Damping Reduction Research Articles

Pseudo-Spectral Damping Reduction Factors for the Himalayan Region Considering Recorded Ground-Motion Data.

Ground-motion prediction equations that are used to predict acceleration values are generally developed for a 5% viscous damping ratio. Special structures and structures that use damping devices may have damping ratios other than the conventionally used ratio of 5%. Hence, for such structures, the intensity measures predicted by conventional ground-motion prediction equations need to be converted to a particular level of damping using a damping reduction factor (DRF). DRF is the ratio of the spectral ordinate at 5% damping to the ordinate at a defined level of damping. In this study, the DRF has been defined using the spectral ordinate of pseudo-spectral acceleration and the effect of factors such as the duration of ground motion, magnitude, hypocenter distance, site classification, damping, and period are studied. In this study, an attempt has also been made to develop an empirical model for the DRF that is specifically applicable to the Himalayan region in terms of these predictor variables. A recorded earthquake with 410 horizontal motions was used, with data characterized by magnitudes ranging from 4 to 7.8 and hypocentral distances up to 520 km. The damping was varied from 0.5–30% and the period range considered was 0.02 to 10 s. The proposed model was compared and found to coincide well with models in the existing literature. The proposed model can be used to compute the DRF at any specific period, for any given value of predictor variables.

Enhancement of Power System Oscillation Damping using Fuzzy Inference System based Coordinated Design of SSSC Controllers

Nowadays, Flexible AC Transmission System (FACTS) devices are widely used in different power systems. As the application of these technologies increases, possible interferences in operational tasks of controllers and inappropriate oscillations in different situations like fault and post-fault conditions make the coordination of their controllers inevitable. In this paper, a Fuzzy Inference System (FIS) based coordinated design of Static Synchronous Series Compensator (SSSC) controllers is presented and discussed. The main advantages of the proposed scheme are good damping and overshoot reduction of oscillations and thereby improving power oscillations damping. The Trajectory Sensitivities (TS) analysis, which is a time domain method to evaluate the stability of a system in the presence of disturbances, is also used to assess the validity of this coordinated controller design method. The comparison of simulation results with the conventional Proportional-Integral-Derivative (PID) controller based system validates the effectiveness of this design.

Resonant passive–active vibration absorber with integrated force feedback control

A general format of a two-terminal vibration absorber is constructed by placing a passive unit in series with a hybrid unit, composed of an active actuator in parallel with a second passive element. The displacement of the active actuator is controlled by an integrated feedback control with the difference in force between the two passive elements as input. This format allows passive and active contributions to be combined arbitrarily within the hybrid unit, which results in a versatile absorber format with guaranteed closed-loop stability. This is demonstrated for resonant absorbers with inertia realized passively by a mechanical inerter or actively by the integrated force feedback. Accurate calibration formulae are presented for two particular absorber configurations and the performance is subsequently demonstrated with respect to both equal modal damping and effective response reduction.

A novel prediction method of vibration and acoustic radiation for rectangular plate with particle dampers

Particle damping technology is widely used in mechanical and structural systems or civil engineering to reduce vibration and suppress noise as a result of its high efficiency, simplicity and easy implementation, low cost, and energy-saving characteristic without the need for any auxiliary power equipment. Research on particle damping theory has focused on the vibration response of the particle damping structure, but the acoustic radiation of the particle damping structure is rarely investigated. Therefore, a feasible modeling method to predict the vibration response and acoustic radiation of the particle damping structure is desirable to satisfy the actual requirements in industrial practice. In this paper, a novel simulation method based on multiphase flow theory of gas particle by COMSOL multiphysics is developed to study the vibration and acoustic radiation characteristics of a cantilever rectangular plate with Particle dampers (PDs). The frequency response functions and scattered far-field sound pressure level of the plate without and with PDs under forced vibration are predicted, and the predictions agree well with the experimental results. Results demonstrate that the added PDs have a significant effect on vibration damping and noise reduction for the primary structure. The presented work in this paper shows that the theoretical work is valid, which can provide important theoretical guidance for low-noise optimization design of particle damping structure. This model also has an important reference value for the noise control of this kind of structure.

Damping Reduction Factors for Crustal, Inslab, and Interface Earthquakes Characterizing Seismic Hazard in Southwestern British Columbia, Canada

High-damping displacement spectra and corresponding damping reduction factors ( η) are important ingredients in seismic design and analysis of structures equipped with seismic protection systems, as well as in displacement-based design methodologies. In this study, we investigated η factors for three types of earthquake characterizing seismic hazard in southwestern British Columbia, Canada: shallow crustal, deep inslab, and interface subduction. We used a large and comprehensive database including records from recent relevant earthquakes, such as the 2011 Tohoku event. Our key observations were as follows: (1) there is negligible dependence of η on soil class; (2) there is significant dependence of η on the frequency content and duration of ground motions that characterize the different record types, and (3) η is dependent on period, particularly for inslab events. Period-dependent equations were proposed to predict η for damping ratios between 5% and 30% corresponding to the three event types.

Multivariable Negative-Imaginary Controller Design for Damping and Cross Coupling Reduction of Nanopositioners: A Reference Model Matching Approach

This paper presents the design and experimental implementation of a novel multi-input multi-output (MIMO) control structure using two negative-imaginary damping controllers to damp the first resonant mode and attenuate cross coupling effects between the axes of a piezoelectric tube scanner. The dynamics of the scanner in the lateral and longitudinal axes are identified from measured data and the design of the controller using a MIMO framework is done based on a reference model matching approach. The controller proposed in the paper is able to achieve a bandwidth near to the first resonance frequency of the scanner and the proposed controller is robust against changes in resonance frequencies that are due to load changes on the scanner. Experimental results are presented to show the effectiveness of the proposed controller.

Stochastic-based damping reduction factors

Most of the actual formulas available in both scientific literature and seismic codes for the damping reduction factors to be used for the seismic design of highly damped structures are derived through statistical analyses of the time-history response of SDOF systems subjected to earthquake accelerograms. In this study, analytical formulations of the damping reduction factor based on power spectral density functions are derived and compared with the main formulas available in the scientific literature. The surface ground motion is modelled with the Kanai–Tajimi power spectral density, i.e. as an “ideal white noise” at the bedrock filtered through the soil deposit. It is found that the ratio between the ground predominant period and the structure fundamental period significantly influences the reduction due to high damping and that, in some cases (e.g. stiff low-rise buildings), the actual code formulations may become unconservative. Finally, simple code-like formulas for the estimation of the damping reduction factor accounting for the ratio between the ground predominant period and the structure fundamental period are proposed.

Direct displacement-based design accuracy prediction for single-column RC bridge bents

In the last decade, displacement-based (DB) methods have become established design procedures for reinforced concrete (RC) structures. They use strain and displacement measures as seismic performance control parameters. As for other simplified seismic design methods, it is of great interest to prove if they are usually conservative in respect to more refined, nonlinear, time history analyses, and can estimate design parameters with acceptable accuracy. In this paper, the current Direct Displacement-Based Design (DDBD) procedure is evaluated for designing simple single degree of freedom (SDOF) systems with specific reference to simply supported RC bridge piers. Using different formulations proposed in literature for the equivalent viscous damping and spectrum reduction factor, a parametric study is carried out on a comprehensive set of SDOF systems, and an average error chart of the method is derived allowing prediction of the expected error for an ample range of design cases. Following the chart, it can be observed that, for the design of actual RC bridge piers, underestimation errors of the DDBD method are very low, while the overestimation range of the simplified displacement-based procedure is strongly dependent on design ductility.

Acoustic performance of a water muffler

A water muffler based on Kevlar-reinforced rubber tube and an inner-noise reduction structure is proposed in this study. This muffler aims to achieve optimum vibration damping and hydrodynamic noise reduction. An experimental system is established to investigate the acoustic performance of the proposed water muffler. The function of the system is confirmed by testing the reference tube. Tests on the reference tube at different velocities indicate that the effect of the flow mainly concentrates at the frequency band lower than 400 Hz. The comparison of results of the tests on the reference tube, rubber tube, and water muffler show that the rubber tube can reduce noise at some frequency bands. The insertion of the inner structure reduces noise at a frequency band of 630 to 3150 Hz. Numerical simulations of the acoustic performance of the rubber tube and the water muffler are conducted in commercial software. The simulated results show a good accordance of general tendency with the experimental results which confirms the noise reduction effect of the proposed water muffler.

A Two-Way Coupled Model of Particle-Laden Turbulence

A model for turbulent suspensions involving two-way coupling between a liquid carrier phase and a solid dispersed phase is presented. Closure relations are obtained from particle kinetic theory, with both drag and virtual mass effects taken into account. It is shown that the feedback on the flow due to the particles mainly depends on the particle concentration, the characteristic Stokes numbers, and the density ratio between the particle and liquid phases. Over a broad parameter range, we find that drag coupling gives turbulence damping and an increased streaming velocity. Added mass coupling has the opposite effect. Some of the model predictions are compared with data given in the literature, and with PIV experimental data. It is found that the model is generally consistent with experiments; in particular, when it comes to the observed turbulence damping and drag reduction effects. The model can be used as a stand-alone tool to calculate turbulent stresses, mean velocities and concentration profiles of both phases. Alternatively, it can serve as basis for a reduced parametric model of particle feedback effects on; for example, the eddy viscosity, and thus the pressure drop and superficial speed.

Automotive Air Conditioning Compressor Noise Source Identification Method

With the improvement of requirements for vehicle comfort, people put forward higher requirements on the noise control of automotive air conditioning. As the power source of the automobile air conditioner, the compressor is also the main noise sources, so it is the major objective of vibration damping and noise reduction. In this paper, with analyzing the noise mechanism of compressor, introduces four identification methods of automotive air conditioning compressor noise source, providing theoretical basis for automobile air conditioning damping and noise reduction.

Prediction of High-Damping Seismic Demands in Eastern North America

This article investigates high-damping seismic demands and associated damping reduction factors in Eastern North America (ENA). A database of hybrid empirical records with moment magnitudes M ≥ 6.0 is first studied to evaluate 5%- to 30%-damped seismic demands. A new magnitude- and distance-based equation is proposed to predict ENA spectral displacements and then used to characterize their sensitivity to variations in period, magnitude, epicentral distance and site conditions. The proposed equation is also used to assess damping reduction factors in ENA. The results contribute to improved assessment of seismic demands in ENA while accounting for added-damping in structural seismic design.

Balanced calibration of resonant piezoelectric RL shunts with quasi-static background flexibility correction

Resonant RL shunt circuits constitute a robust approach to piezoelectric damping, where the performance with respect to damping of flexible structures requires a precise calibration of the corresponding circuit components. The balanced calibration procedure of the present paper is based on equal damping of the two modes associated with the resonant vibration form of the structure, when including a quasi-static contribution from non-resonant vibration modes via a single background flexibility parameter. Explicit calibration formulae are presented, and it is demonstrated by a numerical example that the procedure leads to equal modal damping and effective response reduction, even for rather indirect placement of the transducer, provided that the correction for background flexibility is included in the calibration procedure.

Seismic force reduction factor for steel moment resisting frames with supplemental viscous dampers

Damping is one of the parameters that control the performance of structures when they are subjected to seismic, wind, blast or other transient shock and vibration disturbances. By adding supplemental viscous dampers, the energy input from a transient deformation is absorbed, not only by the structure itself, but also by the supplemental dampers. The aim of this study is to evaluate the values of both damping and ductility reduction factors for steel moment resisting frames with supplemental linear viscous dampers. Two-dimensional finite element models have been established for a range of low to mid rise buildings with different parameters: number of floors; number of bays; and number of dampers with different supplemental damping ratios (from 5% to 30%). A parametric study has been performed using time history analyses and a well-documented research method (N2-method). In addition, an equation has been proposed for each reduction factor based on regression analysis for the obtained results. The results of the Time history analyses are compared with those of a modified N2-method. Moreover, a comparison with values specified in the European code EC8 and the Egyptian code ECP-201 has been performed.

Influence of Ground Motion Duration on Damping Reduction Factor

This article investigates the influences of the effective ground motion duration (GMD) on damping reduction factor. The GMD are associated with 25 Chi-chi earthquake ground motion records and harmonic sine wave. The study shows that damping reduction factor decreases with the increasing of the damping ratio, and decreases with the increasing of the effective duration of the ground motion and the number of cycles of harmonic excitation. A nonlinear multiple regression analysis based on the statistical mean values of the present study is employed, and a modified damping reduction factor considering the effects of GMD is suggested.

A two‐step direct method for estimating the seismic response of nonlinear structures equipped with nonlinear viscous dampers

SUMMARYThe insertion of fluid viscous dampers in building structures is an innovative technology that can improve significantly the seismic response. These devices could be very useful also in the retrofit of existing buildings. The effect of this typology of damping system is usually identified with an equivalent supplemental damping ratio, which depends on the maximum displacement of the structure, so that iterative procedures are required. In this paper, a simplified direct assessment method for nonlinear structures equipped with nonlinear fluid viscous dampers is proposed. The method proposed in this study is composed by two steps. The first one yields the direct estimate of the supplemental damping ratio provided by nonlinear viscous dampers in presence of a linear elastic structural response. The second step extends the procedure to structures with nonlinear behavior. Both graphical and analytical approaches have been developed. The proposed method has then been verified through several applications and comparisons with nonlinear dynamic analyses. Moreover, an investigation has been performed with regard to the influence of the relations that define the damping reduction factor and the hysteretic damping. Copyright © 2014 John Wiley & Sons, Ltd.

Preparation and characterization of EPDM/silica composites prepared through non-hydrolytic sol-gel method in the absence and presence of a coupling agent

Ethylene propylene diene monomer (EPDM) rubber composites containing in situ generated silica particles was prepared through a non-hydrolytic sol-gel (NHSG) method with silicon tetrachloride as precursor. The silica particles were homogenously dispersed in the EPDM matrix, but there were agglomerates at high silica contents. The swelling experiments showed a decrease in the crosslinking density of the vulcanized rubber due to the presence of the silica particles for both the composites prepared in the presence and absence of a coupling agent, bis-[-3-(triethoxysilyl)-propyl]-tetrasulfide (TESPT). Unlike the composites prepared through a hydrolytic sol-gel (HSG) method with TEOS as precursor, the TESPT did not seem to take part in the sol-gel reaction. The presence of TESPT influenced the interaction and dispersion of the silica particles in the EPDM matrix, which gave rise to increased thermal stability of the EPDM when compared to the composites prepared in the absence of TESPT. However, ethylene chloride and TESPT evaporated from the samples at temperatures below the EPDM decomposition range. The values of the Nielsen model parameters, that gave rise to a good agreement with the experimentally determined Young’s modulus values, indicated improved dispersion and reduced size of the silica aggregates in the EPDM matrix. There was also good agreement between the storage modulus and Young’s modulus values. The filler effectiveness (Factor C) indicated a mechanical stiffening effect and a thermal stability contribution by the filler, while the damping reduction (DR) values confirmed that the EPDM interacted strongly with the well dispersed silica particles and the polymer chain mobility was restricted. The tensile properties, however, were in some cases worse than those for the samples prepared through the HSG method in the presence of TEOS.

Improving capacitance/damping ratio in a capacitive MEMS transducer

Damping forces play an important role in capacitive MEMS (microelectromechanical systems) behavior, and typical damper design (parallel-plates) cannot address the design conflict between increase in electrical capacitance and damping reduction. Squeeze-film damping in in-plane parallel-plate MEMS is discussed here and a novel damper geometry for gap-varying parallel-plates is introduced and used to increase the capacitance/damping ratio. The new geometry is compared with a typical parallel-plate design for an silicon-on-insulator process (25 µm thick) and experimental data shows an approximate 25% to 50% reduction for the damping coefficient in structures with 500 µm long dampers (for a gap variation between 0.75 and 3.75 µm), in agreement with computational fluid dynamics simulations, without significantly affecting the capacitance value (∼4% reduction). Preliminary simulations to study the role of the different geometric parameters involved in the improved geometry are also performed and reveal that the channel width is the most critical value for effective damping reduction.

Steigerung der Effizienz bei Straßentransporten mit unterschiedlichen Reifentypen für Traktoren

The tractor as central draught machine on the farm has an increasing amount of road transport work to accomplish, although the classic fieldwork has still to be carried out efficiently with avoidance of soil structure damage. The diversity of agricultural requirements, as well as the narrow time windows for cultivations and harvest, needs tractors that can be used specifically for transport out on the field and on the road. The main distinguishing features of tyres are, in addition to their rolling resistance, their vibration damping and noise reduction abilities, ground contact area and effects on traction performance and fuel consumption.

Analysis of Noise and Vibration in Subway Station Hall

This study use noise and vibration analytical system to test and analyze the noise and vibration of subway station hall, draw the conclusion: analysis the noise test results when the vehicles through the subway station hall. The noise rises as the frequency increases, gets the peak value nearby 5000 Hz, the high of test point gives lesser influence to noise contribution. The vibration occurred in low frequency range, get the peak value in the frequency band from 70 to 80 Hz. Learn from the test position, the noise and vibration nearby escalator are higher than the other positions, that’s because of the vibration and shock come into the escalator moving. The test results above offer the basis to for the subway station hall’s vibration damping and noise reduction design.