Failure experiment on CFRP-strengthened prestressed concrete cylinder pipe with broken wires

The prestressed concrete cylinder pipe (PCCP) has been used widely in hydraulic engineering. However, due to hydrogen embrittlement and corrosion, the prestressing wires in PCCP can break and cause pipe failure. In this study, a retrofitting technique of using externally bonded carbon fiber reinforced polymer (CFRP) to repair PCCP was proposed. The technique is particularly useful when shutting down water is not possible. The proposed strategy was evaluated by using a full-scale PCCP with a 2.8 m inside diameter loaded with internal water pressure. First, the PCCP strains before and after repair were compared under different internal pressures. In the presence of CFRP, the strains near the broken wires significantly decreased under the same internal pressure, and the carrying capacity of the PCCP increased. PCCPs with 13 %, 15 %, and 18 % wire breakage ratios were then evaluated and compared. The strain in each material increased with increasing wire breakage ratio, and the maximum strain in CFRP was observed at the location of wire breakage. Considering the PCCP with 18 % wire breakage ratio, the section 2300 mm from the pipe end was in the linear state under an internal pressure of 0-0.9 MPa, and the PCCP reached its serviceability and elastic limit states when the internal pressure increased to about 1.0 MPa and 1.2 MPa, respectively. Finally, when the internal water pressure was increased to 1.27 MPa, which was higher than the internal design pressure of 1.12 MPa, the PCCP failed due to the rupture of CFRP.