Abstract

This research involves two experimental investigations into the behaviour of prestressed concrete members strengthened using two typical techniques: the first is by application of external post-tensioning using carbon fiber reinforced plastic (CFRP) cables, whereas the second is by bonding composite straps on the tension side of the members. In the first investigation, a total of twelve partially prestressed concrete beams were tested. Nine of the beams were first subjected to loads large enough to cause considerable cracking and deformations and then strengthened with the external CFRP cables and loaded up to failure. The CFRP cables used were CFCC 1 $\times$ 7-5 mm and 7.5 mm diameter, manufactured by Tokyo Rope, Japan. The remaining three beams were loaded monotonically from zero up to failure without strengthening and were used as control beams for comparison purposes. The twelve beams had the same concrete cross-section dimensions and were divided into three groups; each group consisted of four beams of the same length but with different levels of internal prestressing. The purpose was to study the effects of the span-to-depth ratio and the partial prestressing ratio or the reinforcing index on the performance of reinforced or prestressed concrete beams after being strengthened with the external CFCC cables.