Poulton, Matthew;
(2023)
Structural integrity of pultruded GFRP bridge decks with variable fibre misalignments.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The extent to which manufacturing-induced fibre mat misalignments compromise the structural integrity of pultruded GFRP road bridge decks is not properly understood. The problem is often critical at the web-flange junctions, which frequently contain the most severe misalignments and are subjected to high local moment-shear (M-V) combinations due to concentrated tyre load and also global vehicle load effects. Over the last 20 years, several GFRP decks have developed tyre load-induced damage of the top flange, due in large part to the prevalence of fibre misalignments. To address this issue, this thesis presents a hybrid experimental-predictive strategy to investigate the structural integrity of pultruded deck junctions. First, an optical/digital method of mapping the misalignments was used to enable quantification of their severity and definition of their taxonomy based on morphology and manufacturing provenance. Second, a bespoke flange-cantilever test method, including acoustic emission (AE) sensors to detect bursts of fracture activity, was used to apply determinate M-V combinations to and observe the response up to failure of the web-flange junctions, without artificial restraint. Third, the through-depth full-field strains within the loaded junctions were measured using 3D digital image correlation (DIC), which provided further insight into the mechanics underlying damage progression to failure along the misaligned fibre mat layers. Finally, the damage progression within and the wider load response of the junction were reasonably predicted with a non-linear finite element model (FEM) that used cohesive zone modelling and continuum damage mechanics approaches. The results show that, when loaded to ultimate, the junctions underwent up to four damage modes, each linked to a specific category of misalignment. Both the sequence of damage modes and the associated loads were sensitive to the applied M-V combination and to the misalignment profile. For a given M-V combination, the maximum ‘knock-down’ of junction load capacity was 43%. The complementary DIC/FE data reveal that local ‘softening’ of the misaligned fibre mat-to-roving interface began at 50% of the eventual delamination load. In some tests this local softening was accelerated by random transverse cracks within the adjacent roving core, which contributed to significant scatter in junction load capacity. Finally, application of this hybrid cantilever test/AE/DIC/FE approach to other FRP deck systems is discussed.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Structural integrity of pultruded GFRP bridge decks with variable fibre misalignments |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2023. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10166683 |
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