찰하였다. 투수 콘크리트의 특성에 큰 영향을 미치는 공극 분포의 파악을 위하여 확률 분포 함수를 사용하여 투수 콘크리트 공극의 공간적 분포를 분석하였다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2009.04a
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• pp.147-154
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• 2009

화재와 같은 고온의 환경에서 콘크리트의 고강도화는 폭렬(Explosive Spalling)이라는 큰 위험성을 가지고 있으며, 이러한 폭렬의 원인으로는 콘크리트 내부의 수증기압이 가장 큰 원인으로 제기되고 있다. 본 논문은 콘크리트의 폭렬발생 있어서 압축강도 및 함수율이 초기 폭렬특성에 미치는 영향을 실험적으로 검토하기위하여 건축구조물의 화재 온도조건인 ISO834 화재온도이력곡선을 15분, 30분 적용하여 콘크리트의 초기 폭렬특성을 검토하였다. 그 결과 압축강도 가열시간 함수율이 증가할수록 폭렬발생 및 폭렬현상이 증대되는 경향이 나타났으며, 15분, 30분 가열시간에 따른 잔존강도율을 나타내었다. 또한, 압축강도 및 함수율에 따른 폭렬발생영역을 분석하였으며, 압축강도 50${\sim}$100 MPa의 경우 함수율 3%이하, 100 MPa이상의 경우는 1%이하로 제어할 경우 폭렬현상이 발생하지 않을 것으로 판단되었다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.07a
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• pp.107-109
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• 2022

본 논문은 건설구조물 안전의 가장 중요한 요소 중 하나인 콘크리트 압축강도 안정성을 확보하기 위한 시스템으로, 콘크리트 구조물을 만들 재료인 레미콘의 수분 감소율에 따른 압축강도 감소 리스크를 관리할 수 있는 모델을 제시하였다. 동일한 물,시멘트비(W/C)로 생산된 레미콘은 현장타설시까지 교통환경으로 인한 도착시간 지연 및 강우, 강설 등 외부적인 요건으로 감수율이 발생하는 리스크가 발생한다. 이로 인해 콘크리트의 압축강도가 저감하는 중대한 문제가 발생한다. 본 연구에서 제시한 알고리즘을 이용하여 현장 타설전 콘크리트 시료의 함수율을 측정하여 감수율이 발생한 제품 발견시, 실시간으로 Operator로 GCM 기반의 Push Alarm을 전송하여 감수율이 반영된 제품을 제공함으로써 구조물의 안전성을 확보할 수 있는 시스템을 모델링하였다. 본 연구는 기존시스템의 문제점을 실시간으로 개선할 수 있는 것으로 건설현장의 구조물 안정성 확보에 효과가 클 것으로 기대된다.

• Journal of the Korean Geotechnical Society
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• v.38 no.12
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• pp.19-28
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• 2022

Cavities behind concrete walls can adversely affect the stability of structures. Thus study aims to detect cavities behind concrete structures using a microphone in a laboratory model test. A small-scale concrete wall is constructed in a chamber, which is composed of a reinforced concrete plate and dry soil. A plastic bowl is then placed between the plate and soil to simulate a cavity behind the concrete structure. Leaky surface acoustic waves are generated by impacting the concrete plate using a hammer and are measured using a microphone. The measured signals are analyzed using natural frequencies, and cavity-free sections are evaluated. The test results show that the first natural frequency decreases at the cavity section due to the flexural vibration behavior of the plate. In addition, the amplitude corresponding to the first natural frequency decreases as the measurement location becomes farther from the cavity center and significantly decreases at the measurement locations near the rebars. This study demonstrates that a microphone may be useful to detect cavities behind concrete walls.

• Journal of the Korean Geosynthetics Society
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• v.2 no.2
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• pp.25-31
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• 2003

Most recently, environmental problems arise from management waste tires by increasing number of automobiles. Waste tires are not compressible and not easy for degradation in landfill. Even if it were landfill, it is difficult to treat. Total amount of waste tires is about 20 million per year and the collection is 68.6% in this country. Structure of slope stability using waste tire blocks filled with concrete increases durability, reduce construction period, and it can be utilized as an example. Therefore, it reduces the volume of waste and recycles waste. Also, it prevents the air pollution due to the incineration and creates economic value.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.621-624
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• 2008

Repair materials which applied to the concrete structures may have different quality characteristics depending on the environmental factors. Evaluation on durability of domestic repair materials have not yet secured enough quality performance on durability, mainly due to the lack of test methods resulted from various environmental factors. In this study, we carried out the tests on freezing and thawing resistance of domestic repair materials with different environmental factors applied under BS EN 13687, and analyzed the results by comparing with Korea's national test standards(KS F 4716). The results indicate that after the repetition of dry and wet conditions and the test on freezing and thawing with salt immersion resistance bond strength might show great difference depending on the type of repair materials and the size of sample. For securing better quality performance of repair materials, it is required to establish various standards on the test methods of freezing and thawing resistance with different environmental factors applied.

• International Journal of Highway Engineering
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• v.11 no.4
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• pp.107-115
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• 2009

This study was conducted to investigate the effect of the slab thickness on the tensioning design and to determine the optimal slab thickness of the post-tensioned concrete pavement (PTCP). The tensile stresses due to the vehicle and environmental loads were obtained using a finite element analysis model and the tensioning stress was calculated employing an allowable flexural strength. The environmental loads of both the constant temperature gradient and the constant temperature difference between top and bottom of the slab were considered. The tensioning designs for various slab thicknesses were performed considering prestressing losses. The comparison results showed that generally as the thickness increased, the number of tendons became larger. Consequently, the design was not economical for a thicker slab thickness. Even though the number of tendons became smaller with an increase in the thickness under the small environmental load, a thicker PTCP slab was not economical because of a higher cost of concrete than that of steel. Therefore, the slab thickness should be kept in minimum within the construction available thicknesses.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.2
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• pp.168-175
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• 2022

With the recent development of nanotechnology, its application in the field of construction materials is continuously increasing. However, until now, studies on the bond characteristics of concrete and rebar for applying high-strength lightweight concrete with a compressive strength of 50 MPa and a unit weight of 16 kN/m³ to structural members are lacking. Therefore, in this paper, 81 specimens of high-strength lightweight concrete with a compressive strength of 50 MPa and a unit weight of about 16 kN/m³ were fabricated and a direct pull-out tests were performed. The design code for the bond strength of ACI-408R and the experimental results are shown to be relatively similar, and as a result of the CEB-FIP and modified CMR bond behavior models through statistical analysis, it is shown to describe well on average.

• Korean Journal of Construction Engineering and Management
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• v.19 no.4
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• pp.43-51
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• 2018

As the inventory of aged apartments is expected to increase explosively, the importance of maintenance to improve the durability of concrete facilities is increasing. Concrete compressive strength is a representative index of durability of concrete facilities, and is an important item in the precision safety diagnosis for facility maintenance. However, existing methods for measuring the concrete compressive strength and determining the maintenance of concrete facilities have limitations such as facility safety problem, high cost problem, and low reliability problem. In this study, we proposed a model that can predict the concrete compressive strength through images by using deep convolution neural network technique. Learning, validation and testing were conducted by applying the concrete compressive strength dataset constructed through the concrete specimen which is produced in the laboratory environment. As a result, it was found that the concrete compressive strength could be learned by using the images, and the validity of the proposed model was confirmed.