Health monitoring of cuplok scaffold joint connection using piezoceramic transducers and time reversal method

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Cuplok scaffolds are widely used to form temporary supporting structures when constructing bridges and other structures all over the world. The safety and stability of cuplok scaffolds are important issues during construction. Cuplok scaffolds are subjected to various types of vibrations, which may loosen the cuplok connection, negatively impacting the stability of the structure and even leading to severe accidents. In this paper, the authors propose a time reversal (TR) method to monitor the looseness status of the cuplok connection by using stress wave-based active sensing. Lead zirconate titanate (PZT), a commonly used piezoceramic material with a strong piezoelectric effect, is employed. In the proposed approach, PZT patches are used as sensors and actuators to monitor the cuplok joint looseness. One PZT patch is bonded to the vertical bar and two PZT patches are bonded to the cross bars of the cuplok scaffold. The PZT patch on the vertical bar is used as an actuator to generate a stress wave and the other two PZT patches are used as sensors to detect the propagated waves through the cuplok connection, the looseness of which will directly impact the stress wave propagation. The TR method is used to analyse the transmitted signal between the PZT patches through the cuplok connection. By comparing the peak values of the TR focused signal, it can be found that the peak value increases as the tightness of the cuplok connection increases. Therefore, the peak value of the TR focused signal can be used to monitor the tightness of the cuplok connection. In addition, the experimental results demonstrated that the TR method is superior to the energy method in consistency, sensitivity and anti-noise properties.