Experimental Investigation on the Ductillity of Beams Prestressed with FRP

C.J. Burgoyne and M.M. Morais

Engineering Department, University of Cambridge, Cambridge, UK

A perceived problem with the use of fibre reinforced plastic (FRP) materials for prestressing beams is their linear elastic behaviour; this results in a brittle structural failure. However, by using the plastic capacity of concrete and by enhancing it, the ductility of structures can be increased. To test this idea, an experimental programme was conducted that included simply supported rectangular prestressed concrete beams. Some beams were prestressed using steel tendons and others using Aramid Fibre Reinforced Plastics (AFRP) tendons.

Fibre reinforced plastic (FRP) reinforcement exhibits classic behaviour up to failure, without the typical yield plateau of steel. The behaviour of concrete beams prestressed by fibre reinforced plastic (FRP) tendons is non-linearly elastic up to failure. As a result there have been questions concerning the ductility of such structures.

In order to improve the ductility of fibre reinforced plastic (FRP) and prestressed beams, the following measures have been suggested:

(a) The use of partially bonded fibre reinforced plastic (FRP);

(b) The use of hybrid fibre reinforced plastic (FRP) with a bilinear stress strain curve;

(c) The use of compression reinforcement;

(d) The step layering of the FRP’s to have a progressive failure;

(e) Improvements in the strain capacity of the concrete.