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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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Free Vibrations of Tapered Timoshenko Beam by using 4th Order Ordinary Differential Equation
Lee, Byoung-Koo ; Park, Kwang-Kyou ; Lee, Tae-Eun ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 3, 2012, Pages 185~194
DOI : 10.7734/COSEIK.2012.25.3.185
This paper deals with free vibrations of the tapered Timoshenko beam in which both the rotatory inertia and shear deformation are included. The cross section of the tapered beam is chosen as the rectangular cross section whose depth is constant but breadth is varied with the parabolic function. The fourth order ordinary differential equation with respect the vertical deflection governing free vibrations of such beam is derived based on the Timoshenko beam theory. This governing equation is solved for determining the natural frequencies corresponding with their mode shapes. In the numerical examples, three end constraints of the hinged-hinged, hinged-clamped and clamped-clamped ends are considered. The effects of various beam parameters on natural frequencies are extensively discussed. The mode shapes of both the deflections and stress resultants are presented, in which the composing rates due to bending rotation and shear deformation are determined.
Lagrangian Formulation of a Geometrically Exact Nonlinear Frame-Cable Element
Jung, Myung-Rag ; Min, Dong-Ju ; Kim, Moon-Young ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 3, 2012, Pages 195~202
DOI : 10.7734/COSEIK.2012.25.3.195
Two nonlinear frame elements taking into account geometric nonlinearity is presented and compared based on the Lagrangian co-rotational formulation. The first frame element is believed to be geometrically-exact because not only tangent stiffness matrices is exactly evaluated including stiffness matrices due to initial deformation but also total member forces are directly determined from total deformations in the deformed state. Particularly two exact tangent stiffness matrices based on total Lagrangian and updated Lagrangian formulation, respectively, are verified to be identical. In the second frame element, the deformed curved shape is regarded as the polygon and current flexural deformations in iteration process are neglected in evaluating tangent stiffness matrices and total member forces. Two numerical examples are given to demonstrate the accuracy and the good performance of the first frame element compared with the second element. Furthermore it is shown that the first frame element can be used in tracing nonlinear behaviors of cable members.
A Comparative Study on Structural Performance of Wind Turbine Composite Blades with Room-Temperature and Radiation Curing
Jeon, Jae Heung ; Kim, Sung Jun ; Shin, Eui Sup ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 3, 2012, Pages 203~209
DOI : 10.7734/COSEIK.2012.25.3.203
In this paper, cross-sectional stiffnesses, static stresses, and dynamic natural frequencies are analyzed to examine the structural performance of wind turbine composite blades. The material properties of composite materials are based on room-temperature and radiation curing processes. The cross-sectional stiffnesses of composite blades are calculated by applying a beam theory with solid-profile cross sections. The wind turbine blades are modeled with a finite element program, and static analyses are carried out to check the maximum displacement and stress of the blades. In addition, dynamic analyses are performed to predict the rotating natural frequencies of the composite blades including the effects of centrifugal force. By comparing these analysis results, mainly owing to the material properties of composite materials, an improvement in the structural performance of the blades according to the curing process is investigated.
Micromechanics-based Analysis on Tensile Behavior of the Sprayed FRP Composites with Chopped Glass Fibers
Yang, Beom-Joo ; Ha, Seong-Kook ; Lee, Haeng-Ki ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 3, 2012, Pages 211~217
DOI : 10.7734/COSEIK.2012.25.3.211
In this paper, experimental tests and theoretical studies were carried out to evaluate the tensile behavior of the sprayed FRP composite with chopped glass fiber. For this, a series of tensile strength tests with various strain rates were conducted on the specimens of the matrix and sprayed FRP composite. Sprayed FRP composite contained chopped glass fibers with fiber length of 15mm and a specific volume fraction of fibers of 25 %. An inverse simulation was conducted to simulate the strain rate sensitivity based on the present experimental data of the epoxy resin. The simulated viscosity value is adapted to the micromechanics-based viscoelastic damage model(Yang et al., 2012), and the overall tensile behavior of sprayed FRP composites is predicted. It was seen from the comparative study between present experimental data and predication results that the proposed methodology can be used to predict the viscoelastic behavior of the sprayed FRP composite.
Parametric Study on Reinforced Concrete Columns under Blast Load
Choi, Hosoon ; Kim, Min-Sook ; Lee, Young-Hak ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 3, 2012, Pages 219~226
DOI : 10.7734/COSEIK.2012.25.3.219
Columns are the key elements supporting load in structure. Column failure causes the structure to collapse. It is important to evaluate residual strength for damaged columns under blast load for preventing progressive collapse. In this paper, columns were investigated to compare the blast resistance on the change of the number of steel bars within the range of reinforcement ratio. And this study was carried out 4 different analytical models to evaluate effects of aspect ratio. The results indicate that the vertical strain was unaffected by the number of steel bars and aspect ratio. As the number of steel bars facing blast load increase, the blast resisting capacity of the columns was improved in the lateral strain. Also, the analysis results showed that a large moment of inertia of area, as compared to a small one would be superior in residual strength as well as force of restitution.
Analysis on Anisotropy of Void Distribution and Stiffness of Lightweight Aggregate using CT Images
Chung, Sang-Yeop ; Han, Tong-Seok ; Yun, Tae Sup ; Youm, Kwang Soo ; Jeon, Hyun-Gyu ; Kang, Dong Hun ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 3, 2012, Pages 227~235
DOI : 10.7734/COSEIK.2012.25.3.227
The void distribution in concrete materials strongly affects its material properties. Therefore, the identification of spatial distribution of void is important to understand and estimate material behavior. To examine and quantify the void distribution inside lightweight aggregates, CT(computed tomography) image is used. 3D lightweight aggregate images are generated by stacking of cross-sectional images from CT. Spatial distribution of void of aggregate along the direction is visualized on the sphere using probability distribution function. Stiffness of lightweight aggregate for the directions is also examined. It is confirmed that direction-based probability distribution and stiffness from CT images are effective in characterizing void distributions of aggregates.
Optimum Shape Design of Gearbox Housing for 5MW Wind Turbines
Jeong, Ki-Yong ; Lee, Dae-Yeon ; Choi, Eun-Ho ; Cho, Jin-Rea ; Lim, O-Kaung ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 3, 2012, Pages 237~243
DOI : 10.7734/COSEIK.2012.25.3.237
The thickness optimization of the gearbox housing for 5MW wind turbine is carried out with the help of the efficient structure analysis model and the approximation model of objective function. Wind turbine gearbox is a complex structural system composed of a number of gear trains, shafts, bearing and gearbox housing, requiring a tremendous number of elements for the structural analysis and design. In this paper, an effective analysis and design model considering the tooth stiffness of helical gears is proposed. It enables to significantly reduce the total element number and the analysis time. Through the numerical optimization of housing thickness making use of the effective gearbox model and the approximate model of objective function, the total weight of the gearbox housing is minimized. It has been observed from the numerical experiment that the approximation model is reliable and the optimization result is acceptable and verified analysis.
Simplified Analysis Formula for the Interaction of the Launching Nose and the Superstructure of ILM Bridge
Lee, Hwan-Woo ; Jang, Jae-Youp ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 3, 2012, Pages 245~258
DOI : 10.7734/COSEIK.2012.25.3.245
ILM(incremental launching method) is a way of construction, installing a girder producing spot behind the abutment, making the bridge girder infilled with concrete continuously and launching with using by jack. The superstructure of the bridge constructed by this method is temporarily located on the center of the span and the supporting points under construction. Therefore, the sections are structurally undergone maximum positive moment, maximum negative moment, and maximum shear force arising from self weight. On the other hand, launching nose is attached to the front of the girder to decrease the cantilever effect. The magnitude of this temporary stress creating on the upper section is dependent upon the launching nose's characteristics. This study has proposed an analysis formula simplified on the assumption that the launching nose section is a quasi-equivalent section(rigid; equivalent section, weight; tapered section) in order to ensure the accuracy of the analysis formula and improve its usage with reference to the interaction between the launching nose and the upper section; and a prismatic analysis formula modified by displacing a diaphragm's weight by a concentrated load in order to improve the accuracy of the existing analysis formula that assumes the launching nose section as the equivalent section. To judge the accuracy and usage of two analysis formulas proposed, we have compared and analyzed computational structural analysis programs and existing analysis formulas based on actual ILM bridge data. As a result, all of two reveal the superior accuracy and also their usage has been improved by the simplification of analysis formulas.
Seismic Performance Evaluation of Flat Column Dry Wall System and Wall Slab System Structures
Kang, Hyungoo ; Lee, Minhee ; Kim, Jinkoo ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 3, 2012, Pages 259~266
DOI : 10.7734/COSEIK.2012.25.3.259
In this paper the seismic performance of a flat plate wall system structure was evaluated based on the ATC-63 approach, and the results were compared with those of a wall slab structure having the same size. As analysis model structures, a twelve story flat plate wall structure and a wall slab structure were designed based on the KBC-2009, and their seismic performances and collapse behaviors were evaluated by nonlinear static and incremental dynamic analyses(IDA). It was observed that the flat plate wall structure was designed with smaller amount of reinforced concrete, and showed slightly larger displacement response compared with those of the wall slab structure. The collapse margin ratios of the two structures obtained from the incremental dynamic analyses satisfied the limit states specified in the ATC-63, and the structures turned out to have enough capacity to resist the design level seismic load.
Experimental Validation of Crack Growth Prognosis under Variable Amplitude Loads
Leem, Sang-Hyuck ; An, Dawn ; Lim, Che-Kyu ; Hwang, Woongki ; Choi, Joo-Ho ;
Journal of the Computational Structural Engineering Institute of Korea, volume 25, issue 3, 2012, Pages 267~275
DOI : 10.7734/COSEIK.2012.25.3.267
In this study, crack growth in a center-cracked plate is predicted under mode I variable amplitude loading, and the result is validated by experiment. Huang's model is employed to describe crack growth with acceleration and retardation due to the variable loading effect. Experiment is conducted with Al6016-T6 plate, in which the load is applied, and crack length is measured periodically. Particle Filter algorithm, which is based on the Bayesian approach, is used to estimate model parameters from the experimental data, and predict the crack growth of the future in the probabilistic way. The prediction is validated by the run-to-failure results, from which it is observed that the method predicts well the unique behavior of crack retardation and the more data are used, the closer prediction we get to the actual run-to-failure data.