Chris J. Burgoyne
Department of Engineering, University of Cambridge, UK
Hau Yin Leung
City University
of Hong Kong, China
The lack of ductility of fibre reinforced plastics (FRPs) means
that it is desirable for beams containing these elements as reinforcement or
prestressing tendons to fail by concrete crushing, but this leads to sudden,
brittle failure. It was pointed out by Burgoyne that a rational approach to
design was to prestress the Fibre Reinforced Plastic (FRP) tendons, and to use confinement
of the compression zone by spirals of Fibre Reinforced Plastic (FRP) to increase
the strain capacity of the concrete. The result is a beam in which the strain
capacities of the tension and compression zones can be made of similar
magnitude, which leads to reasonable curvatures, efficient use of the
materials, and high ductility. Research at the University of Cambridge
has studied the theoretical behaviour of spirally confined concrete and
conducted tests on samples containing either single spirals or overlapping spirals,
with forces applied either axially or eccentrically. This has led to
predictions for the way a beam made in this way should behave. That work is
reported in detail elsewhere. This paper gives some background information and
presents the final beam test that drew the various aspects of the work
together.
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