• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.5
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• pp.485-492
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• 2009

The thermal fatigue crack(TFC) is one of the life-limiting mechanisms at the nuclear power plant operating conditions. In order to evaluate the structural integrity, various non-destructive test methods such as radiographic test, ultrasonic test and eddy current are used in the industrial field. However, these methods have restrictions that defect detection is possible after the crack growth. For this reason, acoustic emission testing(AET) is becoming one of powerful inspection methods, because AET has an advantage that possible to monitor the structure continuously. Generally, every mechanism that affects the integrity of the structure or equipment is a source of acoustic emission signal. Therefore the noise filtering is one of the major works to the almost AET researchers. In this study, acoustic emission signal was collected from the pipes which were in the successive thermal fatigue cycles. The data were filtered based on the results from previous experiments. Through the data analysis, the signal characteristics to distinguish the effective signal from the noises for the TFC were proven as the waveform difference. The experiment results provide preliminary information for the acoustic emission technique to the continuous monitoring of the structure failure detection.

• Tunnel and Underground Space
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• v.19 no.1
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• pp.19-30
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• 2009

For the purpose of determining the thickness of concrete lining and detect of the cavity where may be located behind tunnel lining, IE (Impact-Echo) method it effectively useful in the tunnel safety diagnosis and the quality control during the construction. As a part of case study, we applied IE method to various tunnel structure types such as road tunnel and subway tunnel constructed by NATM (New Austrian Tunnelling Method) and ASSM (American Steel Support Method). As tunnel specifications estimated from this method were compared with coring data, design drawing and other survey results, it was very good agreement with each other. In conclusion, we verified that IE method shows an accurate and reliable result. The conventional interpretation of IE method in frequency domain gives only vertical information at a certain point. However, the interpretation using time-frequency analysis and depth section imaging technique from two dimensional profiling surveys can show more reliable information about structure inside.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.415-424
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• 2014

The carrying capacity of existing concrete structures is evaluated by the measured data from displacement and strain gauges for given loads and the results of numerical analysis that are compared with the measured ones. Consequently, this process could be accomplished in doing the direct measurement of residual stress on existing concrete. This study is concerned with the development of IITC (Instrumented Indentation Technique for Concrete) system which is based on the experimental stress analysis technique using non-destructive test method to evaluate the residual stress of concrete structures depending on the types of applied loadings in analysing indentation load - indentation depth curve derived experimentally on concrete surface. As a result, in this paper, almost all of systematized H/W and S/W were newly developed to estimate the residual stresses of concrete structures. Thus, the creation of new experimental equations for deriving residual stresses and automatical calculations of residual stresses using the empirical formula can lead to evaluate the structural resistances conveniently in the structures from construction phase to maintenance stage.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.794-801
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• 2003

As it is important to measure the degree of the deterioration and predict service life caused by chloride in concrete structure the methods of measuring chloride in the concrete is raised important problems. This study is to set a new standard for using of the colorimetric method through grasping the character of the colorimetric distinction method, and measuring the chloride content at the place discolored. Also, to predict chloride content around embeded bar and time reaching limit chloride concentration through measuring the chloride content of concrete surface by colorimetric distinction method and this study presents the new concept of concrete degradation and diagnosis of the durability by salt damage. According the results, it is possible to use colorimetric distinction method as simplified measurement to measure the fixed quantity of the chloride concentration. What is more, it would make calculation of concrete surface chloride had a wide fluctuation at the general environment extended. Also, it would be make estimating durability of reinforced concrete structures applied to the basic data.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.1
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• pp.60-67
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• 2014

In this study, an automated cable non-destructive testing(NDT) system was developed to monitor the steel cables that are a core component of cable-stayed bridges. The magnetic flux leakage(MFL) method, which is suitable for ferromagnetic continuum structures and has been verified in previous studies, was applied to the cable inspection. A multi-channel MFL sensor head was fabricated using hall sensors and permanent magnets. A wheel-based cable climbing robot was fabricated to improve the accessibility to the cables, and operating software was developed to monitor the MFL-based NDT research and control the climbing robot. Remote data transmission and robot control were realized by applying wireless LAN communication. Finally, the developed element techniques were integrated into an MFL-based cable NDT system, and the field applicability of this system was verified through a field test at Seohae Bridge, which is a typical cable-stayed bridge currently in operation.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.131-136
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• 2008

We performed a non-destructive geophysical survey such as an elastic wave survey, electric specific resistance survey, plate loading test, etc. in order to grasp the structure and status of the ground around the pillar gate and to provide the directions and design data for preservation and maintenance during reconstruction. The result of electric specific resistance survey shows 50-1300 ohm-m range of general electric specific resistance distribution. Besides, the positions around 1m south of stone pillars, between stone pillar No.3 and 4, and 1m north of stone pillar No.2 and 3 show abnormality of relatively lower electric specific resistance than their surroundings. The abnormality of low electric specific resistance appearing between stone pillar No.3 and 4 shows consistency with the abnormal section appearing from the result of elastic wave reflection survey. The result of a plate loading test shows that allowable bearing force is over $10.70tf/m^2$, and the settlement amount at this time was calculated as 19.635mm. The design load during reconstruction of pillar gates was calculated as $16.37t/m^2$ by applying assumption values, which is far more than the allowable bearing force, so it is judged that a measure to strengthen the foundation ground is necessary.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1520-1520
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• 2001

Food adulteration is a serious consumer fraud and a potentially dangerous practice. Regulatory authorities and food processors require a rapid, non-destructive test to accurately confirm authenticity in a range of food products and raw materials. Olive oil is prime target for adulteration either on the basis of the processing treatments used for its extraction (extra virgin vs virgin vs ordinary oil) or its geographical origin (e.g. Greek vs Italian vs Spanish). As part of an investigation into this problem, some preliminary work focused on the ability of near infrared spectroscopy to discriminate between virgin olive oils from separate regions of the Mediterranean i. e. Crete and the Peloponese. A total of 46 oils were collected: 18 originated in Crete and 28 in the Peloponese. Oils were stored in a temperature-controlled room at 2$0^{\circ}C$ prior to spectral collection at room temperature (15-18$^{\circ}C$). Samples (approximately 0.5$m\ell$) were placed in the centre of the quartz window in a camlock reflectance cell; the gold-plated baking plate was then gently placed into the cell against the glass so as to minimize the formation of air bubbles. The rear of the camlock cell was then screwed into place producing a sample thickness of 0.5mm. Spectra were recorded between 400 and 2498nm at 2nm intervals on a NIR Systems 6500 scanning monochromator. Spectral collection took place over 2-3 days. Data were analysed using both WINISI and The Unscrambler software to investigate the possibility of discriminating between the oils from Crete and the Peloponese. A number of data pre-treatments were used and discriminant models were developed using discriminant PLS (WINISI & Unscrambler) and SIMCA (Unscrambler). Despite the small number of samples involved, a satisfactory discrimination between these two oil types was achieved. Graphical examination of principal component scores for each oil type also holds out the possibility of separating oils from either Crete and the Peloponese on the basis of districts within each region. These preliminary data suggest the potential of near infrared spectroscopy to act as a screening technique for the confirmation of geographic origin of extra virgin olive oils. The sample presentation strategy adopted uses only small volumes of material and produces high quality spectra.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.1
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• pp.1-7
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• 2008

When historical or cultural buildings need to be repaired or reinforced, the changes of original features should be minimized, and the strengths of structures should be improved. Among the existing methods to reinforce historical wood structures, the carbon fiber reinforcement polymer (CFRP) installation method is one of the best ones to achieve the afore-mentioned requirements. Therefore, this study aims at investigating the reinforcing effects and failure modes of timber beams reinforced with the inserted CFRP, a part of roof trusses in modern wood structures, and at providing the fundamental test data to estimate the CFRP rein-forced timber beam in the application of this reinforcing method. The primary parameters in this study were the layout and amount of CFRP. It was observed that, when $0.3{\sim}0.7%$ of CFRP were installed, the strengths of reinforced timber beams increased up to 173% compared to its original strength, but their strengthening effects were heavily influenced by the characteristics of timber such as burls. In order to improve the applicability of this strengthening method, fundamental understandings on the characteristics of wood would be necessary, and there would be in need of researches on the non-destructive test for wood structures as well.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.2
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• pp.113-128
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• 2024

Items of road tunnel PISD (Precise Inspection for Safety and Diagnosis) were reviewed and analyzed using newly enhanced MMS (Mobile Mapping System) technology. Possible items with MMS can be visual inspection, survey and non-destructive test, structural analysis, and maintenance plan. The resolution of 3D point cloud decreased when the vehicle speed of MMS is too fast while the calibration error increased when it is too slow. The speed measurement of 50 km/h is determined to be effective in this study. Although image resolution by MMS has a limit to evaluating the width of crack with high precision, it can be used as data to identify the status of facilities in the tunnel and determine whether they meet disaster prevention management code of tunnel. 3D point cloud with MMS can be applicable for matching of cross-section and also possible for the variation of longitudinal survey, which can intuitively check vehicle clearance throughout the road tunnel. Compared with the measurement of current PISD, number of test and location of survey is randomly sampled, the continuous measurement with MMS for environment condition can be effective and meaningful for precise estimation in various analysis.

• Journal of the Korea Institute of Building Construction
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• v.16 no.1
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• pp.77-85
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• 2016

This study provides the numerical model to assess retrofit and strengthen levels in the dispersal and combat facilities. First of all, it is verified that direct-hitting projectiles are more destructive to the structures rather than close-falling bombs with explosion tests. The protective capacity of dispersal and combat facilities, which are modeled with soil uncertainty and structural field data, is analyzed through finite element method. With structural survivability and facility data, the logistic regression model is drawn. This model could be used to determine the level of the retrofit and strengthen in the dispersal and combat facilities of contact areas. For more reliable model, it could be better to identify more significant factors and adapt non-linear model. In addition, for adapting this model on the spot, appropriate strengthen levels should be determined by hands on staffs associated with military facilities.