Study on loose damage monitoring of mortise-tenon joints in traditional wooden structures based on piezoelectric active sensing

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In traditional Chinese wooden structural buildings, mortise-tenon joints are used as connection nodes. Under the erosion effects from wind and rain, such nodes are prone to aging and loosening. If they are not tracked and repaired in time, they are likely to cause structural damage when they encounter sudden loads such as earthquakes. In accordance with engineering practice, one mortise-tenon joint specimen with a penetrating straight tenon and one mortise-tenon joint specimen without a penetrating tenon were constructed. Active sensing technology based on piezoelectric ceramics was used to identify the loosening state of tenon and mortise joints. The amplitude of the piezoelectric signal, wavelet packet energy, information entropy, and damage index based on the root mean square deviation were analyzed. It was found that with the increase in loosening damage, the amplitude of the signal gradually decreases, and the information entropy gradually increases. When the damage reaches a certain extent, the changes in the monitoring signal characteristics is limited. The proposed monitoring method can be used to identify the damage state for mortise-tenon joints effectively, and the research results can provide a valuable guideline for the repair of mortise-tenon joints used in traditional wooden structures.