Study on Damage Identification Method for Chuan-Dou Timber Frame Structures Based on Evolution of Dynamic Characteristic Parameters

To explore the evolution of dynamic characteristics of Chuan-Dou timber structures under different damage states, this study takes a typical Chuan-Dou timber structure in Southwest China as the research object. A 1:7 scaled model of a two-story timber frame with five main columns and four secondary columns, three bays, and two rooms was designed and fabricated, and combined pseudo-static and dynamic tests were carried out. When the specimen was in three typical states, namely intact, moderate damage, and severe damage, the sudden release method was adopted to obtain structural vibration responses. The natural frequencies and damping ratios in the X- and Y-directions under each state were identified, and the damage sensitivity differences among stiffness, frequency, and damping ratio were compared and analyzed. The test results show that with the aggravation of damage degree, structural stiffness degrades continuously, and the natural frequency shows a monotonic decreasing trend. The X-direction frequency decreases from 11.178 Hz to 7.8 Hz, and the Y-direction frequency decreases from 6.2 Hz to 5.156 Hz. The damping ratio increases significantly. The X-direction damping ratio increases from 3.552% to 8.951% (an increase of 152.0%), and the Y-direction damping ratio increases from 4.391% to 11.94% (an increase of 171.9%). Comparative analysis shows that the change amplitude of the damping ratio is about 5 to 10 times that of the natural frequency, and it has higher identification sensitivity to structural non-linear damage behavior. This paper innovatively applies the frequency-damping ratio dual-index collaborative determination strategy to Chuan-Dou timber structures, establishes a damage identification method based on the evolution of dynamic characteristic parameters, and discusses the engineering application paths of sensor optimal layout strategy, structural health archive establishment, and post-earthquake rapid screening. The research results can provide experimental basis and technical reference for daily health monitoring, post-earthquake rapid identification, and seismic performance evaluation of traditional timber structures of Chuan-Dou timber structures.