Abstract: The grid structural welding connections are prone to damage. In order to ensure the safety of a structure in its service life, a two-step damage identification method was worked out based on wavelet transformation and strain modal methods. In the first step, the acceleration response of every connection was calculated when weld damage occurs at given connection. The singular value of the high-frequency component of the calculated acceleration signal was analyzed by using wavelet transformation method, and then the impacted range by the damaged connection was determined according to the amplitude of singular value, which was used to divide the structural sub-regions. Besides, an accelerometer was placed at the given connection. In the second step, the acceleration responses of these accelerometers were measured and analyzed by using wavelet transformation method to identify the damaged sub-region in the structure. Then, in the identified damaged sub-region, the strain modal analysis method was selected to locate the damaged connection. Finally, the proposed method was verified by the experiment on a gird structural model. The results indicate that the proposed method can be used to identify the sub-region containing damaged welded connection in the structure by using acceleration signals measured from finite accelerometers, and locate the damaged connections in the sub-region, and that the proposed method is feasible to realize damage identification on large complex grid structures because very few sensors are required.

Key words: grid structure, wavelet transform, strain modal method, weld damage, experiment verification