Cyclic performance of overloaded beams externally post-tensioned with CFRP tendons

This paper presents the results of an experimental program conducted to investigate the cyclic behaviour of seven large-scale reinforced concrete beams externally post-tensioned with carbon fibre reinforced polymer (CFRP) tendons. One specimen was tested under monotonic load while the other six beams were cycled until failure. Prior to strengthening, all beams were initially overloaded monotonically to twice their yield capacity. This loading phase aimed to simulate severe loading conditions that reinforced concrete beams may be subjected to during service. The beams were then strengthened using externally post-tensioned CFRP tendons anchored with wedge-type steel anchors (Waterloo anchors) at the ends of the beams. The external tendons were harped at two points along the sides of the beams. The tendons were post-tensioned to 40% of their ultimate tensile capacity. The strengthened beams were subjected to monotonic and cyclic loads at various load ranges until failure occurred. The results showed that external post-tensioning with CFRP tendons considerably increased the fatigue life of the beams at all applied load ranges. All cycled beams failed by the fatigue fracture of the internal steel reinforcing bars. The CFRP tendons exhibited excellent fatigue performance with no sign of distress during the cyclic loading.