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Structural Engineering and Mechanics
  Volume 38, Number 6, June25 2011 , pages 697-714
DOI: https://doi.org/10.12989/sem.2011.38.6.697
 


Design for moment redistribution in FRP plated RC beams
Deric John Oehlers, Matthew Haskett and Mohamed Ali M.S.

 
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 nonhinge 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.
 
Key Words
    reinforced concrete; moment redistribution; member ductility; fibre reinforced polymer; FRP; plated structure; hinge; member strength
 
Address
Deric John Oehlers, Matthew Haskett and Mohamed Ali M.S.: School of Civil, Environmental and Mining Engineering, University of Adelaide, South Australia 5005, Australia
 

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