• Computers and Concrete
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• v.5 no.1
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• pp.37-60
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• 2008

Structural health monitoring of existing infrastructure is currently an important field of research, where elaborate experimental programs and advanced analytical methods are used in identifying the current state of health of critical and important structures. The paper outlines two methods of system identification of beam-like reinforced concrete structures representing bridges, through static measurements, in a distributed damage scenario. The first one is similar to the stiffness method, re-cast and the second one to flexibility method. A least square error (LSE) based solution method is used for the estimation of flexural rigidities and damages of simply supported, cantilever and propped cantilever beam from the measured deformation values. The performance of both methods in the presence of measurement errors is demonstrated. An experiment on an un-symmetrically damaged simply supported reinforced concrete beam is used to validate the developed method. A method for damage prognosis is demonstrated using a generalized, indeterminate, propped cantilever beam.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.10
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• pp.946-949
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• 2007

This paper discusses the lateral vibration of a beam with boundary condition of one end fixed and the other end free. The uniform beam has a solution by summation of some simple exponential functions. But if its shape is not uniform, its solution could be by Bessel's function or mathematical solution could not exist. Even if the solution of Bessel's function exists, as Bessel function is a series function, we must get the solution by numerical method. Author had proposed the solution of the matrix method by Ritz's method and a new mode shape function, and had earned the good results for a wedge beam. Hereby a vibration analysis for the tapered beam with circle cross section was executed, and so good results were showed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.179-179
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• 2021

Top-Down construction method is a method of connecting a beam to a column and using a strut to support earth retaining walls. This method has the advantage of reducing the process of underground construction by reducing the work of installation. Recently, there are a lot of cases of damage and defect occurring in H-beam backfill applied to Top-Down construction method and the concrete slab supporting H-beam backfill. For this, appropriate methods were suggested through finite element analysis of the position and installation form of the H-beam backfill.

• Structural Engineering and Mechanics
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• v.70 no.2
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• pp.199-207
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• 2019

In this paper, a semi-analytical method will be discussed for free vibration analysis of rotating beams with variable cross sectional area. For this purpose, the rotating beam is discretized through applying the transfer matrix method and assumed the axial force is constant for each element. Then, the transfer matrix is derived based on Euler-Bernoulli's beam differential equation and applying boundary conditions. In the following, the frequencies of the rotating beam with constant and variable cross sections are determined using the transfer matrix method in several case studies. In order to eliminate numerical difficulties in the transfer matrix method, the Riccati transfer matrix is employed for high rotation speed and high modes. The results are compared with the results of the finite elements method and Rayleigh-Ritz method which show good agreement in spite of low computational cost.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.864-871
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• 2014

In this paper, we propose an optimization method for obtaining beam curve which minimize the phase errors of Rotman lens. This method is based on idea that 3 path lengths from a beam port through equal phase points, which consist of the center point of array antenna and two points placed symmetrically or asymmetrically along array antenna, to the corresponding phase front are equal. According to this method, the optimal locations of beam ports can be obtained directly by finding each equal phase point set on array antenna to minimize the phase errors for each beam direction. Simulation results show that the proposed method is the most optimal and effective method for determining the beam curve of Rotman lens with low phase errors.

• Earthquakes and Structures
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• v.8 no.5
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• pp.1017-1038
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• 2015

This paper presents a strengthening method that involves the use of ferrocement jackets and chamfers to relocate plastic hinge for non-seismically designed reinforced concrete exterior beam-column joints. An experimental study was conducted to assess the effectiveness of the proposed strengthening method. Four half-scale beam-column joints, including one control specimen and three strengthened specimens, were prepared and tested under quasi-static cyclic loading. Strengthening schemes include ferrocement jackets with or without skeleton reinforcements and one or two chamfers. Experimental results have indicated that the proposed strengthening method is effective to move plastic hinge from the joint to the beam and enhance seismic performance of beam-column joints. Shear stress and distortion within the joint region are also reduced significantly in strengthened specimens. Skeleton reinforcements in ferrocement provide limited improvement, except on crack control. Specimen strengthened by ferrocement jackets with one chamfer exhibits slight decrease in peak strength and energy dissipation but with increase in ductility as compared with that of two chamfers. Finally, a method for estimating moment capacity at beam-column interface for strengthened specimen is developed. The proposed method gives reasonable prediction and can ensure formation of plastic hinge at predetermined location in the beam.

• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.263-274
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• 2018

In this study, we propose a frequency domain spectral element method (SEM) for the vibration analysis of a multi-span beam subjected to a moving point force. This study is an extension of the authors' previous study for a single-span beam subjected to a moving point force, where the two-element model-based SEM was applied. In this study, each span of a multi-span beam is represented by the Timoshenko beam model and the moving point force is transformed into the frequency domain as a series of each stationary point force distributed on the multi-span beam. The span at which a stationary point force is located is represented by two-element model, but all other spans are represented by one-element models. The vibration responses to a moving point force are obtained by superposing all individual vibration responses generated by each stationary point force. The high accuracy and computational efficiency of the proposed SEM are verified by comparing the solutions by SEM with exact analytical solutions by the integral transform method (ITM) as well as the solutions by the finite element method (FEM).

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.4
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• pp.59-65
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• 2022

In this paper, a digital active phased array antenna is briefly introduced and beam forming method for a dual-channel side-lobe blanking applied to blank the side-lobe of the main beam is described. Next, the antenna performance was verified from results of design and antenna near-field measurement for the antenna main beam and side-lobe blanking beam. Then, a single-channel side-lobe blanking beam forming method was proposed to reduce the number of channels than the existing system operating dual-channel side-lobe blanking beam and weight distribution for each element of the side-lobe blanking antenna was designed with the proposed method. Finally, the designed single-channel side-lobe blanking beam pattern and blanking ability were verified and compared with the dual-channel side-lobe blanking beam. In addition, by comparing/verifying the conventional dual-channel and the proposed single-channel side-lobe blanking beam patterns measured through the receiving near-field test of the digital active phased array antenna and their ability to blank side-lobe of the main beam, validity of the proposed method for forming single-channel side-lobe blanking beam was confirmed.

• Structural Engineering and Mechanics
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• v.67 no.4
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• pp.337-346
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• 2018

The purpose of this study is to investigate thermal post-buckling analysis of a laminated composite beam subjected under uniform temperature rising with temperature dependent physical properties. The beam is pinned at both ends and immovable ends. Under temperature rising, thermal buckling and post-buckling phenomena occurs with immovable ends of the beam. In the nonlinear kinematic model of the post-buckling problem, total Lagrangian approach is used in conjunction with the Timoshenko beam theory. Also, material properties of the laminated composite beam are temperature dependent: that is the coefficients of the governing equations are not constant. In the solution of the nonlinear problem, incremental displacement-based finite element method is used with Newton-Raphson iteration method. The effects of the fibber orientation angles, the stacking sequence of laminates and temperature rising on the post-buckling deflections, configurations and critical buckling temperatures of the composite laminated beam are illustrated and discussed in the numerical results. Also, the differences between temperature dependent and independent physical properties are investigated for post-buckling responses of laminated composite beams.

• Interaction and multiscale mechanics
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• v.5 no.4
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• pp.385-397
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• 2012

In this paper the dynamic stiffness matrix method was used for the free vibration analysis of axially moving micro beam with constant velocity. The extended Hamilton's principle was employed to derive the governing differential equation of the problem using the modified couple stress theory. The dynamic stiffness matrix of the moving micro beam was evaluated using appropriate expressions of the shear force and bending moment according to the Euler-Bernoulli beam theory. The effects of the beam size and axial velocity on the dynamic characteristic of the moving beam were investigated. The natural frequencies and critical velocity of the axially moving micro beam were also computed for two different end conditions.