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Title: Wave propagation in reinforced concrete beams with application to non-destructive testing
Author: El Masri, Evelyne
ISNI:       0000 0004 7656 2472
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2018
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Steel reinforcements bars (rebars) are vital to reinforced concrete (RC) structures and their damage leads to catastrophic failure. Most damage occurs due to corrosion and delamination, and an early detection is necessary. Wave based methods are popular for detecting the damage remotely. However, most of these techniques require direct contact with the rebars. The aim of this project is to exploit guided waves to detect damage of the rebars via measurements only on the concrete surface. The Wave Finite Element (WFE) is well suited to predict the wave characteristics of RC waveguides. It requires knowledge of the mass and stiffness matrices of only a segment of the waveguide which can be obtained from conventional FE analysis. A new RC model approach using embedded reinforcements is suggested and compared to conventional FE models. Next, the WFE methodology is discussed including associated numerical and ill conditioning errors. Wave solutions for RC beams with and without prestress, in the form of dispersion curves and mode shapes, were found to be similar. Having established free wave solutions for an undamaged RC waveguide, one can couple it to a damaged segment that can be modelled in FE. Alternatively, if the damage is modelled as a reduction in rebar diameter over a certain length, then this permits the WFE coupling approach to couple damaged and undamaged RC models for better computational efficiency. High magnitudes for the reflection coefficients due to damage are found, which are associated with evanescent waves at their cut-on frequencies. Based on these findings, a new damage identification algorithm is proposed in which the amplitudes of left and right propagating waves are estimated from surface measured forced responses. The experimental based methodology was successful in detecting rebar reduction without any prior knowledge of the dispersion relations. Experimental validation of the algorithm is found to be successful and in good agreement with simulations. The potential and limitations of the algorithm for practical structures are discussed.
Supervisor: Ferguson, Neil Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available