Influence of Bond on Rotation Capacity of Concrete Pretensioned with AFRP

C.J. Burgoyne and J.M. Lees

Engineering Department, University of Cambridge, Cambridge, UK

The whole concept of reinforced and prestressed concrete design needs to be re-evaluated in the light of the properties of fibre reinforced plastic (FRP) reinforcement. In conventional design with steel reinforcement, beams are under-reinforced. With increasing loads, the steel yields, large deflections ensue and finally the concrete crushes. Concrete crushing is typically deemed to be a brittle mode of failure and hence should occur after the steel has yielded. With fibre reinforced plastic (FRP) materials, rupture of the tendons is also a brittle failure mode and hence undesirable. The concept of "ductility", defined as being the ability to do plastic work, is no longer applicable when referring to FRP materials.

The present study considers the flexural behaviour of concrete beams pre-tensioned with aramid fibre reinforced plastic (AFRP) tendons. Aramid fibre reinforced plastic (AFRP) materials are linearly elastic and do not yield. Hence, failure due to the tendons rupturing is brittle and sudden. However, failure due to concrete crushing is also deemed to be undesirable. The current work demonstrates how a high rotational capacity can be achieved using a composite made up of two brittle materials.

References

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