Ductility of externally prestressed continuous concrete beams

Ductility is a desirable structural property that allows stress redistribution and provides warning of impending failure. Factors affect the ductility of beams prestressed with external FRP tendons are different than those affect the ductility of ordinary bonded prestressed concrete beams due to lack of bond and linear stress-strain relationship of FRP tendons. This paper investigated the effect of several variables on the ductility of continuous concrete beams, externally strengthened using Parafil ropes. The test variables included external prestressing force value, depth of external prestressing tendons, loading pattern, tendon profile and location of deviators. Test results show that the ductility of the externally prestressed concrete beams significantly reduced due to prestressing. Also, the eccentricity of the prestressing force and the tendon profile had the main influence on ductility of the externally prestressed beams, while the variation in prestressing force value, loading pattern and location of deviators had a less effect.