• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.209-212
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• 2006

Bond between reinforcing bar and surrounding concrete is supposed to transfer load safely in the process of design of reinforced concrete structures. The effects of defomation properties on bond of reinforcing bars to concrete are studied. Beam-end tests are used to investigate the effects of machining of bars in addition to rib angle and relative rib area. The test results show that bond strength of machined bars were higher than the conventional bars produced in factory. Higher rib height bars with rib angle $30^{\circ}{\sim}60^{\circ}$ showed higher bond strength than lower rib height bars with low angle.

• 한국지반환경공학회 논문집
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• 제11권6호
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• pp.21-29
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• 2010

본 논문에서는 소음과 진동이 거의 없고 환경친화적 공법으로 기대되는 무소음 무진동을 위한 스크류콘크리트말뚝공법을 소개하였고, 기존 PHC말뚝과 스크류콘크리트말뚝에 대하여 수치해석을 실시하였다. 그 결과 각 말뚝의 지지력 및 침하량 거동을 분석하였고 비교하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.53-54
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• 2022

This study is a basic study to establish the relationship between the conventional fluidity evaluation data of concrete and the rheology parameters. the slump flow and rheology parameters were measured according to the elapsed time after the concrete was mixed. The correlation between the slump flow and the rheology constant was analyzed and the effect of the elapsed time after concrete beating on the correlation between the two data was analyzed.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.293-294
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• 2021

For the successful introduction of the construction automation system, it is necessary to define the consideration factors and target tasks for the necessity of automating the conventional methods. In this study, the factors for automation were derived through brainstorming and questionnaires, and calculated the relative importance through the pairwise comparison using the AHP analysis method. In addition, the detailed type of concrete work was classified into 32 detailed works, and the automation score for each work was calculated by investigating the factors considering the necessity of automation. As a result of the automation score analysis, it was concluded that the need for automation of concrete placing work was the highest. Based on this study, we will consider the strategy of a concrete construction automation system.

• Structural Engineering and Mechanics
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• 제78권1호
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• pp.41-52
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• 2021

Inelastic static pushover analysis has been used in the academic-research widely for seismic analysis of structures. Nowadays, the variety pushover analysis methods have been developed, including Modal pushover, Adaptive pushover, and Cyclic pushover, in which some weaknesses of the conventional pushover method have been rectified. In the conventional pushover analysis method, the effects of cumulative growth of cracks are not considered on the reduction of strength and stiffness of RC members that occur during earthquake or cyclic loading. Therefore, the Cyclic Pushover Analysis Method (CPA) has been proposed. This method is a powerful technique for seismic evaluation of regular reinforced concrete buildings in which the first mode of them is dominant. Since the bridges have different structures than buildings, their results cannot necessarily be attributed to bridges, and more research is needed. In this study, a cyclic pushover analysis with four loading protocols (suggested by valid references) by the Opensees software was conducted for seismic evaluation of two regular reinforce concrete bridges. The modeling method was validated with the comparison of the analytical and experimental results under both cyclic and dynamic loading. The failure mode of the piers was considered in two-mode of flexural failure and also a flexural-shear failure. Along with the cyclic analysis, conventional analysis has been studied. Also, the nonlinear incremental dynamic analysis (IDA) method has been used to examine and compare the results of pushover analyses. The time history of 20 far-field earthquake records was used to conduct IDA. After analysis, the base shear vs. displacement in the middle of the deck was drawn. The obtained results show that the cyclic pushover analysis method is able to evaluate an accurate seismic behavior of the reinforced concrete piers of the bridges. Based on the results, the cyclic pushover has proper convergence with IDA. Its accuracy was much higher than the conventional pushover, in which the bridge piers failed in flexural-shear mode. But, in the flexural failure mode, the results of each two pushover methods were close approximately. Besides, the cyclic pushover method with ACI loading protocol, and ATC-24 loading protocol, can provided more accurate results for evaluating the seismic investigation of the bridges, specially if the bridge piers are failed in flexural-shear failure mode.

• 한국정보통신학회논문지
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• 제14권6호
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• pp.1353-1358
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• 2010

본 논문에서는 콘크리트 균열 영상에서 퍼지 기법을 이용하여 균열을 자동으로 검출하는 방법을 제안한다. 본 논문에서 제안하는 콘크리트 표면 균열 검출 방법은 콘크리트 균열 영상의 R,G,B 채널 값을 퍼지 기법에 적용하여 후보 균열을 검출한다. 검출된 균열 후보 영역에 대해 밀도 정보를 이용하여 세부적인 잡음을 제거 한 후에 최종적으로 균열을 검출한다. 실제 콘크리트 균열 영상을 대상으로 실험한 결과, 제안한 방법이 기존의 방법보다 균열 검출 성능이 개선되었음을 확인할 수 있었다.

• Advances in concrete construction
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• 제6권1호
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• pp.87-102
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• 2018

Utilization of waste tires may be considered as one of the solution to the problems faced by the local authorities in disposing them. Reclaimed rubber (RR) is being used in concrete for replacing conventional aggregates. This research work is focused on the strength prediction of reclaimed rubber concrete using a Genetic Algorithm (GA) for M40 grade of concrete and comparing it with experimental results. 1000 sets were taken and 100 iterations were run during training of GA models. A base study has been carried out in this research work partially replacing cement with three types of fillers such as Plaster of Paris (POP), Fly Ash (FA) and Silica Fume (SF). A total of 243 cubes were cast and tested for compression using a Universal Testing Machine. It was found that SF produced maximum strength in concrete and was used in the main study with reclaimed rubber. Tests were conducted on 81 cube samples with a combination of optimum SF percent and various proportions of RR replacing coarse aggregates in concrete mix. Compressive strength tests of concrete at 7, 14 and 28 days reveal that the maximum strength is obtained at 12 percent replacement of cement and 9 percent replacement of coarse aggregates respectively. Moreover the GA results were found to be in line with the experimental results obtained.

• Computers and Concrete
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• 제21권1호
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• pp.47-54
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• 2018

Artificial neural network models can be successfully used to simulate the complex behavior of many problems in civil engineering. As compared to conventional computational methods, this popular modeling technique is powerful when the relationship between system parameters is intrinsically nonlinear, or cannot be explicitly identified, as in the case of concrete behavior. In this investigation, an artificial neural network model was developed to assess the residual compressive strength of self-compacted concrete at elevated temperatures ($20-900^{\circ}C$) and various relative humidity conditions (28-99%). A total of 332 experimental datasets, collected from available literature, were used for model calibration and verification. Data used in model development incorporated concrete ingredients, filler and fiber types, and environmental conditions. Based on the feed-forward back propagation algorithm, systematic analyses were performed to improve the accuracy of prediction and determine the most appropriate network topology. Training, testing, and validation results indicated that residual compressive strength of self-compacted concrete, exposed to high temperatures and relative humidity levels, could be estimated precisely with the suggested model. As illustrated by statistical indices, the reliability between experimental and predicted results was excellent. With new ingredients and different environmental conditions, the proposed model is an efficient approach to estimate the residual compressive strength of self-compacted concrete as a substitute for sophisticated laboratory procedures.

• 콘크리트학회지
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• 제11권1호
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• pp.77-87
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• 1999

일반적으로 프리스트레스트 콘크리트 박스거더교량의 설계에서는 단순화된 단면에 대하여 탄성이론에 근거하여 설계를 수행하고 있다. 이러한 단순화에 따른 제약조건을 개선하기 위해서 본 연구에서는 변단면의 프리스트레스트 콘크리트 박스거더교량을 해석하기 위한 매크로요소를 사용하였다. 해석프로그램에서 재료 비선형모델을 사용하여 극한하중 해석이 가능하도록 하였다. 또한, 교량의 장기거동을 예측하기 위해서 재료의 시간의존적 해석모델을 프로그램에 적용하여 교량의 장기 거동해석을 수행할 수 있게 하였다. 따라서, 재료비선형 모델과 시간의존 해석을 포함하는 비선형 매크로요소는 임의의 형상을 가진 프리스트레스트 박스거더 교량의 실제적인 거동해석에 유용하게 사용할 수 있을 것으로 사료된다.

• 한국구조물진단유지관리공학회 논문집
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• 제9권3호
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• pp.195-202
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• 2005

본 연구에서는 순수 휨을 받는 중공 원형강관, 내부에 경량기포콘크리트 및 보통콘크리트를 충전한 원형강관 부재에 대하여 강재의 압축부에 대한 좌굴특성을 고려하고, 충전된 콘크리트의 삼축압축응력 발생에 따른 강도증가 현상을 고려하여 모멘트-곡률 관계를 계산하였다. 경량기포콘크리트를 충전하더라도 해석적으로 간편하게 모멘트-곡률 관계를 계산할 수 있다는 것을 확인하였으며, 보통콘크리트를 충전한 경우에는 해석값이 실험값에 근접한 결과를 추정함을 알 수 있었다. 또한 기존의 실험결과를 이용하여 본 연구에서 개발된 모멘트-곡률 관계 해석방법의 유효성을 검증하였다.