Scott R. Lang

Publication Date


Document Type


First Advisor

Pauschke, Joy M.||Bobis, James P.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Electrical Engineering


Structural dynamics; Detectors; Structural analysis


Accurate measurements of the displacements in large- scale structures (e.g., buildings, dams, bridges, and lifeline facilities) are important to characterize the response to wind, impact, seismic, or other extreme loads. Traditionally, structural displacements have been recorded indirectly using accelerometers strategically placed throughout a structure. The acceleration data is subsequently post-processed off-line to obtain the displacement time histories. The development of a method to compute structural displacements more quickly, easily, and accurately has been identified as a research need by several recent national workshops. More recent technologies such as fiber optics, lasers, photogrammetry, ultrasonics, and micromachined silicon accelerometers are reviewed to determine their suitability as a basis for a structural displacement sensor. A conceptual design for a fiber optic optical time domain reflectometry (OTDR) sensor is presented as an alternative technology to the widely used accelerometer method to measure displacements. Because accelerometers are widely used to record structural response, a prototype real-time acceleration processing (RAP) circuit is developed and tested which utilizes existing accelerometer arrays to directly obtain displacements in real-time. Based on artificial input test signals, the displacements computed by the RAP system show close accuracy with the displacements calculated from numerical integration of the acceleration signal and with the output of a linear variable differential transformer. Initial tests of the temperature response of the RAP system indicate that the circuit performs satisfactorily when subjected to extreme temperature.


Includes bibliographical references (pages [138]-142)


ix, 142 pages




Northern Illinois University

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