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

Recent advances in nonlinear passive vibration isolators

A thermodynamical constitutive model for shape memory materials. Part I. The monolithic shape memory alloy

Structural systems often show nonlinear behavior under severe excitations generated by natural hazards. In that condition, the restoring force becomes highly nonlinear showing significant hysteresis. The hereditary nature of this nonlinear restoring force indicates that the force cannot be described as a function of the instantaneous displacement and velocity. Accordingly, many hysteretic restoring force models were developed to include the time dependent nature using a set of differential equations. This survey contains a review of the past, recent developments and implementations of the Bouc-Wen model which is used extensively in modeling the hysteresis phenomenon in the dynamically excited nonlinear structures.

The Hysteresis Bouc-Wen Model, a Survey

Aseismic base isolation: review and bibliography

A comparative study of performances of different base isolators for shear beam type structures is carried out. Several leading base isolation systems, including the laminated rubber bearing with and without lead plug, the resilient-friction base isolator with and without sliding upper plate, and the EDF system are considered. Displacement and acceleration response spectra for a shear beam structure subject to the accelerograms of the N00W component of El Centro 1940 and the N90W component of Mexico City 1985 earthquakes and their magnified forms are evaluated. A series of parametric studies is carried out and advantages and disadvantages of various base isolation systems are identified. Comparisons of the results with the response spectra of a fixed-base structure show that the base isolation systems are, in general, highly effective in reducing the peak acceleration transmitted to the superstructure. Thus, the deflections and stresses generated in a base-isolated structure are significantly lower than those of a fixed-base one. Furthermore, the results of the study also show that the friction-type base isolators are less sensitive to severe variations in frequency content and amplitude of the ground acceleration.

A comparative study of performances of various base isolation systems, part I: Shear beam structures

A comparative study of effectiveness of various base isolators is carried out. These include the laminated rubber bearing with and without lead plug and several frictional base isolation systems. The structure is modeled as a rigid mass and the accelerograms of the NOOW component of the El Centro 1940 earthquake and the N90W component of the Mexico City 1985 earthquake are used. The performances of different base isolation devices under a variety of conditions are evaluated and compared. Combining the desirable features of various systems, a new design for a friction base isolator is also developed and its performance is studied. It is shown that, under design conditions, all base isolators can significantly reduce the acceleration transmitted to the superstructure.

Comparative study of base isolation systems

The rectilinear motion and the conditions of reattachment and separation of a rigid body, in friction contact with another body are considered. A graphical representation of the motion is indicated, and analytical expressions for the velocities and displacements are derived. The existence of limiting values of velocity and displacement is shown for a special class of periodic ground motions which include harmonic motions. Also, the equations of motion and the conditions of reattachment and separation of a two degrees of freedom model of a sliding structure and foundation are derived. The numerical integration of the response of this system is carried out, as well as a parametric study showing the effect of different values of the mass ratio, coefficient of friction and amplitude of the ground acceleration. Use of results of the parametric study, concerning amount of slippage, resonance frequency ratios, minimum allowable frequency for sticked mode, etc. in the design for structural base isolation is indic...

Response of Sliding Rigid Structure to Base Excitation

A method of random vibration analysis of base isolated structures with hysteretic dampers is employed. The hysteretic restoring force is modelled by a nonlinear differential equation. The equations of motion for shear type structures are linearized in closed form. Nonstationary response statistics for evolutionary nonwhite excitation are determined by solving the associated Lyapunov matrix differential equation. An optimization study which is based on the stationary response is also presented.

Hysteretic dampers in base isolation: Random approach

Embedding of shape memory alloy (SMA) fibers in slender flexible bodies results in shape changes of the host medium, whenever shape recovery of the SMA fibers takes place. The shape change of a cylindrical rod with a single off-axis embedded SMA fiber is modeled. The distributed axial compressive force and bending moment due to phase transformation in the SMA fiber is evaluated using an approximate analytical model and the deformed shape of the flexible rod is found by solving the equations of equilibrium of the rod. The stability analysis for the linearized theory is carried out and the critical value of the phase transformation induced strain for buckling is evaluated.

https://iopscience.iop.org/article/10.1088/0964-1726/1/2/010/pdf

Iradj G. Tadjbakhsh

Papers

A comparative study of performances of various base isolation systems, part I: Shear beam structures

Comparative study of base isolation systems

Response of Sliding Rigid Structure to Base Excitation

Hysteretic dampers in base isolation: Random approach

Active flexible rods with embedded SMA fibers