C.J. Burgoyne
Engineering Department, University
of Cambridge, Cambridge, UK
The paper addresses the definitions
of ductility and deformability that are causing significant problems to
advocates of the use of fibre reinforced plastics (FRPs) in prestressed and reinforced
concrete, and confusion for those who are considering its application. The use
of the words for steel-reinforced structures is discussed, as are the questions
of plasticity theory, energy absorption and warning of failure. It is shown
that structures that have a significant ability to deform, and at the same
time, absorb energy, are desirable. It is shown that structures with confinement
of the concrete in the compression zone can give the ideal moment-curvature
relationship, with a slowly rising response (giving large displacements), and a
concave unloading curve (giving large energy absorption). It is suggested that
these ideas should be combined with partially bonded or external tendons to
achieve optimal results.
Discussions with practising design
engineers about the use of Fibre Reinforced Plastic (FRP) always return to the question of
the lack of ductility. At some point in the discussion someone will say “But fibre reinforced plastics
(FRPs) are brittle”, with the implication that they therefore cannot be
used. The advocate of Fibre Reinforced Plastic (FRP) will talk about the rotation
capacity of the beams, but the initiative has been lost and it is very unlikely
that fibre
reinforced plastics (FRPs) will be used in the structure under
discussion.
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