Repozytorium publikacji - Politechnika Gdańska

The thesis concentrates on comprehensive theoretical, numerical and experimental analysis of guided wave propagation in bars embedded in concrete or mortar. The investigations are focused on a particular type of objects representing a laboratory model of a ground anchor. Complex description of wave propagation phenomena in partially embedded bars is given and its application in detection of various types of defects is analysed. The first part of thesis is focused on dispersive relations describing multimode wave propagation in free and multilayered bars of circular cross-section. Analytical solution in the form of dispersion curves is an important element of the analyses presented in the subsequent parts of the work regarding wave propagation in undamaged specimens, specimens with debonding and specimens with localized and surface damages. Experimental and numerical analysis of wave propagation in undamaged anchors with variable bonding lengths allowed to derive relations enabling estimation of major geometric parameters on the basis of time -domain signals. Next, the influence of debonding length and its location on the wave propagation phenomena was described. The research carried out in the further part of the work proved thepossibility of using guided waves for detection of relatively small-size debonding, as well as corrosion and point damage located in both embedded and free parts. The last stage of non-destructive testing concerned the wave propagation in a real drill-hollow bar commonly used for execution of geotechnical facilities. The influence of couplers connecting individual bars on the wave attenuation was analysed. Additionally, drill-hollow bar was used for real small-scale anchor performed in the ground. The possibility of guided wave application in the monitoring of the hardening process of cement mortar forming anchor body was demonstrated. Comparison of the results for anchor placed in the ground and the anchor after excavation allowed to determine the surrounding ground medium impact on the registered time signals. Finally, the most important conclusions of the conducted research and future planswere pointed out.

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