Chris J. Burgoyne and Janet M. Lees
Department of Engineering, University of Cambridge,
Cambridge, UK
An analytical model was developed
to describe the flexural behaviour of a series of pre-tensioned concrete beams
with partially-bonded aramid fibre reinforced plastic (AFRP) tendons. The model was
based on a rigid body formulation and procedures were incorporated which
considered a number of events that could occur during testing. The flexural
response of the beams was found to be particularly dependent on two key events;
bond breakdown and concrete cracking. The correlation between the predicted
analytical and experimental results was good.
Unlike steel, fibre reinforced plastics
(FRPs) are elastic materials and do not yield. In a concrete beam prestressed
with steel, the steel yields as the load increases beyond a certain limit and
the ensuing deflections provide ample warning of failure. In contrast, the
failure of FRP materials is brittle and sudden. As the material properties of fibre reinforced plastics
(FRPs) are fundamentally different to those of steel, it is questionable
whether conventional design methods based on the use of steel reinforcement are
applicable to fibre
reinforced plastic (FRP) reinforced structures.
The focus of the current work is to
investigate the nature of a flexural design method which reflects an
understanding of both the strengths and weaknesses of fibre reinforced plastic (FRP)
materials. In particular, the influence of the bond between an aramid fibre
reinforced plastic (AFRP) tendon and concrete on the flexural response
of a pre-tensioned concrete beam is considered.
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