Journal articles on the topic 'Crack width'
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1
Ge, Bao Zhen, Qi Jun Luo, Bin Ma, Yong Jie Wei, Bo Chen, and Sheng Zhao Jiang. "The Algorithm to Measure Crack Width with Incircle." Advanced Materials Research 684 (April 2013): 481–85. http://dx.doi.org/10.4028/www.scientific.net/amr.684.481.
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Crack is a major defect of buildings. Digital image methods are often used to detect cracks. But incorrect or un-unique results may be inverted with an inappropriate algorithm. An image processing way is presented to obtain the sole width value. Meanwhile, the crack with several branches can be measured. In the processing, the crack skeleton is first calculated. Then each of the points on the skeleton is served as a center of a group of circles, one by one. The radius of the circles is increased step by step. The iterations will not stop until any point in the circle goes out of the crack. Thus the last circle in the iteration is served as an incircle of the crack. The diameter of the incircle is a crack width in a given skeleton point. The maximal and average width of the crack will be calculated after all the incircles with all the skeleton point are traversed. The experimental results show the proposed method can extract the width of cracks in a complex context.
2
Zhu, Hongguang, Qingjie Huo, Jingchong Fan, Sen Pang, Hongyu Chen, and Cheng Yi. "The Depth–Width Correlation for Shrinkage-Induced Cracks and Its Influence on Chloride Diffusion into Concrete." Materials 13, no. 12 (June 17, 2020): 2751. http://dx.doi.org/10.3390/ma13122751.
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This study examined the depth–width correlation of actual shrinkage-induced cracks and its influence on the diffusion properties of concrete. An experimental setup of restrained slabs was utilized to induce the shrinkage cracks, and the geometry characteristics were quantified with image analysis technology. The results indicated the depth–width scaling λ of shrinkage cracks increases with crack width and was almost constant when the crack width was approximately 0.3 mm or more, and the tip angle of shrinkage cracks is about 1–2 degrees. The diffusion coefficients of concretes were measured by a conductivity test method. A series-parallel composite model with λ was devised to evaluate the diffusivity of shrinking cracked concrete. It was shown that the equivalent diffusion coefficient depended greatly on the crack depth instead of the crack width, and it was found to be a nonlinear relationship versus the width combining with λ . The diffusion coefficient of the crack Dcr was correlated to both crack width and λ , and increased with crack width. When the crack width is higher than 0.2 mm Dcr becomes constant, where the value obtained was 87% of the diffusion coefficient in free solution.
3
Li, Yue, Juhui Zhang, Zhongguo Guan, and Youliang Chen. "Experimental Study on the Correlation between Crack Width and Crack Depth of RC Beams." Materials 14, no. 20 (October 10, 2021): 5950. http://dx.doi.org/10.3390/ma14205950.
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The depth of cracks propagating inside reinforcement concrete (RC) components is barely able to be detected by visual inspection. Without any help from facilities, crack width can provide us with a proper way to explore the depth of cracks developing. Therefore, this paper tried to explore the correlation between crack width on the surface and crack depth. A static loading test was conducted on eight RC beams, considering the variation of concrete strength, cover, and reinforcement ratio. The test results indicate that concrete strength has a certain impact on cracking load and the propagation of cracks is mainly related to reinforcement ratio. The linear changes in load and crack width can be found. Originally, crack depth markedly increased with loading, but when restricted by compression zone of concrete and the height of beams, crack depth stopped extending finally. The correlation between crack width and crack depth was analyzed by studying work phases of a cross-section and experimental data. The fitting function achieved in this paper was determined to be a good agreement between the theoretical and the experimental relationship.
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Shi, Nan Nan, and Da Hai Huang. "Experimental Study on Early-Age Crack of RC Using TSTM." Advanced Materials Research 919-921 (April 2014): 119–22. http://dx.doi.org/10.4028/www.scientific.net/amr.919-921.119.
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Thermal stress is a major cause of early-age crack of massive concrete structures. In order to analyze the influencing factors of concrete crack under thermal loads, a series of tests were conducted using the improved Temperature Stress Testing Machine (TSTM). Effects of temperature on crack resistance of concrete were studied on different concrete placing temperatures and curing temperatures. Meanwhile, the roles of reinforcement on concrete crack resistance and crack-width limitation were quantitative analyzed, which compare cracks of plain concrete and reinforced concrete with the same mix proportion. The results indicate that reinforcement can improve the crack resistance of the structures by approximately twenty percents, which against the engineering experience. After concrete cracks, the cracks photos show that reinforcement can induce the smaller cracks formation, and the crack width of reinforced concrete is about 1/10 of the plain concrete crack width.
5
Li, Xiaoke, Songwei Pei, Kunpeng Fan, Haibin Geng, and Fenglan Li. "Bending Performance of Steel Fiber Reinforced Concrete Beams Based on Composite-Recycled Aggregate and Matched with 500 MPa Rebars." Materials 13, no. 4 (February 19, 2020): 930. http://dx.doi.org/10.3390/ma13040930.
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To promote the engineering application of recycled aggregate for concrete production with good adaptability and economic efficiency, this paper performed a campaign to investigate the flexural performance of steel fiber reinforced composite-recycled aggregate concrete (SFR-CRAC) beams matched with 500 MPa longitudinal rebars. The composite-recycled aggregate has features of the full use recycled fine aggregate and small particle recycled coarse aggregate, and the continuous grading of coarse aggregate ensured by admixing the large particle natural aggregate about 35% to 45% in mass of total coarse aggregate. The properties of SFR-CRAC have been comprehensively improved by using steel fibers. With a varying volume fraction of steel fiber from 0% to 2.0%, 10 beam specimens were produced. The flexural behaviors of the beams during the complete loading procedure were experimentally studied under a four-point bending test. Of which the concrete strain at mid-span section, the appearance of cracks, the crack distribution and crack width, the mid-span deflection, the tensile strain of longitudinal rebars, and the failure patterns of the beams were measured in detail. Results indicated that the assumption of plane cross-section held true approximately, the 500 MPa longitudinal rebars worked at a high stress level within the limit width of cracks on reinforced SFR-CRAC beams at the normal serviceability, and the typical failure occurred with the yield of 500 MPa longitudinal rebars followed by the crushed SFR-CRAC in compression. The cracking resistance, the flexural capacity, and the flexural ductility of the beams increased with the volume fraction of steel fiber, while the crack width and mid-span deflection obviously decreased. Finally, by linking to those for conventional reinforced concrete beams, formulas are suggested for predicting the cracking moment, crack width, and flexural stiffness at normal serviceability, and the ultimate moment at bearing capacity of reinforced SFR-CRAC beams.
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Yoon, In Seok, Erik Schlangen, Mario R. de Rooij, and Klaas van Breugel. "The Effect of Cracks on Chloride Penetration into Concrete." Key Engineering Materials 348-349 (September 2007): 769–72. http://dx.doi.org/10.4028/www.scientific.net/kem.348-349.769.
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This study is focused on examining the effect of critical crack width in combination with crack depth on chloride penetration into concrete. Because concrete structures have to meet a minimum service-life, critical crack width has become an important parameter. Specimens with different crack width / crack length have been subjected to rapid chloride migration testing (RCM). The results of this study show a critical crack width of about 0.012 mm. Cracks smaller than this critical crack width are considered not to have a significant influence on the rate of chloride transport inwards, while chloride penetration does proceed faster above this critical crack width.
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Yang, Bin, Hua Tan, Jia Xi Deng, and Chan Pang. "Influences on the Axle Load Stress of the Cement-Concrete Pavement Structure Caused by the Crack or Cutting Crack of the Semi-Rigid Base." Advanced Materials Research 857 (December 2013): 200–203. http://dx.doi.org/10.4028/www.scientific.net/amr.857.200.
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Some horizontal cracks will appear during the strength formation of the semi-rigid base, for the influences of dry shrinkage and temperature shrinkage exist, so the engineers often adopt the manual method of equidistant cutting crack to avoid the irregular cracks. In order to analyse the influences on the axle load stress of the cement-concrete pavement slab which caused by the width and position of the base cracks or cutting cracks, the 3D FEM was used to study them under the different working conditions considering the crack, width and position. By the above research, the results show the existing cracks affect the integrity and continuity of the pavement structure; The crack width has no large influence on the stress of the pavement slab, while the base stress decreases apparently with the increasing width, and it becomes stable finally; The stress of the pavement slab is maximum when the crack or cutting crack is located in the middle, while it's small when the crack or cutting crack is located in the one fourth of the pavement slab.
8
Shen, Bei, Yinghua Ye, Bo Diao, and Xiaoning Zheng. "Mechanical Performance and Chloride Diffusivity of Cracked RC Specimens Exposed to Freeze-Thaw Cycles and Intermittent Immersion in Seawater." Advances in Materials Science and Engineering 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/5973467.
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The effects of crack width on chloride ingress and mechanical behavior of reinforced concrete (RC) specimens were experimentally studied after exposure to 300 cycles of freeze-thaw and seawater immersion (75 times). Cracks were induced prior to exposure by an eccentric compression load which was sustained until the end of the exposure period. The maximum cracks widths induced in the four column specimens were 0, 0.06, 0.11, and 0.15 mm, respectively. Results show that when the crack width was less than 0.06 mm, the effect of cracks on chloride ingress could be neglected. However, when the crack width was more than 0.11 mm, chloride ingress was accelerated. Results of static loading tests show that both yield load and ultimate load of RC columns decreased as crack width increased. When the crack width was 0.15 mm, yield load and ultimate load of RC column specimen decreased by 17.0% and 18.9%, respectively, compared to a specimen without cracks. It was concluded that crack width significantly promoted local chloride ingress and mechanical performance degradation of RC structures in cold coastal regions or exposed to deicing salts.
9
Shuang-rui, Chen, Shi Zheng, and Yan Quan-sheng. "Concrete Crack Width Detecting System for Android Platform." Open Civil Engineering Journal 9, no. 1 (October 13, 2015): 846–51. http://dx.doi.org/10.2174/1874149501509010846.
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In order to measure crack width accurately and automatically, an Android-based Automatic Crack Width Measuring System (ACWMS) has been developed, taking advantage of the high portability of Android devices. After capturing the image using mobile phone camera, the image is processed by image processing techniques, including graying, binaryzation, denoising and edge recognition. A specified algorithm is executed to calculate the crack width according to the provided edge data. Measurements has been done to each of the 10 cracks in the same concrete beam, using Samsung Galaxy S3 mobile phone and WYSX-40X Crack detector, respectively. Test result shows that the maximum crack width accuracy reaches 95.26%, which satisfies the construction needs. Therefore, this system can greatly improve the efficiency and accuracy during crack width measurement.
10
Carrasco, Miguel, Gerardo Araya-Letelier, Ramiro Velázquez, and Paolo Visconti. "Image-Based Automated Width Measurement of Surface Cracking." Sensors 21, no. 22 (November 12, 2021): 7534. http://dx.doi.org/10.3390/s21227534.
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The detection of cracks is an important monitoring task in civil engineering infrastructure devoted to ensuring durability, structural safety, and integrity. It has been traditionally performed by visual inspection, and the measurement of crack width has been manually obtained with a crack-width comparator gauge (CWCG). Unfortunately, this technique is time-consuming, suffers from subjective judgement, and is error-prone due to the difficulty of ensuring a correct spatial measurement as the CWCG may not be correctly positioned in accordance with the crack orientation. Although algorithms for automatic crack detection have been developed, most of them have specifically focused on solving the segmentation problem through Deep Learning techniques failing to address the underlying problem: crack width evaluation, which is critical for the assessment of civil structures. This paper proposes a novel automated method for surface cracking width measurement based on digital image processing techniques. Our proposal consists of three stages: anisotropic smoothing, segmentation, and stabilized central points by k-means adjustment and allows the characterization of both crack width and curvature-related orientation. The method is validated by assessing the surface cracking of fiber-reinforced earthen construction materials. The preliminary results show that the proposal is robust, efficient, and highly accurate at estimating crack width in digital images. The method effectively discards false cracks and detects real ones as small as 0.15 mm width regardless of the lighting conditions.
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Lekshmi, U., Margrete Sherin Joseph, and S. Krishna Kumar. "Experimental Study on Crack Width Evaluation of R.C Beams and Comparison with Various Codes." Applied Mechanics and Materials 857 (November 2016): 95–100. http://dx.doi.org/10.4028/www.scientific.net/amm.857.95.
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Development of cracks is the most common cause of premature deterioration in structures. For the design of reinforced concrete structures, crack width is one of the most important factors to be considered. It also affects the serviceability of reinforced concrete members. This paper presents the experimental study on crack width evaluation of R.C beams and comparison with various international codes. Following international codes: Eurocode2 1992-1 (2009), Egyptian Code ECP203-2007, ACI Code 318-95, 318-05, BS 8110-1997/IS: 456-2000 was used to calculate the crack width for comparison purpose.
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Wu, Jun Hua, and Song Yang. "Study on Crack Spacing and Width of Expansive Soil due to Evaporation." Advanced Materials Research 690-693 (May 2013): 728–33. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.728.
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The expressions of crack spacing and width were deduced from the aspect of force-balance. The concept of maximum spacing and width of crack were put forward accordingly and they were verified and consistent with the site test results. Their relationships with soil parameters were discussed in detail. The new cracks do not appear until the spacing of adjacent cracks is greater than the maximum spacing, and the width of cracks will not be greater than the maximum width. The maximum spacing and width are judgments for describing and represent the final characteristic of cracks due to evaporation.
13
Zhang, Sheng, Longfei Wang, and Mingzhong Gao. "Numerical Simulation of the Influence of Width of a Prefabricated Crack on the Dimensionless Stress Intensity Factor of Notched Semi-Circular Bend Specimens." Shock and Vibration 2019 (May 5, 2019): 1–10. http://dx.doi.org/10.1155/2019/3291730.
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To analyze the effect of the width of a prefabricated crack on the dimensionless stress intensity factor of notched semi-circular bend (NSCB) specimens, ABAQUS software was employed to perform numerical calibration of the crack tip stress intensity factor for the width of prefabricated cracks in the range of 0.0∼2.0 mm. The relative errors of the dimensionless stress intensity factor for different widths of prefabricated cracks were analyzed. The results indicate that the dimensionless stress intensity factor shows an approximate linear increase as the width of the prefabricated crack increases. The longer is the length of the prefabricated crack, the “faster” is the increase in speed. The effect of the dimensionless support spacing on the increase in the speed of the dimensionless stress intensity factor due to the increase in crack width is minimal. When the prefabricated crack width is 2.0 mm, the maximum relative error of the dimensionless stress intensity factor is 4.325%. The new formula for the dimensionless stress intensity factor that eliminates the influence of the width of a prefabricated crack is given, which provides a theoretical basis for the more accurate fracture toughness value measured using an NSCB specimen.
14
Wang, Qiannan, Guoshuai Zhang, Yunyun Tong, and Chunping Gu. "A Numerical Study on Chloride Diffusion in Cracked Concrete." Crystals 11, no. 7 (June 25, 2021): 742. http://dx.doi.org/10.3390/cryst11070742.
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The cracks in concrete are a fast transport path for chlorides and influence the service life of concrete structures in chloride environments. This study aimed to reveal the effect of crack geometry on chloride diffusion in cracked concrete. The chloride diffusion process in cracked concrete was simulated with the finite difference method by solving Fick’s law. The results showed that the apparent chloride diffusivity was lower in more tortuous cracks, and the cracks with more narrow points also showed lower apparent chloride diffusivity. For tortuous cracks, a higher crack width meant relatively more straight cracks, and consequently, higher apparent chloride diffusivity, while a lower crack width resulted in more tortuous cracks and lower apparent chloride diffusivity. The crack depth showed a more significant influence on the chloride penetration depth in cracked concrete than crack geometry did. Compared with rectangular and V-shaped cracks, the chloride diffusion process in cracked concrete with a tortuous crack was slower at the early immersion age. At the same crack depth, the crack geometry showed a marginal influence on the chloride penetration depth in cracked concrete during long-term immersion.
15
Liu, Guangyan, Song Mu, Jingshun Cai, Deqing Xie, Ying Zhou, and Xiaocheng Zhou. "Influence of Crack on Concrete Damage in Salt-Freezing Environment." Advances in Materials Science and Engineering 2021 (June 16, 2021): 1–13. http://dx.doi.org/10.1155/2021/5543286.
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The damage development trend of concrete with cracks in salt-freezing environment is systematically studied. The cracks are also tested in intact concrete for comparison, and crack characterization is introduced. The mass loss, the relative dynamic elastic modulus, and the change of crack width are analyzed. Results show that the crack width increases as the salt-freezing cycle progresses. Following the development trend of the cracks, concrete cracks can be divided into three categories: 0–40, 40–100, and 100–150 μm. The mass loss increases significantly, and the change of relative dynamic elastic modulus decreases in concrete with an initial crack compared with the intact concrete. When the crack width is 80 μm, a maximum mass loss rate of 0.19% and a minimum relative dynamic elastic modulus of 75.81% can be obtained. These test results prove that crack and freeze-thaw coupling can influence each other and accelerate the failure of concrete. Overall, this study can serve as a basis for the durability design and life improvement of concrete structures.
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Goszczyńska, Barbara, Wiesław Trąmpczyński, and Justyna Tworzewska. "Analysis of Crack Width Development in Reinforced Concrete Beams." Materials 14, no. 11 (June 3, 2021): 3043. http://dx.doi.org/10.3390/ma14113043.
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The reliability and durability of reinforced concrete structures depend on the amount of concrete cracking. The risk associated with cracks generates a need for diagnostic methods for the evaluation of reinforced concrete structures. This paper presents the results of a study of 10 single-span reinforced concrete beams to follow the process of crack formation and changes in their width. The beams were loaded to failure with two forces in a monotonic manner with unloading and in a cyclic manner. Continuous observation of the crack formation process was provided by the digital image correlation system. The simplified method for estimating the maximum crack width is proposed. The presented results confirmed the stochastic character of the process of crack formation and development. The maximum crack widths calculated on the basis of the proposed formula were on the safe side in relation to those calculated according to Eurocode 2. It was also confirmed that the distances between cracks do not depend on the loading manner. Hence the density function describing the distribution of distances between cracks can be used to assess the condition of reinforced concrete elements. The research has also shown the suitability of the DIC system (ARAMIS) for testing concrete elements.
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Tomczak, Kamil, Jacek Jakubowski, and Przemysław Fiołek. "Method for Assessment of Changes in the Width of Cracks in Cement Composites with Use of Computer Image Processing and Analysis." Studia Geotechnica et Mechanica 39, no. 2 (June 27, 2017): 73–80. http://dx.doi.org/10.1515/sgem-2017-0017.
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Abstract Crack width measurement is an important element of research on the progress of self-healing cement composites. Due to the nature of this research, the method of measuring the width of cracks and their changes over time must meet specific requirements. The article presents a novel method of measuring crack width based on images from a scanner with an optical resolution of 6400 dpi, subject to initial image processing in the ImageJ development environment and further processing and analysis of results. After registering a series of images of the cracks at different times using SIFT conversion (Scale-Invariant Feature Transform), a dense network of line segments is created in all images, intersecting the cracks perpendicular to the local axes. Along these line segments, brightness profiles are extracted, which are the basis for determination of crack width. The distribution and rotation of the line of intersection in a regular layout, automation of transformations, management of images and profiles of brightness, and data analysis to determine the width of cracks and their changes over time are made automatically by own code in the ImageJ and VBA environment. The article describes the method, tests on its properties, sources of measurement uncertainty. It also presents an example of application of the method in research on autogenous self-healing of concrete, specifically the ability to reduce a sample crack width and its full closure within 28 days of the self-healing process.
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Katinic, Marko, Drazan Kozak, Mirko Pavisic, and Pejo Konjatic. "A numerical creep analysis on the interastion of twin parallel edge cracks in finite width plate under tension." Thermal Science 18, suppl.1 (2014): 159–68. http://dx.doi.org/10.2298/tsci130212181k.
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In many practical situations, high-temperature structures and components contain more than one crack. An interaction of such multiple cracks has significant influence on the service life of structures and components. In this paper, the interaction of two identical parallel edge cracks in a finite plate subjected to the remote tension is numerically analyzed. The results show that interaction effect of multiple cracks at creep regime is obviously greater than at linear elastic regime. The intensity of creep crack interaction increases with increasing creep exponent m. The crack intensity and the crack interaction limit at creep regime depend on crack distance ratio d/a, crack width ratio a/W and creep exponent m.
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Soehardjono, Agoes, and Candra Aditya. "ANALYSIS OF THE EFFECT OF SLAB THICKNESS ON CRACK WIDTH IN RIGID PAVEMENT SLABS." EUREKA: Physics and Engineering, no. 2 (March 29, 2021): 42–51. http://dx.doi.org/10.21303/2461-4262.2021.001693.
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Cracks that occur in rigid pavements include longitudinal cracks, transverse cracks, and corner cracks. The relatively large crack width not only spoils the aesthetics of the concrete structural elements but can also lead to structural failure. This study aims to determine the crack width of a rigid pavement concrete slab located above the subgrade which is considered a beam on an elastic foundation, so that a minimum rigid pavement concrete slab thickness can be recommended. The specimen will be observed at various thicknesses to obtain the optimum thickness. The load used is a centralized monotonous load, which represents the load of the truck vehicle. The research limitation is using a test object in the form of a concrete plate measuring 2000x600 mm which is placed on the ground with CBR=6 %. The quality of reinforced concrete slabs is fc'=40 MPa and fy=440.31 MPa. The thickness of the concrete slab varies between 100 mm, 150 mm, and 200 mm. The slab placed on the ground is then given a central loading in the form of a centralized monotonic load. The loading range starts from a load of 2–180 kN with a load interval of 2 kN. The experimental results show that the rigid pavement slab has a bending failure so that the crack pattern that occurs begins with the first crack on the underside of the slab. The crack pattern in terms of slab thickness variation has a similar pattern. The initial crack width on the slab is 0.04 mm. The thicker the slab smaller the crack width at the same load. Based on the maximum allowable crack width=0.3 mm. For loads between (80–100) kN (Road Class I, II, and III), a minimum thickness of rigid pavement slabs (70–80) mm is recommended. For loads between (130–140) kN, the minimum thickness of the rigid pavement slab (105–115) mm is recommended
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Shehata, Hesham M., Yasser S. Mohamed, Mohamed Abdellatif, and Taher H. Awad. "Crack Width Estimation Using Feed and Cascade Forward Back Propagation Artificial Neural Networks." Key Engineering Materials 786 (October 2018): 293–301. http://dx.doi.org/10.4028/www.scientific.net/kem.786.293.
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Automatic crack inspection techniques that limit the necessity of human have the potential to lower the cost and time of the process. In this study, a maximum crack width estimation approach is presented. Seventy nine segments of cracks are used for training the neural networks and twenty six segments are used for examination. The maximum width for each segment is measured using laser scanning microscope and segment image is captured and magnified using the microscope camera in order to obtain the extracted crack profile number of pixels. Feed and cascade forward back propagation artificial neural networks are designed and constructed. The input and output for the networks are the crack width in terms of number of pixels and the maximum estimated crack width respectively. It is shown that, the artificial neural networks technique can effectively be used to estimate the crack width. The feedforward back propagation structure which is designed with two layers and training function TRAINLM gives the best results in examination.
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Yang, Gang, Jianchao Wu, and Qing Hu. "Rapid detection of building cracks based on image processing technology with double square artificial marks." Advances in Structural Engineering 22, no. 5 (November 1, 2018): 1186–93. http://dx.doi.org/10.1177/1369433218810183.
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In order to measure the crack width of dangerous buildings quickly and accurately, this article presents a new crack width measurement method, which is based on image processing technology, using double square artificial markers to identify building cracks and calculate crack width. It makes two 10 mm × 10 mm black square artificial marks and places them near the sides of the crack. Then it uses a camera to collect crack images and transfer photos to a computer. The crack image is subjected to image graying, binarization, denoising, image segmentation, and pixel calibration based on the image processing technique. Finally, the actual length value of the unit pixel is calculated. Then it can calculate the actual width of the crack according to the number of pixels included in the test crack. The calculation results show that the accuracy of the proposed method is 98.56% compared with the measured data. The calculation method can accurately and effectively detect the crack width of dangerous buildings and improve work efficiency. At the same time, it can avoid long hours of work in dangerous operating environments.
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Wang, Xianghong, Jun Liu, Zhimin Luo, and Hongwei Hu. "Influence of Different Crack Factors on Acoustic Wave Signals Using Orthogonal Analysis." Materials Evaluation 79, no. 2 (February 1, 2021): 136–48. http://dx.doi.org/10.32548/2021.me-04156.
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The existence of cracks in key components of engineering equipment is a huge threat to the safe operation of the equipment. The influence of four factors (length, location, orientation, and width of the crack) on the attenuation characteristic of signal propagation is studied through simulation and experiment. The orthogonal experimental design is applied to design the simulation scheme, and the signal affected by the four factors is simulated by the finite-difference time-domain method. The degree of influence of the different factors is evaluated by conducting an analysis of range and an analysis of variance. The results show that the influence of crack length and location on signal relative attenuation is more remarkable according to the significance level α = 0.05, followed by crack orientation and crack width. The attenuation trend in the experimental results is similar to the simulation. Therefore, the longer the crack length is, the easier it is to be detected by the acoustic wave technique, while the effect of crack orientation and crack width on identifying cracks is limited. The study successfully establishes the relationship between signal parameters and crack factors and offers a theoretical foundation for evaluating the status of cracks in key components.
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Yankelevsky, David Z., Yuri S. Karinski, and Vladimir R. Feldgun. "Analytical Modeling of Crack Widths and Cracking Loads in Structural RC Members." Infrastructures 7, no. 3 (March 14, 2022): 40. http://dx.doi.org/10.3390/infrastructures7030040.
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Crack width is a major performance criterion in reinforced-concrete structures, in general, and is of utmost importance in ensuring bridge performance, in particular. A reliable theory-based method is required to assess crack widths and gain insight into their dependence on material, geometry, and loading parameters. A new, exact analytical method is proposed for a one-dimensional reinforced concrete element based on equilibrium, constitutive, and kinematic relationships, accounting for the geometrical and material behavior of the concrete and reinforcement. A linear interfacial bond stress slip is assumed to represents the small slips associated with the limited allowed crack width. Closed-form expressions have been developed and a wealth of information can be calculated immediately, such as the cracking load levels, the crack width dependence on the load level, the expected number of cracks, and the cracks spacing. The entire nonlinear force-displacement relationship of a cracked reinforced-concrete element may be depicted, demonstrating the tension-stiffening behavior that depends on the variations in the crack width throughout the loading history. Comparisons of the model with experimental data demonstrate very good agreement.
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Wang, Xiao-Yong, and Li-Na Zhang. "Simulation of Chloride Diffusion in Cracked Concrete with Different Crack Patterns." Advances in Materials Science and Engineering 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/1075452.
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Chloride-induced corrosion of steel rebar is one of the primary durability problems for reinforced concrete structures in marine environment. Furthermore, if the surfaces of concrete structures have cracks, additional chloride can penetrate into concrete through cracked zone. For chloride ingression into cracked concrete, former researches mainly focus on influence of crack width on chloride diffusion coefficients. Other crack characteristics, such as chloride depth, crack shape (equal-width crack or tapered crack), crack density, and spacing, are not studied in detail. To fill this gap, this paper presents a numerical procedure to simulate chloride ingression into cracked concrete with different crack geometry characteristics. Cracked concrete is divided into two parts, sound zone and cracked zone. For stress-free concrete, the diffusion coefficient of sound zone is approximately assumed to be the same as sound concrete, and the diffusion coefficient of cracked zone is expressed as a piecewise function of crack width. Two-dimensional finite element method is used to determine chloride concentration. It is found that, with the increasing of crack width, crack depth, and crack amount, chloride ingression will aggravate. The analysis results generally agree with experimental results.
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Zhan, Xue Fang, and Yu Hui Zhang. "Influence of Traffic Load on the Crack Widths of Full Jointless Bridges." Applied Mechanics and Materials 847 (July 2016): 401–6. http://dx.doi.org/10.4028/www.scientific.net/amm.847.401.
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Traffic load not only increases the original crack widths of the reinforced approach pavement of full jointless bridges, but also generates the development of new small cracks. Using lab experiments, this paper mainly studies the influence of traffic load on the crack width of the approach pavement of full jointless bridges. The results show that the load of traffic not only increases the crack width, but also increases the vertical settlement. In order to control the crack width we need to consider the influence of the traffic load. And the traffic load influence factor here we choose to be equal to 1.45.
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Colom, Mateu, Javier Rodríguez-Aseguinolaza, Arantza Mendioroz, and Agustín Salazar. "Sizing the Depth and Width of Narrow Cracks in Real Parts by Laser-Spot Lock-In Thermography." Materials 14, no. 19 (September 28, 2021): 5644. http://dx.doi.org/10.3390/ma14195644.
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We present a complete characterization of the width and depth of a very narrow fatigue crack developed in an Al-alloy dog bone plate using laser-spot lock-in thermography. Unlike visible micrographs, which show many surface scratches, the thermographic image clearly identifies the presence of a single crack about 1.5 mm long. Once detected, we focus a modulated laser beam close to the crack and we record the temperature amplitude. By fitting the numerical model to the temperature profile across the crack, we obtain both the width and depth simultaneously, at the location of the laser spot. Repeating the process for different positions of the laser spot along the crack length, we obtain the distribution of the crack width and depth. We show that the crack has an almost constant depth (0.7 mm) and width (1.5 µm) along 0.7 mm and features a fast reduction in both quantities until the crack vanishes. The results prove the ability of laser-spot lock-in thermography to fully characterize quantitatively narrow cracks, even below 1 µm.
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Zhao, Sizeng, Fei Kang, and Junjie Li. "Non-Contact Crack Visual Measurement System Combining Improved U-Net Algorithm and Canny Edge Detection Method with Laser Rangefinder and Camera." Applied Sciences 12, no. 20 (October 21, 2022): 10651. http://dx.doi.org/10.3390/app122010651.
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Cracks are the main damages of concrete structures. Since cracks may occur in areas that are difficult to reach, non-contact measurement technology is required to accurately measure the width of cracks. This study presents an innovative computer vision system combining a camera and laser rangefinder to measure crack width from any angle and at a long distance. To solve the problem of pixel distortion caused by non-vertical photographing, geometric transformation formulas that can calculate the unit pixel length of the image captured at any angle are proposed. The complexity of crack edge calculation and the imbalance of data in the image are other problems that affect measurement accuracy, and a combination of the improved U-net convolutional networks algorithm and Canny edge detection method is adopted to accurately extract the cracks. The measurement results on the different concrete wall indicate that the proposed system can measure the crack in a non-vertical position, and the proposed algorithm can extract the crack from different background images. Although the proposed system cannot achieve fully automated measurement, the results also confirm the ability to obtain the crack width accurately and conveniently.
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Yoon, Jonghyeon, Hyunkyu Shin, Mihwa Song, Heungbae Gil, and Sanghyo Lee. "A Crack Width Measurement Method of UAV Images Using High-Resolution Algorithms." Sustainability 15, no. 1 (December 27, 2022): 478. http://dx.doi.org/10.3390/su15010478.
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The need for maintenance is increasing due to the aging of facilities. In this study, we proposed a crack width measurement method for images collected at safe distances using UAVs (Unmanned Aerial Vehicles). It is a method of measuring the widths of cracks using a high-resolution (VDSR) algorithm, which measures by increasing the resolution of images taken at 3 m intervals on the wall where cracks exist. In addition, the crack width measurement value was compared with a general photographed image and a high-resolution conversion image. As a result, it was confirmed that the crack width measurement of the image to which the high resolution was applied was similar to the actual measured value. These results can help improve the practical applicability of UAVs for facility safety inspections by overcoming the limits of camera resolution and distances between UAVs and facilities introduced in the facility safety inspection. However, more detailed image resolution is required to quantitatively measure the crack width; we intend to improve this through additional studies.
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Song, Jing, and Yanzhen Zhao. "Quantitative evaluation of surface crack in ferromagnetic materials based on Bayesian network in eddy current testing." International Journal of Applied Electromagnetics and Mechanics 64, no. 1-4 (December 10, 2020): 1073–79. http://dx.doi.org/10.3233/jae-209423.
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Quantitative evaluation of surface cracks using detection signal is of great significance for accurate prediction of cracks in eddy current testing. It is very difficult to evaluate both the width and depth of small cracks. A quantitative evaluation method based on Bayesian network is proposed for estimating the width and depth of surface cracks in the ferromagnetic materials. First, the simulation model of eddy current testing (ECT) is established and verified by the experimental results. Then, the variation of induced voltage with crack size is studied. Four feature points of real and imaginary part of induced voltage of the receiver coil are selected to characterize the crack size. Finally, a Bayesian network is applied to evaluate the crack size based on numerical simulation results. The evaluation results show that Bayesian network can accurately estimate the width and depth of small cracks.
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Wu, Lizhou, Jianting Zhou, Jun Yang, Jingzhou Xin, Hong Zhang, and Bu Li. "Initiation and Fracture Characteristics of Different Width Cracks of Concretes under Compressional Loading." Applied Sciences 12, no. 10 (May 10, 2022): 4803. http://dx.doi.org/10.3390/app12104803.
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A stress concentration at a crack tip may cause fracture initiation even under low-stress conditions. The maximum axial stress theory meets the challenges of explaining the fracture propagation of a non-closed fracture of cracked concretes under compressional loading. Uniaxial loading tests of single-crack concrete specimens were carried out and a numerical simulation of fracture propagation under uniaxial compression was performed. The radial shear stress criterion for a mode-II fracture is proposed to examine the stress intensity factor (SIF) of the pre-crack specimens under compressional loading. When the maximum radial shear stress at the crack tip is larger than the maximum axial tensile stress, and the maximum dimensionless SIFs can satisfy frθmax/fθmax > 1 and frθmax/fθmax > KIIC/KIC (fθmax=KIe/σyπa and frθmax=KIIe/σyπa are maximum dimensionless mode-I and mode-II SIFs, respectively), the crack will extend along the direction of the maximum radial shear stress. The influence of the single-crack angle and width on the mechanical properties of the specimens was examined. The experimental and numerical results indicate that the existence of cracks can considerably weaken the strength of the specimen. The distribution and width of the cracks had a significant effect on the specimen strength. The strength of the concrete specimen initially decreased and then increased with increasing fracture angle. The failure mechanism and rupture angle of pre-crack brittle material while considering crack width will be discovered.
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Wang, Chao, Zengqiang Han, Yiteng Wang, Chuanying Wang, Jinchao Wang, Shuangyuan Chen, and Sheng Hu. "Fine Characterization Method of Concrete Internal Cracks Based on Borehole Optical Imaging." Applied Sciences 12, no. 18 (September 9, 2022): 9080. http://dx.doi.org/10.3390/app12189080.
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The internal cracks of concrete are very important in the safety evaluation of structures, but there is a lack of fine characterization methods at present. Borehole cameras are a piece of in situ borehole detection technology which can measure the structural elements of a borehole wall with high precision. In this paper, borehole camera technology is used to measure the concrete cracks of a tunnel floor, and the morphological characteristics (depth, width, and orientation) of the cracks are analyzed. The results show that the average extension depth of the crack extending from the orifice exceeds 1.195 m, and the width decreases with the increase in depth. The crack orientation is basically stable, with the maximum deviation of 19° at the orifice of different boreholes and 30° at different depths of the same borehole. The crack inside the concrete (not extending to the orifice) usually has a small extension depth and a relatively stable width, but the crack orientation changes greatly. The coarse aggregate and concrete interface have different effects on the extension direction of cracks. This paper also conducted a second measurement on two of the boreholes after an interval of 15 days, and found the difference in crack development in the two measurements. The work of this paper provides a new attempt for the detection and monitoring of concrete crack morphology.
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Kim, Sang-Hyo, Syed Haider Ali Shah, Sang-Kyun Woo, Inyeop Chu, and Chungwook Sim. "Probability-Based Crack Width Estimation Model for Flexural Members of Underground RC Box Culverts." Applied Sciences 12, no. 4 (February 16, 2022): 2063. http://dx.doi.org/10.3390/app12042063.
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Crack control for slabs and beams in current design practices in Korea are based on the Frosch’s model, which is adapted in ACI 318. It is more difficult to have consistent quality control in underground construction sites, such as the RC box culverts used for electric power distribution built below the ground level. There are more discrepancies between the as-built dimensions and the design dimensions provided in drawings in these structures. Due to this variability in construction error, the crack widths measured in such structures have higher potential to have more differences than the calculated values. Although crack control is a serviceability concern, if the owner chooses to have a target crack width that needs better control, crack width estimations can be improved by considering such construction variability. The probability-based crack width model suggested in this study will allow minimizing the discrepancies between the measured and calculated crack widths and provide reliable estimations of crack widths. Typical size of slabs and beams ranging between 300 mm (12 in.) to 500 mm (20 in.) used in underground RC box culverts in Korea were tested under the four-point bending test program. The thicker specimens had smaller bar spacings which created more cracks with smaller crack widths. However, with smaller crack widths generated in these specimens, there were more errors between the measurements and calculated values. From site investigations in Korea, the thickness of slabs in underground box culverts varied the most among all parameters. As a result, the bottom concrete covers had the highest variability. Bottom concrete covers and bar spacings are the two most important parameters in concrete crack control. A probability-based crack width estimation model for flexural members was developed in this study to consider this construction variability. Monte Carlo simulations were performed to evaluate the probabilistic characteristics of the design surface crack widths with a target width of either 0.3 mm (12 mils) or 0.5 mm (20 mils). The probabilistic models of design variables included in the crack width estimation model were generated based on field-collected information from construction sites in Korea. Because the surface crack widths in RC flexural members are sensitive to the construction errors of concrete cover depths, and since there are differences between the assumed and actual stress distribution closer to the reinforcing bars, the probability of having surface cracks of 0.3 mm width (12 mils) is found to be quite high, such as 89% at the positive moment region (mid-span, bottom surface) of the top slab in RC box culverts and 45% for the negative moment region (support area, top surface) of the top slab with current design practice. In order to ensure crack widths to be smaller than the design target width, probability-based crack width factors are recommended in this study to improve estimations depending on the selected target reliability levels.
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Lee, Ji-Sun, Hyun-Woo Kim, Jun-Seo Lee, Hyun-Soo An, and Chan-Moon Chung. "Microcapsule-Type Self-Healing Protective Coating That Can Maintain Its Healed State upon Crack Expansion." Materials 14, no. 20 (October 19, 2021): 6198. http://dx.doi.org/10.3390/ma14206198.
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The purpose of this study was to develop a microcapsule-type self-healing coating system that could self-heal cracks and then maintain the healed state even upon crack expansion. Mixtures consisting of a photoinitiator and two methacrylate components, bismethacryloxypropyl-terminated polydimethylsiloxane (BMT-PDMS) and monomethacryloxypropyl-terminated PDMS (MMT-PDMS), were transformed into viscoelastic semi-solids through photoreaction. The viscoelasticity of the reacted mixtures could be controlled by varying the mass ratio of the two methacrylates. Through a stretchability test, the optimal composition mixture was chosen as a healing agent. Microcapsules loaded with the healing agent were prepared and dispersed in a commercial undercoating to obtain a self-healing coating formulation. The formulation was applied onto mortar specimens, and then cracks were generated in the coating by using a universal testing machine (UTM). Cracks with around a 150-μm mean width were generated and were allowed to self-heal under UV light. Then, the cracks were expanded up to 650 μm in width. By conducting a water sorptivity test at each expanded crack width, the self-healing efficiency and capability of maintaining the healed state were evaluated. The B-M-1.5-1-based coating showed a healing efficiency of 90% at a 150-μm crack width and maintained its healing efficiency (about 80%) up to a 350-μm crack width. This self-healing coating system is promising for the protection of structural materials that can undergo crack formation and expansion.
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Li, Zai-Wei, Xiao-Zhou Liu, Hong-Yao Lu, Yue-Lei He, and Yun‐Lai Zhou. "Surface Crack Detection in Precasted Slab Track in High-Speed Rail via Infrared Thermography." Materials 13, no. 21 (October 29, 2020): 4837. http://dx.doi.org/10.3390/ma13214837.
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The surface crack of ballastless track slab can seriously reduce the serviceability and durability of high-speed railway (HSR). Aiming at accurately and efficiently detecting the slab cracks, this research proposes an infrared thermography (IRT)-based method for the surface crack, which is the most serious and common crack type in track slab. A three dimensional finite element (FE) model of IRT detection of concrete slab with surface cracks is established. The relation between the width of detectable cracks and the ambient temperature can be thereby obtained by inputting the measured thermodynamic parameters in the model. Parametric study shows that with ambient temperature higher than 15 °C, cracks with a width of no less than 0.2 mm can be well detected. Scale model test and field test are conducted, IRT method can effectively locate the slab surface cracks with width as small as 0.14 mm when ambient temperature is no less than 20 °C.
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Şahmaran, Mustafa, and İ. Özgür Yaman. "Influence of transverse crack width on reinforcement corrosion initiation and propagation in mortar beams." Canadian Journal of Civil Engineering 35, no. 3 (March 2008): 236–45. http://dx.doi.org/10.1139/l07-117.
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This paper discusses the relationship between crack widths, chloride diffusivity, and corrosion rate of cracked mortar beams. Flexural loads are introduced to generate crack widths ranging from 29 to 390 µm. The specimens were subjected to accelerated corrosion by immersion in a 5% NaCl solution and a constant voltage of 12 V. In addition, salt ponding tests were conducted to determine the chloride ion transport properties. The results showed that as the crack width increased, the effective diffusion coefficient (corrosion initiation) and mass loss of steel reinforcing bars due to the accelerated corrosion (corrosion propagation) also increased. For crack widths less than about 135 µm, the effect of crack width on the effective diffusion coefficient and mass loss of steel reinforcing bars embedded in mortar specimens was found to be marginal when compared with the virgin specimens. Therefore, it was concluded that the effect of crack width on the corrosion initiation and propagation period was more pronounced when the crack width is greater than about 135 µm. Moreover, a significant amount of self-healing was observed for the cracks that have widths below 50 µm when subjected to the NaCl solution exposure.
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Manea, Simona Eugenia, Vali Ifigenia Nicolof, and Teodor Sima. "Critical Stresses in Materials with Cracks." Revista de Chimie 70, no. 7 (August 15, 2019): 2442–46. http://dx.doi.org/10.37358/rc.19.7.7358.
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The fracture mechanics concepts, as well as the concepts introduced on the basis of principle of critical energy, correlated with strength of materials with cracks is analysed. The equivalent stress method of strength was applied to cracked materials, by using the concept of local critical stress. This one depends on the material behavior and the deterioration due to crack. Experimental results have been obtained with specimens of OL304 steel with different cracks. The influence of crack depth and crack width is put into evidence.
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Zhang, Shi Ping, Lan Zong, and Jia Ping Liu. "Chloride Diffusivity in Cracked Concrete." Advanced Materials Research 250-253 (May 2011): 113–17. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.113.
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A detailed observation on the penetration profile of chloride ions through a crack in concrete structures was carried out. Cracks were induced using a splitting tensile test, and average crack width was measured using an image analysis technique. Chemical analysis tests were conducted on cracked specimens, which were exposed to NaCl solution at a temperature of 20°C, after being cured for 28d. The results showed that the concrete specimens having cracks showed rapid penetration of chloride ion. The diffusion coefficient calculated according to Fick’s law also indicated that the chloride permeability increased with the increasing crack width.
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Solovyev, Sergey A., Anastasia A. Solovyeva, Alexander A. Kochkin, and Timur R. Akhmetov. "Reliability analysis of the existing reinforced concrete beams with normal cracks by rebar strength criteria." E3S Web of Conferences 220 (2020): 01043. http://dx.doi.org/10.1051/e3sconf/202022001043.
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The paper describes the problem of the reliability analysis for individual reinforced concrete (RC) beams by the rebar strength criterion in cross section with a normal crack. It is proposed to evaluate the stress in the rebar by measurements of the crack width at the level of the rebar using the functional dependence of the crack width and the strain (deformation) in the reinforcement. It is also proposed to replace the modulus of elasticity of steel reinforcement on the secant modulus of elasticity, taking into account the increased reinforcement strain in cross section with crack. The work considers two options of the crack width in beam: less and greater than the ultimate crack width. The reliability analysis of RC beams by the rebar strength is based on the possibility theory and fuzzy set theory by the reason of small statistical data from measurements on existing individual RC beams. The use of offered reliability analysis methods will allow preventing the failures of reinforced concrete beams and in some cases to obtain economic benefit from the possibility of further operation of RC beams with cracks, even with a crack width more than ultimate value.
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Mengel, Lena, Hans-Werner Krauss, and Dirk Lowke. "Water Transport through Cracked Concrete Structures—Effect of Mixture Proportion on Separating Crack Geometry and Permeability." Materials 15, no. 17 (August 23, 2022): 5807. http://dx.doi.org/10.3390/ma15175807.
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The increase in fluid transport due to separating cracks can lead to significant deterioration in the durability of reinforced concrete structures. Besides reinforcement and stress state, concrete mixture proportion has a significant effect on crack geometry. In this study, we investigated concrete mixtures with different aggregate size and shape, aggregate gradation, cement type and water-to-cement ratio with regard to crack geometry and resulting water permeation. Besides surface-crack width and length, we determined inner-crack width variation over depth and tortuosity by X-ray micro-computed tomography. Furthermore, we conducted permeation tests for each specimen. Among the mixture components tested, aggregates have the strongest effect on crack geometry and flow rate. Increasing aggregate size results in increasing tortuosity and decreasing flow rate. Furthermore, the replacement of round with angular aggregates results in slightly higher flow rates for a given crack width.
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Ghalehnovi, Mansour, Arash Karimipour, Jorge de Brito, and Hamid Reza Chaboki. "Crack Width and Propagation in Recycled Coarse Aggregate Concrete Beams Reinforced with Steel Fibres." Applied Sciences 10, no. 21 (October 28, 2020): 7587. http://dx.doi.org/10.3390/app10217587.
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Reducing the crack width is a vital feature for protecting rebars from corrosion. In this investigation, the impact of steel fibres (SFs) on the cracking of recycled coarse aggregate reinforced concrete (RCARC) beams was investigated. Twenty-seven reinforced concrete (RC) experimental samples (150 mm × 200 mm × 1500 mm) were manufactured. Shear rebars were considered with different spacings. Specimens were tested under a four-point flexural setup. Recycled coarse aggregate (RCA) from a destroyed building was employed at 0%, 50% and 100% by weight. SFs were added at three contents (0%, 1% and 2%) in order to reduce the crack width. The mid-span load–displacement relationship and the crack propagation and width were measured during the tests. Therefore, this study intended to assess the impact of utilising RCA and natural coarse aggregate on cracks’ spacing and propagation in RC beams when SFs were employed. The obtained outcomes were compared with the requirements of CSA S474, NS 3473E, EC2-04, CEB-FIP and ACI 224R-01. It was found that enough shear rebars should be provided through the beams to control the crack width and propagation, but that SFs enhanced the bending performance of RCARC with no shear rebars.
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Lai, Jun, Jian Cai, Qing-Jun Chen, An He, and Mu-Yang Wei. "Influence of Crack Width on Chloride Penetration in Concrete Subjected to Alternating Wetting–Drying Cycles." Materials 13, no. 17 (August 28, 2020): 3801. http://dx.doi.org/10.3390/ma13173801.
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To investigate the durability of reinforced concrete (RC) beams under the combined actions of transverse cracks and corrosion, corrosion tests were conducted on a total of eight RC beams with different water–cement ratios and cracking states. The effects of the transverse crack width, water–cement ratio, and the length of the wetting–drying cycle on the distribution of the free chloride concentration, the cross-sectional loss of the tensile steel bars, and the chloride diffusion coefficient are analyzed. The results show that the widths of the transverse crack and the water–cement ratio of concrete greatly affected the chloride profile and content of the RC beam specimens. Specifically, the chloride contents in all the cracked RC beams at the depth of the steel bar exceeded the threshold value of 0.15%. As the width of the cracks increased, the chloride concentration and penetration of the cracked concrete beam increased. However, the chloride concentration at the reinforcement position did not seem to be obviously affected by increasing the wetting–drying cycles from 182 days to 364 days. Moreover, the decrease of the water–cement ratio effectively inhibited the penetration of chloride ions in the RC beam specimens. In terms of the cross-sectional loss of the steel bars, the average loss of the steel bar increases with increasing crack width for the beams with 182-day cycles, while the effect of crack width on the average loss is not as noticeable for the beams with 364-day cycles. Finally, a model is proposed to predict the relationship between the crack width influence coefficient, μ, and the crack width, w, and this model shows good agreement with the experimental results.
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Abdul Halim, Siti Aisyah, Ruslizam Daud, Yazid Bajuri, S. K. Zaaba, Khairul Salleh Basaruddin, N. A. M. Zain, and Nurul Najwa Mansor. "The Relationship between Strain Energy Release Rate with Crack-to-Width Ratio of Human Phalanx Bone." Applied Mechanics and Materials 786 (August 2015): 141–46. http://dx.doi.org/10.4028/www.scientific.net/amm.786.141.
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Bone fracture can occur in all parts of human skeletal cortical bone including phalanx bone of finger bone. Sometime, it leaves permanent damage and a long period of recovery. This situation can be prevented if we understand the mechanics and the process of the bone fracture. This study aims is to evaluate stress shielding induced by crack interaction using a simple model on Linear Elastic Fracture Mechanics (LEFM). Numerical simulation had been carried out in this study to understand the stress shielding induced by crack interaction. The results revealed that the interaction of two cracks is directly proportional to the stress intensity factor (SIF) magnitude at crack tips. Finally, as the crack-to-width ratio increase and the strain energy release rate also increased.
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MAL, DIBYENDU, SUPARNA SINHA, TAPATI DUTTA, S. MITRA, and SUJATA TARAFDAR. "FRACTAL CRACK PATTERNS IN LAPONITE FILMS AND THEIR SCALING BEHAVIOR." Fractals 14, no. 04 (December 2006): 283–88. http://dx.doi.org/10.1142/s0218348x06003301.
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We study crack patterns in laponite films of different thickness. The patterns show a self-similarity under coarse-graining, the fractal dimension determined by box-counting has a value around 1.66, independent of film thickness. The cracks on layers of different thickness show a remarkable scaling bahavior. We have measured the cumulative area covered by the cracks versus minimum crack-width resolved. Curves representing crack area for different thickness collapse onto a single curve, when the crack widths are scaled by the film thickness.
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Zhang, Wei, Beibing Dai, Zhen Liu, and Cuiying Zhou. "Numerical algorithm of reinforced concrete lining cracking process for pressure tunnels." Engineering Computations 35, no. 1 (March 5, 2018): 91–107. http://dx.doi.org/10.1108/ec-11-2016-0394.
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Purpose The cracking of a reinforced concrete lining has a significant influence on the safety and leakage of pressure tunnels. This study aims to develop, validate and apply a numerical algorithm to simulate the lining cracking process during the water-filling period of pressure tunnels. Design/methodology/approach Cracks are preset in all lining elements, and the Mohr−Coulomb criterion with a tension cutoff is used in determining whether a preset crack becomes a real crack. The effects of several important factors such as the water pressure on crack surfaces (WPCS) and the heterogeneity of the lining tensile strength are also considered simultaneously. Findings The crack number and width increase gradually with the increase in internal water pressure. However, when the pressure reaches a threshold value, the increase in crack width becomes ambiguous. After the lining cracks, the lining displacement distribution is discontinuous and steel bar stress is not uniform. The measured stress of the steel bar is greatly determined by the position of the stress gauge. The WPCS has a significant influence on the lining cracking mechanism and should not be neglected. Originality/value A reliable algorithm for simulating the lining cracking process is presented by which the crack number and width can be determined directly. The numerical results provide an insight into the development law of lining cracks and show that the WPCS significantly affects the cracking mechanism.
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Xu, Xianghong, Wenjun Yuan, and Cheng Tian. "Dependence of Thermal Shock Crack on Specimen Width for Ceramic Materials." International Journal of Applied Mechanics 08, no. 03 (April 2016): 1650042. http://dx.doi.org/10.1142/s1758825116500423.
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Knowledge of size effect of thermal shock properties of ceramics is a prerequisite in engineering applications. In the present study, the size effect of the cracking in the ceramic materials subjected to water quenching has been experimentally conducted. Based on the Rizk model, the equivalent specimen width of the elastic strip with cracks is introduced and modified to describe the effect of cracks on the deformation of the elastic strip underwater quenching. It is found that the simulation obtained from the proposed modified model is in good agreement with the experimental results. And the reasons for the size effect of crack depth and crack growth into the compressive region are well analyzed by theoretical results. The proposed model is expected to provide a powerful tool to characterize and predict the size effect on thermal shock crack of ceramic materials.
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Ekaputri, J. J., M. S. Anam, Y. Luan, C. Fujiyama, N. Chijiwa, and D. H. E. Setiamarga. "Application of GGBFS and Bentonite to Auto-Healing Cracks of Cement Paste." Journal of Advanced Civil and Environmental Engineering 1, no. 1 (April 30, 2018): 38. http://dx.doi.org/10.30659/jacee.1.1.38-48.
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Cracks are caused by many factors. Shrinkage and external loading are the most common reason. It becomes a problem when the ingression of aggressive and harmful substance penetrates to the concrete gap. This problem reduces the durability of the structures. It is well known that self – healing of cracks significantly improves the durability of the concrete structure. This paper presents self-healing cracks of cement paste containing bentonite associated with ground granulated blast furnace slag. The self-healing properties were evaluated with four parameters: crack width on the surface, crack depth, tensile strength recovery, and flexural recovery. In combination with microscopic observation, a healing process over time is also performed. The results show that bentonite improves the healing properties, in terms of surface crack width and crack depth. On the other hand, GGBFS could also improve the healing process, in terms of crack depth, direst tensile recovery, and flexural stiffness recovery. Carbonation reaction is believed as the main mechanism, which contributes the self-healing process as well as the continuous hydration progress.
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Wu, Guangming, Haibo Bai, Luyuan Wu, Shixin He, and Bin Du. "Analysis of Factors Influencing Stability of Overlying Soil Layer on Thin Bedrock Based on Crack Development-Closure Test." Advances in Civil Engineering 2019 (December 31, 2019): 1–20. http://dx.doi.org/10.1155/2019/3648650.
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The water-blocking properties of the clay layer at the bottom of the Cenozoic overburden in China are an important factor influencing the safety of thin bedrock coal seam mining. Clay has remolding properties that are unlike the nonreversible characteristics of cracks in brittle rock, and failure cracks in clay can reclose or continue to expand under the influence of different external factors. In this work, the soil layer on top of thin bedrock is the research object, and the influences of the particle composition, water content, soil layer thickness, and crack width on the crack development-closure state of soil layer are analyzed by the orthogonal test method. Visual analysis shows that the order of influence of each factor on the stability of soil layer is the crack width, particle composition, soil layer thickness, and water content. The stability of soil layer decreases with increasing crack width and sand content and decreasing soil layer thickness; in addition, soil layer stability decreases first and then increases with increasing water content. Further variance analysis shows that the crack width and particle composition are key factors that impact the stability of soil layer and that the soil layer thickness has some influence, while the water content has little effect on the stability of soil layer. In addition, the crack will reclose when the sand content in soil is less than 50% and the crack width is less than or equal to 1.0 mm, and the soil layer is prone to further failure when the sand content in soil is more than 50% and the crack width is greater than or equal to 3.0 mm; when the soil layer thickness is 15.0 cm, its stability is better than when the soil layer thickness is 10.0 cm or 5.0 cm.
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Du, Fengyin, Zuquan Jin, Chuansheng Xiong, Yong Yu, and Junfeng Fan. "Effects of Transverse Crack on Chloride Ions Diffusion and Steel Bars Corrosion Behavior in Concrete under Electric Acceleration." Materials 12, no. 15 (August 5, 2019): 2481. http://dx.doi.org/10.3390/ma12152481.
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Cracks greatly impact the durability of concrete structures due to their influence on the migration of chloride ions and the corrosion process of steel bars. This study investigates the effects of transverse cracks on chloride diffusion and the corrosion behavior of two types of steel bars (low carbon steel and corrosion resistant steel) in fly ash concrete with 1 kg/m3 solution-polymerized super absorbent polymer. Electrochemical impedance spectroscopy was used to monitor the chloride-induced corrosion behavior of steel bars in concrete. The chloride profile around cracks was tested via chemical titration. The corrosion products diffusion area was photographed and measured to evaluate the influences of cracks on the corrosion degree of steel bars. Transverse cracks greatly influence the chloride ion transport. When their width is less than 0.15 mm, cracks exert little influence on both chloride diffusion and steel corrosion. When the crack width exceeds 0.15 mm, the chloride ion transmission coefficient is significantly improved and steel corrosion is accelerated. However, when the crack width exceeds 0.20 mm, this effect is gradually weakened. Based on the experimental data, a quantitative relationship between the crack width and the chloride ion transmission coefficient in electric acceleration was established.
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Zhong, Mianqing, Lichun Sui, Zhihua Wang, and Dongming Hu. "Pavement Crack Detection from Mobile Laser Scanning Point Clouds Using a Time Grid." Sensors 20, no. 15 (July 28, 2020): 4198. http://dx.doi.org/10.3390/s20154198.
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This paper presents a novel algorithm for detecting pavement cracks from mobile laser scanning (MLS) data. The algorithm losslessly transforms MLS data into a regular grid structure to adopt the proven image-based methods of crack extraction. To address the problem of lacking topology, this study assigns a two-dimensional index for each laser point depending on its scanning angle or acquisition time. Next, crack candidates are identified by integrating the differential intensity and height changes from their neighbors. Then, morphology filtering, a thinning algorithm, and the Freeman codes serve for the extraction of the edge and skeleton of the crack curves. Further than the other studies, this work quantitatively evaluates crack shape parameters: crack direction, width, length, and area, from the extracted crack points. The F1 scores of the quantity of the transverse, longitudinal, and oblique cracks correctly extracted from the test data reached 96.55%, 87.09%, and 81.48%, respectively. In addition, the average accuracy of the crack width and length exceeded 0.812 and 0.897. Experimental results demonstrate that the proposed approach is robust for detecting pavement cracks in a complex road surface status. The proposed method is also promising in serving the extraction of other on-road objects.
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Zhang, Jihua, Lianguo Wang, Yun Dong, Yadong Chen, Yang Jiang, Huasheng Sun, Jiarui Chen, and Yuqing Fan. "Research on the Development Mechanism of Postpeak Cracks in Sandstone under Different Confining Pressures." Mathematical Problems in Engineering 2019 (May 2, 2019): 1–10. http://dx.doi.org/10.1155/2019/6208207.
Full textAbstract:
Water inrush happens occasionally during deeper roadways excavation. It is mainly due to the lack of understanding in the formation and development mechanism of cracks and its spatial distribution pattern under ground stress. In view of this, this paper used different stress levels to represent the fracture state of different parts of the surrounding rock of the deep roadway; CT detection technique is used to scan the fractured sandstone in the postpeak state; and the CT images under different confining pressures are thus obtained. The geometrical parameters such as area, length, and width of the crack are used to describe the distribution patterns based on CT images processing technique and statistical principle. These patterns are then analyzed under varying postpeak stress levels and confining pressures. The result shows that, as the area, length, and width of the cracks get larger, number of cracks increases with decreasing stress level; at different stress levels, sandstone crack area probability density, crack length probability density, and crack width probability density form exceptional, linear, and Gaussian distribution, respectively. The amount of confining pressure affects the size of cracks and the extent of expansion. This means that the higher the confining pressure is, the easier the internal crack will be penetrated and expanded and the bigger the cracks are, and the number of cracks gets lesser. Such research results can be used to describe the propagation and evolution law of cracks under different stress states of postpeak rock, which also provide an important basis for further analysis of its permeability and the stability of roadway surrounding rock.