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Fire Resistance of FRP Reinforced Concrete Beams

Fire Resistance of FRP Reinforced Concrete Beams. Presented By: Abu Naim Md Rafi December 6, 2010 Department of Civil and Environmental Engineering University of Windsor. Outline. Research Significance Concrete in Fire FRPs in Fire Comparison of FRP and Steel Experimental Study

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Fire Resistance of FRP Reinforced Concrete Beams

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  1. Fire Resistance of FRP Reinforced Concrete Beams Presented By: Abu Naim Md Rafi December 6, 2010 Department of Civil and Environmental Engineering University of Windsor

  2. Outline • Research Significance • Concrete in Fire • FRPs in Fire • Comparison of FRP and Steel • Experimental Study • Finite Element Analysis • Conclusion

  3. Fire Performance of Concrete • Internal stresses increased by • Evaporation of free moistures • Dehydration of CSH • Thermal expansion of aggregate • Excessive increase in internal • pressure results spalling • Strength and stiffness reduces • significantly due to exposure Figure : Concrete Strength Reduction Factor with Temperature (This figure is produced from the value presented by Wang et al. (2009) based on Eurocode 2)

  4. Fire Performance of FRP • High temperature behaviour of FRP is different than the high temperature behaviour of steel and concrete. • It is well established that material properties of FRPs deteriorate with increasing temperature. • Fibres are relatively more resistant to thermal effect so degradation of mechanical properties are governed by properties of polymer matrix. • The critical temperature is commonly taken to be the glass transition temperature of the polymer matrix. • Typical range of is between 65-120˚C for matrix used for infrastructure application.

  5. Fire Performance of FRP • Due to anisotropy ,transverse properties are more affected by elevated temperature and the transverse strength and stiffness decreases rapidly above glass transition temperature. • When used as a reinforcement the most important properties of FRP influencing structural behaviour at elevated temperature are • Strength • Stiffness and • Bond properties with the concrete

  6. Fire Performance of FRP Strength Figure : Variation of Tensile Strength of FRP with Temperature (This figure is produced from best fit sigmoid curves presented by Bisby et al. (2005) based on data presented in the literature.)

  7. Fire Performance of FRP Stiffness GFRP and AFRP CFRP Figure : Variation of Stiffness of FRP with Temperature (This figure is produced from equations presented by Saafi (2002) based on experimental results collected by Blontrock et al. (1999))

  8. Fire Performance of FRP Comparison with steel Figure : Comparison of Strength and Stiffness of FRP with Steel at Elevated Temperature (Strength and stiffness of steel are according to CSA S-16 (2009))

  9. Fire Performance of FRP Bond properties with concrete • Katz et al. (1999) performed experimental study to evaluate bond strength of FRP and steel with concrete at elevated temperature • A reduction of between 80 and 90% in the bond strength was observed as the temperature is increased from 20˚C to 250˚C. • Ordinary deformed steel rebars showed a reduction of only 38% in the same temperature range.

  10. FRP Reinforced Beams in Fire • The research work performed to understand the behavior of FRP reinforced concrete beams at elevated temperature can be divided into two groups • Experimental work • Analytical Work • Abbasi and Hogg (2005) • Rafi et al. (2007) • Rafi and Nadjai (2008) • Saafi (2002) • Abbasi and Hogg (2005)

  11. FRP Reinforced Beams in Fire Abbasi and Hogg (2005) • Tested three RC beams • 350 x 400mm cross section • Compressive strength of concrete was 42 MPa (100mm cube) • Six point bending test

  12. FRP Reinforced Beams in Fire Abbasi and Hogg (2005) • The control specimen tested at room temperature • Load-deflection become non-linear after an applied load of 60 kN • For fire test 40 kN load was applied and subjected to standard fire • Subjected to heating on three sides • Early Failure of beam 2 is due to weaker bond strength • Clear cover of 70 mm recommended Figure: Heating time-deflection curve (Abbasi and Hogg, (2005))

  13. Methodology • Experimental Study • Finite Element Analysis Based Parametric Study

  14. Experimental Study Parameters • Pipe Diameter to Thickness (D/t) Ratio • Pipe Material • Indenter Shape • Internal Pressure • Depth of Indentation

  15. Results • Comparison of queue length for short queue • Figure 5-5

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