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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Computational Structural Engineering Institute of Korea
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Journal DOI :
The Computational Structural Engineering Institute
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Volume & Issues
Volume 25, Issue 6 - Dec 2012
Volume 25, Issue 5 - Oct 2012
Volume 25, Issue 4 - Aug 2012
Volume 25, Issue 3 - Jun 2012
Volume 25, Issue 2 - Apr 2012
Volume 25, Issue 1 - Feb 2012
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Nonlocal Peridynamic Models for Dynamic Brittle Fracture in Fiber-Reinforced Composites: Study on Asymmetrically Loading State
Ha, Youn Doh ; Cho, Seonho ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 279~285
DOI : 10.7734/COSEIK.2012.25.4.279
In this paper a computational method for a homogenized peridynamics description of unidirectional fiber-reinforced composites is presented. For these materials, dynamic brittle fracture and damage are simulated with the proposed peridynamic model. Compared with observations from dynamic experiments by Coker et al.(2001), the peridynamic computational model can reproduce various characteristics of dynamic fracture and supersonic or intersonic crack growth in asymmetrically loaded unidirectional fiber-reinforced composite plates. Also we analyze the same model in the symmetric loading condition and figure out that the asymmetric loading leads to a much higher propagation speed. Consistent results have been reported in the experiments.
Local Fault Detection Technique for Steel Cable using Multi-Channel Magnetic Flux Leakage Sensor
Park, Seunghee ; Kim, Ju-Won ; Lee, Changgil ; Lee, Jongjae ; Gil, Heung-Bae ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 287~292
DOI : 10.7734/COSEIK.2012.25.4.287
In this study, Multi-Channel Magnetic Flux Leakage(MFL) sensor - based inspection system was applied to monitor the condition of cables. This inspection system measures magnetic flux to detect the local faults(LF) of steel cable. To verify the feasibility of the proposed damage detection technique, an 8-channel MFL sensor head prototype was designed and fabricated. A steel cable bunch specimen with several types of damage was fabricated and scanned by the MFL sensor head to measure the magnetic flux density of the specimen. To interpret the condition of the steel cable, magnetic flux signals were used to determine the locations of the flaws and the level of damage. Measured signals from the damaged specimen were compared with thresholds set for objective decision making. In addition, the magnetic flux density values measured from every channel were summed to focus on the detection of axial location. And, sum of flux density were displayed with threshold. Finally, the results were compared with information on actual inflicted damages to confirm the accuracy and effectiveness of the proposed cable monitoring method.
Delamination Analysis of Orthotropic Laminated Plates Using Moving Nodal Modes
Ahn, Jae-Seok ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 293~300
DOI : 10.7734/COSEIK.2012.25.4.293
In this study, the delamination analysis has been implemented to investigate the initiation and propagation of crack in composite laminates composed of orthotropic materials. A simple modeling was achieved by moving nodal technique without re-meshing work when crack propagation occurred. This paper aims at achieving two specific objectives. The first is to suggest a very simple modeling scheme compared with those applied to conventional h-FEM based models. To verify the performance of the proposed model, analysis of double cantilever beams with composite materials was implemented and then the results were compared with reference values in literatures. The second one is to investigate the behavior of interior delamination problems using the proposed model. To complete these objectives, the full-discrete-layer model based on Lobatto shape functions was considered and energy release rates were calculated using three-dimensional VCCT(virtual crack closure technique) based on linear elastic fracture mechanics.
Analysis on Thermomechanical Response to Tensile Deformation of GaN Nanowires
Jung, Kwangsub ; Zhou, Min ; Cho, Maenghyo ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 301~305
DOI : 10.7734/COSEIK.2012.25.4.301
In this work the mechanical behaviors of GaN nanowires are analyzed during tension, compression, and unloading deformations. The thermal conductivity of the nanowires at each deformed state is evaluated using an equilibrium Green-Kubo approach. Under tensile loading, the -oriented nanowires with hexagonal cross-sections undergo a phase transformation from wurtzite to a tetragonal structure. The phase transformation is not observed under compressive loading. The thermal conductivity decreases on going from compressive strains to tensile strains. The strain dependence of the thermal conductivity results from the relaxation time of phonon. A reverse transformation from the tetragonal structure to the wurtzite structure is observed during unloading. The thermal conductivities in the intermediate states are lower than the conductivity in the wurtzite structure at same strain. Such differences in the thermal conductivity between different atomic structures are mainly due to changes in the group velocity of phonon.
IFC-based Representation Method of Part Information in Superstructure Module of Modular Steel Bridge with Assembly System
An, Hyun Jung ; Lee, Sang-Ho ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 307~314
DOI : 10.7734/COSEIK.2012.25.4.307
IFC-based representation method of part library for superstructure module of modular steel bridge is proposed. The library is capable of efficiently offering and exchanging part information in process of manufacture, assembly, design, and construction of modular steel bridge. Entities, representing physical part information in IFC model, are matched semantically with parts of the superstructure module for representation of part information with IFC model. Either types of matched entities are applied in order to verify the role of each part, or new types are defined as a user-defined types. In addition, assembly system has been classified and defined into 4 levels of LoD(Level of Detail) to provide appropriate part information efficiently from the part library in each step of the process. Then, new property is defined for representing the LoD information with IFC Model. Finally, IFC-based test library of modular steel bridge is generated by applying the matched entities and entity types to the actual the superstructure module of modular steel bridge.
A Study on the Sequential Multiscale Homogenization Method to Predict the Thermal Conductivity of Polymer Nanocomposites with Kapitza Thermal Resistance
Shin, Hyunseong ; Yang, Seunghwa ; Yu, Suyoung ; Chang, Seongmin ; Cho, Maenghyo ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 315~321
DOI : 10.7734/COSEIK.2012.25.4.315
In this study, a sequential multiscale homogenization method to characterize the effective thermal conductivity of nano particulate polymer nanocomposites is proposed through a molecular dynamics(MD) simulations and a finite element-based homogenization method. The thermal conductivity of the nanocomposites embedding different-sized nanoparticles at a fixed volume fraction of 5.8% are obtained from MD simulations. Due to the Kapitza thermal resistance, the thermal conductivity of the nanocomposites decreases as the size of the embedded nanoparticle decreases. In order to describe the nanoparticle size effect using the homogenization method with accuracy, the Kapitza interface in which the temperature discontinuity condition appears and the effective interphase zone formed by highly densified matrix polymer are modeled as independent phases that constitutes the nanocomposites microstructure, thus, the overall nanocomposites domain is modeled as a four-phase structure consists of the nanoparticle, Kapitza interface, effective interphase, and polymer matrix. The thermal conductivity of the effective interphase is inversely predicted from the thermal conductivity of the nanocomposites through the multiscale homogenization method, then, exponentially fitted to a function of the particle radius. Using the multiscale homogenization method, the thermal conductivities of the nanocomposites at various particle radii and volume fractions are obtained, and parametric studies are conducted to examine the effect of the effective interphase on the overall thermal conductivity of the nanocomposites.
Experimental Verification of a Liquid Damper with Changeable Natural Frequency for Building Response Control
Kim, Dong-Ik ; Min, Kyung-Won ; Park, Ji-Hun ; Kim, Jae-Keon ; Hwang, Kyu-Seok ; Gil, Yong-Sik ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 323~330
DOI : 10.7734/COSEIK.2012.25.4.323
This study deals with the experiments of liquid dampers with multi cells whose vertical tubes are divided into several square columns for easily changing natural frequencies. Shaking table test is performed to verify control effectiveness of the dampers which are installed on a building structure. To design liquid dampers, a 64-story building structure is reduced to a SDOF structure with 1/20 of similitude laws based on acceleration. The structure model is made up to adjust its mass and stiffness easily, with separate mass and drive parts. Mass parts indicate real structure's weights and drive parts indicate real structure's stiffness with springs and LM guides. Manufactured liquid damper has 18 cells and its natural frequency ranges are 0.65Hz to 0.81Hz. Shaking table test is carried out with one way excitation to compare with only accelerations of a large-scale structure and a structure installed with liquid dampers. Control performance of the liquid damper is expressed by the transfer function from shaking table accelerations to the large-scale structure ones. Testing results show that the liquid damper reduced a large-scale structure's response by tuned natural frequencies.
Application of Time-Series Model to Forecast Track Irregularity Progress
Jeong, Min Chul ; Kim, Gun Woo ; Kim, Jung Hoon ; Kang, Yun Suk ; Kong, Jung Sik ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 331~338
DOI : 10.7734/COSEIK.2012.25.4.331
Irregularity data inspected by EM-120, an railway inspection system in Korea includes unavoidable incomplete and erratic information, so it is encountered lots of problem to analyse those data without appropriate pre-data-refining processes. In this research, for the efficient management and maintenance of railway system, characteristics and problems of the detected track irregularity data have been analyzed and efficient processing techniques were developed to solve the problems. The correlation between track irregularity and seasonal changes was conducted based on ARIMA model analysis. Finally, time series analysis was carried out by various forecasting model, such as regression, exponential smoothing and ARIMA model, to determine the appropriate optimal models for forecasting track irregularity progress.
Structural Analysis using Equivalent Models of Active Control Devices
Park, Ji-Hun ; Yun, Soo-Yong ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 339~346
DOI : 10.7734/COSEIK.2012.25.4.339
In this paper, equivalent models for active control devices are proposed so that building structures with such devices are analyzed using commercial structural analysis programs for the assessment of the structural members under active vibration control. Equivalent link models represent active control device with a virtual linear spring and dashpot, and equivalent force models are control force history acting at the installation point in structural models. Active controllers are designed based on the reduced-order models for a vertical cantilever model and a high-rise building model and corresponding equivalent models are determined from control gain matrices. Based on acceleration, displacement and member force responses, the effectiveness of the equivalent models is verified. As a result, proposed equivalent models, of which equivalent link model showed better performance, appear to enable detailed investigation of structural behavior to the extent of member force level.
The Prediction of Nonlinear behavior of Double Coil Shape Memory Alloy Spring
Lee, Jong-Gu ; Ahn, Sung-Min ; Cho, Kyu-Jin ; Cho, Maenghyo ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 347~354
DOI : 10.7734/COSEIK.2012.25.4.347
The recovery force and displacement occur due to the phase transformation from the martensite phase to the austenite phase induced by the mechanical loading or thermal loading. These recovery force and displacement depend on an initial geometrical configuration of SMAs and loading conditions. Although the SMAs generally generates large recovery forces, the sufficient recovery displacement cannot be expected without a proper design strategy. The functionality of SMAs is limited due to the unbalance between the large recovery force and the small recovery displacement. This study suggests the double coil SMA spring in order to amplifying the recovery displacement induced by the phase transformation. By predicting the recovery displacement of doble coil SMA springs and one coil SMA springs induced by thermal loading, we show that the double coil SMA spring not only mitigate the unbalance of performance but also have a large recovery displacement for its recovery force than one coil SMA spring.
A Comparison Study of Model Parameter Estimation Methods for Prognostics
An, Dawn ; Kim, Nam Ho ; Choi, Joo Ho ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 355~362
DOI : 10.7734/COSEIK.2012.25.4.355
Remaining useful life(RUL) prediction of a system is important in the prognostics field since it is directly linked with safety and maintenance scheduling. In the physics-based prognostics, accurately estimated model parameters can predict the remaining useful life exactly. It, however, is not a simple task to estimate the model parameters because most real system have multivariate model parameters, also they are correlated each other. This paper presents representative methods to estimate model parameters in the physics-based prognostics and discusses the difference between three methods; the particle filter method(PF), the overall Bayesian method(OBM), and the sequential Bayesian method(SBM). The three methods are based on the same theoretical background, the Bayesian estimation technique, but the methods are distinguished from each other in the sampling methods or uncertainty analysis process. Therefore, a simple physical model as an easy task and the Paris model for crack growth problem are used to discuss the difference between the three methods, and the performance of each method evaluated by using established prognostics metrics is compared.
Information-Based Hybrid Modeling Framework on the Systematic use of Artificial Neural-Networks
Kim, JunHee ; Jamshid, Ghaboussi ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 4, 2012, Pages 363~372
DOI : 10.7734/COSEIK.2012.25.4.363
In this study, a new information-based hybrid modeling framework is proposed. In the hybrid framework, a conventional mathematical model is complemented by the informational methods. The basic premise of the proposed hybrid methodology is that not all features of system response are amenable to mathematical modeling, hence considering informational alternatives. This may be because (i) the underlying theory is not available or not sufficiently developed, or (ii) the existing theory is too complex and therefore not suitable for modeling within building frame analysis. The role of informational methods is to model aspects that the mathematical model leaves out. Autoprogressive algorithm and self-learning simulation extract the missing aspects from a system response. In a hybrid framework, experimental data is an integral part of modeling, rather than being used strictly for validation processes. The potential of the hybrid methodology is illustrated through modeling complex hysteretic behavior of beam-to-column connections.