Date of Defense
20-11-2025 5:00 PM
Location
F3-0040
Document Type
Dissertation Defense
Degree Name
Doctor of Philosophy in Civil Engineering
College
COE
Department
Civil and Environmental Engineering
First Advisor
Prof. Tamer El Maaddawy
Keywords
RC columns, circular, corrosion, concentric loading, eccentric loading, FRCM, FRP, strengthening, repair.
Abstract
Reinforced concrete (RC) columns exposed to aggressive environments are highly susceptible to corrosion-induced deterioration, resulting in significant reductions in load-carrying capacity. This research investigates the structural performance of RC circular short columns with varying levels of corrosion damage and evaluates the effectiveness of two composite-based repair techniques, namely carbon fabric-reinforced cementitious matrix (C-FRCM) and carbon fiber-reinforced polymer (C-FRP) composites, combined with concrete cover replacement. The study aims to establish these methods as practical solutions for rehabilitating corrosion-damaged columns under concentric and eccentric loading conditions. The experimental program included 30 RC column specimens tested in two phases. Phase I involved thirteen undamaged columns subjected to eccentricity-to-depth ratios (e/h) ranging from 0.0 to 0.3, eight of which were strengthened using one or two C-FRCM layers. Phase II examined seventeen corroded columns with accelerated corrosion in longitudinal bars (up to 27%) and steel ties (up to 45%), tested under the same e/h ratio range. Six corroded columns were tested without repair, while eleven were repaired using two layers of either C-FRCM or C-FRP composite wraps in the hoop direction before testing. Phase I experimental results indicated that columns with two C-FRCM layers achieved up to 39% load capacity gain under eccentric loading compared to 17% under concentric loading, whereas single-layer strengthening provided minimal improvement due to insufficient confinement and premature fabric–mortar debonding. Phase II experimental results showed that corrosion reduced load capacity by up to 41% under concentric loading and by an average of 17% under eccentric loading, with the effect diminishing at higher eccentricities. Both repair systems restored original capacity, with C-FRP providing superior load capacity enhancement (80%–167%) compared to C-FRCM (49%–86%), attributed to better confinement efficiency. While premature debonding limited C-FRCM performance, it contributed to improved ductility through gradual post-peak degradation. A mechanics-based analytical model was developed and validated against experimental results and literature data to predict column capacity before and after repair. The model accounts for corrosion effects, material nonlinearities, and the interaction between internal steel tie confinement and external composite wrapping. The analytical model aligns well with experimental results and supports the use of advanced composites in the practical rehabilitation of corrosion-damaged RC columns, confirming its reliability and applicability as a simple, accurate tool for structural evaluation and retrofit design. The model also generated P–M interaction diagrams that reasonably reflected the experimental trends, validating its applicability as a robust tool for structural assessment, strengthening, and retrofit design.
Included in
REHABILITATION OF REINFORCED CONCRETE COLUMNS PRE-DAMAGED BY CORROSION USING ADVANCED COMPOSITE MATERIALS
F3-0040
Reinforced concrete (RC) columns exposed to aggressive environments are highly susceptible to corrosion-induced deterioration, resulting in significant reductions in load-carrying capacity. This research investigates the structural performance of RC circular short columns with varying levels of corrosion damage and evaluates the effectiveness of two composite-based repair techniques, namely carbon fabric-reinforced cementitious matrix (C-FRCM) and carbon fiber-reinforced polymer (C-FRP) composites, combined with concrete cover replacement. The study aims to establish these methods as practical solutions for rehabilitating corrosion-damaged columns under concentric and eccentric loading conditions. The experimental program included 30 RC column specimens tested in two phases. Phase I involved thirteen undamaged columns subjected to eccentricity-to-depth ratios (e/h) ranging from 0.0 to 0.3, eight of which were strengthened using one or two C-FRCM layers. Phase II examined seventeen corroded columns with accelerated corrosion in longitudinal bars (up to 27%) and steel ties (up to 45%), tested under the same e/h ratio range. Six corroded columns were tested without repair, while eleven were repaired using two layers of either C-FRCM or C-FRP composite wraps in the hoop direction before testing. Phase I experimental results indicated that columns with two C-FRCM layers achieved up to 39% load capacity gain under eccentric loading compared to 17% under concentric loading, whereas single-layer strengthening provided minimal improvement due to insufficient confinement and premature fabric–mortar debonding. Phase II experimental results showed that corrosion reduced load capacity by up to 41% under concentric loading and by an average of 17% under eccentric loading, with the effect diminishing at higher eccentricities. Both repair systems restored original capacity, with C-FRP providing superior load capacity enhancement (80%–167%) compared to C-FRCM (49%–86%), attributed to better confinement efficiency. While premature debonding limited C-FRCM performance, it contributed to improved ductility through gradual post-peak degradation. A mechanics-based analytical model was developed and validated against experimental results and literature data to predict column capacity before and after repair. The model accounts for corrosion effects, material nonlinearities, and the interaction between internal steel tie confinement and external composite wrapping. The analytical model aligns well with experimental results and supports the use of advanced composites in the practical rehabilitation of corrosion-damaged RC columns, confirming its reliability and applicability as a simple, accurate tool for structural evaluation and retrofit design. The model also generated P–M interaction diagrams that reasonably reflected the experimental trends, validating its applicability as a robust tool for structural assessment, strengthening, and retrofit design.