• Journal of Korean Society of Steel Construction
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• v.28 no.5
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• pp.365-371
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• 2016

In the case of the superstructure which is consist of two I girders and slab, the section can behave as II section, so that the neutral axis with respect to out of plane direction flexure can be regarded as major axis. Therefore in-plane flexural mode might govern the free vibration mode. Meanwhile, horizontally curved girders always experience not only bending moments but also torsional moments although the primary load is usually supposed to be gravitational load. The interaction due to bending and torsional moments make the behavior complicated and torsional mode may govern the free vibration mode. In other words, structure can have different dynamic characteristic due to its initial curvature. In this research, using 3-dimensional sell elements, free-vibration analyses are carried out due to initial curvature. The analysis models are assumed to be composite and non-composite and finally natural frequency and eigen mode are discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.181-187
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• 2011

This paper deals with free vibrations of the Timoshenko beam supported by two elastomeric bearings at two far ends. The ordinary differential equation governing free vibrations of such beam is derived, in which both effects of rotatory inertia and shear deformation are included as the Timoshenko beam theory. Also, boundary conditions of the free end are derived based on the Timoshenko beam theory. The ordinary differential equation is solved by the numerical methods for calculating natural frequencies and mode shapes. Both effects of the rotatory inertia and shear deformation on natural frequencies are extensively discussed. Also, relationships between natural frequencies and slenderness ratio, foundation modulus and bearing length are presented. Typical mode shapes of bending moment and shear force as well as deflection are given in figures which show the positions of maximum amplitudes and nodal points.

• Journal of Korean Society of Steel Construction
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• v.11 no.1 s.38
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• pp.55-67
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• 1999

The ratios of elastic to shear modulus of the structures as laminated composite plates and shells, are very large. They are much susceptible to effect of shear deformation. In order to obtain the accurate solutions of laminated composite plate and shells, the effects of shear strain should be considered for the analysis and design of them. Especially, the more exact solution can be obtained in applying to higher-order shear deformation theory. Therefore, in this paper, the third-order shear deformation theory is used to present the distributions of bending, the characteristics of natural frequencies and the buckling load according to the effects of ply orientation, number of layers for the laminated composite plates and shells with simply supported boundary conditions.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.185-194
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• 2012

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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.764-767
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• 2005

This paper deals with the flexural-torsional free vibrations of circular strip foundations with a variable breadth. The breadth of strip foundation varies with the linear functional fashion, which is symmetric about the mid-arc. Differential equations governing free vibrations of such foundations are derived, in which Winkler foundation is considered as the model of elastic soils. Effects of the rotatory and torsional inertias and shear deformation are included in the governing equations. Differential equations are numerically solved to calculate the natural frequencies. In the numerical examples, the free-free end constraint is considered. Effects of the rotatory and torsional inertias and shear parameter on the natural frequencies are reported. Parametric studies between frequency parameters and various system parameters are investigated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.3
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• pp.279-293
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• 2004

The analysis of linear static and free vibration problems of isotropic and laminated composite plates and shells is performed by the improved 9-node shell element with the new strain displacement relationship. In that relationship, the effect of new additional terms between the bending strain and displacement has been investigated in the warping problem. Natural co ordinate based strains, stresses and constitutive equations are used. The assumed natural strain method is used to alleviate both membrane and shear locking behavior from the element. The Lanczos method is employed in the calculation of the eigenvalues of laminated composite structures and the Gauss integration rule is adopted to evaluate the mass matrix. The numerical examples are compared with the analytical solutions to validate the current formulation and the results presented could be useful for the understanding of the behaviour of laminates under free vibration conditions.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.31-40
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• 2002

Free vibration of a thin-walled laminated composite beam is studied. A general analytical model applicable to the dynamic behavior of a thin-walled channel section composite is developed. This model is based on the classical lamination theory, and accounts for the coupling of flexural and torsional modes for arbitrary laminate stacking sequence configuration. i.e. unsymmetric as well as symmetric, and various boundary conditions. A displacement-based one-dimensional finite element model is developed to predict natural frequencies and corresponding vibration modes for a thin-walled composite beam. Equations of motion are derived from the Hamilton's principle. Numerical results are obtained for thin-walled composite addressing the effects of fiber angle. modulus ratio. and boundary conditions on the vibration frequencies and mode shapes of the composites.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1047-1052
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• 2010

Influence of lateral spring constant on energy dissipation and load reduction factor with erespect to lateral vibration of steel sheet pile installed by vibratory pile driver. Energy dissipation and load reduction factor varying with free length of steel sheet pile are more affected by eccentricity than flexural rigidity of steel sheet pile regardless of the magnitudes of lateral spring constants. Load reduction factors were converged when lateral spring constant was equal or larger than 10000N/m.

• Journal of Korea Foresty Energy
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• v.17 no.1
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• pp.36-46
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• 1998

The aim of this study was to develop the noise and vibration damping wood-based composites by using viscoelastic polymer materials. Polyvinylchloride(PVC) was plasticized with 20-140 phr bis(2-ethylhexyl) phthalate(DOP) and the dynamic tensile mechanical properties were measured at 110Hz and approximate temperature range -100 to 150$^{\circ}$ using a Rheovibron Instrument. The PVC/DOP blends were shown to be compatible in all proportions, and both T(E”$_{max}$) and T(tan${\delta}_{max}$) shifted to the lower temperature side as the DOP content increased. The vibration damping properties of wood/polymer composites were measured using the Rheovibron instrument in a bending mode. The composite damping factor(tan ${\delta}_{c}$) of wood /PVC-DOP/wood sandwich structure correlated with the loss factor and that of the coated structure correlated with the loss modulus(E”) of the polymer layer. In addition, the sandwich structure was found to be more effective in damping than the coated structure. The logarithmic decrement (${\Delta}$c) curve of a sandwich structure, which was determined by the free-free flexural vibration method was similar in shape to the tan ${\delta}_{c}$ curve.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.795-798
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• 2010

본 논문에서는 상사진동에서의 응답을 통해 구성된 모드유연도에 의해 추정되는 손상유발 변위를 이용하여 전당빌딩의 손상을 탐지하는 진동기반의 손상탐지 방법을 제시하였다. 이 방법은 전단빌딩의 층간변위를 활용하여 오직 손상이 존재할 때에만 발생하는 Damage-induced inter-story deflection (DI-ID)을 통해 손상탐지를 수행하는 방법이다. 구조물의 전체 자유도에 양의 전단력을 발생시킴으로써 층간변위를 분명히 파악할 수 있도록 하는 양전단력 탐색하중(Positive Shear Inspection Load)을 통해 DI-ID를 산정한다. 제안된 방법의 검증을 위해 5층의 전단빌딩 축소모형을 대상구조물로 선정하여 수치모의실험을 수행했다. 단일손상과 다중손상의 모사를 위해 1층과 3층의 휨강성을 각각 10% 씩 저감시켰고, 수치모의실험 결과, 단일손상과 다중손상 모두 정확히 손상발생 구역을 확인했다.