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In the last few decades, piezoceramic (PZT) transducers have been extensively used either as actuators or as sensors in the vibration and noise control of aero, civil, and mechanical (ACM) systems. Only in the last decade, PZT transducers have been used in the electromechanical impedance (EMI) models as both sensor and actuator for the structural health monitoring of ACM systems. In the EMI models, the PZT transducers are generally surface bonded to the host structure and are then subjected to one-dimensional (ID) voltage to interrogate the structure for the desired frequency range. The interrogation results in the prediction of electromechanical admittance signatures. These signatures serve as indicators of the health/ integrity of the structure. However, the existing single PZT--structure interaction models consider the PZT transducer to be negligible in mass and thus ignored. Moreover, they impose restrictions on the PZT shape, size, and isotropy. This paper presents it novel semianalytical multiple three-dimensional PZT--structure interaction model which considers the 'mass' of the PZT transducers, and the transducers are subjected to parallel (1D) sinusoidal voltage. Further, the model does not impose restriction on the shape (square or rectangular), size (thin or thick), and electrical properties (isotropic or anisotropic) of PZT. The derived model is also experimentally verified using lab-sized aluminum plate. As it is generic, the model is expected to be applicable for the nondestructive evaluation of most ACM systems. DOI: 10.1061/(ASCE)0893-1321(2008)21:1(35) CE Database subject headings: Three-dimensional models; Vibration; Noise control; Sensors; Nondestructive tests.

Piezoceramic transducers (PZTs) are extensively used in vibration and noise control, and damage detection of various engineering structures. In the last decade, its application has been extended to include their interactions with the host structure in electromechanical impedance models. The interaction between the host structure and PZT is governed by both the extensional and longitudinal vibrations of the transducer. However, the interaction models developed in the last decade consider only the one-dimension or two-dimension extensional actuations, ignoring the longitudinal actuations. This study examines the three-dimensional (3D) interaction of a transducer with the host structure, considering both the extensional and the longitudinal actuations of the transducer. It does not impose any restriction on the shape, size, and electrical properties of the PZT and thus contains additional features over the existing PZT-structure interaction models. This paper is Part I of a two-part paper, which presents a new 'directional sum' numerical-analytical admittance formulation with experimental verification. Part II of this paper will elaborate on the damage analysis and characterization of PZT properties for the new 3D model. DOI: 10.1061/(ASCE)0893-1321(2007)20:1(53) CE Database subject headings: Structural reliability; Monitoring; Three-dimensional models; Damage.

Piezoceramic transducers (PZTs) are extensively used in the nondestructive evaluation of damages in various engineering structures. This paper, the second of a two-part paper, focuses on the application of a PZT using three-dimensional (3D) directional sum impedance (DSI). The semianalytical 3D admittance has been formulated and experimentally validated in the first paper. This part deals with the application of the 3D DSI model in damage analysis where by damages were numerically simulated for various types of specimens and the DSI admittance signatures were predicted and compared. The deviations of the signature from that of the undamaged state provide an indicator for the health of the structure. This technique is nondestructive in nature, and the damages were quantified using root-mean-square deviation in signatures with respect to the undamaged state signature. In Part I, the properties of the PZT and their influences on admittance signatures were briefly presented. In this part, a thorough investigation was made and the importance of all the PZT properties in damage analysis was presented. DOI: 10.1061/(ASCE)0893-1321(2007)20:1(63) CE Database subject headings: Structural reliability; Monitoring; Three-dimensional models; Damage.

In this paper, modeling of the vibration of cylindrical shell components of space structures incorporating piezoelectric sensor/actuators (S/As) for optimal vibration control is proposed and formulated. The parameters of the control system, which include the placement and sizing of the piezoelectric S/As and the feedback control gains, were considered as design variables and optimized simultaneously. The effect of the amount of piezoelectric patches was investigated as well. The criterion based on the maximization of energy dissipation was employed for the optimization of the control system. A modified real-encoded genetic algorithm (GA) dealing with various constraints has been developed and applied to search for the optimal placement and size of the piezoelectric patches as well as the optimal feedback control gains. The results of three numerical examples, which include a simply supported plate, a simply supported cylindrical shell, and a clamped-simply supported plate, demonstrated significant vibration suppression based on the optimal design of the control system. It was also found that for specific controlled vibration modes, the optimal distribution of the piezoelectric S/As should be located at the areas separated by the nodal lines to achieve the optimal control effect. This finding would be useful for the practical design of smart structures. DOI: 10.1061/(ASCE)0893-1321(2006)19:2(68) CE Database subject headings: Optimization: Vibration; Algorithms; Cylindrical shells; Plates; Control systems; Intelligent structures.

This paper describes a generic impedance-based model for predicting the electromechanical (EM) impedance of one-dimensional (ID) and two-dimensional (2D) structure-piezoceramic (PZT) interacting systems. The vibration of a PZT patch is first analyzed. The effect of the host structure is then represented by its force impedance, which is obtained by a semianalytical method. Finally, experiments are carried out on beams and plates to simulate 1D and 2D problems, respectively. It is found that the predicted EM impedance of the structure-PZT interacting system coincides very well with the experimentally measured data. The results show that the predicted peaks match the natural frequencies of the host structure. The very small shift of the peaks from the natural frequencies caused by the interaction between the host structure and the PZT patch indicates that the small size PZT patch can be permanently bonded to the structure for on-line health monitoring without changing the mechanical properties of the structure too much. It is concluded that the proposed impedance-based model for general structure-PZT interacting systems can be potentially used in structural health monitoring. CE Database subject headings: Structural reliability; Monitoring; Beams; Plates; Models

The electromechanical impedance (EMI) technique, which employs piezoelectric-ceramic lead-zirconate-titarate (PZT) patches as impedance transducers, has emerged as a powerful nondestructive evaluation technique during the last few years. This series of two papers present a new simplified methodology to diagnose structural damages by means of surface bonded piezo-impedance transducers. The first part introduces a new PZT-structure electroelastic interaction model based on the concept of 'effective impedance.' The proposed formulations can be conveniently employed to extract the mechanical impedance of any 'unknown' structural system from the admittance signatures of a surface bonded PZT patch. This is an improvement over the existing models, whose complexity prohibits direct application in similar practical scenarios. This also eliminates the requirement of any a priori information concerning the phenomenological nature of the structure. The proposed model is experimentally verified by means of test on a smart system comprising an aluminum block with a PZT patch instrumented on it. Part II of this paper outlines a new methodology to evaluate structural damages using the extracted impedance spectra. The proposed approach is found to be suitable for diagnosing damages in structures ranging from miniature precision machine and aerospace components to large civil structures. DOI: 10.1061/(ASCE)0893-1321(2004)17:4(154) CE Database subject headings: Damage; Impedance; Structural reliability; Monitoring; Models.

An impedance-based structural health monitoring technique is presented. By analyzing the in-plane vibration of a thin lead-zirconate-titanate (PZT) patch, the electromechanical impedance of the PZT patch is predicted. The force impedances of a beam and a plate with damage are calculated by Ritz method using polynomial as shape functions. The damage is then identified from the changes of the impedance spectra caused by the appearance of damage. A hybrid evolutionary programming is employed as a global search technique to back-calculate the damage. A specially designed fitness function is proposed, which is able to effectively reduce the inaccuracy in representing the real structure using analytical or numerical models. Experiments are carried out on a beam and a plate to verify the numerical predictions. The results demonstrate that the proposed method is able to effectively and reliably locate and quantity the damage in the beam and the plate. DOI: 10.1061/(ASCE)0893-1321(2004)17:4(182) CE Database subject headings: Impedance; Structural reliability; Monitoring; Damage; Evolutionary computation.

This paper, the second in a two-part series, presents a new methodology for structural identification and nondestructive evaluation by piezo-impedance transducers. The theoretical development and experimental validation of the underlying lead-zirconium-titanate (PZT)-structure interaction model was presented in the first part. In our newly proposed method, the damage in evaluated on the basis of the equivalent system parameters 'identified' by the surface-bonded piezo-impedance transducer. As proof of concept, the proposed method is applied to perform structural identification and damage diagnosis on a representative lab-sized aerospace structural component. It is then extended to identify and monitor a prototype reinforced concrete bridge during a destructive load test. The proposed method was found to be able to successfully identify as well as evaluate damages in both the structures. DOI: 10.1061/(ASCE10893-1321(2004)17:4(166) CE Database subject headings: Damage: Cracking; Impedance: Concrete, reinforced: Bridges; Structural reliability.