• International conference on construction engineering and project management
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• 2022.06a
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• pp.912-919
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• 2022

The study is an image-based assessment that uses image processing techniques to determine the condition of concrete with surface cracks. The preparations of the dataset include resizing and image filtering to ensure statistical homogeneity and noise reduction. The image dataset is then segmented, making it more suited for extracting important features and easier to evaluate. The image is transformed into grayscale which removes the hue and saturation but retains the luminance. To create a clean edge map, the edge detection process is utilized to extract the major edge features of the image. The Otsu method is used to minimize intraclass variation between black and white pixels. Additionally, the median filter was employed to reduce noise while keeping the borders of the image. Image processing techniques are used to enhance the significant features of the concrete image, especially the defects. In this study, the tonal zones of the histogram and its properties are used to analyze the condition of the concrete. By examining the histogram, the viewer will be able to determine the information on the image through the number of pixels associated and each tonal characteristic on a graph. The features of the five tonal zones of the histogram which implies the qualities of the concrete image may be evaluated based on the quality of the contrast, brightness, highlights, shadow spikes, or the condition of the shadow region that corresponds to the foreground.

• Structural Engineering and Mechanics
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• v.88 no.1
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• pp.67-81
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• 2023

The reinforced concrete (RC) structures might need strengthening or upgradation due to adverse environmental conditions, design defects, modification requirements, and to prolong the expected lifespan. The RC beams have been efficiently strengthened using the near surface mounted (NSM) approach over the externally bonded reinforcing (EBR) system. In this study, the performance of RC beam elements strengthened with NSM-steel rebars was investigated using an experimental program and nonlinear finite element modeling (FEM). Nine medium-sized, rectangular cross-section RC beams total in number made up for the experimental evaluation. The beams strengthened with varying percentages of NSM reinforcement, and the number of grooves was assessed in four-point bending experiments up to failure. Based on the experimental evaluation, the load-displacement response, crack features, and failure modes of the strengthened beams were recorded and considered. According to the experimental findings, NSM steel greatly improved the flexural strength (up to about 84%) and stiffness of RC beams. The flexural response of the tested beams was simulated using a 3D non-linear finite element (FE) model. The findings of the experiments and the numerical analysis showed good agreement. The effect of the NSM groove and reinforcement on the structural response was then assessed parametrically.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.137-138
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• 2023

The floating floor is a structure which introduced to reduce the noise of apartment houses. This structure can decrease vibration energy through resilient materials. However, it is limited to completely construct resilient materials in South Korea due to floor heating structure and other reasons. And It is a controversial issue how well the resilient materials should be constructed to prevent floor impact noise. These resilient defect areas are typically found in wall corners, door sills, hot water dispenser in kitchen and areas where thermal insulation is attached. This study investigates the acoustical effect of the defect areas in two ways. First, it is analyzed by several assumption conditions and calculated how much deviation would occur. Then we researched the deviation of the 76 field test data about light-weight floor impact noise. This study could be useful for a constructor to determine how much should minimize resilient materials defect areas.

• Korean Journal of Construction Engineering and Management
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• v.21 no.6
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• pp.84-94
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• 2020

Modular architecture is very important not only in the design phase but also in the construction planning phase because it affects construction methods and module sizes depending on transport equipment. There are economic risks as well as quality, as there may be defects such as internal interiors or elimination of deadlines during transportation, and structural torsion caused by rainfall and shock. However, there is a lack of objective criteria or data to refer to in determining transport equipment that has a material effect on transport. Accordingly, there is no decision model to determine the optimum transportation equipment for each construction site. Therefore, it is necessary to develop a decision support model that can be compared to the review of transport equipment selection factors. The purpose of this study is to propose the transport equipment impact factors and decision support models for systematic review and objective decision making of each construction plan in the construction of small and medium-sized modulators. The decision model proposed in this study can be used as basic data for transport studies, ensuring objectivity and transparency in the equipment selection process.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.23-30
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• 2001

The Financial Cost in construction industry today is tend to increasing the burden of business management on account of lowered profit due to the mege-competition and decreasing investment of construction, multi-interfacing. system in it's attribute and various unreasonable governeing enactments. It is becoming the most important aspects for the management of construction business on how to preserve the profit from the various risks. The ultimate aims of this study is to pursue the contractual equity between the parties by establishing the fundamentals of framework for the compensation of Financial Charges through the review of the precedent studies and analysis of inquiries. As a result of the study, improvable measures for any practical inequality and/or institutional defects of current public contract system in recovering the Financial Cost incurred to Contractor are delivered as below; (1) $\lceil$Working Rules for Construction Industry Accounting Standards$\rfloor$ shall be amended and supplemented so as the incurred interest to be recognized as an operative cost by live return over the collection period. (2) The long-term phase contract system of which is enforcing contractor to bear the certain losses shall be diminished and/or abolished gradually. (3) The unreasonable legislations on compensation for financial cost in contract conditions shall be improved in response to practical circumstances. (4) The use of Critical-Path Method for Time Management shall be activated together with EVMS. (5) Independent application of Contract Enactments for construction industry shall be adopted.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.5
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• pp.580-585
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• 1988

In this paper, a low frequency acoustic microscope system has been built for the purpose of detecting subsurface defects in materials. The lateral resolution of acoustic microscope is studied and analyzed in order to evaluate that system performance. And a NDE technique is demonstrated by using this system. In the focused and defocused mode of operation, the acoustic microscope system showed in experiment that its lateral resolution was about 0.5 mm at a frequency of operation of 3MHz on a fused-quartz sample with seeded circular cracks ranged in size from 0.2 mm to 1.0 mm in diameter wihtin 1 mm of the surface. It also showed the acoustic image of 100 won coin with fine contrast.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.127-132
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• 2008

As economic rapid growth, large structures are damaged by defects from design and construction process of the formation and environments. Therefore, safety diagnosis and monitoring skills are bringing importance into relief and legislate for safety diagnosis of large structures. However, the existing monitoring systems are difficult by using wire cable because of cost, error of date, location, revise. In this paper, wireless sensor network which are accelerator, temperature sensor system using ubiquitous had been field test on Sea-Hea Grand bridge. We compare accelerator, temperature sensor system with wire and wireless sensor network.

• Archives of Reconstructive Microsurgery
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• v.24 no.2
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• pp.50-55
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• 2015

In the hand, few vessels can be classified as 'perforators'. Even today, the debate continues on whether or not branches of the digital artery should be considered as perforators. However, 'perforator' and 'perforator flaps' have become extremely popular within the microsurgery literature, and as such, the terminology has found widespread adoption across the hand surgery field. The finger is the most important sensory organ for tactile stimulation. The glabrous skin can be distinguished between the fingertip and the proximal tissue, with the fingertip having a higher functional and, therefore, reconstructive priority. Thus, sacrifice of the proximal glabrous skin can be justified in the reconstruction of fingertip defects. In this paper, the author reviews two flaps, 'lateral digital artery perforator flap' and 'volar digital artery perforator flap', both of which uses short branches of the digital artery as a vascular pedicle and are useful in fingertip construction.

• Tunnel and Underground Space
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• v.7 no.1
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• pp.75-83
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• 1997

The interest of diagnosis and maintenance of construction is increasing due to the collapse of infastructures. To obtain the complete, reliable and reproducible data ont he state of the entire structure, various non-destructive techniques are available, Especially, specific constructional characteristics of tunnels make the application of non-destructive tests more difficult. Despite of the complications of these conditions, non-destructive techniques should be capable of providing a description of the state of the tunnel lining, without the removal of the tunnel installations. In this paper, the infrared thermography technique using the difference of surface temperature was studied. The optimum equipment was selected and introduced, the principle, testing method and data anlaysis were investigated. Also, through the case study for inspection of concrete tunnel lining, this technique has proven to be a valuable non-destructive test for detecting the defects such as crack, leakage of water and exfoliation of concrete. The applicability and usefulness of this technique for estimation of concrete tunnel lining have been conformed.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.391-396
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• 2001

Exposed concrete execution is utilized insufficiently due to surface honecomb and undesirable appearance by entrapped air when existing placing method is applied. Therefore, surface glossing and impact properties of cement mortar incorporating fiber glass net blast furnace slag, expansive admixture and Polypropylene fiber are investigated in order to develop precast exposed concrete pannel by dry construction method. The kinds of the forms, placing method and admixture contents are varied. According to test results, surface glossing decrease with elapse of age. Considering the form kinds, surface glossing with acryle + astage shows the best performance. Placing horizontally shows positive results in reducing surface defects such as honecomb. Impacting resistance shows the best performance when glass fiber net applied, due to the enhance in toughness and absorption of impact.