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Behavior of Slender Circular Columns Made of Fiber-Reinforced Green Concrete and Hybrid Steel-GFRP Reinforcement
Hegazy, Nouran
Hegazy, Nouran
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35.232-2024.74a Nouran Hegazy.pdf
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Description
A Master of Science thesis in Civil Engineering by Nouran Hegazy entitled, “Behavior of Slender Circular Columns Made of Fiber-Reinforced Green Concrete and Hybrid Steel-GFRP Reinforcement”, submitted in August 2024. Thesis advisor is Dr. Mohammad AlHamaydeh Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).
Abstract
The inherent issue of steel corrosion in reinforced concrete structures has elicited the need to find viable alternatives. Glass Fiber-Reinforced Polymer (GFRP) bars have emerged as a competitive alternative to steel reinforcement owing to their superior properties, such as being noncorrodible, non-magnetic, and possessing a high strength-to-weight ratio. Nonetheless, owing to their low modulus of elasticity and low compressive strength, the currently available FRP RC design codes, such as ACI 440.11-22 and CSA S806-12, neglect the contribution of FRP bars to the columns’ ultimate capacities. Another sustainable construction material employed in this study is green concrete, made with ground granulated blast-furnace slag (GGBS), as an alternative to conventional concrete. The concrete mix is complimented by the addition of synthetic fibers to enhance crack control, material durability, and overall capacity. The combination of these materials promotes sustainable RC construction with a competitive performance. This study presents the analysis of experimental tests conducted on full-scale slender circular reinforced concrete columns made with fiber-reinforced green concrete and reinforced with a novel double-layer hybrid arrangement of steel and GFRP bars, subjected to concentric and eccentric loading. In addition, a control group of full-scale steel RC columns are tested. All specimens had constant longitudinal reinforcement and transverse reinforcement ratios. The key design parameters investigated were the longitudinal reinforcement type (steel and GFRP bars), loading eccentricity (e/h = 0, 9.6%, 28.8% and 48.1%), transverse reinforcement type (steel and GFRP spirals) and reinforcement configuration (single and double layers). The results showed that hybrid steel-GFRP RC columns have similar overall compression behavior to their steel RC counterparts. However, the axial capacity of hybrid specimens was on average 30% to 60% lower than their steel RC counterparts. Moreover, hybrid RC columns showed slightly higher ductility than steel RC columns at all loading eccentricities, with calculated average ductility indices of 21.9 and 18.6, respectively. Nonetheless, the contribution of GFRP bars in compression to the ultimate capacities of the columns was around 15% as compared to 60% for steel bars. Furthermore, the experimental load capacities of the columns are compared to theoretical predictions based on analytical equations available in the literature.