• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.452-461
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• 2003

The effect of initial combined load on the lateral free vibration of arches is investigated. For the analysis, P-M interaction own for the arches are obtained. The arches are circular arches which have constant cross-section and simply supported. Also, the arches are subjected both radial uniform distributed load which results in an axial compression on the cross-section and end moments that cause uniform bending action at the same time. All analysis are performed by finite element method based on Kang and Yoo's curved beam theory.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.2
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• pp.1-14
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• 1991

A computer program for the linear elastic buckling anlalysis of thin walled members is developed using a 3-node triangular shell element. The element has real stiffness value for a kinematic degree of freedom associated with rotation about the surface normal at each node. The validity of the present computer program is demonstrated through the plate buckling analysis and the lateral-torsional buckling analysis of a straight beam. Then, simply supported circular arches subjected to uniform bending are analyzed and the results are compared with existing solutions.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.661-669
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• 1999

이 논문은 탄성지반위에 놓인 원호형 곡선보의 자유진동에 관한 연구이다. 회전관성 및 전단변형을 고려하여 두 개의 매개변수로 표현되는 탄성지반위에 놓인 원호형 곡선보의 자유진동을 지배하는 미분방정식을 유도하고, 이를 수치적분기법과 시행착오적 행렬값탐사법이 결합된 수치해석기법으로 해석하였다. 회전-회전, 회전-고정 및 고정-고정의 단부조건을 갖는 곡선보의 최저차모드 3개의 고유진동수를 산출하였다. 곡선보의 수평높이 지간길이비, Winkler 지반계수, 전단지반계수에 따른 고유진동수 변화를 분석하였으며, 회전관성 및 전단변형의 영향을 고찰하였다.

• Structural Engineering and Mechanics
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• v.59 no.2
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• pp.243-259
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• 2016

This research develops a finite element code for the transient dynamic analysis of tapered fiber reinforced polymer (FRP) poles with hollow circular cross-section and flexible joints used in power transmission lines. The FRP poles are modeled by tapered beam elements and their flexible joints by a rotational spring. To solve the time equations of transient dynamic analysis, precise time integration method is utilized. In order to verify the utilized formulations, a typical jointed FRP pole under step, triangular and sine pulses is analyzed by the developed finite element code and also ANSYS commercial finite element software for comparison. Thereafter, the effect of joint flexibility on its dynamic behavior is investigated. It is observed that by increasing the joint stiffness, the amplitude of the pole tip deflection history decreases, and the time of occurrence of the maximum deflection is earlier.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11A
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• pp.822-830
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• 2009

The spectrum efficiency of mobile communication networks can be improved dramatically adopting multiple antennas technologies. In order to guarantee the licensed rights of primary user (PU), the cognitive radio system should perform in a relatively low interference manner when it gets access to the spectrum of licensed networks. In this paper, we explore a uniformly distributed circular antenna array to implement beamforming algorithm that is accomplished by optimization method at the base station of cognitive radio networks, and therefore we can suppress the interference to PU by steering quite low transmission power toward PU and constructing a narrow beam toward cognitive user (CU). By reducing the constraint number of the optimization problem, we also propose a null steering algorithm that steers rather low radiation power toward PU, while the other areas in the same cell are covered by radiation power except the local area around PU. It is pursued to reduce the computation load and enlarge the capacity of cognitive radio networks extremely. The simulation results demonstrate that the proposed algorithms process superior performance.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.55-61
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• 1999

The torsional and axial vibrations of shaft system have been calculated independently because of both the limitation of computing time and the complexity of crankshaft model. In actual system, however, the torsional and axial vibrations are coupled. Therefore, in recent, many works in the coupled vibration analysis have been done to find out the more exact dynamic behavior of shaft system. The crankshaft model is very important in the vibration analysis of shaft system because most of excitation forces act on the crankshaft. It is, however, difficult to establish an exact model of crankshaft since its shape is very complex. In this work, an efficient method is proposed to construct the stiffness matrix of crankshaft using a finite element model of half crankthrow. The proposed and existing methods are compared by applying to both a simple thick beam with circular cross section and an actual crankshaft.

• Steel and Composite Structures
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• v.21 no.6
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• pp.1211-1226
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• 2016

In this study, free vibration and damping characteristics of composite beams with holes are investigated, experimentally and numerically. Two types of samples with different fabrics are used: unidirectional and woven. The effects of diameter, number and location of circular holes on the vibration characteristics of composite beams are examined. The effects of rotation angle and minor to major diameter ratio of the elliptical hole are also investigated numerically. Moreover, the mode shapes of all types of beams are obtained numerically. According to the results, the natural frequency decreases with increasing hole diameter but increases very little with increasing the distance between the hole center and the clamped end. Damping ratio decreases by increasing the diameter of hole. But it fluctuates by increasing the diameters of holes of beam having three holes. Furthermore it decreases by increasing the distance between hole center and clamped end except for the range 50 mm to 100 mm.

• Structural Engineering and Mechanics
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• v.77 no.2
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• pp.273-291
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• 2021

The strut-and-tie method (STM) has been widely accepted and used as a rational approach for the design of disturbed regions ('D' regions) of reinforced concrete members such as in corbels and deep beams, where traditional flexure theory does not apply. This paper evaluates the applicability of the equilibrium based STM in strength predictions of deep beams (with rectangular and circular cross-section) and corbels using the available experiments in literature. STM is found to give fairly good results for corbel and deep beams. The failure modes of these deep members are also studied, and an optimum amount of distribution reinforcement is suggested to eliminate the premature diagonal splitting failure. A comparison with existing empirical and semi empirical methods also show that STM gives more reliable results. The nonlinear finite element analysis (NLFEA) of 50 deep beams and 20 corbels could capture the complete behaviour of deep members including crack pattern, failure load and failure load accurately.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.355.2-355
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• 2002

The receptance method was applied for the analysis of a cylindrical shell with a spherical cap attached at an arbitrary axial position of the shell. The boundary condition of the shell considered here was clamped-free condition. Before the analysis of the shell/spherical cap combined structure, natural frequencies of the cap and the shell were calculated separately and then they were used in the calculation of the frequencies of the combined structure by the receptance method. (omitted)

• International Journal of Computer Science & Network Security
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• v.24 no.3
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• pp.71-82
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• 2024

This paper proposes a new communication system for e-learning applications to mitigate the negative impacts of COVID-19 where the online massive demands impact the current commu-nications systems infrastructures and capabilities. The proposed system utilizes high-altitude platforms (HAPs) for fast and efficient connectivity provision to bridge the communication in-frastructure gap in the current pandemic. The system model is investigated, and its performance is analyzed using adaptive antenna arrays to achieve high quality and high transmission data rates at the student premises. In addition, the single beam and multibeam HAP radio coverage scenarios are examined using tapered uniform concentric circular arrays to achieve feasible communication link requirements.