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

Temperature dependence of Young's modulus in Si3N4-based ceramics: roles of sintering additives and of SiC-particle content

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The Effect of Microstructure in Aluminum Oxide Ceramics on Acoustic Loss Mechanisms

Microstrains and defects are introduced during synthesis and crystal-growth stages of energetic particles and increase during processing stages such as grinding, mixing, and extrusion. The detection and quantification of these microstrains and defects in a given particle population is a difficult task that requires highly sensitive techniques. In this study a novel X-ray diffraction technique (XAPS) based on simultaneous rocking-curve analysis of individual particles was successfully applied to CL-20 powders. The effects of synthesis, grinding, and static loads on the extent of microstrain and defect development in CL-20 particles were quantitatively determined as frequency versus half-width of rocking curves. The greater half-width values observed for the samples subjected to grinding and static loads indicated greater microstrain and defect density in comparison to the as-received samples of CL-20. It may be possible to relate the findings of such analysis to combustion calculations for energet...

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Microstrain and Defect Analysis of CL-20 Crystals by Novel X-Ray Methods

Ultrasonic S0 waves (fundamental symmetric Lamb modes) are being considered in several laboratories for the nondestructive characterization of the texture (preferred grain orientation) and formability of metal sheets and plates. In a typical experimental setup, the velocities of the S0 waves are measured as a function of wave propagation angle with respect to the rolling direction of the plate. However, the S0 waves are known to be dispersive, and that dispersion must be considered in order to isolate the small, texture‐induced shifts in the S0 wave velocity. Currently, there are two approximate dispersion correction methods, one proposed by Thompson et al.9 and the other introduced by Hirao and Fukuoka.20 In this paper, these two methods will be evaluated using an exact theory for wave propagation in orthotropic plates. Through the evaluation, the limits of the current texture measurement techniques are established. It is found that when plate thickness to wavelength ratio is less than 0.15, both Thompso...

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1010&context=ameslab_pubs

Effects of dispersion on the inference of metal texture from S0 plate mode measurements. Part I. Evaluation of dispersion correction methods.

This book contains the proceedings of a symposium on nondestructive monitoring of materials properties. The papers include: NDT techniques for monitoring material degradation and A study of high temperature damage processes using microradiography.

J. Holbrook

Papers

Nondestructive monitoring of materials properties