Shear Capacity of Ultra-High Performance Concrete Rectangular Beams

Pourbaba, Masoud | 2017

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  1. Type of Document: Ph.D. Dissertation
  2. Language: English
  3. Document No: 49984 (53)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Joghataie, Abdolreza
  7. Abstract:
  8. The application of ultra-high performance concrete (UHPC) as an alternative to conventional/ normal concrete (NC) has grown rapidly in recent years. However, there is limited knowledge on its shear behavior, which is essential for developing design guidelines for structural applications. A detailed parametric study was conducted on 38 beam specimens, half of which were made of UHPC and the other half made of NC. To ensure applicability of findings, two types of UHPC mixes were used, a proprietary and a generic mix. Eighteen of the beams were prepared and tested in Tabriz, Iran, while the other 20 were made and tested in Miami, FL. Test parameters included type of concrete (UHPC and NC), shear span-to-depth ratio (0.8, 1.2, and 2.8), reinforcement ratio (2.2% to 7.8%) and reinforcement anchorage. All specimens had the same length but different cross sections. Test results proved UHPC specimens to have much higher shear strength and ductility than NC beams. Normalized shear and shear strength both increased for shorter shear spans and higher reinforcement ratios. The anchorage did not affect UHPC beams, while it improved ductility of NC beams. The results are compared with estimations by ACI 318, RILEM, Kazemi et al equation, ACI 544.4r, Australian guideline and Iranian national building regulations. To compare the code estimations, the ratio of experimental shear strength to predicted shear strength, denoted by EP ratio is calculated for each code. Based on the results, the authors conclude that ACI 544 and Australian guideline with EP ratio of 2.56 and 3.16 provide the minimum EP ratios respectively while the Iranian National Building Regulations with an EP ratio of about 11 provides the highest EP ratio. Using RILEM gave an EP ratio of 4.06 and this value for first and second equation of ACI 318 was about 8.49 and 10.69 respectively. The second equation of Iranian and first equation of ACI 318 codes provide basically the same strength estimation but both are very conservative, which may be interpreted as mainly because the codes are dubious about the precision of their own estimations. However, RILEM and Australian codes, estimate the shear resistance with reasonable margin of safety
  9. Keywords:
  10. High Performance Concrete ; Interlayer Shear Strength ; Safety Factor ; Shear Span to Depth Ratio ; Experimental Shear Strength to Theorical Ratio

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