• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.128-138
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• 2015

Carbonation is one of the most critical deterioration phenomena to concrete structures exposed to high $CO_2$ concentration, sheltered from rain. Lots of researches have been performed on evaluation of carbonation depth and changes in hydrate compositions, however carbonation modeling is limitedly carried out due to complicated carbonic reaction and diffusion coefficient. This study presents a simplified carbonation model considering diffusion coefficient, solubility of $Ca(OH)_2$, porosity reduction, and carbonic reaction rate for low concentration. For verification, accelerated carbonation test with varying temperature and MIP (Mercury Intrusion Porosimetry) test are carried out, and carbonation depths are compared with those from the previous and the proposed model. Field data with low $CO_2$ concentration is compared with those from the proposed model. The proposed model shows very reasonable results like carbonation depth and consuming $Ca(OH)_2$ through reduced diffusion coefficient and porosity compared with the previous model.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.68-77
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• 2012

The joint of existing steel grid composite deck is composed of lap splice of reinforcing bar with end hooks and field-placed concrete. In this study, bending tests of deck joint composed of concrete shear key and high tension bolts are carried out for the design variable, concrete shear key strengthened with steel plate or not, and test results are compared with flexural performance of the existing deck joint. Test results showed that the mechanical deck joint has about 30% ~ 60% more ultimate bending strength than the existing joint. According to analysis results of moment-curvature relationship, the initial bending stiffness of the existing deck joint is some higher than that of mechanical joint. But, after crack failure the structural performance of the existing deck joint is rapidly reduced. Furthermore, the deck joint with the strengthened shear key with steel plate has more bending moment capacity than the deck joint without strengthening. And strengthening of shear key has positive influence on the increase of bending stiffness.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.91-97
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• 2017

The purpose of this study is to get a more precise frequency of hollow core slabs by comparing the observed values from the actual free vibration tests and the predicted values based on the analysis model. The actual free vibration tests were carried out in the construction field using ${\Omega}$ shaped hollow core slabs. Modal analysis is conducted based on the analysis model that takes into account the differences in section properties due to void parts of slab. The differences between the predicted values based on the modal analysis with analysis model and the measured data from the actual tests range from 2~7%. This study demonstrates that the analysis model that incorporates void parts of slab could be used in evaluating serviceability of hollow core slabs with reasonable accuracies.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.139-146
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• 2003

The objective of the presented study is to develop an efficient procedure of proof load testing for existing bridges. By analytical methods, some of these bridges are not adequate to carry normal highway traffic. However, the actual load carrying capacity is often much higher than what can be determined by conventional analysis. Proof load testing can reveal the hidden strength reserve and thus verify the adequacy of the tested bridge. Proof load level required for meaningful tests should be sufficiently higher than legal load. In the state of Michigan, the legal 11-axle truck can weigh up to 685 kN. In this study, a combination of two military tanks and two Michigan 11-axle trucks was used. The proof loads were gradually increased to ensure the safety of the test. After each move, measurements were taken. For the considered bridge, stress levels were rather low compared to pre-test analysis results. This is due to incorrect material strength, structural contribution of nonstructural components such as parapets and railings, and partially fixed supports.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.64-77
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• 2012

In this study, the crack detecting system with digital image processing techniques based on the mathematical morphology method was developed to detect cracks in concrete structures. In the developed system, the image combining technique of reconstructing multiple images as an entire single image considering efficient management of analysis results was applied as an additional module. The developed system was verified through a field test with the cracked concrete culvert and the crack width of 0.2 mm was able to be detected in the 40m span. In the image analysis, the difference between calculated crack width and actual crack width were less than 0.08mm. For image combination in the stitching test of pattern images, the stitched image was identical with the original picture of entire subject in the visual perception level.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.141-147
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• 2018

In this study, a cyclic loading test was carried out for a reinforced concrete frame installed a TS(tension-spring) damper for the purpose of verifying the seismic strengthening effect of the TS seismic reinforcing method. The test specimens are four specimens of non - reinforced frame and three reinforced frame specimens. Experimental parameters are Shape of damper and construction method of damper. As a result, the construction method of inserting type inside window was twice as much in terms of strength and stiffness, and the method of externally attached type showed a performance improvement of about 2 times in terms of energy dissipation. From these results, it can be confirmed that the TS seismic reinforcing method is a superior method for field application and seismic strengthening.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.359-366
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• 2021

In this study, It was developed an monitoring cracks system based on image processing techniques in order to measure cracks, which are major damages in concrete, and to convert them into a database. The crack monitoring system consists of crack image captured equipment and a crack detection and analysis software. This system provides objective and quantitative data by replacing the conventional visual inspection. The crack detection algorithm w as verified through an indoor test using virtual cracks, and the amount of crack detection and crack width change was monitored by applying it to the self-healing repair mortar construction site. In the case of the crack width detected through image analysis, the maximum difference from the actual crack width was 0.0334mm. It was possible to detect microcracks of 0.1mm or less, and the effect of crack healing over time of the self-healing repair mortar was confirmed trough the field test.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.15 no.1
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• pp.46-52
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• 2019

This work proposes a noncontact ultrasonic transducer for detecting wall-thinning of containment liner plates of nuclear power plants by measuring their thickness without physical contact. Because the containment liner plate is designed to prevent atmospheric leakage of radioactive substances under severe nuclear accident, its wall-thinning inspection is important for safety of nuclear power plants. Wall-thinning investigation of containment liner plates have been carried out by measuring their thickness with contact-type ultrasonic thickness gauge by inspectors and needs a lot of time and cost. As an alternative, an electromagnetic acoustic transducer measuring precisely thickness of containment liner plates without any physical contact or couplant was suggested in this research. A transducer generating and measuring shear ultrasonic waves in thickness direction was designed and wave field produced by the transducer was analyzed to verify the design. The working performance of the suggested transducer was tested with carbon steel plate specimens with various thicknesses. The test result shows that the proposed transducer can measure thickness of the specimens precisely without any couplant and implies that swift scanning of wall-thinning of containment liner plates will be possible with the proposed transducer.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.59-65
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• 2024

In this study, in order to improve the mechanical properties and durability of asphalt mixtures, a modifier (CSM, Cationized Silicate Modifier) was applied to asphalt to derive optimal mixing ratio conditions. Design of asphalt mixture using modified asphalt binder was conducted, and moisture resistance and dynamic stability were evaluated for optimal mixing conditions. The evaluation results showed that it exceeded the standards stipulated in the relevant guidelines, and as a result of conducting a water permeability test on the optimal mixing condition, it was confirmed that impermeable performance was secured. As a result of examining the noise reduction performance through field test, a noise reduction performance of about 10 dB was secured compared to before paving. It will be necessary to secure reliability through continuous noise generation evaluation in the future.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.4 s.56
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• pp.170-179
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• 2009

Channel-type lining board(CLB) is a welded steel structure used in the field of open cut subway excavation and building basement construction. Lining board is generally installed at the underground environment which is exposed to corrosion factors such as humidity, temperature and corrosive gases. This study evaluates reusability of the corroded lining board by experimental and analytical method. Static loading tests were performed to know serviceability of corroded CLB after checking thickness loss of the used CLB parts. Strain of the plates and middle point deflection was measured simultaneously. According to experimental test results and comparison with numerical analysis, the thickness loss of the plates by corrosion makes more vertical displacements and stresses in members under the DB vehicle load considering impact factor. As a result, this paper is proposed a way to evaluate used and corroded CLB by checking the plates thickness and it makes construction engineers easy to know optimal time to replace their old CLBs with new one.