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Experimental verification of a novel system identification technique that can detect defects at the element level is successfully accomplished. The method can be used for in-service health assessment of real structures without disrupting normal operations. This study conclusively verifies the method.Analytical verification of the proposed algorithm has been successfully completed by the research team at the University of Arizona. Vo and Haldar (2004) experimentally verified the method by conducting tests on fixed-ended and simply supported defect-free and defective beams. The purpose of this research was to validate the method by conducting experiments with more realistic structures. A three-story one-bay steel frame, built to 1/3 scale to fit the experimental facility, was considered. The frame was excited by harmonic or impulsive excitation forces. The transverse acceleration responses were collected using capacitive accelerometers. The angular displacement responses were measured using an autocollimator. The dynamic responses of the frames were collected by a data acquisition system with simultaneous sampling capability. Using only experimentally collected response information and completely ignoring the excitation information, the stiffness of all the structural elements were identified. The method identified the defect-free frame very accurately. Defects, in terms of removing a beam, reducing cross sectional area over a small segment of a beam, and cutting notches in a beam, were introduced. The method correctly identified the defect location in all cases. Additional sensors were placed around the location of the defect in an effort to identify the defect spot more accurately. The proposed method also successfully identified defect with improved accuracy. To increase the implementation potential of the proposed method, the defect-free and defective frames are then identified using limited response information. A two-stage Kalman filter-based approach is used. It is denoted as Generalized Iterative Least Square Extended Kalman Filter with Unknown Input (GILS-EKF-UI) method. A sub-structure approach is used for this purpose. The GILS-EKF-UI method also identified the state of the structure using only limited response information. As expected, in this case the error in the identification goes up as less information is used. However, the error is much smaller than other methods currently available in the literature, even when input excitation was used for the identification purpose. The method is very robust and can identify defects caused by different types of loadings. The method can be used as a nondestructive defect assessment technique for structures.

The main objective of this study is to theorize a possible method of compatibility between macro-rhetorical analyses and micro-dynamic analyses of power, discourse, and the subject. The vehicle for application is conflict over privacy rights, and the proposed bridge between the two levels of analysis is the grammatical-pragmatic relation of modality and positionality. This investigation thus draws upon key theoretical elements from conventional structuralism, post-structuralism, and pragmatics. These form the framework for discussion of a number of analyses of selected textual features that reflect moves to truth and power, and the shifting status of the subject. Two general sets of analyses emerge. One focuses on rhetorically-motivated constructions of the subject, and the other on the uses of modality as indices of subject position. I have chosen the example of the conflict over privacy rights because the strongest instances occur in power struggles between individuals and institutions. The samples for analysis are drawn from the discourse of individuals and institutions involved in this conflict. My investigation focuses on power relations involved in control over the hermeneutic authority that influences the determination of speaking subjects and the establishment of truth. At the center of this discussion is the philosophical question of the subject, not only in terms of power over subject construction, but also in terms of the status of subject hood per se. The relationship between the self and discursive constructions of the self is thus examined. At issue is an ethical concern: the individual seems to need both conventionally approved constructions of herself in social contexts, and a measure of independent control over her self such that she has subject integrity. Three types of analyses, corresponding to the three levels of theoretical orientation identified above, inform this investigation: 1.conventional rhetorical analyses (structuralist), as they are exemplified in Kenneth Burke's dramatistic and logological calculus (at the level of global power struggle) 2.micro-analyses (post-structuralist), as they are ex-emplified in Foucault's archaeological approach to power, knowledge, and the speaking subject (at the level of local relations of force and their indices in "statements") 3.^grammatical-pragmatic analyses of modality, evidentiality, and the "statement," informed by studies in social semiotics (at the grammatical level of modality as a linguistic index of power and positionality) This work is intended to contribute to speculative research on how the three levels of analysis might be integrated. The results of this study show correlations between grammatical features of modality and subject status. Where there is a positive correlation, the uses of modality indicate conformity and acceptance in terms of institutional norms. Where there is a negative correlation, modality is not aligned with subject construction, and the "subject" involved is therefore institutionally powerless. She cannot receive a serious audience for her discourse. In the former case the authority invested in speaking subjects also sanctions credibility in the construction of truth and facts. Both reinforcements of, and changes in, the status quo occur only where modality and subject status are aligned with each other in terms of a specific organizational structure and situation. In the latter case where discourse is divorced from salient positionality, the speaker can utter only empty rhetoric. Resourceful individuals, however, may manoeuver within these institutional constraints to both utilize the conventions of discourse and to activate resistance to these restrictions in a field of low-level detectability. Such individuals (bricoleurs) are able to play with the aletheic phemonemon of truth: they retain the social character of convention and at the same time exercise a certain degree of independence or freedom in order to protect the ethical core or integrity of the self. This play is rhetorical strategy par excellence: the individual finds a way of co-existing with the institution. Resistance is thus survival by troping the world. It involves using the modality of the situation and moving the self strategically in and out of position. The bricoleur constructs resourceful faces that please yet deceive, that bend to discursive technology yet serve the self, and that disclose yet conceal. The modality of strategic aletheia is non-canonical and ordinary. One constructs the truths that protect, however temporary. And, however transitory, one makes a self that is at home in the world.

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The shear horizontal wave propagation and vibration of piezoelectric coupled structures under an open circuit electrical boundary condition are studied. Following the studies on the dynamic response of piezoelectric coupled structures, the repair of both crack/notch and delaminated structures using piezoelectric materials are conducted. The main contribution was the proposed the active structural repair design using piezoelectric materials for different structures. An accurate model for the piezoelectric effect on the shear wave propagation is first proposed to guide the application of piezoelectric materials as sensors and actuators in the repair of engineering structures. A vibration analysis of a circular steel substrate surface bonded by a piezoelectric layer with open circuit is presented. The mechanical models and solutions for the wave propagation and vibration analysis of piezoelectric coupled structures are established based on the Kirchhoff plate model and Maxwell equation. Following the studies of the dynamic response of piezoelectric coupled structures, a close-loop feedback control repair methodology is proposed for a vibrating delaminated beam structure by using piezoelectric patches. The electromechanical characteristic of the piezoelectric material is employed to induce a local shear force above the delamination area via an external actuation voltage, which is designed as a feedback of the deflection of a vibrating beam and a delaminated plate, to reduce the stress singularity around the delamination tips. Furthermore, an experimental realization of an effective repair of a notched cantilever beam structure subjected to a dynamic loading by use of piezoelectric patches is reported. A small piezoelectric patch used as a sensor is placed on the notch position to monitor the severity of the stress singularity around the notch area by measuring the charge output on the sensor, and a patch used as an actuator is located around the notch area to generate a required bending moment by employing an actuation voltage to reduce the stress singularity at the notch position. The actuation voltage on the actuator is designed from a feedback circuit process. Through the analytical model, FEM simulation and experimental studies, the active structural repair method using piezoelectric materials is realized and proved to be feasible and practical.