• Journal of the Korean Society for Precision Engineering
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• v.29 no.9
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• pp.938-945
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• 2012

To design and estimate material failures of Type III pressure vessels, which have excellent stability and performance, various modeling techniques have been introduced. This paper provided a hybrid modeling technique composed of ply-based modeling for a cylinder part and laminate-base modeling technique for a dome part for enhancing modeling efficiency. The ply-based modeling technique provided accurate ply stresses directly for predicting material failure, on the other hand, additional manipulations in stress calculations, which may cause some errors, were needed for the case of the laminate-based modeling technique. The ply stresses in fiber, transverse and in-plane shear directions were compared with the corresponding material strengths to predict material failure.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.247-252
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• 1996

In the concrete structures, cracks occur in various causes and the cracks seriously affect the functions of structures. The analysis techniques of progressive crack in the concrete have been improved with the advance of numerical techniques. The discrete crack model used in finite element program for the analysis of progressive failure is very effective, but it can not be easily implemented into numerical procedures because of difficult handing of nodal points in finite element meshes for crack growth. This paper introduces one of the techniques which skips the difficulty. In this paper, the modeling of progressive failure using finite element formulation is explained for the analysis of concrete fracture. The discontinuous element using the discontinuous shape function and the dual mapping technique in the numerical integration are implemented into finite element code for this purpose. It is shown that developed finite element program can predict the quasi-brittle behavior of concrete including ultimate load. The comparisons of the analysis results with other data are also shown.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.9
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• pp.62-68
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• 2011

Power system needs to sustain high reliability due to its complexity and security. The reliability prediction method is usually based on independent failure. However, in practice, the Common Cause Failures(CCF) and Cascading failure occur to the facilities in power system as well as independent failures in many cases. The CCF and Cascading failure turn out the system collapse seriously in a wide range. Therefore to improve the reliability of the power system practically, it is required that the analysis is conducted by using the CCF and Cascading failure. This paper describes the CCF and Cascading failure modeling combined with independent failure. The incorporated model of independent failure, CCF and cascading failure is proposed and analyzed, and it is applied to the distribution power system in order to examine this method.

• Journal of the Korean Society of Systems Engineering
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• v.9 no.1
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• pp.65-84
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• 2013

This paper introduces a systems engineering approach to reliability centered maintenance to address some of the weaknesses. Reliability centered maintenance is a systematic, disciplined process that produces an efficient equipment management strategy to reduce the probability of failure [1]. The study identifies the need for RCM, requirements analysis, design for RCM implementation. Value modeling is used to evaluate the value measures of RCM. The system boundary for the study has been selected as containment spray pump and its motor drive. Failure Mode and Criticality Effects analysis is applied to evaluate the failure modes while the logic tree diagram used to determine the optimum maintenance strategy. It is concluded that condition based maintenance tasks should be enhanced to reduce component degradation and thus improve reliability and availability of the component. It is recommended to apply time directed tasks to age related failures and failure finding tasks to hidden failures.

• Advances in Computational Design
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• v.8 no.2
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• pp.97-112
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• 2023

The Finite Element (FE) modeling of Reinforced Concrete (RC) under seismic loading has a sensitive impact in terms of getting good contribution compared to experimental results. Several idealized model types for simulating the nonlinear response have been developed based on the plasticity distribution alone the model. The Continuum Models are the most used category of modeling, to understand the seismic behavior of structural elements in terms of their components, cracking patterns, hysteretic response, and failure mechanisms. However, the material modeling, contact and nonlinear analysis strategy are highly complex due to the joint operation of concrete and steel. This paper presents a numerical simulation of a chosen RC column under monotonic and cyclic loading using the FE Abaqus, to assessthe hysteretic response and failure mechanisms in the RC columns, where the perfect bonding option is used for the contact between concrete and steel. While results of the numerical study under cyclic loading compared to experimental tests might be unsuccessful due to the lack of bond-slip modeling. The monotonic loading shows a good estimation of the envelope response and deformation components. In addition, this work further demonstrates the advantage and efficiency of the damage distributions since the obtained damage distributions fit the expected results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.3
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• pp.411-416
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• 2015

This paper presents the thermal modeling and analysis of Line power Start Permanent magnet Motor (LSPM). Thermal analysis of electrical machines is important because temperatures that are consistently too high will reduce the life time of machines and may lead to serious failure. Coefficients of convection are calculated according to the types of operating conditions. And computational fluid dynamics (CFD) technique is performed in order to predict thermal characteristic. The results are compared to the test results.

• Composites Research
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• v.14 no.3
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• pp.42-50
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• 2001

Modeling of damage initiation in singly oriented ply (SOP) Fiber Metal Laminate (FML) under concentrated loading conditions was studied. The finite element method (FEM) base on the first order shear deformation theory is used for th\ulcorner modeling of damage initiation in SOP FML. The failure indices (FI) of the fiber prepreg and the metal laminate were calculated by using the Tasi-Hill failure criterion and the Miser yield criterion, respectively. To verify the present method, the failure analysis was conducted under uniaxial loading and cylindrical bending, then the analysis under concentrated load was conducted. The results show that the analysis is reasonable. An indentation test was conducted to compare a damage initiation load with a calculated FI. The test was conducted under two side clamped conditions to study the fiber orientation effect. Indentation curve was fitted using the Hertz equation and a damage initiation load is defined that the point which deviate the fitted curve from the real indentation curve. The damage initiation loads were obtained under various fiber orientations and compared with calculated FIs. The experiment was well matched with calculated FI. This results shows that the present method is suitable for the damage initiation modeling of SOP FML.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7B
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• pp.744-750
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• 2009

In this paper, the unified Markov modeling of hardware and software for AVTMR(AlI Voting Triple Modular Redundancy) system is proposed and the dependability is analyzed. In hardware case, a failure rate is fixed to no time varying parameter. But, in software case, failure rate is applied with time varying parameter. Especially, the dependability(Reliability, Availability, Maintainability, Safety) of software is analyzed with G-O/NHPP for Markov modeling. The dependability of single and AVTMR system is analyzed and simulated with a unified Markov modeling method, and the characteristic of each system is compared accroding to failure rate. This kind of fault tolerat system can be applied to an airplane and life critical system to meet the requirement for a specific requirement.

• International Journal of Contents
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• v.5 no.4
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• pp.88-93
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• 2009

It is important for communication networks to possess the capability to overcome failures and provide survivable services. We address modeling and analysis of performability affected by both performance and availability of system components for a token ring network under failure and repair conditions. Stochastic reward nets (SRN) is an extension of stochastic Petri nets and provides compact modeling facilities for system analysis. In this paper, hierarchical SRN modeling techniques are used to overcome state largeness problem. The upper level model is used to compute availability and the lower level model captures the performance. And Normalized Throughput Loss (NTL) is obtained for the composite ring network for each node failures occurrence as a performability measure. One of the key contributions of this paper constitutes the Petri nets modeling techniques instead of complicate numerical analysis of Markov chains and easy way of performability analysis for a token ring network under SRN reward concepts.

• Computers and Concrete
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• v.31 no.5
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• pp.419-432
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• 2023

Beam-column joints are a critical component of reinforced concrete frame structures. They are responsible for transferring forces between adjoining beams and columns while limiting story drifts and maintaining structural integrity. During severe loading, beam-column joints deform significantly, affecting, and sometimes governing, the overall response of frame structures. While most failure modes for beam and column elements are commonly considered in plastic-hinge-based global frame analyses, the beam-column joint failure modes, such as concrete shear and reinforcement bond slip, are frequently omitted. One reason for this is the dearth of published guidance on what type of hinges to use, how to derive the joint hinge properties, and where to place these hinges. Many beam-column joint models are available in literature but their adoption by practicing structural engineers has been limited due to their complex nature and lack of practical application tools. The objective of this study is to provide a comparative review of the available beam-column joint models and present a practical joint modeling approach for integration into commonly used global frame analysis software. The presented modeling approach uses rotational spring models and is capable of modeling both interior and exterior joints with or without transverse reinforcement. A spreadsheet tool is also developed to execute the mathematical calculations and derive the shear stress-strain and moment-rotation curves ready for inputting into the global frame analysis. The application of the approach is presented by modeling a beam column joint specimen which was tested experimentally. Important modeling considerations are also presented to assist practitioners in properly modeling beam-column joints in frame analyses.