Abstract

This study investigated the effect of 5-dimensional hooked-end fiber (5D) on the structural performance of beams and compared its efficiency with other fibers in strengthening structural performance of reinforced concrete (RC) beams with an increase in reinforcement ratio (ρ). The potential of using fibers to reduce the longitudinal rebar based on various design criteria was investigated. The fibers included 5D, a combination of 80 % 3-dimensional hooked-end and 20 % short steel fibers (STST), and two combinations of macro synthetic fibers A and B (MSF). Experimental results indicated that, compared to non-fibrous beams, using 5D was the most efficient in enhancing the yield load (53 %) and ultimate load (29 %) of RC beams, followed by STST (38 % and 7 %), and MSF (26 % and 15 %). However, using STST had superior efficiency in improving cracking load (90 %) and mitigating crack development before the yield point than beams with other fibers. Using MSF reduced the cracking widths at the ultimate load by 36 %-48 % compared to beams with macro steel fibers. With an increase of ρ, the effect of 5D or STST in improving flexural load of RC beams increased and was higher than that of RC beams made with MSF. The reason was that in beams with a high ρ, most macro steel fibers were not pulled out or caused matrix spalling because of smaller crack widths. This allowed 5D or STST to work with rebars to support the applied load. However, partial macro steel fibers might be pulled out or cause matrix spalling when beams with 0.43 % ρ were subjected to the same level load. Additionally, the flexible MSF embedded in beams were curved, which might delay the period of the tightening process of MSF. Most MSF in RC beams with a high of ρ might be tightened later to resist the crack after achieving the ultimate load compared to beams with macro steel fibers. The addition of macro steel fibers reduced the ρ to 50 %-77 %, 23 %-60 %, and 12 %-32 % based on design criteria of maximum allowable crack width, acceptable deflection criteria, and the ultimate load, respectively, whereas such values were 40 %-60 %, 4 %-14 %, and 11 %-19 %, respectively, for MSF. However, the use of MSF in beams achieved 18 %-43 % reduction of reinforcing bar in the criteria of crack width at ultimate load, which was more effective than beams with 5D or STST fibers (7 %-28 %).

Department(s)

Civil, Architectural and Environmental Engineering

Comments

Missouri University of Science and Technology, Grant 00062318

Keywords and Phrases

Flexural behavior; Hooked-end steel fibers; Macro synthetic fibers; Reduction of reinforcing steel ratio; Reinforcement ratios; Super workable concrete

International Standard Serial Number (ISSN)

0950-0618

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2024 Elsevier, All rights reserved.

Publication Date

09 Aug 2024

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