Description
This investigation proposes an integrated technology for monitoring and strengthening the prestressed concrete cylinder pipe (PCCP) with broken wires, which is based on distributed acoustic sensing (DAS) and self-prestressing iron-based shape memory alloy (Fe-SMA). The technology was evaluated in a full-scale study on two PCCPs with an inner diameter of 1400 mm and a length of 6000 mm. A single optical fiber was pasted/embedded on the surface of the PCCP mortar coating along the length direction, and the signals generated by wire breakage were monitored by the DAS system. After the monitoring, the Fe-SMA bars were externally wrapped outside the surface of the PCCP with a wire breakage ratio of 10%, and heated to 200 ℃ through electrical resistance heating, to generate the circumferential prestress. Following this, the wire breakage ratio was increased to 15%, and the Fe-SMA bars were heated secondary to a higher temperature of 300 ℃ to increase the circumferential prestress, further limiting the negative effect caused by wire breakage development. The results show that the DAS system can identify the time and location of wire breakage, where the wire breakage signal is characterized by a high amplitude and short duration. Following prestress strengthening with Fe-SMA bars, there was a discernible reduction in both the width and length of the principal crack. Moreover, significant decreases were observed in the strains of concrete, mortar coating, and prestressed steel wires. Additionally, the higher activation temperature of Fe-SMA bars can effectively offset the negative impact caused by the wire breakage development of PCCP. Combined Fe-SMA with the DAS monitoring system, it enables precise positioning and efficient strengthening of in-service PCCP with broken wires.
