scholarly journals Research on Damping Engagement Methodology in Dynamic Analysis of Isolated Structure

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Miao Han ◽  
Jinwei Jiang ◽  
Hongkai Du ◽  
Sijia Feng
Keyword(s):  
Dynamic Analysis ◽  
Frame Structure ◽  
Viscous Damping ◽  
Vibration Frequencies ◽  
Optimal Frequency ◽  
Isolation Layer ◽  
Rayleigh Damping ◽  
Priority Order ◽  
Nonproportional Damping ◽  
Structure Test

Damping has a significant influence on the calculation of structural seismic response. In this paper, we compare the commonly used viscous damping (Rayleigh damping (RD) and Caughey damping (CD)) in combination with the isolated structure test. To avoid the arbitrariness of choosing two reference vibration frequencies in constructing RD, all the combinations of the first several vibration frequencies were calculated. Because the material characteristics of the isolation layer and the superstructure are significantly different and the deformation of the isolation layer is large, we construct nonproportional damping according to these two kinds of damping and make a comparative analysis. Analyzing experimental data, we can obtain the optimal frequency combination of RD and nonproportional damping during dynamic analysis of the isolated structure, the priority order of choosing damping models. For the calculation of RD, the 1st modal frequency of the structure should be included, and the 2nd and 3rd modal frequencies of the nonisolated structure are proposed to calculate the nonproportional damping based on Rayleigh damping (NP-RD) for the three-story frame structure in this paper. RD and nonproportional damping based on Caughey damping (NP-CD) are firstly recommended to be used in the calculation of the isolated structure, followed by NP-RD and then CD.

Simplified characteristics of active magnetic bearings

2002 ◽  
Vol 216 (5) ◽  
pp. 623-628 ◽  
Author(s):  
D J Peel ◽  
C M Bingham ◽  
Y Wu ◽  
D Howe
Keyword(s):  
Natural Vibration ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Viscous Damping ◽  
Vibration Frequencies ◽  
Active Magnetic Bearings ◽  
Complex Dynamic ◽  
Speed Range ◽  
Constant Coefficients ◽  
System Characteristics

Traditionally, active magnetic bearing (AMB) systems are designed as an integral component of machines having generally complex dynamic characteristics. An AMB supported rotor has been tested over a speed range that included system natural vibration frequencies. A linear stiffness and viscous damping AMB characteristic with constant coefficients was identified which was independent of the overall system characteristics and which can thus provide simple and transferable data for a machine designer.

scholarly journals INFLUENCE OF MATERIAL DAMPING ON THE RESPONSE OF UNDERGROUND STRUCTURES SUBJECTED TO EARTHQUAKE

2020 ◽  
Vol 26 ◽  
pp. 64-70
Author(s):  
Veronika Pavelcová ◽  
Tereza Poklopová ◽  
Michal Šejnoha ◽  
Tomáš Janda
Keyword(s):  
Damping Ratio ◽  
Underground Structure ◽  
Eurocode 8 ◽  
Viscous Damping ◽  
Material Damping ◽  
Underground Structures ◽  
Fixed Boundary ◽  
Design Spectrum ◽  
Rayleigh Damping ◽  
Element Simulation

The paper describes a finite element simulation of the response of a real underground structure subjected to earthquake using GEO5 FEM program. It concentrates on the influence of material damping with respect to a specific type of boundary condition prescribed at the bottom of the analyzed domain. It is seen that considering material damping is inevitable particularly in case of so called fixed boundary conditions to arrive at meaningful results. This is demonstrated on an artificial earthquake generated according to a design spectrum defined in Eurocode 8. A viscous damping ratio combined with the results of eigenvalue analysis is used to derive parameters of Rayleigh damping for three specific scenarios promoting the approach based on the lowest natural frequency as sufficiently accurate for the present task.

Rayleigh Damping Effects on Global Analysis of Umbilicals

2011 ◽  
Author(s):  
Lauro Massao Yamada da Silveira ◽  
Rafael Loureiro Tanaka ◽  
Joa˜o Paulo Zi´lio Novaes
Keyword(s):  
Global Analysis ◽  
Time History ◽  
Systems Design ◽  
Hydrodynamic Drag ◽  
Viscous Damping ◽  
Structural Damping ◽  
Peak Period ◽  
Rayleigh Damping ◽  
Drag Forces ◽  
Offshore Industry

Despite global analysis of umbilicals is a well-known area in the offshore systems design, some topics are still opened for discussions. One of these topics refers to the structural damping. Obviously, the viscous damping caused by hydrodynamic drag forces is the major source of damping to the whole system. However, in some severe load cases, the host vessel dynamics may induce high snatch loads to the umbilical top end and these loads are more related to structural damping, specifically in tension–elongation hysteresis, than to viscous damping. The snatch loads must be taken into account in the whole design process, which leads to an umbilical designed to resist to higher tension loads and implies also, in most cases, in over-dimensioned accessories, such as the bending limiters. Actually, due to the high level of friction between layers, the umbilical presents some level of structural damping which is, in fact, related to hysteretic moment-curvature and tension-elongation relations. This intrinsic structural damping may in fact contribute to the reduction of the snatch loads and considering it may reduce the level of conservatism in the design. However, due to the complexity and diversity of umbilical designs, it is not straightforward to come up with general-use hysteretic curves. A simplification then is to apply classic Rayleigh damping. Typically, damping levels of 5% are accepted in the offshore industry when using stiffness-proportional Rayleigh damping (the 5% damping is a percentage of the critical damping and is accounted for at the regular wave period or irregular wave spectral peak period). The problem here is that stiffness-proportional Rayleigh damping increases linearly with the frequency and the damping level at 1Hz, for example, may get to 60%. This fact indicates that the high-frequency part of the response may be simply discarded from the results, which in turn may lead to an incorrect, over-damped analysis. The present work aims tackling the Rayleigh damping issue, evaluating its effects on tension levels and spectral density of the tension time history. A recommendation of how to apply Rayleigh damping is proposed.

Similarity Relations for Vibrating Cylinder with Temperature Gradient across the Thickness

1965 ◽  
Vol 69 (654) ◽  
pp. 412-414 ◽  
Author(s):  
V. J. Modi
Keyword(s):  
Temperature Gradient ◽  
Dynamic Analysis ◽  
High Speed ◽  
Considerable Importance ◽  
Mode Shapes ◽  
Flight Vehicle ◽  
Vibration Frequencies ◽  
Structural Stiffness ◽  
Similarity Relations ◽  
Similarity Law

The dynamic analysis of heated structures is of considerable importance. Significant heating of a flight vehicle may take place at high speed causing reduction in its structural stiffness and vibration frequencies. Such changes in frequencies and mode shapes can substantially affect various static and dynamic aeroelastic instabilities.In general, availability of a similarity law simplifies the solution of a problem. The following presentation studies similarity relations existing between an unheated vibrating cylinder and one with temperature gradient across its thickness.

Dynamic Analysis of Flapper/Nozzle Electrohydraulic Servovalve Considering the Influence of the First-Stage Parameters

2014 ◽  
Vol 687-691 ◽  
pp. 316-321
Author(s):  
Wei Zhang ◽  
Song Jing Li
Keyword(s):  
Dynamic Response ◽  
Dynamic Analysis ◽  
Simulation Model ◽  
Discharge Coefficient ◽  
Mathematic Model ◽  
Viscous Damping ◽  
Response Characteristics ◽  
The Past ◽  
Simulation Results ◽  
Dynamic Response Characteristics

The mathematic model of flapper/nozzle electrohydraulic servovalves is rearranged, many factors are reconsidered which have been omitted in the past analysis which are for the purposes of convenience or on the assumption that they are of no particular significance. According to the rearranged mathematic model, the simulation model of the servovalve is established using the Matlab/simulink software, dynamic response characteristics of the servovalve is simulated when the parameters of the discharge coefficient of nozzles and the viscous damping constant of torque motor and flapper are changed. Simulation results show that the change of the parameters influence the dynamic response of the spool displacement.

Optimal Design of Semi-Trailer Frame Based on Topology Optimization

2012 ◽  
Vol 197 ◽  
pp. 502-507
Author(s):  
Li Li Dai ◽  
Jing Gang Wang ◽  
Shuang Zhao ◽  
Ya Qiong Deng ◽  
Nan Jia
Keyword(s):  
Topology Optimization ◽  
Optimal Design ◽  
Dynamic Analysis ◽  
Dynamic Characteristics ◽  
Frame Structure ◽  
Topological Optimization ◽  
Static Characteristics ◽  
Manufacturing Efficiency ◽  
Original Frame ◽  
The Cost

40t semi-trailer frame is optimized by usage of topological optimization and static/dynamic analysis technology. After the optimization, The static characteristics of frame completely satisfy requirement of intensity and stiffness, and the quality is reduced by 10% compared with the original frame. The dynamic characteristics of the new frame have been improved greatly, which indicate that the optimized frame structure is more reasonable, and lay the foundation for reducing the cost and improving manufacturing efficiency.

Comparative Analysis of Seismic Responses of Different Layer Height Structures with Broken Stone Isolation Layers

2012 ◽  
Vol 238 ◽  
pp. 876-880
Author(s):  
Xin Zhong Zhang ◽  
Lian Juan Miao ◽  
Ke Dong Tang
Keyword(s):  
Comparative Analysis ◽  
Dynamic Analysis ◽  
Vibration Isolation ◽  
Tall Building ◽  
Ground Movement ◽  
Building Structures ◽  
Layer Height ◽  
Multistory Buildings ◽  
Isolation Layer ◽  
Multistory Building

For the purpose of doing modal and dynamic analysis, tall building structures and multistory building For the purpose of doing modal and dynamic analysis, tall building structures and multistory building structures of vibration isolation foundation and non-isolation models were established respectively. To elaborate the broken stone isolating layer efficacy, top ten order frequencies and modes, sliding displacements of isolation layer, storey drift angles, storey accelerations, top floor relative displacements compared to the ground movement are obtained and contrasted. The result of the present work implies that the broken stone isolation layers are suitable for multistory buildings.

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