Passive Structural Vibration Control Research Articles

Effects of thermal aging on mechanical properties of laminated lead and natural rubber bearing

Laminated rubber bearing is very popular base isolation of earthquake engineering pertaining to the passive structural vibration control technologies. Rubber used in fabricating NRB and LRB can be easily attacked by various environmental factors such as oxygen, heat, light, dynamic strain, and organic liquids. Among these factors, this study carried out thermal aging test to investigate the effect of thermal aging on the mechanical properties of laminated rubber bearings in accelerated exposure condition of <TEX>$70^{\circ}C$</TEX> temperature for 168 hours. The compressive-shear test was carried out to identify the variation of compressive and shear properties of the rubber bearings before and after thermal aging. In contrast to tensile strength and elongation tests, the hardness of rubber materials showed the increasing tendency dependent on exposure temperature and period. Based on the test results, the property changes of rubber bearing mainly aged by heat are quantitatively presented.

Passive Vibration Control of Structures Subjected to Random Ground Excitation Utilizing Sloshing in Rectangular Tanks

Passive vibration control of an elastic structure carrying a rectangular tank, partially filled with liquid, is investigated when the structure is subjected to horizontal, narrowband, random ground excitation. The modal equations of motion for liquid sloshing are derived using Galerkin's method, considering the nonlinearity of sloshing. The system response statistics including mean square values, correlation coefficients, and probability density functions (PDFs) are numerically estimated from the time histories using the Monte Carlo simulation when the natural frequency of the structure is close to that of liquid sloshing. The influences of the excitation center frequency, its bandwidth, and the liquid level on the system responses are examined. As a result, it is found that the mean square responses of the structure decrease when the center frequency is close to the natural frequency of the structure due to sloshing. Tuned liquid dampers (TLDs) are found to be most effective for comparatively low liquid levels.

Semiactive–passive structural vibration control strategy for adjacent structures under seismic excitation

The objective of this paper is to study a structural vibration control strategy for seismic protection of multi-structure systems that combines interstructure passive damping elements with local feedback control systems implemented in the substructures. These local feedback control systems are independently designed and operated, and use semiactive devices with limited actuation capacity as force actuators. The combined action of local semiactive feedback control systems and passive interstructure links can produce an appropriate reduction in the substructures' vibrational response and, simultaneously, provides additional protection against interstructure collisions. The proposed semiactive–passive control strategy is remarkably robust against large external disturbances and failures of the local feedback control systems, and also has a number of particular characteristics that can be specially relevant in practical implementations: low cost and power requirements, design and implementation flexibility, and conceptual simplicity. Due to the complexity of a general multi-structure system, a particular two-building system has been chosen to present the main ideas.

Nonlinear Model of Pseudoelastic Shape Memory Alloy Damper Considering Residual Martensite Strain Effect

Recently, there has been increasing interest in using superelastic shape memory alloys for applications in seismic resistant-design. Shape memory alloys (SMAs) have a unique property by which they can recover their original shape after experiencing large strains up to 8% either by heating (shape memory effect) or removing stress (pseudoelastic effect). Many simplified shape memory alloy models are suggested in the past literature for capturing the pseudoelastic response of SMAs in passive vibration control of structures. Most of these models do not consider the cyclic effects of SMA's and resulting residual martensite deformation. Therefore, a suitable constitutive model of shape memory alloy damper which represents the nonlinear hysterical dynamic system appropriately is essential. In this paper a multilinear hysteretic model incorporating residual martensite strain effect of pseudoelastic shape memory alloy damper is developed and experimentally validated using SMA wire, based damper device. A sensitivity analysis is done using the proposed model along with three other simplified SMA models. The models are implemented on a steel frame representing an SDOF system and the comparison of seismic response of structure with all the models is made in the numerical study.

Active constrained-layer damping: A state-of-the-art review

In this paper the authors discuss the progress that has been made over the past decade in active constrained-layer damping (ACLD). ACLD treatments combine the best features of passive and active control of structural vibrations. By way of introduction the paper describes well-established techniques for passive control of structural vibrations and noise. A concise discussion of the development of so-called ‘smart’ (or ‘intelligent’) actuators and sensors and the emergence of suitable control algorithms show how passive techniques were extended to produce ACLD. A comprehensive literature review follows. It is shown how the passive and active components of ACLD complement each other to enable control of both high and low frequency modes of vibration. The active elements allow structures to adapt to suit a changing environment while the passive elements provide a fail-safe mechanism. Because of the available technology, these benefits are available without significant penalties in terms of cost, weight and complexity.

A Mathematical Model for Pseudoelasticity of Shape Memory Alloy and Its Application in Passive Control

Pseudoelasticity of shape memory alloy (SMA) has attracted great attention in passive vibration control of structures due to its large energy dissipation. In this paper, a first-order differential equation—based versatile model to describe the constitutive relation of the pseudoelasticity of SMA is presented. In this model, there are several parameters used to adjust hysteretic shape, and therefore, a variety of pseudoelastic relations can be described by this model. Based on this model, the damping behaviors of pseudoelasticity of an SMA spring are investigated by analyzing the response of a mass-SMA spring system. The results show that the pseudoelasticity of the SMA can effectively damp the vibration of the system when the vibration amplitude is relatively large.

Vibration control of structures using adjustable slippage elements

A new method for passive control of structural vibrations is introduced and investigated. The method is based on providing nonlinearity to the stiffness of a structure by installing elements with adjustable slippage in the proper locations. An adjustable slippage element (ASE) is a mechanical link with a two-branch elastic force–displacement response. The slippage threshold, which is the transition point between the two branches, can be adjusted within a relatively broad range, and can thus control the shape of the force–displacement curve of the element. An ASE can be used to rearrange the elastic restoring forces in the structure protected, and can be used separately or in combination with other passive control systems such as conventional damping devices. A structure equipped with such elements may gain enhanced dynamic performance, because the ASE redistributes elastic and plastic deformations, decreases force transmissibility, and improves resonance escape properties. These effects are achieved by separating the characteristic displacement within the ASE device among four prestressed elastic springs. The relative deformation between these elastic springs is controlled by their designed stiffness and also by the level of prestressing. The latter also controls the value of the slippage threshold of the device. The present study investigates the behavior and effectiveness of the proposed elements by considering a single-degree-of-freedom (SDOF) system equipped with an ASE and subjected to harmonic loading and earthquake base excitation.

Aspects of Passive Control of Structural Vibrations

A preliminary attempt to organize innovative strategies such as Base Isolation, Supplemental Energy Dissipation, Tuned Mass Damping and other combined approaches recently proposed by the authors, in a more general theory of Structural Control, is presented. To visualize the relationships between dynamic variables and subsystems, the block-diagram representations are used in order to obtain the regulation properties of the systems. It has been proven that the Base Isolation technique applies an open-loop control law and that Tuned Mass Damping and Supplemental Energy Dissipation realize closed-loop control laws. The block-diagram of the new combined strategy Base Isolation and Tuned Mass Damping is presented. The objectives of the regulating criteria are also discussed in order to shape the dynamic response in the frequency domain. The H 2 and H ∞ methods are considered as optimal control algorithms.

Reduction of structural vibrations by multiple-mode liquid dampers

Tuned liquid dampers are low cost devices for passive control of structural vibrations. This paper investigates the combined use of liquid dampers which are tuned to different vibration frequencies of a multi-degree-of-freedom structure. A liquid damper model which was verified by experimental means for nonperiodic excitations is adopted. In the numerical study, a suspension bridge subjected to earthquake excitations is considered. The effectiveness in the reduction of horizontal vibration by using multiple-mode dampers is investigated. The results show that it is beneficial to use dampers tuned to several vibration modes of the structure. The effectiveness of the dampers is dependent on the frequency content of the earthquake spectrum and the positions where the dampers are placed. The optimal positions and optimal mass proportions of liquid dampers of different modes are determined.