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Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/1222

Title: Experimental characterization of towers in cable-supported bridges by ambient vibration testing
Authors: Grimmelsman, Kirk Alexander
Keywords: Mechanical engineering;Bridges--Vibration;Bridges, Long-span
Issue Date: 19-Jan-2007
Abstract: The objective of this thesis is to address several unresolved issues related to the experimental characterization of the modal properties for the towers in cable-supported bridges by the ambient vibration testing. A number of these unresolved issues were identified during the application of this method to the towers in a landmark suspension bridge. The research that was undertaken included both experimental and analytical components. The experimental components consisted of: (1) characterizing the ambient vibration environment for the masonry towers in the Brooklyn Bridge and evaluating the limitations associated with the conventional approach for identifying the dynamic properties by ambient vibration testing, (2) a laboratory investigation to compare and evaluate the effectiveness of the most common and basic modal identification approach for bridges, a multiple-reference channel extension of the basic approach and several more sophisticated identification methods for the conditions of ambient dynamic excitation that can occur for the towers in a cable-supported bridge, and (3) an comparative evaluation of these same methods for characterizing the Brooklyn Bridge towers. The focus of the analytical component was to characterize the fundamental dynamic behavior for the towers using a idealized analytical model of a suspension bridge. This research indicated that the towers in a cable-supported bridge can have modes which are distinct from the spans and vice-versa. Furthermore, it was possible to identify the most likely dynamic properties of a tower by considering a spectrum of characteristics and parameter values associated with each identification result for the complex vibration output spectra associated with the towers in cable-supported bridges; however, the identified properties will not be free from uncertainty. The most consistent and meaningful modal properties were identified by the peak picking identification method using multiple reference locations. Visually comparing the consistency of the operating mode shapes computed from multiple reference locations was also found to be a very effective and intuitive approach for identifying spurious or poorly-excited modes in the identification results.
URI: http://hdl.handle.net/1860/1222
Appears in Collections:Drexel Theses and Dissertations

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