• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.72-78
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• 2008

In this study, advanced (fluid-structure interaction (FSI)) analysis system has been developed in order to predict turbine cascade performance with blade deformation effect due to aerodynamic loads. Intereference effects due to the relative movement of the rotor cascade with respect to the stator cascade are also considered. Reynolds-averaged Navier-Stokes equations with one equation Spalart-Allmaras and two-equation k-ω SST turbulence models are solved to accurately predict fluid dynamic loads considering flow separation effects. A fully implicit time marching scheme based on the (coupled Newmark time-integration method) with high artificial damping is efficiently used to compute the complex fluid-structure interaction problem. Predicted aerodynamic performance considering structural deformation effect of the blade shows somewhat different results compared to the case of rigid blade model. Cascade performance evaluations for different elastic axis positions are importantly presented and its aeroelastic effects are investigated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.1
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• pp.17-24
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• 2024

This paper assesses the structural performance of the Daeungbojeon Hall of Magoksa in Gongju, a representative multi-tiered roof traditional timber structure from the Joseon Dynasty, under vertical loads. Employing midas Gen, a structural analysis software, we developed a three-dimensional analysis model closely resembling the actual structure. Static analysis was employed to evaluate the safety and serviceability of the main vertical and horizontal members under vertical loads. While all members met the safety and serviceability criteria, structural weaknesses were identified in the Daelyang of the lower floor, particularly as a transitional beam, necessitating improvement. For the evaluation of dynamic behavior characteristics, eigenvalue analysis was conducted, assuming a relative rotational stiffness of 5% at the main joints. The natural period was determined to be 1.105 seconds, placing it within the category of a Hanok of similar size. The first mode manifested as a translational movement in the forward and backward direction of the building.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.75-82
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• 2019

Slab panels are very important to develop asphalt concrete (AC) track for minimizing the roadbed stress due to the train load and reducing the plastic deformation of infrared-sensitive AC. In this study, the slab panel for AC track was developed through the shape design and the indoor performance test and its structural integrity has been investigated through the finite element analysis under the flexural tensile stress and the design moment according to various static load combination by KRL-2012 standard train load model and KR-C code. In order to verify the suitability of the slab panel for AC track, static bending strength test and dynamic bending strength test were performed according to EN 13230-2. Results show that the slab panel for AC track satisfies all the performance standards required by European standards such as crack loads and crack extension.

• Journal of Electrical Engineering and Technology
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• v.7 no.5
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• pp.653-658
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• 2012

Load modeling has a significant influence on power system analysis and control. In recent years, measurement-based load modeling has been widely practiced. In the load modeling algorithm, the model structure is determined and the parameters of the established model are estimated. For parameter estimation, least-squares optimization method is applied. The model parameters are estimated so that the error between the measured values and the predicted values is to be minimized. By introducing sliding window concept, on-line load modeling method can be performed which reflects the dynamic behaviors of loads in real-time. For the purpose of data acquisition, the measurement system including PMU is implemented in university level. In this paper, case studies are performed using real PMU data from Korea Univ. and Seoul National University of Science and Technology. The performances of modeling real and reactive power behaviors using exponential and ZIP load model are evaluated.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.48-56
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• 2003

This paper investigates the collapse characteristics of CF/Epoxy composite tubes subjected to axial loads as changing interlaminar number and outer ply orientation angle. The tubes are aften used for automobiles, aerospace vehicles, trains, ships, and elevators. We have performed static and dynamic impact collapse tests by a way of building impact test machine with vertical air compression. It is fanad that CF/Epoxy tube of the 6 interlaminar number (C-type) with 90$^{\circ}$ outer orientation angle and trigger absorbed more energy than the other tubes (A. B and D-types). Also collapse mode depended upon outer orientation angle of CF/Epoxy tubes and loading type as well； typical collapse modes of CF/Epoxy tubes are wedged, splayed and fragmentcl.

• Journal of Drive and Control
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• v.15 no.3
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• pp.49-56
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• 2018

Construction machinery is used to improve productivity in civil engineering work and construction work, and it is a lengthy operation, and consumes considerable fuel to cope with large loads. As a result, productivity and fuel consumption of the construction machine become the main deciding factors. In the hydraulic system of the excavator, the main control valve is the most critical position for control. The flow distribution for control performance is achieved by the metering orifice, that causes critical energy loss. To improve this, we propose a combination of a three port proportional pressure reducing valve and a poppet type flow control valve as an IMV to replace the existing spool type MCV. To validate the proposal, we analyze static characteristics by modeling mathematically, and analyze dynamic characteristics. Simulation using the AMESim software on the regeneration circuit of the boom cylinder up-down operation, verifies the energy-saving effect compared to the existing MCV when IMV is used.

• Advances in materials Research
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• v.7 no.2
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• pp.119-136
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• 2018

In this paper, static and vibration analysis for anti-symmetric cross-ply and angle- ply carbon/glass hybrid laminates rectangular composite plate are presented. In this analysis, the equations of motion for simply supported thick laminated hybrid rectangular plates are derived and obtained through the use of Hamilton's principle. The closed-form solutions of anti-symmetric cross-ply and angle- ply laminates are obtained using Navier solution. The effects of side-to-thickness ratio, aspect ratio, and lamination schemes on the fundamental frequencies loads are investigated. The study concludes that shear deformation laminate theories accurately predict the behavior of composite laminates, whereas the classical laminate theory over predicts natural frequencies. The excellent accuracy of the present analytical solution is confirmed by making some comparisons of the present results with those available in the literature. It can be concluded that the proposed theory is accurate and simple in solving the free vibration behaviors of anti-symmetric cross-ply and angle- ply hybrid laminated composite plates.

• Steel and Composite Structures
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• v.45 no.4
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• pp.555-562
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• 2022

Improving the mechanical properties of concrete in the construction industry in order to increase resistance to dynamic and static loads is one of the essential topics for researchers. In this work, vibration analysis of elastic nanocomposite beams reinforced by nanoparticles based on mathematical model is presented. For modelling of the strucuture, sinusoidal shear deformation beam theory (SSDBT) is utilized. Mori-anak model model is utilized for obtaining the effective properties of the strucuture including agglomeration influences. Utilizing the energy method and Hamilton's principal, the motion equations are calculated. The frequency of the elastic nanocomposite beam is obtanied by analytical method. The aim of this work is investigating the effects of nanoparticles volume percent and agglomeration, length and thickness of the beam on the frequency of the structure. The results show that the with enhancing the nanoparticles volume percent, the frequency is increased. In addition, the water absorption of the concrete is presented in this article.

• Structural Engineering and Mechanics
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• v.48 no.1
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• pp.57-75
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• 2013

It is still inadequate for investigating the highly nonlinear and complex mechanical behaviors of single-layer latticed domes by only performing a force-based demand-capacity analysis. The energy-based balance method has been largely accepted for assessing the seismic performance of a structure in recent years. The various factors, such as span-to-rise ratio, joint rigidity and damping model, have a remarkable effect on the load-carrying capacity of a single-layer latticed dome. Therefore, it is necessary to determine the maximum load-carrying capacity of a dome under extreme loading conditions. In this paper, a mechanical model for members of the semi-rigidly jointed single-layer latticed domes, which combines fiber section model with semi-rigid connections, is proposed. The static load-carrying capacity and seismic performance on the single-layer latticed domes are evaluated by means of the mechanical model. In these analyses, different geometric parameters, joint rigidities and roof loads are discussed. The buckling behaviors of members and damage distribution of the structure are presented in detail. The sensitivity of dynamic demand parameters of the structures subjected to strong earthquakes to the damping is analyzed. The results are helpful to have a better understanding of the seismic performance of the single-layer latticed domes.

• KIEE International Transactions on Power Engineering
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• v.12A no.1
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• pp.15-19
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• 2002

The power transfer capability is determined by the thermal, dynamic stability and voltage limits of the generation and transmission systems. The voltage stability depends on the reactive power limit and it affects the power transfer capability to a great extent. Then, in most load flow analysis, the reactive power limit is assumed as fixed, relatively different from the actual case. This paper proposes a method for determining the power transfer capability from a static voltage stability point of view using the IPLAN which is a high level language used with PSS/E program. The f-V curve for determining the power transfer capability is determined using Repeated Power Flow method. It Is assumed that the loads are constant and the generation powers change according to the merit order. The maximum reactive power limits are considered as varying similarly with the actual case and the effects of the varied maximum reactive power limits to the maximum power transfer capability are analyzed using a 5-bus power system and a 19-bus practical power system.