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Experimental Investigation on the Development Length of Steel Rebars with End Hook in Rubberized Concrete

Mohammadi Naserou, Mohsen | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 58391 (53)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Khaloo, Alireza; Najafgholipour, Mohammad Amir
  7. Abstract:
  8. Each year, a considerable amount of waste tires is disposed of in landfills, causing significant environmental concerns. One potential solution to mitigate these effects is the partial replacement of natural fine aggregates in concrete with recycled crumb rubber. Although the inclusion of crumb rubber typically results in reduced compressive strength and elastic modulus, previous studies have shown that rubberized concrete can still be viable for structural applications. In reinforced concrete structures, adequate bond between the steel reinforcement and surrounding concrete is essential; hence, the concept of development length is used to ensure proper anchorage. Where providing the required development length is not feasible—such as in beam-column joints—hooked bars are commonly employed to reduce the necessary embedment length. This study investigates the anchorage performance of hooked bars embedded in rubberized concrete in which 20% of the fine aggregate volume is replaced with crumb rubber. A total of sixteen beam-column joint specimens were cast and tested, using hooked bars of 20-, 25-, and 28-mm diameters. Key variables included the presence of transverse confining reinforcement, embedment length, and bar diameter. The results indicated that rubber replacement had negligible impact on the anchorage strength of 20 mm bars, while a reduction in anchorage strength was observed for specimens with 25 mm and 28 mm bars. A secondary analysis revealed that the effects of confinement, bar size, and embedment length were similar in both rubberized and conventional concrete. Finally, the applicability of ACI 318-25 provisions for development length of hooked bars in tension was evaluated. The findings suggest that current design expressions remain conservative for bars up to 20 mm in diameter in rubberized concrete. However, for larger bars (25 mm and 28 mm), the degree of conservatism is reduced in rubberized concrete compared to conventional concrete, indicating a potential need for revisiting these provisions
  9. Keywords:
  10. Lap-Splice Length ; Rubberized Concrete ; Shredded Tire ; Crumbed Rubber ; Hooks Bars

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