• 한국도로학회논문집
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• 제17권1호
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• pp.83-90
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• 2015

PURPOSES : The purpose of this study is to investigate the relationship between the crack propagation depth through a slab and crack width movement in continuously reinforced concrete slab systems (CRCSs). METHODS : The crack width movements in continuously reinforced concrete pavement (CRCP) and continuously reinforced concrete railway track (CRCT) were measured in the field for different crack spacings. In addition, the crack width movements in both CRCP and CRCT were simulated using finite element models of CRCP and CRCT. The crack width movements, depending on the unit temperature change, were obtained from both the field tests and numerical analysis models. RESULTS : The experimental analysis results show that the magnitudes of the crack width movements in CRCSs were related to not only the crack spacing, but also the crack propagation depth. In CRCP, the magnitudes of the crack width movements were more closely related to the crack propagation depths. In CRCT, the crack width movements were similar for different cracks since most were through cracks. If the numerical analysis was performed to predict the crack width movements by assuming that the crack propagates completely through the slab depth, the predicted crack width movements were similar to the actual ones in CRCT, but those may be overestimated in CRCP. CONCLUSIONS : The magnitudes of the crack width movements in CRCSs were mainly affected by the crack propagation depths through the slabs.

• Advances in concrete construction
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• 제10권1호
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• pp.21-34
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• 2020

Precast deck joints have larger crack width than cast-in-place concrete decks. The initial crack typically occurs at the maximum moment but cracks on precast joints are significant and lead to failure of the deck. The present crack equation is applied to cast-in-place decks, and requires correction to calculate the crack width of precast deck joints. This research aims to study the crack width correction equation of precast decks by performing static tests using high strength and normal strength concrete. Based on experimental results, the bending strength of the structural connections of the current precast deck is satisfied. However it is not suitable to calculate and control the crack width of precast loop connections using the current design equation. A crack width calculation equation is proposed for crack control of precast deck loop joints. Also included in this paper are recommendations to improve the crack control of loop connections.

• 한국도로학회논문집
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• 제18권3호
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• pp.75-86
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• 2016

PURPOSES : The purpose of this study is to investigate characteristics of crack spacing and crack width and their relationship in continuously reinforced concrete pavement (CRCP) based on the data obtained from long-term field observations. METHODS : The crack spacings and crack widths are measured periodically over 10 years at two different CRCP sections: one with asphalt bond breaker beneath concrete slab, and the other with bonded lean concrete base beneath concrete slab. The effects of steel ratio, type of underlying layer, terminal treatment method, and seasonal temperature change on the crack characteristics are evaluated by analyzing the measured data. RESULTS : The CRCP with lean concrete base shows smaller crack spacings than those of the CRCP with asphalt bond breaker. As the steel ratio increases, both the crack spacing and crack width tend to decrease. The crack width becomes larger as the crack age increases, but once the crack age is over a certain value the crack width tends to converge. When the terminal anchor lug system is not used and the expansion joints are employed at the terminals, the crack spacings and crack widths increase near the terminal sections. The crack spacing and crack width seem to be proportional each other, but not necessarily linearly, and their relationship is more distinguished in the summer when the crack widths become smaller. CONCLUSIONS : The steel ratio, underlying layer type, terminal treatment method, and seasonal temperature change affect the characteristics of cracks and the crack spacing and crack width are related to each other.

• Smart Structures and Systems
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• 제32권4호
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• pp.219-233
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• 2023

Crack width is an important indicator to evaluate the health condition of the concrete structure. The crack width is measured by manual using crack width gauge commonly, which is time-consuming and laborious. In this paper, we have proposed a fast and simplified crack width quantification method via deep Q learning and geometric calculation. Firstly, the crack edge is extracted by using U-Net network and edge detection operator. Then, the intelligent decision of is made by the deep Q learning model. Further, the geometric calculation method based on endpoint and curvature extreme point detection is proposed. Finally, a case study is carried out to demonstrate the effectiveness of the proposed method, achieving high precision in the real crack width quantification.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.227-232
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• 2002

This paper describes a calculation of an average crack spacing and the maximum crack width for the high-strength concrete tensile and flexural members. Based on the uniform bond stress distribution of the average steel and concrete strains over the transfer length, the crack spacing and the crack width are proposed to utilize influence of the concrete strength and the cover thickness. This analytical results presented in this paper indicate that the proposed equations can be more effectively estimated the maximum crack width and the average crack spacing of the reinforced concrete flexural and tensile members.

• 한국도로학회논문집
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• 제18권2호
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• pp.43-49
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• 2016

PURPOSES : The field application and performance of continuously reinforced concrete pavement (CRCP), constructed by using the mechanical tube-feeding method, are evaluated in this study. METHODS: The location of the rebar was evaluated by using the MIRA system. The early-age CRCP performance was evaluated via visual survey, in which the crack spacing and crack width were examined. RESULTS: The location of longitudinal reinforcing bars was evaluated via MIRA testing and the results showed that the longitudinal rebars all lie within a given tolerance limit (${\pm}2.5cm$) of the target elevation. In addition, owing to the low temperature when the concrete was pured, the crack spacing in the Dae-Gu direction is slightly wider than that of the Gwang-Ju direction. Almost all of the crack spacings lay within the range of 1.0 m~3.0 m. A crack width of <0.3 mm was measured at the pavement surface. However, as revealed by the field survey, the crack spacing was not correlated with the crack width. CONCLUSIONS : In CRCP constructed by using the mechanical tube-feeding method, almost all of the longitudinal reinforcing bars lay within the tolerance limit (2.5 cm) of the target elevation. The concrete-placing temperature affects the crack spacing, owing to variations in the zero-stress temperature. Crack survey results show that there is no correlation between the crack spacing and crack width in CRCP.

• 콘크리트학회논문집
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• 제19권6호
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• pp.707-715
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• 2007

다공질성 특성을 갖는 콘크리트는 충분한 다짐과 양생 조건에서 장수명을 갖으며, 유해 물질의 주요 경로는 공극이다. 그러나 균열이 발생한 콘크리트의 경우, 균열은 염소이온과 같은 유해 물질의 우선적인 침투 경로가 된다. 균열이 염소에 미치는 영향은 균열폭과 균열 깊이의 크기에 의존한다. 본 연구는 미세균열이 콘크리트의 염소이온 침투에 미치는 영향을 다룬 실험적 연구로서, 연구 목적은 균열폭과 균열 깊이 등의 균열 크기 효과가 염소이온에 미치는 영향을 고찰하는 것이다. 균열을 통한 염소이온의 침투를 시각화 하기 위하여, 급속 염소이온 침투 실험인 RCM (rapid chloride migration) 실험을 수행하였다. 균열폭과 균열 깊이는 전자 현미경으로 관찰하였고, 평균적인 균열폭을 산정하기 위하여 균열 개구 변위가 측정되었다. 다양한 균열 크기에 따른 염소이온의 침투 깊이 및 염소이온 확산계수의 변화율로부터 염소이온이 침투되지 않는 균열 깊이 및 이에 대응한 균열폭이 도출되었다.

• 한국안전학회지
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• 제21권3호
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• pp.114-121
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• 2006

As one of the serviceability limit states, the prediction and control of crack width in reinforced concrete bridges or PSC bridges are very important for the design of durable structures. However, the current bridge design specifications do not provide quantitative information for the prediction and control of crack width affected by the initiation and propagation of corrosion. Considering life span of concrete bridges, an improved control equation about the crack width affected by time-dependent general corrosion is proposed. The developed corrosion and crack width control models can be used for the design and the maintenance of prestressed and non-prestressed reinforcements by varying time, w/c, cover depth, and geometries of the sections. It can also help the rational criteria for the quantitative management and the prediction of remaining life of concrete structures.

• 대한토목학회논문집
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• 제5권4호
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• pp.103-111
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• 1985

본(本) 논문(論文)에서는 철근콘크리트 휨부재의 균열폭과 균열간격 결정에 관한 연구(硏究)가 이루어 졌다. 철근콘크리트 휨부재의 균열폭 및 균열간격의 유도는 최근에 진전된 균열이론에 의거하였으며, 설계(設計) 및 해석시(解析時)에 실제적으로 사용할 수 있는 균열폭 및 균열간격 예측 공식을 제안하였다. 제안된 공식과의 비교를 위하여 철근콘크리트보에 대한 균열거동 실험이 수행되었다. 본(本) 예측 공식(公式)을 본(本) 연구(硏究)의 실험결과 및 타연구자(他硏究者)의 실험자료와 비교한 결과 만족스런 결과를 얻었다. 본(本) 연구(硏究)에서 제안된 공식을 현재 ACI 시방서(示方書)에서 채택하고 있는 Gergely & Lutz 공식(公式)과도 비교한 결과, 본(本) 공식(公式)이 거의 모든 경우, 더 정확한 예측을 하고 있음을 알 수 있었으며, 실제 설계 및 해석시에 지침이 될 수 있을 것으로 사료된다.

• Structural Engineering and Mechanics
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• 제15권2호
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• pp.159-180
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• 2003

In this paper spacing and width of flexural cracks in reinforced concrete beams are determined using two-dimensional finite element analysis. At early loading stages on the beam the primary crack spacing is based on the slip length, which is the development length required to resist the steel stress increment that occurs at a cracked section on the formation of the first flexural crack. A semi-empirical formula is presented in this paper for the determination of the slip length for a given beam. At higher load levels, the crack spacing is based on critical crack spacing, which is defined as the particular crack spacing that would produce a concrete tensile stress equal to the flexural strength of concrete. The resulting crack width is calculated as the relative difference in extensions of steel reinforcement and adjacent concrete evaluated at the cracked section. Finally a comparative study is undertaken, which indicates that the spacing and width of cracks calculated by this method agree well with values measured by other investigators.