• Structural Engineering and Mechanics
• /
• v.57 no.6
• /
• pp.969-988
• /
• 2016

Vibration analysis of the beams on elastic foundation has gained the great interest of many researchers. In the literature, there are many studies that focus on the free vibration analysis of the beams on one or two parameter elastic foundations. On the other hand, there are no sufficient studies especially focus on the comparison of dynamic response including the bending moment and shear force of the beams resting on Winkler and two parameter foundations. In this study, dynamic response of the axially loaded Timoshenko beams resting on modified Vlasov type elastic soil was investigated by using the separation of variables method. Governing equations were obtained by assuming that the material had linear elastic behaviour and mass of the beam was distributed along its length. Numerical analysis were provided and presented in figures to find out the differences between the modified Vlasov model and conventional Winkler type foundation. Furthermore, the effect of shear deformation of elastic soil on the dynamic response of the beam was investigated.

• Journal of Power System Engineering
• /
• v.4 no.1
• /
• pp.60-67
• /
• 2000

As the speed of rotating machines increases and also their weight decreases, the coupling between lateral and torsional vibrations must be considered. In the past, rotordynamics and geardynamics have tended to treat the lateral and torsional vibrations of the system elements as separate and decoupled mechanisms. In the paper, the coupled lateral-torsional free and forced vibration of rotors trained by gears is analyzed using finite element method. Also the complicated variation of the meshing stiffness as a function of contact point along the line of action is estimated correctly. The gear mesh model is assumed to be linear with constant average mesh stiffness.

• Steel and Composite Structures
• /
• v.11 no.1
• /
• pp.59-76
• /
• 2011

Dynamic analysis of an embedded single-walled carbon nanotube (SWCNT) traversed by a moving nanoparticle, which is modeled as a moving load, is investigated in this study based on the nonlocal Timoshenko beam theory, including transverse shear deformation and rotary inertia. The governing equations and boundary conditions are derived by using the principle of virtual displacement. The Galerkin method and the direct integration method of Newmark are employed to find the dynamic response of the SWCNT. A detailed parametric study is conducted to study the influences of the nonlocal parameter, aspect ratio of the SWCNT, elastic medium constant and the moving load velocity on the dynamic responses of SWCNT. For comparison purpose, free vibration frequencies of the SWCNT are obtained and compared with a previously published study. Good agreement is observed. The results show that the above mentioned effects play an important role on the dynamic behaviour of the SWCNT.

• Wind and Structures
• /
• v.4 no.2
• /
• pp.85-100
• /
• 2001

The mechanism of wind-induced ovalling vibrations of cylindrical shells is numerically investigated by using a vortex method. The subject of this paper is limited to a two-dimensional structure in the subcritical regime. The aerodynamic stability of the ovalling vibrations in the second to fourth circumferential modes is discussed, based on the results of a forced-vibration test. In the analysis, two modal configurations are considered; one is symmetric and the other is anti-symmetric with respect to a diameter parallel to the flow direction. The unsteady pressures acting on a vibrating cylinder are simulated and the work done by them for one cycle of a harmonic motion is computed. The effects of a splitter plate on the flow around the cylinder as well as on the aerodynamic stability of the ovalling vibrations are also discussed. The consideration on the mechanism of ovalling vibrations is verified by the results of a free-vibration test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.128-135
• /
• 2006

This paper presents a finite element method to analyze the free vibration of a flexible HDD composed of the spinning disk-spindle system with fluid dynamic bearings(FDBs), the head-suspension-actuator with pivot bearings, and the base plate with complicated geometry. Experimental modal testing shows that the proposed method well predicts tue vibration characteristics of a HDD. This research also shows that even the vibration motion of the spinning disk corresponding to half-speed whirl and the pure disk mode are transferred to a head-suspension-actuator and base plate through the air bearing and the pivot bearing consecutively. The proposed method can be effectively extended to investigate the forced vibration of a HDD and to design a robust HDD against shock.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.1 s.118
• /
• pp.24-32
• /
• 2007

This paper presents a finite element method to analyze the free vibration of a flexible HDD composed of the spinning disk-spindle system with fluid dynamic bearings(FDBs), the head-suspension-actuator with pivot bearings, and the base plate with complicated geometry. Experimental modal testing shows that the proposed method well predicts the vibration characteristics of a HDD. This research also shows that even the vibration motion of the spinning disk corresponding to half-speed whirl and the pure disk mode are transferred to a head-suspension-actuator and base plate through the air bearing and the pivot bearing consecutively. The proposed method can be effectively extended to investigate the forced vibration of a HDD and to design a robust HDD against shock.

• Journal of Power System Engineering
• /
• v.11 no.4
• /
• pp.78-85
• /
• 2007

In order to analyze accurately the vibration of a structure by using the finite element method (FEM), we have to model a analytical structure as a numerical model with many degrees-of-freedom. However, in this case, the FEM needs much computation time and storage. The authors developed the finite element-transfer stiffness coefficient method (FE-TSCM) for overcoming the drawback of the FEM. In this paper, the authors apply the FE-TSCM to the in-plane vibration analysis of general plates with various shapes. Two numerical examples, a rectangular plate and a triangular plate, are used to compare the results of the FE-TSCM and the FEM. Through the numerical calculation, we confirm that the FE-TSCM can be applied to the in-plane free or forced vibration analysis of the general plates with various shapes and is effective to in-plane vibration analysis of general plates.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.4 s.50
• /
• pp.15-24
• /
• 2006

This work reports the results of our study on the dynamic response of various buried pipelines depending on their boundary conditions. We have studied behavior of the buried pipelines both along the axial and the transverse direction. The buried pipelines are modeled as beams on elastic foundation while the seismic wave as a ground displacement in the form of a sinusoidal wave. The natural frequency, its mode, and the effect of parameters have been interpreted in terms of free vibration. In order to investigate the response on the ground wave, the resulting frequency and the mode shape obtained from the free vibration have been utilized to derive the mathematical formula for the forced vibration. The natural frequency varies most significantly by the soil stiffness and the length of the buried pipelines in the case of free vibration. The effects of the propagation direction and velocity and the frequency of ground wave on the dynamic responses of concrete, steel, and FRP pipes have been analyzed and then dynamic responses depending on the type of pipes have been compared. Through performing dynamic analyser for various boundary conditions and estimation of the location of maximum strain has been estimated for the type of pipes and boundary conditions.

• Structural Engineering and Mechanics
• /
• v.61 no.5
• /
• pp.617-624
• /
• 2017

Piezoelectric nanobeams are used in several nano electromechanical systems. The first step in designing these systems is conducting a vibration analysis. In this research, the free vibration of a piezoelectric nanobeam is analyzed by using the nonlocal elasticity theory. The nanobeam is modeled based on Euler-Bernoulli beam theory. Hamilton's principle is used to derive the equations of motion and also the boundary conditions of the system. The obtained equations of motion are solved by using both Galerkin and the Differential Quadrature (DQ) methods. The clamped-clamped and cantilever boundary conditions are analyzed and the effects of the applied voltage and nonlocal parameter on the natural frequencies and mode shapes are studied. The results show the success of Galerkin method in determining the natural frequencies. The results also show the influence of the nonlocal parameter on the natural frequencies. Increasing a positive voltage decreases the natural frequencies, while increasing a negative voltage increases them. It is also concluded that for the clamped parts of the beam and also other parts that encounter higher values of stress during free vibrations of the beam, anti-nodes in voltage mode shapes are observed. On the contrary, in the parts of the beam that the values of the induced stress are low, the values of the amplitude of the voltage mode shape are not significant. The obtained results and especially the mode shapes can be used in future studies on the forced vibrations of piezoelectric nanobeams based on Galerkin method.

• Earthquakes and Structures
• /
• v.25 no.6
• /
• pp.455-467
• /
• 2023

This study focuses on demonstrating the effectiveness of vibration control of tuned rotary mass damper (TRMD) for reducing the bidirectional and torsional response of the irregular asymmetric structure with voided slabs under earthquake excitations. The TRMD arranged in plane of one-story eccentric structure is proposed as a distributed tuned rotary mass damper (DTRMD) system. Lagrange's equation is used to derive the equations of motion of the controlled system. The optimum position and number of TRMD are numerically investigated under harmonic excitation and the control effects of different distributions are discussed. Furthermore, a shaking table test is conducted under different excitation cases, including free vibration, forced vibration and seismic wave to investigate the absorption performance of the device. The numerical simulations of different distributions of the TRMDs show that the DTRMDs are more effective in reduction of the displacement response of the asymmetric structure under the same mass ratio, even when the degree of eccentricity becomes large. However, with small degree of eccentricity, the unreasonable asymmetrical arrangement may cause the increase of the peak value of the rotational angular displacement. Finally, the experimental investigations exhibit similar results of translational displacement of the structure. It is concluded that the vibration of the irregular asymmetric structure can be controlled more economically and effectively by reducing the mass ratio through reducing the quantity of TRMDs at the high stiffness end.