Flexural behavior of continuous and simply supported beams prestressed with hybrid (CFRP and steel) tendons
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Nasreddine, Wassim.
Flexural behavior of continuous and simply supported beams prestressed with hybrid (CFRP and steel) tendons. Retrieved from
https://doi.org/doi:10.7282/t3-g8y0-mj84
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TitleFlexural behavior of continuous and simply supported beams prestressed with hybrid (CFRP and steel) tendons
Date Created2022
Other Date2022-05 (degree)
Extent204 pages : illustrations
DescriptionThe use of unbonded tendons in prestressed concrete members has major advantages on the performance of structures. They can be easily implemented on-site, and they present an effective and reliable method in repair and rehabilitation. However, unbonded steel tendons are susceptible to corrosion due to exposure to water and de-icing salt infiltration. Thus, there is a constant need for inspection and maintenance. In addition, when unbonded tendons are used in combination with other bonded tendons for prestressing, they form a hybrid system whose behavior is different from bonded or unbonded systems. The behavior of hybrid systems is not well established in design codes, especially for estimating the stress at ultimate stress in the unbonded tendons. Carbon fiber reinforced polymer (CFRP) tendons present a good alternative due to their high tensile strength, low relaxation, and full resistance to corrosion. In this research, CFRP unbonded tendons are utilized in combination with steel (or CFRP) tendons in simply supported and continuous beams. Ten simply supported and eight continuous beams were cast and tested until failure, to investigate the behavior of CFRP tendons in hybrid prestressed beams. Testing parameters included the prestressing type (bonded, unbonded or hybrid), tendon material (steel or CFRP), tendon area and depth. The experimental investigation includes the load-deflection, load-strain, and cracking behaviors. The analytical investigation includes the use of generalized incremental analysis to estimate the beam deflection and the ultimate stress in unbonded tendons. In addition, the existing approaches for estimating post-cracking deflection as well as predicting the ultimate stress in unbonded tendons are investigated and assessed.
This study concludes that CFRP tendons can be effectively used in simply supported and continuous beams, in straight or parabolic profiles. However, when used as bonded tendons, CFRP tendons reduce the overall ductility of the beams due to their low ultimate strain compared to steel tendons. Also, the linear stress-strain relationship in CFRP tendons reduces crack widths after unloading, compared to steel tendons whose yielding produces residual strain and thus wider cracks after unloading. The generalized incremental analysis (GIA) procedure predicts the stress at ultimate in unbonded tendons with good accuracy, but it is less effective at predicting deflections in hybrid beams. Additionally, it was concluded that all code equations underestimate the ultimate stress of unbonded tendons. However, their accuracy is dependent on the type of beam (Hybrid or Unbonded) and the material of the tendon (steel or CFRP). Finally, the PCI bilinear approach provided a close post-cracking deflection estimation in simply supported beams, while the other approaches (e.g., ACI 318-19 and PCI) either underestimate, or overestimate (e.g., Bischoff et al.) the deflections.
NotePh.D.
NoteIncludes bibliographical references
Genretheses
LanguageEnglish
CollectionSchool of Graduate Studies Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.