Date of Award
M.S. in Engineering Science
Christopher L. Mullen
Vibration based damage detection in bridges is examined with the objective of defining a relationship between substructure stiffness degradation and frequency and mode shape modulation induced by damage. The relationship is explored through finite element modeling of primarily an experimental representation of a three-span concrete bridge structure located at the entrance to the main campus of The University of Mississippi in Oxford. Equivalent beam and 3D finite element models are created of an experimental setup incorporating levels of damage simulated using deck slab bearing pads of varying stiffness. Eigenvalue analysis is performed to examine the change of frequencies for characteristic deck slab deformation modes for each case of simulated damage. Results for each damage case are compared to a reference one with no bearing pads. The variation of frequency with vertical stiffness at mid span is then developed to quantify the sensitivity of the change of frequency to the change of stiffness over a broad range of values. Supplemental studies are performed including time history analysis of an impulsive forced vibration of each experimental bridge model to estimate motion levels for characteristic deck responses at mid span. A typical pier of the campus bridge is also modeled at full scale dimensions using frame elements. The three-span deck system is then modeled with a lumped spring system incorporating the effective stiffness of the piers, and the effect on the vertical deck frequencies is established. Distributed substructure damage is studied using this modeling approach by considering a uniform reduction in concrete modulus for the pier elements as might occur during long term environmental exposure. Damage is applied to a single pier as well as both piers to examine the effect of asymmetry.
Bethay, James Kyle, "Fe Modeling In Support Of Vibration Based Damage Detection In Bridges" (2013). Electronic Theses and Dissertations. 422.
Emphasis: Civil Engineering