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Title: The efffect of elastomeric bearing degradation on bridge dynamic response
Author: Swan, Iain Peter
ISNI:       0000 0004 2677 5584
Awarding Body: Edinburgh Napier University
Current Institution: Edinburgh Napier University
Date of Award: 2006
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The dynamic response of highway bridges is a topic that has been thoroughly researched over many years. However, understanding of how the dynamic response of bridges is affected by the performance of their bearings over an extended period of time is, at present, not clearly defined. Although health monitoring of bridge structures is relatively advanced, the scope for further research is wide. The study presented in this thesis contains research on plate structures; ranging from a simple Euler-Bernoulli method to determine natural frequencies; modal analysis of a plate structure in the laboratory; FEA of the plate structure; modal analysis on a full-scale structure subjected to vehicle loading; and FEA of a simplified model representing the full-scale structure. A combination of these methods has allowed the conclusions presented herein to be drawn with respect to the effects of support degradation, and the consequent effect on structural performance. In the laboratory, modal analysis of a small-scale, thin rectangular plate of Perspex' has been completed. A series of boundary conditions have been investigated through altering the support offered to the plate by a series of springs, each with a different stiffness, to simulate bearings with different stiffnesses. Vibrations of varying frequency have also been forced upon the plate, and its response recorded. Displacement values provided the clearest indication of the effect of bearing stiffness, with the least stiff spring resulting in the largest displacement. Alteration of support stiffness in the model can have a marked effect on the resonant frequency of the plate (approx. 23 % frequency change between spring 1 (1.22 Nmm 1) and 5 (15.62 Nmm 1)). Full-scale testing on a highway bridge at Berwick-upon-Tweed on the Al, over the River Tweed, was completed in May 2005. These data form the baseline for future dynamic testing and condition monitoring of the structure. To describe the dynamic properties of the structure, the force generated by each type of vehicle traversing the structure was determined using instrumentation already in place on the bridge. Statistics drawn from the data are presented, which indicate that the bearings are functioning as expected, but are subjected to forces of a much larger magnitude due to overloaded HGVs than in current design specifications. Larger HGVs made up a small percentage of overall vehicles recorded, but contribute a much higher proportion of damage caused to the bridge. Displacement and frequency were both valid measures of bearing performance and therefore state of degradation. The method is offered as a condition monitoring test for bridges and their bearings.
Supervisor: Fairfield, Charles Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TG Bridge engineering