scholarly journals Coupling of Flexural and Longitudinal Damped Vibration in a Two-Layered Beam

1998 ◽  
Vol 5 (5-6) ◽  
pp. 337-341
Author(s):  
F. Pourroy ◽  
S. Shakhesi ◽  
P. Trompette
Keyword(s):  
Damping Ratio ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Resonance Frequencies ◽  
Layered Beam ◽  
Flexural Vibrations

In dynamics, the effect of varying the constitutive materials’ thickness of a two-layered beam is investigated. Resonance frequencies and damping variations are determined. It is shown that for specific thicknesses the coupling of longitudinal and flexural vibrations influences the global modal damping ratio significantly.

scholarly journals Dynamic behaviour of a gymnasium floor

1986 ◽  
Vol 13 (3) ◽  
pp. 270-277 ◽  
Author(s):  
J. H. Rainer ◽  
J. C. Swallow
Keyword(s):  
Concrete Slab ◽  
Damping Ratio ◽  
Mode Shapes ◽  
Resonant Frequencies ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Load Factors ◽  
Resonance Frequencies ◽  
Floor Vibrations ◽  
Vibration Tests

Ten mode shapes, natural frequencies, and modal damping values have been measured for a steel-joist concrete-slab floor spanning 32.1 m. From ambient vibrations and steady-state shaker tests the frequency of the fundamental mode was determined to be 3.5 Hz, and the modal damping ratio to be approximately 1% of critical. A comparison of vibration criteria in Appendix G of CAN3-S16.1-M84 confirms satisfactory performance for walking, but for other rhythmic exercises disturbing vibrations developed. These occurred primarily at the forcing frequency of the exercises and not at floor resonance frequencies. Values of dynamic load factors, α, for rhythmic loadings of this floor were evaluated in accordance with the guidelines on floor vibrations in the Commentary to the National Building Code of Canada 1985. Key words: floors, gymnasiums, vibration tests, resonant frequencies, mode shapes, dynamic loads, dynamic response.

scholarly journals Model Updating for Systems with General Proportional Damping Using Complex FRFs

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Xinhai Wu ◽  
Huan He ◽  
Yang Liu ◽  
Guoping Chen
Keyword(s):  
Model Updating ◽  
Damping Ratio ◽  
Viscous Damping ◽  
Rayleigh Damping ◽  
Damping Matrix ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Resonance Frequencies ◽  
Updating Procedure ◽  
Damping Model

In this paper, we propose a model updating method for systems with nonviscous proportional damping. In comparison to the traditional viscous damping model, the introduction of nonviscous damping will not only reduce the vibration of the system but also change the resonance frequencies. Therefore, most of the existing updating methods cannot be directly applied to systems with nonviscous damping. In many works, for simplicity, the Rayleigh damping model has been applied in the model updating procedure. However, the assumption of Rayleigh damping may result in large errors of damping for higher modes. To capture the variation of modal damping ratio with frequency in a more general way, the diagonal elements of the modal damping matrix and relaxation parameter are updated to characterize the damping energy dissipation of the structure by the proposed method. Spatial and modal incompleteness are both discussed for the updating procedure. Numerical simulations and experimental examples are adopted to validate the effectiveness of the proposed method. The results show that the systems with general proportional damping can be predicted more accurately by the proposed updating method.

Modal damping ratio analysis of dynamical system with non-stationary responses

2016 ◽  
Vol 59 ◽  
pp. 138-146 ◽  
Author(s):  
Da Tang ◽  
Ran Ju ◽  
Qianjin Yue ◽  
Shisheng Wang
Keyword(s):  
Dynamical System ◽  
Damping Ratio ◽  
Ratio Analysis ◽  
Modal Damping Ratio ◽  
Modal Damping

ODS Analysis on the Rack of Batching System Mixer

2013 ◽  
Vol 437 ◽  
pp. 257-260
Author(s):  
Li Zhang ◽  
Guang Yuan Nie
Keyword(s):  
Working Condition ◽  
Damping Ratio ◽  
Side Surface ◽  
Modal Parameters ◽  
Modal Shape ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Before And After ◽  
Structure Vibration ◽  
Batching Machine

By using ODS (Operating Deflection Shapes) technology, the modal parameters of the rack of a batching system mixer under operating condition are identified and the modal shape and modal damping ratio of the rack in a few working frequencies are obtained. The results show that, the batching machine rack on working condition has a significant effect on some frequency and the work principal modes that appear as before and after exercise of two beams above the rack and swaying motion of the brackets of the two side surface. This paper provides a valuable reference for the structure vibration optimization of batching system mixer.

Free Vibration Analysis of Frame-Core Tube Structures Attached with Damped Outriggers

2012 ◽  
Vol 238 ◽  
pp. 648-651
Author(s):  
Zhi Hao Wang
Keyword(s):  
Damping Ratio ◽  
Free Vibration Analysis ◽  
Structural System ◽  
Viscous Dampers ◽  
Core Tube ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
New Energy ◽  
Energy Dissipation System ◽  
Simplified Calculation

The classical outrigger in frame-core tube structure cantilevering from the core tube or shear wall connected to the perimeter columns directly, which can effectively improve the lateral stiffness of the structure. A new energy-dissipation system for such structural system is studied, where the outrigger and perimeter columns are separate and vertical viscous dampers are equipped between the outrigger and perimeter columns to make full use of the relative big displacement of two components. The effectiveness of proposed system is evaluated by means of the modal damping ratio based on the proposed simplified model. The mathematic models of the structural system are obtained with both the assumed mode shape method and finite element method according to the simplified calculation diagram. Based on the modal damping ratio, the optimal damping coefficients of linear viscous dampers are determined, and effectiveness of proposed system is confirmed.

scholarly journals Topology Optimization of Constrained Layer Damping on Plates Using Method of Moving Asymptote (MMA) Approach

2011 ◽  
Vol 18 (1-2) ◽  
pp. 221-244 ◽  
Author(s):  
Zheng Ling ◽  
Xie Ronglu ◽  
Wang Yi ◽  
Adel El-Sabbagh
Keyword(s):  
Topology Optimization ◽  
Energy Dissipation ◽  
Design Variable ◽  
Optimization Design ◽  
Damping Ratio ◽  
Design Tool ◽  
Optimization Approach ◽  
Constrained Layer Damping ◽  
Modal Damping Ratio ◽  
Modal Damping

Damping treatments have been extensively used as a powerful means to damp out structural resonant vibrations. Usually, damping materials are fully covered on the surface of plates. The drawbacks of this conventional treatment are also obvious due to an added mass and excess material consumption. Therefore, it is not always economical and effective from an optimization design view. In this paper, a topology optimization approach is presented to maximize the modal damping ratio of the plate with constrained layer damping treatment. The governing equation of motion of the plate is derived on the basis of energy approach. A finite element model to describe dynamic performances of the plate is developed and used along with an optimization algorithm in order to determine the optimal topologies of constrained layer damping layout on the plate. The damping of visco-elastic layer is modeled by the complex modulus formula. Considering the vibration and energy dissipation mode of the plate with constrained layer damping treatment, damping material density and volume factor are considered as design variable and constraint respectively. Meantime, the modal damping ratio of the plate is assigned as the objective function in the topology optimization approach. The sensitivity of modal damping ratio to design variable is further derived and Method of Moving Asymptote (MMA) is adopted to search the optimized topologies of constrained layer damping layout on the plate. Numerical examples are used to demonstrate the effectiveness of the proposed topology optimization approach. The results show that vibration energy dissipation of the plates can be enhanced by the optimal constrained layer damping layout. This optimal technology can be further extended to vibration attenuation of sandwich cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles as an invaluable design tool.

scholarly journals Equivalent Modal Damping Ratios of a Composite Tube-Type Tall Building to Dynamic Wind Loading

1996 ◽  
Vol 3 (2) ◽  
pp. 99-105 ◽  
Author(s):  
B.C. Huang ◽  
K.M. Lam ◽  
A.Y.T. Leung ◽  
Y.K. Cheung
Keyword(s):  
Damping Ratio ◽  
Computing Methods ◽  
Tall Building ◽  
Wind Loading ◽  
Composite Tube ◽  
Equivalent Damping ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Detailed Method ◽  
Tube Type

This article discusses computing methods of the equivalent modal damping ratio for a composite tube-type tall building. The equivalent damping ratio of a composite structure under wind-induced vibrations encompasses the combined effects from the different values of damping, mass, and stiffness of the external and internal tubes. A detailed method incorporating Rayleigh damping and the transfer matrix method is proposed for the determination of the equivalent modal damping ratio. A simplified method for engineering applications is also proposed. Results for a 40-story building are presented exemplifying the computation and relationships between the properties of the external and internal tubes.

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