• Structural Engineering and Mechanics
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• v.84 no.1
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• pp.1-16
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• 2022

An efficient and accurate classification method for failure modes of reinforced concrete (RC) columns was proposed based on key characteristic parameters. The weight coefficients of seven characteristic parameters for failure modes of RC columns were determined first based on the support vector machine-recursive feature elimination. Then key characteristic parameters for classifying flexure, flexure-shear and shear failure modes of RC columns were selected respectively. Subsequently, a support vector machine with key characteristic parameters (SVM-K) was proposed to classify three types of failure modes of RC columns. The optimal parameters of SVM-K were determined by using the ten-fold cross-validation and the grid-search algorithm based on 270 sets of available experimental data. Results indicate that the proposed SVM-K has high overall accuracy, recall and precision (e.g., accuracy>95%, recall>90%, precision>90%), which means that the proposed SVM-K has superior performance for classification of failure modes of RC columns. Based on the selected key characteristic parameters for different types of failure modes of RC columns, the accuracy of SVM-K is improved and the decision function of SVM-K is simplified by reducing the dimensions and number of support vectors.

• Journal of Korean Institute of Industrial Engineers
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• v.33 no.1
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• pp.52-60
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• 2007

Estimating parameters of the lifetime distribution is investigated when field failure data are not completelyreported. To take into account the reality and the accuracy of the estimates in such a case, the failure reportingprobability is incorporated in estimating parameters, Firstly, method of maximum likelihood estimate (MLE) isused to estimate parameters of the lifetime distribution when failure reporting probability is known, Secondly,Expectation and Maximization (EM) algorithm is used to estimate the failure reporting probability and parame-ters of the lifetime distribution simultaneously when failure reporting probability is unknown. For both cases,procedures of estimation are illustrated for single Weibull distribution and mixed Weibull distribution. Simula-tion results show that MLE obtained by the proposed method is more accurate than the conventional MLE.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.678-685
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• 2005

Estimating parameters of the lifetime distribution is investigated when field failure data are not completely reported. To take into account the reality and the accuracy of the estimates in such a case, the failure reporting probability is incorporated in estimating parameters. Firstly, method of maximum likelihood estimate(MLE) is used to estimate parameters of the lifetime distribution when failure reporting probability is known. Secondly, Expectation and Maximization(EM) algorithm is used to estimate the failure reporting probability and parameters of the lifetime distribution simultaneously when failure reporting probability is unknown. For both case, procedures of estimation are illustrated for single Weibull distribution and mixed Weibull distribution. Simulation results show that MLE obtained by the proposed method is more accurate than the conventional MLE.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.585-594
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• 2009

In this present study, to performed the model test and estimated the behavior characteristics of twin tunnel in accordance with the variation of the whole failure parameters which is the strength of the ground, distance of tunnel, angle of the joint, installation of tension bolts and the blasting load. To carry out the numerical analysis for verification of model test results and analyze the sensitivity on failure parameters using model test and numerical analysis results. Based on sensitivity analysis results, to propose the most habitually failure parameters in tunnel scale model test.

• Journal of Applied Reliability
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• v.17 no.4
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• pp.355-361
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• 2017

Purpose: The purpose of this research is to establish the life test method for ceramic heater and identify the failure mechanisms. Methods: We do accelerated life test in the condition of thermal shock and failure analysis for failed samples. Conclusion: The main failure mechanisms of ceramic heater are identified as overstress failure mechanisms as results of failure analysis and the shape parameters of weibull distribution by accelerated life test are identified as 0.8, 1.2 and 0.4 each at $400^{\circ}C$, $600^{\circ}C$ and $900^{\circ}C$. At $900^{\circ}C$, the shape parameter 0.4 means that It is exactly initial failure caused that the stress exceeds the strength of ceramic heater highly and the shape parameters 0.8, 1.2 at $400^{\circ}C$, $600^{\circ}C$ means that the shape parameters are around 1.0 so that the main failure mechanism is overstress failure which is same result as failure analysis. It means that the appropriate life test method for ceramic heater is reliability qualification test method rather than accelerated life test.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.3
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• pp.92-100
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• 1995

This experimental study is mainly investigated on the mean cutting forces and AE(acoustic emission) parameters in order to detect and estimate the tool failure in the pachinig of SUS304 by face milling Mean cutting forces and AE parameters can detect the tool failure in face milling. Effective detection parameters are AE RMS, AE energy, AE count, AE duration, and z-direction mean cutting force. From the analysis of cutting tool failure detection, the tool failure of face milling is caused by sudden increasing of the cutting force.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1331-1336
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• 2008

This paper suggests a method using Bayesian inference to estimate the parameters of Weibull distribution and acceleration parameters under the condition that the stresses are time-dependent functions. A Bayesian model based on the discrete time approximation is formulated to infer the parameters of interest from the failure data of the virtual tests and a statistical analysis is considered to decide the most probable mean values of the parameters for reasoning of the failure data.

• Tunnel and Underground Space
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• v.7 no.1
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• pp.31-38
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• 1997

Residual shear strength should be taken into consideration as well as peak one when analysing stability of slopes constituted by weathered rock or overconsolidated soils since such materials could be subjected to progressive failure mechanism. When landslide of a slope is related to progressive failure phenomenon, the failure might occur even though shear strength of the slope materials does not reach their residual shear strength over the whole slip surface. Therefore, stability of the slope concerned may be overstimated or underestimated when using only its peak or residual shear srength parameters. Mechanical description for progressive failure phenomenon is given by Bjerrum(1967). In parameters. Mechanical description for progressive failure phenomenon is given by Bjerrum(1967). In this study, his theory has been extended to estimate the distance of failed zone for a plane slope and the results calculated by this extended equatio has been compared with that obtained by numerical modelling using FLAC. In addition, stress state on the slip surface has been, in detail, analysed to understand failure mechanism when a limited progressive failure occurs. Effects of mechanical and hydraulic factors on progressive failure have also been analysed.

• Geomechanics and Engineering
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• v.9 no.1
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• pp.115-124
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• 2015

Determination of mobilized shear strength parameters (that identify stresses on the failure plane) is required for analyzing the stability by limit equilibrium method. Generalized Hoek-Brown (GHB) and Mohr-Coulomb (MC) failure criteria are usually used for obtaining stresses on the plane of failure. In the present paper, the applicability of these criteria for determining the stresses on failure plane is investigated. The comparison is based on stresses on the real failure plane which are obtained from the Mohr stress circle. To do so, 18 sets of data (consist of principal stresses and angle of failure plane) presented in the literature are used. In addition, the values account for (VAF) and the root mean square error (RMSE) indices were calculated to check the determination performance of the obtained results. Values of VAF and RMSE for the normal stresses on the failure plane evaluated from MC are 49% and 31.5 where for GHB are 55% and 30.5, respectively. Also, for the shear stresses on failure plane, they are 74% and 36 for MC, 76% and 34.5 for GHB. Results show that the obtained stresses and angles of failure plane for each criterion differ from real ones, but GHB results are closer to the empirical results. Also, it is inferred that results are affected by the failure envelope not real failure plane. Therefore, obtained shear strength parameters are not mobilized. Finally, a multivariable regressed relation is presented for determining the stresses on the failure plane.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.709-712
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• 1999

This paper was aimed to investigate the shear strengthening effect of the pre-loaded reinforced concrete beams strengthened by carbon fiber sheet (CFS). Main tet parameters was the magnitude of pre-loading at the time of the retrofit and the strengthening method of carbon fiber sheet. A series of nine specimens was tested to evaluate the corresponding effect of each parameters such as maximum load capacity, load-deflection relationship, and failure mode. The results of this study showed that the failure mode is bonding failure between the concrete and the CFS before the tensile failure strain of the CFS is reached.