This tutorial/survey paper: (1) provides a concise point of departure for researchers and practitioners alike wishing to assess the current state of the art in the control and monitoring of civil engineering structures; and (2) provides a link between structural control and other fields of control theory, pointing out both differences and similarities, and points out where future research and application efforts are likely to prove fruitful. The paper consists of the following sections: section 1 is an introduction; section 2 deals with passive energy dissipation; section 3 deals with active control; section 4 deals with hybrid and semiactive control systems; section 5 discusses sensors for structural control; section 6 deals with smart material systems; section 7 deals with health monitoring and damage detection; and section 8 deals with research needs. An extensive list of references is provided in the references section.

Structural control: past, present, and future

Dynamics of structures

In recent years, considerable attention has been paid to research and development of structural control devices, with particular emphasis on alleviation of wind and seismic response of buildings and bridges. In both areas, serious efforts have been undertaken in the last two decades to develop the structural control concept into a workable technology. Full-scale implementation of active control systems have been accomplished in several structures, mainly in Japan; however, cost effectiveness and reliability considerations have limited their wide spread acceptance. Because of their mechanical simplicity, low power requirements, and large, controllable force capacity, semiactive systems provide an attractive alternative to active and hybrid control systems for structural vibration reduction. In this paper we review the recent and rapid developments in semiactive structural control and its implementation in full-scale structures.

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State of the art of structural control

We review some applications of fractional calculus developed by the author (partly in collaboration with others) to treat some basic problems in continuum and statistical mechanics. The problems in continuum mechanics concern mathematical modelling of viscoelastic bodies (Sect. 1), and unsteady motion of a particle in a viscous fluid, i.e. the Basset problem (Sect. 2). In the former analysis fractional calculus leads us to introduce intermediate models of viscoelasticity which generalize the classical spring-dashpot models. The latter analysis induces us to introduce a hydrodynamic model suitable to revisit in Sect. 3 the classical theory of the Brownian motion, which is a relevant topic in statistical mechanics. By the tools of fractional calculus we explain the long tails in the velocity correlation and in the displacement variance. In Sect. 4 we consider the fractional diffusion-wave equation, which is obtained from the classical diffusion equation by replacing the first-order time derivative by a fractional derivative of order $0< \beta <2$. Led by our analysis we express the fundamental solutions (the Green functions) in terms of two interrelated auxiliary functions in the similarity variable, which turn out to be of Wright type (see Appendix), and to distinguish slow-diffusion processes ($0 < \beta < 1$) from intermediate processes ($1 < \beta < 2$).

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Fractional Calculus: Some Basic Problems in Continuum and Statistical Mechanics

Supplemental energy dissipation: state-of-the-art and state-of-the- practice

Development of Seismic Isolation Worldwide. Theoretical Basis of Seismic Isolation. Isolation System Components. Code Provisions for Seismic Isolation. Mechanical Characteristics and Modeling of Isolators. Buckling and Stability of Elastomeric Isolators. Design Earthquake Ground Motions. Design Examples. Computer Applications. Specifications for Design, Manufacturing, and Testing of Isolation Devices. Appendix. References. Index.

Design of seismic isolated structures : from theory to practice

1 Seismic Isolation for Earthquake-Resistant Design.- 1.1 Introduction.- 2 Vibration Isolation.- 2.1 Introduction.- 2.2 Theory of Vibration Isolation.- 2.3 Frictional Vibration Isolators.- 3 Seismic Isolation.- 3.1 Review of Fixed-Base Structural Analysis.- 3.2 Linear Theory of Base Isolation.- 3.3 Isolation of Very Flexible Structures.- 4 Extension of Theory to Buildings.- 4.1 M-Degree-of-Freedom Equations of Motion.- 4.2 Modal Analysis of M-DOF System.- 4.3 Estimates of Displacements and Forces for M-DOF System.- 5 Earthquake Regulations for Seismically Isolated Structures.- 5.1 Introduction.- 5.2 1994 Uniform Building Code.- 5.3 Design Methods.- 5.4 Static Analysis.- 5.5 Dynamic Analysis.- 5.6 Computer Programs for Analysis of Seismically Isolated Structures.- 5.7 Other Requirements for Nonstructural Components.- 5.8 Review.- 5.9 Design Requirements for Isolators.- 5.10 Base-Isolated Structures under Extreme Earthquake Loading.- 6 Coupled Lateral-Torsional Response of Seismically Isolated Buildings.- 6.1 Introduction.- 6.2 Case I: Three Close Frequencies.- 6.3 Case II: Equal Lateral Frequencies, Distinct Torsional Frequency.- 7 Behavior of M?ltilayered Bearings Under Compression and Bending.- 7.1 Introduction.- 7.2 Shear Stresses Produced by Compression.- 7.3 Bending Stiffness of a Single Pad.- 7.4 Pure Compression of Single Pads with Large Shape Factors.- 7.5 Compression Stiffness for Circular Pads with Large Shape Factors.- 7.6 Compression Stiffness for Square Pads with Large Shape Factors.- 7.7 Bending Stiffness of Single Pads with Large Shape Factors.- 8 Buckling Behavior of Elastomeric Bearings.- 8.1 Stability Analysis of Bearings.- 8.2 Stability of Annular Bearings.- 8.3 Influence of Vertical Load on Horizontal Stiffness.- 8.4 Downward Displacement of the Top of a Bearing.- 8.5 A Simple Mechanical Model for Bearing Buckling.- 8.6 Postbuckling Behavior.- 8.7 Influence of Compressive Load on Bearing Damping Properties.- 8.8 Rollout Stability.- 9 Design Process for Multilayered Elastomeric Bearings.- 9.1 Preliminary Bearing Design Process.- 9.2 Experimental Studies of Elastomeric Isolator Performance.- 9.3 Compact Design Bearings.- Afterword.- References.- Appendix A.- A.I Base-Isolated Buildings and Projects in the United States.- A.2 Retrofit Base-Isolated Buildings and Projects in the United States.- Appendix B.- B.I N-PAD.- B.2 3D-BASIS.- B.3 SADSAP.- B.4 General Nonlinear Three-Dimensional Analysis Programs.

Earthquake-Resistant Design with Rubber

Aseismic base isolation: review and bibliography

Design of seismic isolated structures

Three analytical studies of base-isolated structures are carried out. First, six pairs of near-fault motions oriented in directions parallel and normal to the fault were considered, and the average of the response spectra of these earthquake records was obtained. This study shows that in addition to pulse-type displacements, these motions contain significant energy at high frequencies and that the real and pseudo-velocity spectra are quite different.

The second analysis modelled the response of a model of an isolated structure with a flexible superstructure to study the effect of isolation damping on the performance of different isolation systems under near-fault motion. The results show that there exists a value of isolation system damping for which the superstructure acceleration for a given structural system attains a minimum value under near-fault motion. Therefore, although increasing the bearing damping beyond a certain value may decrease the bearing displacement, it may transmit higher accelerations into the superstructure.

Finally, the behaviour of four isolation systems subjected to the normal component of each of the near-fault motions were studied, showing that EDF type isolation systems may be the optimum choice for the design of isolated structures in near-fault locations. Copyright © 2001 John Wiley & Sons, Ltd.

James M. Kelly

Papers

Design of seismic isolated structures : from theory to practice

Earthquake-Resistant Design with Rubber

Aseismic base isolation: review and bibliography

Design of seismic isolated structures

Base isolation for near-fault motions