| Deterioration of concrete structures, due to corrosion of prestressing and reinforcing steels, has led to a search for corrosion-resistant reinforcing materials such as fibre reinforced polymer (FRP) or stainless steel. This thesis describes a study into the behaviour of partially-prestressed concrete beams containing a hybrid arrangement of partially-bonded prestressing carbon FRP (CFRP) tendons and non-prestressed stainless steel bars. Five such beams, with variable bonding pattern of the CFRP tendons, have been constructed and tested to obtain the complete load-deflection relationship during loading and unloading, and a numerical model, capable of predicting the loading and unloading responses of a partially-prestressed bonded concrete section, is presented. Since conventional measures of ductility based on the yielding of reinforcement are not directly applicable to concrete beams with FRP reinforcement, because of the linearly elastic characteristic of FRP up to failure, other measures of the deformation capabilities of the beams have been examined. These have been used as either deformability or ductility measures, with deformability being related to yielding of the stainless steel reinforcement, and ductility being based on the consumed plastic and stored elastic energies obtained from the complete loading and unloading load-deflection relationship of a beam. Test results indicate that, while the bonding pattern has an influence on the amounts of plastic and elastic energies, it has an insignificant effect on ductility. However, increasing the unbonded length of the CFRP tendons improves deformability. It is concluded that deformability and ductility should not be assumed to be interchangeable. |
