• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.52-59
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• 2015

The aim of the paper is to introduce the statistical definition of the specified compressive strength of the concrete to be used for safety evaluation of the existing structure in domestic practice and to present the practical method to obtain the specified strength by utilizing the non-destructive test data as well as the limited number of core test data. The statistical definition of the specified compressive strength of concrete in the design codes is reviewed and the consistent formulations to statistically estimate the specified strength for assessment are described. In order to prevent estimating an unrealistically small value of the specified strength due to limited number of data, it is proposed that the information from the non-destructive test data is combined to that of the minimum core test data. The the sample mean, standard deviation and total number of concrete test are obtained from combined test data. The proposed procedures are applied to an example test data composed of the artificial numerical values and the actual evaluation data collected from the bridge assessment reports. The calculation results show that the proposed statistical estimation procedures yield reasonable values of the specified strength for assessment by applying the non-destructive test data in addition to the limited number of core test data.

• 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.

• Geomechanics and Engineering
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• v.25 no.4
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• pp.317-330
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• 2021

This paper reports the results of advanced data analysis involving artificial neural networks for the prediction of the unconfined compressive strength of granite using only two non-destructive test indexes. A data-independent site-independent unbiased database comprising 182 datasets from non-destructive tests reported in the literature was compiled and used to train and develop artificial neural networks for the prediction of the unconfined compressive strength of granite. The results show that the optimum artificial network developed in this research predicts the unconfined compressive strength of weak to very strong granites (20.3-198.15 MPa) with less than ±20% deviation from the experimental data for 70% of the specimen and significantly outperforms a number of available models available in the literature. The results also raise interesting questions with regards to the suitability of the Pearson correlation coefficient in assessing the prediction accuracy of models.

• Journal of Auto-vehicle Safety Association
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• v.13 no.2
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• pp.50-56
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• 2021

The purpose of this study is to investigate vulnerable parts of tower crane structures by analyzing extensive non-destructive test data. Approximately ten percent of domestically registered tower cranes were inspected by using magnetic particle inspection. The testing was carried out as advised in KS B 0213. The non-destructive results was analyzed with respect to jib types, age and crane size. As a result, the number of crack occurrences were the largest in mast parts, followed by main jib part. Moreover, it was found that turntables were important parts deserved to be noticed at the perspective of safe maintenance.

• Journal of Welding and Joining
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• v.17 no.6
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• pp.100-107
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• 1999

In this paper, we deal with the speckle noise reduction and parameter estimation of ultrasonic NDT(non-destructive test) signals obtained during weld inspection of piping. The overall approach consists of three major steps, namely, speckle noise analysis, proposition of wavelet domain AR(autoregressive) model and flaw detection by proposed model parameter. The data are first processed whereby signals obtained using vertical and angle beam transducer. Correlation properties of speckle noise are then analyzed using multiresolution analysis in wavelet domain. The parameter estimation curve obtained using the proposed model is classified a flaw in weld region where is contaminated by severe speckle noise and also clear flaw signal is obtained through CA-CFAR threshold estimator that is a nonlinear post-processing method for removing the noise from reconstructed ultrasonic signal.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.385-390
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• 2000

In this study, the Non-Destructive Testing Equipment was introduced for the compaction control and the evaluation of pavements properties and the developing process was showed. Falling Weight Deflectometer(FWD) is a system for performing non-destructive testing of pavement and the other foundation structures. The system develops forces from the acceleration caused by the arrest of a falling weight and these forces are transmitted onto the surface of a structure causing it to deflect much as it would due to the weight of a passing wheel load. The structure will bend downward and exhibit a deflection basin. FWD uses a set of velocity sensors to determine the amplitude and shape of the deflection basin. The deflection response, when related to the applied loading, can provide information about the strength and condition of the various elements of the test structure. In this study, a computer program was developed that can be used to evaluate pavement and foundation structures from the data produced by FWD. The Falling Weight Deflectometer, non-destructive testing equipment, is increasing used at the whole world.

• Journal of the Korean Wood Science and Technology
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• v.32 no.4
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• pp.74-81
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• 2004

The ultrasonic non-destructive method was used for wood decay test. The temperature change and moisture contents of wood were estimated how the ultrasonic wave velocity changes. The relationship between weight loss of wood decayed by T. palustris and ultrasonic wave velocity was investigated. The non-destructive methods of different condition of logwood were estimated. Decay map of old wood was made by non destructive methods. Through these tests, we can accumulate the data to judge the degree of wood decay. The decay map of wood could be used for the analysis of old wood.

• Korean Journal of Agricultural Science
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• v.39 no.1
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• pp.111-116
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• 2012

Nondestructive evaluation of seed viability is one of the highly demanding technologies for seed production industry. Conventional seed sorting technologies, such as tetrazolium and standard germination test are destructive, time consuming, and labor intensive methods. Near infrared spectroscopy technique has shown good potential for nondestructive quality measurements for food and agricultural products. In this study, FT-NIR spectroscopy was used to classify normal and artificially aged lettuce seeds. The spectra with the range of 1100~2500 nm were scanned for lettuce seeds and analyzed using the principal component analysis(PCA) method. To classify viable seeds from nonviable seeds, a calibration modeling set was developed with a partial least square(PLS) method. The calibration model developed from PLS resulted in 98% classification accuracy with the Savitzky-Golay $1^{st}$ derivative preprocessing method. The prediction accuracy for the test data set was 93% with the MSC(Multiplicative Scatter Correction) preprocessing method. The results show that FT-NIR has good potential for discriminating non-viable lettuce seeds from viable ones.

• Journal of the Korea Institute of Building Construction
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• v.16 no.3
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• pp.229-235
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• 2016

In construction field, it used various technique for concrete formwork. Part of them, non-destructive test has been conducted to estimate a compressive strength of concrete easily such as rebound method and ultrasonic pulse velocity method etc. Former research has recommend proposed equation based on experimental data to investigate strength of concrete but it was sometimes deferent actual value of that from in field because of the few of data in case of early strength concrete. In this study, an experiment was conducted to analyze strength properties for early strength concrete using cylinder mold and $1,000mm{\times}1,000mm{\times}200mm$ rectangular specimen. And compressive strength of concrete was tested by non-destructive test, and calculated by the equation proposed former research. As a result, the non-destructive test results showed approximately 70 percent of the failure test value for all conditions, and worse reliability was obtained for high strength concrete samples when the ultrasonic pulse velocity method was used. Based on the scope of this study, the experimental equation for estimating compressive strength of early strength concrete from 24MPa to 60MPa was proposed.

• Journal of Ocean Engineering and Technology
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• v.15 no.1
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• pp.73-78
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• 2001

Soundness evaluation of a structure being constructed under the sea is usually difficult. In this study, a cross-hole sonic logging(CSL) which have been used for non-destructive test of concrete piles is adopted for the integrity test and monitoring of DCM(deep cement mixing) treated soils. Chemical and physical characteristics of raw ground materials are analysed to delineate ground environmental effects on the strength of DCM treated soils. In order to convert cross-hole sonic logging data into compressive strength, correlations between compressive strengths and wave velocities of core samples have been obtained. It is found that there is little effect of ground environment on the strength of the DCM treated soils, and the density distribution of core samples and cross-hole logging data show that a defective zone may exist in the DCM treated soils. With the time lapse, however, the defective zone has been cured and consequently, compressive strength of the DCM treated soils increases and satisfies the design parameter. From this study it can be concluded that the cross-hole sonic logging can be used for the integrity test as well as monitoring the curing stage of the structures, successfully.