Structural Engineering and Mechanics

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Design for moment redistribution in FRP plated RC beams

  • Oehlers, Deric John (School of Civil, Environmental and Mining Engineering, University of Adelaide) ;
  • Hasketta, Matthew (School of Civil, Environmental and Mining Engineering, University of Adelaide) ;
  • Mohamed Ali, M.S. (School of Civil, Environmental and Mining Engineering, University of Adelaide)
  • Received : 2009.10.14
  • Accepted : 2011.02.22
  • Published : 2011.06.25
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Abstract

Assessing the ductility of reinforced concrete sections and members has been a complex and intractable problem for many years. Given the complexity in estimating ductility, members are often designed specifically for strength whilst ductility is provided implicitly through the use of ductile steel reinforcing bars and by ensuring that concrete crushing provides the ultimate limit state. As such, the empirical hinge length and neutral axis depth approaches have been sufficient to estimate ductility and moment redistribution within the bounds of the test regimes from which they were derived. However, being empirical, these methods do not have a sound structural mechanics background and consequently have severe limitations when brittle materials are used and when concrete crushing may not occur. Structural mechanics based approaches to estimating rotational capacities and rotation requirements for given amounts of moment redistribution have shown that FRP plated reinforced concrete (RC) sections can have significant moment redistribution capacities. In this paper, the concept of moment redistribution in beams is explained and it is shown specifically how an existing RC member can be retrofitted with FRP plates for both strength and ductility requirements. Furthermore, it is also shown how ductility through moment redistribution can be used to maximise the increase in strength of a member. The concept of primary and secondary hinges is also introduced and it is shown how the response of the non-hinge region influences the redistribution capacity of the primary hinges, and that for maximum moment redistribution to occur the non-hinge region needs to remain elastic.

Keywords

References

  1. AS 3600-2001 (2001), Standards Australia.
  2. Concrete Society (2000) "Design guidance for strengthening concrete structures using fibre composite materials", Technical Rep. No. 55, Crowthorne, Berkshire, U.K.
  3. Bencardino, F., Spadea, G. and Swamy, N. (2002), "Strength and ductility of reinforced concrete beams externally reinforced with carbon fiber fabric", ACI Struct. J., 99, 163-171.
  4. Benlloch, J., Parra, C.J. and Valcuende, M. (2002), "Ductility of reinforced concrete beams strengthened with CFRP strips and fabric", ACI, Proceedings of the 6th International Symposium on FRP Reinforcement for Concrete Structures, FRPRCS-6, 337-346.
  5. Duthinh, D. and Starnes, M. (2004), "Strength and ductility of concrete beams reinforced with carbon fiberreinforced polymer plates and steel", J. Compos. Constr., 8(1), 59-69. https://doi.org/10.1061/(ASCE)1090-0268(2004)8:1(59)
  6. El-Refaie, S.A., Ashour, A.F. and Garrity, S.W. (2003), "Sagging and hogging strengthening of continuous reinforced concrete beams using carbon fiber-reinforced polymer sheets", ACI Struct. J., 100(4), 446-453.
  7. International Federation for Structural Concrete, fib Task Group 9.3 (2001), "Externally bonded FRP reinforcement for RC structures", Technical Rep., Lausanne, Switzerland.
  8. Hashemi, S.H., Maghsoudi, A.A. and Rahgozar, R. (2008a), "Flexural ductility of reinforced HSC beams strengthened with CFRP sheets", Struct. Eng. Mech., 30(4), 403-426. https://doi.org/10.12989/sem.2008.30.4.403
  9. Hashemi, S.H., Maghsoudi, A.A. and Rahgozar, R. (2008b), "Flexural ductility of reinforced HSC beams strengthened with CFRP sheets", Struct. Eng. Mech., 30(4), 403-426. https://doi.org/10.12989/sem.2008.30.4.403
  10. Haskett, M.H., Oehlers, D.J., Mohamed Ali M.S. and Wu, C. (2010), "Analysis of moment redistribution in FRP plated RC beams", J. Compos. Constr.-ASCE, 14(4), 424-433 https://doi.org/10.1061/(ASCE)CC.1943-5614.0000098
  11. Haskett, M.H., Oehlers D.J., Mohamed Ali, M.S. and Wu, C. (2009), "Rigid body moment-rotation mechanism for reinforced concrete beam hinges", Eng. Struct., 31, 1032-1041. https://doi.org/10.1016/j.engstruct.2008.12.016
  12. Howser, R., Laskar, A. and Mo, Y.L. (2010), "Seismic interaction of flexural ductility and shear capacity in reinforced concrete columns", Struct. Eng. Mech., 35(5), 593-616. https://doi.org/10.12989/sem.2010.35.5.593
  13. Liu, I.S.T., Oehlers, D.J. and Seracino, R. (2006), "Tests on the ductility of reinforced concrete beams retrofitted with FRP and steel near-surface mounted plates", J. Compos. Constr., 10(2), 106-114. https://doi.org/10.1061/(ASCE)1090-0268(2006)10:2(106)
  14. Mahini, S.S. and Ronagh, H.R. (2009), "Numerical modelling of FRP strengthened RC beam-column joints", Struct. Eng. Mech., 32(5), 649-665. https://doi.org/10.12989/sem.2009.32.5.649
  15. Mukhopadhyaya, P., Swamy, N. and Lynsdale, C. (1998), "Optimizing structural response of beams strengthened with GFRP plates", J. Compos. Constr., 2(2), 87-95. https://doi.org/10.1061/(ASCE)1090-0268(1998)2:2(87)
  16. Oehlers, D.J. and Seracino, R. (2004), Design of FRP and Steel Plated RC Structures: Retrofitting Beams and Slabs for Strength, Stiffness and Ductility, Elsevier, Oxford, U.K.
  17. Oehlers, D.J, Liu, I., Ju, G. and Seracino, R. (2004), "Moment redistribution in continuous plated RC beams. Part 1 Tests", Eng. Struct., 26(14), 2197-2207. https://doi.org/10.1016/j.engstruct.2004.08.003
  18. Oehlers, D.J., Haskett, M.H., Mohamed Ali, M.S. and Griffith, M.C. (2010), "Moment redistribution in reinforced concrete beams", Proc. ICE Struct. Build., 163(3), 165-176. https://doi.org/10.1680/stbu.2010.163.3.165
  19. Panagiotakos, T.B. and Fardis, M.N. (2001), "Deformations of reinforced concrete members at yielding and ultimate", ACI Struct. J., 98(2), 135-148.
  20. Sharma, A., Reddy, G.R., Eligehausen, R., Vaze, K.K., Ghosh, A.K. and Kushwaha, H.S. (2010), "Experiments on reinforced concrete beam-column joints under cyclic loads and evaluating their response by nonlinear static pushover analysis", Struct. Eng. Mech., 35(1), 99-117. https://doi.org/10.12989/sem.2010.35.1.099
  21. Yeh, F.Y. and Chang, K.C. (2007), "Confinement efficiency and size effect of FRP confined circular concrete columns", Struct. Eng. Mech., 26(2), 127-150. https://doi.org/10.12989/sem.2007.26.2.127