• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.369-372
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• 2006

In this paper, analysis method of HPFRCC is proposed as predicting properties flexural behavior. For analyzing HPFRCC beam, properties of strain-hardening, multiple cracking, and crack spacing control are considered as non-homogeneous material properties of the beam. This paper focused on the deflection, maximum moment of the flexural beam, distribution of crack width with the monte carlo simulation.

• Journal of the Korean Society of Safety
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• v.17 no.2
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• pp.1-7
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• 2002

In this paper, the maximum minimum strain energy density criterion was applied to the mixed mode fatigue test of A5052 H34 alloy. In this study result we can have seen that the authors stress intensity factor for the finite width specimen and method of determining testing load, based on the plastic zone size and the limited maximum stress intensity factor by ASTM STANDARD E-647-95, is useful.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.1
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• pp.43-47
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• 1984

The purpose of this paper is to investigate theoretically the effect of residual stress due to welding in stress intensity factor of a plate containing the Model I Crack in different crack size and location, and on fatigue crack growth rate. The initiation of crack is found to be possible only in the region of tensile residual stress. The most dangerous crack has the values of d/b and a/b equal to about 0.6 and 1.0, respectively, where d/b is the ratio of distance from the crack to welding bead and the width of tensile residual stress region and a/b is the ratio of crack length and tensile residual stress region. The crack perpendicular to and on the line of welding bead and with a/b equal to about 0.6 has maximum stress intensity factor. The theoretical fatigue crack growth rate under residual stress and applied stress, which is obtained from Forman's Law by stress superposition, is relatively in good agreement with Glinka's[8] experimental value. The fatigue crack growth is shown to be retarded due to residual stress distribution.

• Smart Structures and Systems
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• v.33 no.2
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• pp.105-118
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• 2024

In order to realize tiny bridge crack discovery by UAV-based machine vision, a novel method combining deep learning and tensor voting is proposed. Firstly, the grid images of crack are detected and descripted based on SE-ResNet50 to generate feature points. Then, the probability significance map of crack image is calculated by tensor voting with feature points, which can define the direction and region of crack. Further, the crack detection anchor box is formed by non-maximum suppression from the probability significance map, which can improve the robustness of tiny crack detection. Finally, a case study is carried out to demonstrate the effectiveness of the proposed method in the Xiangjiang-River bridge inspection. Compared with the original tensor voting algorithm, the proposed method has higher accuracy in the situation of only 1-2 pixels width crack and the existence of edge blur, crack discontinuity, which is suitable for UAV-based bridge crack discovery.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.9
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• pp.194-200
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• 2013

In this paper, we propose a multi-scale crack detection method using scaling. It is based on morphology algorithm, crack features, and scaling. We use a morphology operator which extracts patterns of crack. It segments cracks and background using opening and closing operations. Morphology based segmentation is better than existing integration methods using subtraction in detecting a crack it has small width. However, morphology methods using only one structure element could detect only fixed width crack. Thus, we use a scaling method. We use bilinear interpolation for scaling. Our method calculates values of properties such as the number of pixels and the maximum length of the segmented region. We decide whether the segmented region belongs to cracks according to those data. Experimental results show that our proposed multi-scale crack detection method has better results than those of existing detection methods.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.694-701
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• 2018

Larger crack widths can be observed more in FRP-reinforced concrete members than in steel-reinforced concrete members as a result of the lower elastic modulus and bond strength of FRP reinforcement. The ACI 440.1R-15 design guide provides equations derived as the maximum bar spacing to control the crack widths indirectly. On the other hand, it is not concerned with long-term effects on the crack control design provisions. This study provides suggestions for how to incorporate time-dependent effects into the crack width equation. The work presented herein includes the results from 8 beams composed of four rectangular and T-shaped FRP-reinforced concrete beams tested for one year under four-point bending. Over a one year period, the crack widths increased as much as 2.6~3.0 times in GFRP and AFRP-reinforced specimens and 1.1~1.4 times in the CFRP-reinforced specimens compared to steel-reinforced specimens. In addition, the average multiple for crack width at one year relative to the instantaneous crack width upon the application of the sustained load was 2.4 in the specimens with a rectangular section and 3.1 in the specimens with a T-shaped section. As a result, it is recommended conservatively that the time-dependent coefficient be taken as 2.5 for the rectangular beams and 3.5 for T-beams.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.10a
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• pp.16-23
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• 1993

The new p-version crack model is proposed to estimate the bending stress intensity factors of the thick cracked plate under flexure. The proposed model is based on high order theory and $C^{\circ}$-plate element including shear deformation. The displacements fields are defined by integrals of Legerdre polynomials which can be classified into three groups such as basic mode, side mode and internal mode. The computer implementation allows arbitrary variations of p-level up to a maximum value of 10. The bending stress intensity factors are computed by virtual crack extention approach. The effects of ratios of thickness to crack length(h/a), crack length to width(a/W) and boundary conditions are investigated. Very good agreement with the existing solution in the literature are shown for the uncracked plate as well as the cracked plate.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.395-398
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• 2005

To understand an influence of rectangular openings on the structural behavior in reinforced concrete deep beams, results of 52 specimens were analyzed. The structural behavior such as load-deflection relationship, load-maximum crack width relationship, and maximum strength was significantly affected by inclination of concrete strut beneath opening.

• Steel and Composite Structures
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• v.49 no.5
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• pp.571-585
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• 2023

The application of relatively low volumes of fibres in normal strength concrete has been shown to be of significant benefit when applied to composite slabs with profiled sheet decking. This paper reports on an experimental study aimed at quantifying further potential benefits that may arise from applying ultra-high performance fibre reinforced concrete. To assess performance six simply supported beams were tested under hogging and sagging loading configurations along with three two span continuous beams. Fibre contents are varied from 0% to 2% and changes in strength, deformation, crack width and moment redistribution are measured. At the serviceability limit state, it is shown that the addition of high fibre volumes can significantly enhance member stiffness and reduce crack widths in all beams. At the ultimate limit state it is observed that a transition from 0% to 1% fibres significantly increases strength but that there is a maximum fibre volume beyond which no further increases in strength are possible. Conversely, member ductility and moment redistribution are shown to be strongly proportional to fibre volume.

• Transactions of Materials Processing
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• v.26 no.4
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• pp.210-215
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• 2017

In this paper, utilizing the theory of ductile fracture a chevron crack in a 4-stage open cold extrusion process is predicted by the finite element methods and then compared with previous experiments. The normalized Cockcroft-Latham damage model is employed and the material is identified using a tensile test based material identification technique that gives fracture information as well as flow stress at large strain. A large difference between the predicted cracks and actual experiments is observed, specifically narrower width and greater maximum height of the crack. This reveals the limitation of this approach based on the conventional theory of ductile fracture. Based on the observations and the related criticisms, a new approach for predicting the chevron crack is proposed, suggesting that either the critical damage should not be a fixed material constant, or that the conventional fracture theory should be considered with the effects of embrittlement due to accumulated plastic deformation while the duration of crack generation and plastic deformation should be reduced.