Showing papers on "Damper published in 1995"

Performance of Multiple Mass Dampers Under Random Loading

Abstract: The dynamic characteristics and effectiveness of multiple mass dampers (MMDs), a collection of several mass dampers with distributed natural frequencies, under random loading are investigated in this paper. The MMD attached in a parallel configuration modifies the transfer function of the damper-building system by flattening the peaks observed in a typical single tuned mass damper-building transfer function. The MMD parameters considered here include the frequency range of MMDs, damping ratio of individual dampers, and the number of dampers. Uniform and variable frequency increments in a specified frequency range and mass variation alone, and in combination, are considered. The secondary inertial effect can be represented by conventional mass dampers or liquid sloshing or oscillating liquid column dampers. A parameter study is conducted to delineate the influence of several parameters on the effectiveness and robustness of MMDs in comparison with a single tuned mass damper (TMD). The random loads considered here include wind and seismic excitations. It is demonstrated that the MMD configuration is more effective in controlling the motion of the primary system. It offers the advantages of portability and ease of installation (because of the reduced size of an individual damper) which makes it attractive not only for new installation, but also for temporary use during construction or for retrofitting existing structures.

Method and apparatus for providing damping force feedback

Abstract: A method and apparatus for interfacing the motion of an object with a digital processing system includes a sensor for detecting movement of the object along a degree of freedom. A passive pneumatic or hydraulic damper is coupled to the object to provide a damping resistance to the object along the degree of freedom and resist a movement of the object. The damping resistance is provided by regulating the control of a fluid with a digital computing apparatus, thus providing a low-cost, low-power force-feedback interface that is safe for the user. The damper and sensor provide an electromechanical interface between the object and the electrical system. A gimbal or other interface mechanism can be coupled between the damper and the object. The interface is well suited for simulations or video games in which an object such as a joystick is moved and manipulated by the user.

Air conditioner for vehicles

Abstract: An air conditioner for vehicles includes a damper for switching among an outside-air inlet mode, an inside-air inlet mode and an outside/inside-air inlet mode, a manual switch for selecting any one of the respective inlet modes, an automatic switch for automatically selecting one of the respective inlet modes, a heating and cooling operation unit, an inside-air temperature sensor, an outside-air temperature sensor and a control unit for selectively controlling the respective inlet modes based on the condition of the heating and cooling operation unit, the condition of the respective switches and the difference between the temperatures detected by the respective temperature sensors. In the air conditioner, an optimum air conditioning in correspondence to the load required for air conditioning can be realized from the viewpoint of saving of energy and efficient operation.

Experimental and analytical investigation of seismic retrofit of structures with supplemental damping : Part.1 - Fluid viscous damping devices

Abstract: This report, the first in a series, presents the evaluation of fluid viscous dampers used as additional braces in reinforced concrete frame structures. This is part of a larger experimental investigation of different damping devices being carried out at the University at Buffalo. A series of shaking table tests of a 1:3 scale reinforced concrete frame incorporating a variety of damping devices were performed after the frame was damaged by prior severe (simulated) earthquakes. An analytical platform fro evaluation of structures integrating such devices was developed and incorporated in IDARC Version 3.2. The experimental and analytical study shows that the dampers can reduce inelastic deformation demands and, moreover, reduce the damage, quantified by an index monitoring permanent deformations.

Seismic behavior of steel frame with added viscoelastic dampers

Abstract: This paper describes the results of an extensive study on the seismic behavior of a viscoelastically damped structure under mild and strong earthquake ground motions. Shaking-table studies were conducted on a 2/5-scale five-story steel model with added viscoelastic (VE) dampers under various ambient temperatures, damper-placement cases, and earthquake intensities. Three types of VE dampers distinguished by dimensions and viscoelastic materials designed to provide the structure with similar damping ratios at room temperature were used. Analytical studies were carried out to predict the equivalent damping ratios and seismic response of the viscoelastically damped structure. Experimental results show that the VE dampers are effective in attenuating seismic structural response under mild and strong earthquake ground motions. Numerical results show that the structural damping and structural response with added VE dampers can be easily and accurately calculated by the proposed analytical methods. The methods are readily available to practical applications.

MODELING OF VISCOELASTIC DAMPERS FOR STRUCTURAL ApPLICATIONS

Abstract: This paper presents an analytical model for predicting the hysteretic behavior of viscoelastic dampers based on the Boltzmann's superposition principle and the method of reduced variables. The model parameters have physical meaning and they can be determined from simple time-domain and frequency-domain tests. The presented model is checked against damper tests performed under different strain inputs and shows good results. Test procedure and determination of model parameters are also discussed. Under certain conditions, it is shown that a significant simplification results in determining the frequency and temperature dependency of the shear storage and shear loss moduli of the viscoelastic material, leading to useful applications to viscoelastic damper design and structural applications. Finally, the presented model is compared with the ones based on the concept of fractional derivatives.

Closed loop structural control using electrorheological dampers

Abstract: Electrorheological (ER) dampers are attractive in control applications where external power cannot be guaranteed. ER dampers are inherently nonlinear, and the sign of the damper force is constrained by a passivity condition. Idealizing these nonlinearities and using a Lyapunov-based control synthesis leads to a bang-bang control rule which minimizes the rate at which the energy from the disturbance is transmitted to the structure. This control rule is applicable to linear and nonlinear structural systems. Simulation results of a bilinear hysteretic structure disturbed by earthquake ground motions, and controlled by modulating the electric field in an ER device, illustrate the control performance. The primary effect of the control is to attenuate peak responses in the early seconds of the earthquake.

The properties of tuned liquid dampers using a TMD analogy

Abstract: Liquid motions in shallow Tuned Liquid Dampers (TLDs) with rectangular, circular, and annular tanks, subject to harmonic base excitation, are measured experimentally. Using a Single-Degree-of-Freedom (SDOF) Tuned Mass Damper (TMD) analogy, equivalent mass, stiffness and damping of the TLD are calibrated from the experimental results. These parameters are functions of the TLD base amplitude. Some important properties of the TLD are discussed on the basis of these results.

Control of buildings using active tuned mass dampers

Abstract: A closed-loop complete-feedback control algorithm is proposed for the control of a building modeled as a single-degree-of-freedom (SDOF) system using an active tuned mass damper (ATMD). The control force is calculated from the acceleration, velocity, and displacement feedbacks of the SDOF system and the active mass damper. The passive-control-device properties, including the stiffness and damping constants of the tuned mass damper and the three gain coefficients of the actuator, are derived by minimizing the displacement variance of the SDOF system. Simulations are performed to evaluate the performance of the active-tuned-mass-damper design on the examples of a SDOF system and a 10-story three-bay building frame. The results show that the control efficiency of the ATMD based on velocity feedback depends on the passive-control-device properties assumed. Also, the ATMD with optimal passive properties using complete feedback results in further reduction in the structural displacement. The results also show t...

Hybrid control of seismic‐excited bridge structures

Abstract: Recently, several hybrid protective systems have been explored for applications to seismic-excited bridge structures. In particular, two types of aseismic hybrid protective systems have been shown to be quite effective: (i) rubber bearings and variable dampers (or actuators), and (ii) sliding bearings and actuators. In this paper, control methods are presented for these hybrid protective systems. The control methods are based on the theory of variable structure system (VSS) or sliding mode control (SMC). Emphasis is placed on the static (direct) output feedback controllers using only the information measured from a few sensors without an observer. Simulation results demonstrate that the control methods presented are robust with respect to system parametric uncertainties and the performance is quite remarkable. Sensitivity studies are conducted to evaluate the effectiveness of hybrid protective systems and passive sliding isolators for reducing the response of seismic-excited bridge structures. The advantages of each protective system are demonstrated by simulation results for a wide range of earthquake intensities.

Electronic Thermostat Having High and Low Voltage Control Capability

Abstract: An electronic thermostat having high and low voltage control capability and varied functional capabilities. The thermostat is particularly suited for use with fan coil heating and cooling units. Specifically the thermostat uses relays to actuate external devices such as heating and cooling equipment, fans and dampers. The use of relays permits control voltages for these external devices to be different (e.g. 24 VAC, 208-230 VAC or 277 VAC).

Force Control of a Semi-Active Damper

Abstract: SUMMARY Two strategies are investigated for controlling a semi-active damper to track a prescribed force demand signal: (i) ‘open loop’ control, using a model of the damping force versus velocity characteristics; and (ii) force feedback (closed loop) control. The damping characteristics and switching transients of a prototype damper were measured, and used to develop a mathematical model of the dynamics of the damper. The two control strategies were investigated using an idealised (constant velocity) test. Their performance was also simulated and measured under realistic operating conditions using the Hardware-in-the-Loop testing method. Open loop damper control was generally found to give superior performance to force feedback control, due to its smaller phase lag at high frequencies.

Stable blade vibration damper for gas turbine engine

Abstract: An improved, highly stable blade-to-blade vibration damper (22) configuration is disclosed which provides substantially continuous blade vibration damping and sealing of an interplatform gap due to positional stability thereof. Disposed in a subplatform cavity, the damper (22) is comprised of a generally triangular shaped body having a vertex (42) thereof aligned with the interplatform gap (64). A primary damper load face (38) abuts a first inclined platform load face (66) and a secondary damper load (40) face abuts a second inclined platformload face (68). Maintenance of sliding planar contact between primary (38) and first load (66) faces and sliding linear contact between secondary (40) and second load (68) faces is afforded by orienting inclined platform faces to have an included angle greater than that of the damper vertex (42) and offsetting a damper center of gravity (58) toward the primary load face (38). The damper (22) may include one or more legs (52,54) to orient the damper in the cavity and one or more extending tabs (56) to discourage hot gas flow thereby. In a preferred embodiment, the damper is utilized as an as-cast member, without the need for additional processing or machining, and the vertex (42) included angle is greater than about 90 degrees.

Behavior of Metallic Plate Dampers in Seismic Passive Energy Dissipation Systems

Abstract: Metallic plate dampers, when incorporated into a structure, provide one of the most effective energy dissipation mechanisms available during an earthquake. Increasingly, they are applied in the seismic retrofit of structures which are found to be deficient. The design of these devices, however, has been largely based upon experiments and macroscopic modeling. In order to gain more insight into the response behavior of metallic plate dampers, a microscopic mechanistic approach is followed in this paper. Included is the development of an inelastic constitutive model for the damper material. Numerical results obtained for a class of metallic plate dampers are presented and comparisons are made with experimental data for validation of the mathematical model. It is also shown that this approach sheds light on several aspects of the damper response which heretofore have not been addressed adequately.

Damper Models for Heavy Vehicle Ride Dynamics

Abstract: SUMMARY A laboratory rig for testing hydraulic dampers using the ‘hardware-in-the-loop’ method is described, and the accuracy of the test method is investigated. A mathematical model of a hydraulic shock absorber is then developed. The model is suitable for vehicle simulations and has seven parameters which can be determined by simple dynamic measurements on a test damper. The shock absorber model is validated under realistic operating conditions using the test rig, and the relative importance of various features of the model on the accuracy of vehicle simulations is investigated.

Indoor air quality control for constant volume heating, ventilating and air conditioning units

Abstract: A system for circulating ventilating air in a space includes a supply air chamber configured for communication with a supply duct, a return air chamber configured for communication with a return air duct, and an outside air chamber configured to receive outside air from an outside air intake. The outside air chamber includes an outside air damper having a plurality of settings for varying outside air flow volume in the outside air chamber. The outside air damper establishes a predetermined relationship between each outside air damper setting and the outside air flow volume. The outside air damper establishes each setting in response to a damper control signal. The system further includes a mixed air plenum in communication with the return air chamber and the outside air chamber and a fan positioned between the mixed air plenum and the supply air chamber, the fan supplying a constant volume of air to the supply air chamber in response to a fan control signal. The system further includes a controller coupled to the outside air damper and the fan for providing the damper control signal and the fan control signal to establish a minimum outside air flow volume to the mixed air plenum.

System for providing integrated zone indoor air quality control

Abstract: A system for providing air quality control for an indoor area divided into a plurality of zones, controls air quality both centrally and at each of the zones, and includes a central controller (101), a central damper (103), a supply air stream duct (105), a return air duct (107), a plurality of zone controllers (111, 113, 115), a plurality of zone dampers (121, 123, 125), a plurality of air quality sensors (131, 133, 135) (e.g. CO₂, volatile organic compounds, humidity, etc...) and a plurality of temperature sensors (141, 143, 145). An output value of an air quality sensor (131-135) from one of the zones, is compared with a zone maximum threshold value and a zone minimum threshold value. The damper (123-125) of the corresponding zone is modulated to vary the supply air flow into the zone. These steps are repeated for each zone. A predetermined function (e.g. average, maximum, minimum, etc...) of the output values from all of the zones is compared with a central maximum threshold value and a central minimum threshold value, and the central damper is modulated to vary the flow of outside air into the supply air stream based on this comparison.

The Seismic Response of a 1:3 Scale Model R.C. Structure with Elastomeric Spring Dampers

Abstract: In this experimental study, elastomeric spring dampers, which have a distinct re‐centering characteristic, are used to retrofit a non‐ductile, previously damaged 1/3 scale model reinforced concrete building frame structure which is subjected to a variety of ground motions in shaking table tests. A velocity dependent analytical model is developed and verified for the elastomeric spring dampers. This model is implemented in the widely available non‐linear dynamic time history analysis computer program DRAIN‐2DX to produce response predictions which are in good agreement with experimental observations. The elastomeric spring damper devices significantly attenuate the seismic response of the structure and provide a considerable amount of energy dissipation while the main non‐ductile reinforced concrete structural load carrying elements remain elastic. The effect of varying the damper configuration on the structural response was also investigated.

Particle beam damper

Abstract: Particle dampers are utilized to damp the fundamental modes of vibration of two antennae mounted at the tip end of cantilever beams. The damper is composed of a closed container which is partially filled with metallic particles. The damper is bolted near the tip of the booms where the amplitude of vibratory motion is greatest. It is shown experimentally that significant damping can be obtained with this very simple and low cost device.

Dynamic analysis of viscoelastic-fluid dampers

Abstract: A solution methodology is presented for computing the dynamic stiffnesses in all vibration modes of viscoelastic-fluid dampers with mechanical properties that depend strongly on both frequency and temperature. The method of reduced variables is introduced to construct the master curves of the dynamic modulus of the fluid at some reference temperature from experimental data at different temperatures. Three generalized-derivative (fractional and complex order) constitutive models are proposed to approximate the dynamic modulus of the polybutane fluid over a wide frequency range. The complex parameters of the proposed models are obtained by finding the best fitting of the master curves. The solution of the problem is obtained by transforming the constitutive and balance equations in the Laplace domain, and developing a boundary-element formulation. The resulting method is applied in the prediction of the mechanical properties of a damper containing the polybutane viscoelastic fluid. Results using the three p...

Silica-containing vibration damper and method

Abstract: A method for vibrationally damping an article that is subject to resonant vibrations comprises the steps of providing a vibration damper and applying the vibration damper to the article to damp the resonant vibrations. The vibration damper comprises an acrylate viscoelastic vibration damping material and an effective amount of hydrophobic silica. The invention also relates to vibration dampers that utilize the acrylate viscoelastic vibration damping material as well as articles that incorporate the vibration dampers.

Constrained layer damper with slit(s) and/or cutout(s)

Abstract: The present invention provides a constrained layer damper having slits and/or cutout(s) therein, which provides improved vibration damping performance. The constrained layer damper of the invention is useful, for example, for damping rotatable spacer articles and also rotatable storage media such as compact disks.

Full-Scale Viscoelastically Damped Steel Frame

Abstract: A full-scale five-story steel-frame structure with added viscoelastic (VE) dampers is studied experimentally and analytically. The experimental program includes free-vibration and harmonic forced-vibration tests. Dynamic scaling relations between the full-scale and 2/5-scale models with VE dampers are presented. Test results confirm that damping in the full-scale structure can be significantly increased by incorporating relatively small VE dampers. The modal strain energy method used to estimate the structural damping for the 2/5-scale model structure is also applicable to the full-scale structure. The damper design procedure developed from the 2/5-scale model can also be used for the full-scale structure. This study provides an important base for utilizing the extensive data generated from the reduced scale-model tests for incorporating VE dampers into full-scale structures.

Mass Damper Using Friction-Dissipating Devices

Abstract: The paper proposes and studies a nonlinear mass damper that uses friction dampers acting transversely to the direction of the motion of the mass damper as a means for energy dissipation. The resistant scheme of this mass damper shows a hysteretic damping mechanism in which the dissipation of energy is quadratic in the amplitude of deformation. The effectiveness of the mass damper in reducing vibrations of the main structural system to which it is attached is investigated. The statistical linearization technique is used to estimate the mean square response of the system subjected to random excitation. The optimum parameters of this mass damper are defined as those that minimize the mean square deformation of the main structural system subjected to random excitation. The study confirms that the efficacy of this nonlinear tuned mass damper (TMD) system is comparable to that of a linear TMD system for a wide range of excitation intensity.