• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2A
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• pp.155-162
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• 2009

This paper deals with the strongest beams with the solid regular polygon cross-section, whose volumes are always held constant. The differential equation of the elastic deflection curve of such beam subjected to the concentrated and trapezoidal distributed loads are derived and solved numerically. The Runge-Kutta method and shooting method are used to integrate the differential equation and to determine the unknown initial boundary condition of the given beam. In the numerical examples, the simple beams are considered as the end constraint and also, the linear, parabolic and sinusoidal tapers are considered as the shape function of cross sectional depth. As the numerical results, the configurations, i.e. section ratios, of the strongest beams are determined by reading the section ratios from the numerical data related with the static behaviors, under which static maximum behaviors become to be minimum.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3A
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• pp.251-258
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• 2009

This paper deals with the strongest beams with the solid regular polygon cross-section, whose volumes are always held constant. The differential equation of the elastic deflection curve of such beam subjected to the concentrated and trapezoidal distributed loads are derived and solved by using the double integration method. The Simpson's formula was used to numerically integrate the differential equation. In the numerical examples, the clamped-clamped and clamped-hinged ends are considered as the end constraints and the linear, parabolic and sinusoidal tapers are considered as the shape function of cross sectional depth. As the numerical results, the configurations, i.e. section ratios, of the strongest beams are determined by reading the section ratios from the numerical data obtained in this study, under which static maximum behaviors become to be minimum.

• Journal of KSNVE
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• v.6 no.5
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• pp.587-594
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• 1996

The differential equation governing both the free vibrations and buckling loads of tapered beam-columns of regular polygon cross-section with constant volume were derived and solved numerically. The parabolic and sinusoidl tapers were chosen as the variable depth of cross-section for the tapered beam-column. In numerical examples, the clamped-clamped, hinged-clamped and hinged-hinged end constraints were considered. The variations of frequency parameters and first buckling load parameters with the non-dimensional system parameters are reported in figures, and typical vibrating mode shapes are presented. Also, the configurations of strongest columns were determined.

• Computational Structural Engineering
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• v.9 no.3
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• pp.135-143
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• 1996

The differential equations governing both the free vibrations and buckling loads of tapered beam-columns of circular cross-section with constant volume are derived and solved numerically. The effects of axial load are included in the differential equations. The parabolic equation is chosen as the variable radius of circular cross-section for the tapered beam-column. In numerical examples, the clamped-clamped, clamped-hinged and hinged-hinged end constraints are considered. The variations of the frequency parameters and buckling load parameters with the non-dimensional system parameters are presented in figures and the configurations of strongest columns are obtained.

• International Journal of Concrete Structures and Materials
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• v.11 no.2
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• pp.185-197
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• 2017

In this study, we propose a new equation that evaluates the shear strength of beam-column connections in reinforced concrete and steel beam (RCS) composite materials. This equation encompasses the effect of shear keys, extended face bearing plates (E-FBP), and transverse beams on connection shear strength, as well as the contribution of cover plates. Mobilization coefficients for beam-column connections in the RCS composite system are suggested. The proposed model, validated by statistical analysis, provided the strongest correlation with test results for connections containing both E-FBP and transverse beams. Additionally, our results indicated that Architectural Institute of Japan (AIJ) and Modified AIJ (M-AIJ) equations should be used carefully to evaluate the shear strength for connections that do not have E-FBP or transverse beams.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.1
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• pp.66-73
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• 2011

This paper deals with free vibrations of the tapered beams with the constant surface area. The surface area of the objective beams are always held constant regardless shape functions of the cross-sectional depth. The shape functions are chosen as the linear and parabolic ones. Ordinary differential equations governing free vibrations of such beams are derived and solved numerically for determining the natural frequencies. In the numerical examples, hinged-hinged, hinged-clamped and clamped-clamped end constraints are considered. As the numerical results, the relationships between non-dimensional frequency parameters and various beam parameters such as section ratio, surface area ratio, end constraint and taper type are reported in tables and figures. Especially, section ratios of the strongest beam are calculated, under which the maximum frequencies are achieved.

• Advances in nano research
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• v.9 no.3
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• pp.211-220
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• 2020

This paper investigates the effect of linear and non-linear distribution of carbon nanotube volume fraction in the FG-CNTRC beams on the critical buckling by using higher-order shear deformation theories. Here, the material properties of the CNTRC beams are assumed to be graded in the thickness direction according to a new exponential power law distribution in terms of the carbon nanotube volume fractions. The single-walled carbon nanotube is aligned and distributed in the polymeric matrix with different patterns of reinforcement; the material properties of the CNTRC beams are described by using the rule of mixture. The governing equations are derived through using Hamilton's principle. The Navier solution method is used under the specified boundary conditions for simply supported CNTRC beams. The mathematical models provided in this work are numerically validated by comparison with some available results. New results of critical buckling with the non-linear distribution of CNT volume fraction in different patterns are presented and discussed in detail, and compared with the linear distribution. Several aspects of beam types, CNT volume fraction, exponent degree (n), aspect ratio, etc., are taken into this investigation. It is revealed that the influences of non-linearity distribution in the beam play an important role to improve the mechanical properties, especially in buckling behavior. The results show that the X-Beam configuration is the strongest among all different types of CNTRC beams in supporting the buckling loads.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.221-228
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• 1997

The main purpose of this paper is to determine the dynamic optimal shapes of simple beam-columns with the constant volume. The parabolic function is chosen as the variable equation for the depth of regular polygon cross-section. The ordinary differential equation including the effect of axial load is applied to calculate the natural frequencies. The Runge-Kutta and Regula-Falsi methods are used to integrate the differential equation and compute the frequencies, respectively. Then the dynamic optimal shape whose lowest natural frequency is highest is determined by reading the critical value of the frequency versus section ratio curve plotted by the frequency data. In the numerical examples, the simple beam-columns are analysed and the numerical results of this study are shown in tables and figures.

• Steel and Composite Structures
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• v.44 no.4
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• pp.451-471
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• 2022

In the present paper, the static bending and buckling responses of functionally graded carbon nanotubes-reinforced composite (FG-CNTRC) beam under various boundary conditions are investigated within the framework of higher shear deformation theory. The significant feature of the proposed theory is that it provides an accurate parabolic distribution of transverse shear stress through the thickness satisfying the traction-free boundary conditions needless of any shear correction factor. Uniform (UD) and four graded distributions of CNTs which are FG-O, FG-X, FG- and FG-V are selected here for the analysis. The effective material properties of FG-CNTRC beams are estimated according to the rule of mixture. To model the FG-CNTRC beam realistically, an efficient Hermite-Lagrangian finite element formulation is successfully developed. The accuracy and efficiency of the present model are demonstrated by comparison with published benchmark results. Moreover, comprehensive numerical results are presented and discussed in detail to investigate the effects of CNTs volume fraction, distribution patterns of CNTs, boundary conditions, and length-to-thickness ratio on the bending and buckling responses of FG-CNTRC beam. Several new referential results are also reported for the first time which will serve as a benchmark for future studies in a similar direction. It is concluded that the FG-X-CNTRC beam is the strongest beam that carries the lowest central deflection and is followed by the UD, V, Λ, and FG-O-CNTRC beam. Besides, the critical buckling load belonging to the FG-X-CNTRC beam is the highest, followed by UD and FG-O.

• Applied Science and Convergence Technology
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• v.25 no.4
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• pp.81-84
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• 2016

InP/InGaP quantum structures (QSs) grown on GaAs substrates by a migration-enhanced molecular beam epitaxy method were studied as a function of growth temperature (T) using photoluminescence (PL) and emission-wavelength-dependent time-resolved PL (TRPL). The growth T were varied from $440^{\circ}C$ to $520^{\circ}C$ for the formation of InP/InGaP QSs. As growth T increases from $440^{\circ}C$ to $520^{\circ}C$, the PL peak position is blue-shifted, the PL intensity increases except for the sample grown at $520^{\circ}C$, and the PL decay becomes fast at 10 K. Emission-wavelength-dependent TRPL results of all QS samples show that the decay times at 10 K are slightly changed, exhibiting the longest time around at the PL peak, while at high T, the decay times increase rapidly with increasing wavelength, indicating carrier relaxation from smaller QSs to larger QSs via wetting layer/barrier. InP/InGaP QS sample grown at $460^{\circ}C$ shows the strongest PL intensity at 300 K and the longest decay time at 10 K, signifying the optimum growth T of $460^{\circ}C$.