A mode shape identification method of timber pieces based on relative rigid displacement decomposition

As a commonly used method in the field of structural dynamic characteristics, mode shape identification currently relies largely on animation demonstrations of finite element modal analysis. This method is highly susceptible to the observer’s perspective and subjective factors, making it difficult to accurately identify the mode shapes of timber pieces. To address this issue, the plane deformation decomposition theory of 2D-4 node quadrilateral elements was adopted to perform relative rigid body displacement decomposition on mode shapes, thereby achieving quantitative and visual identification of the overall mode shapes of timber pieces. The correctness of the proposed method was verified by comparison with the modal mass participation ratio method. In addition, this method can also determine the dominant rigid body displacement type of each element in the mode shapes of timber pieces, which highlights its superiority.