Physical Interpretation of Principal Component Analysis for Structural Dynamics Through String Vibration

Principal component analysis (PCA) has been successfully applied in structural dynamics in recent years. However, it is usually used as a black-box, resulting in a gap between the application aspect and the physics essence of the problem. Thus a physical interpretation of PCA is necessary, along with further investigation, especially on the mechanism involved. This paper provides a physical meaning of the PCA by the theoretical analysis and numerical experiment on the vibration of a 1D string. Conditions that make the interpretation feasible were identified. The theoretical derivation and numerical simulation results indicate that the PCA gives a good estimation of the modal participation ratio in terms of energy, and the principal component coefficient (PCC) can be used to estimate the structural modes. The physical interpretation gives a new perspective on how the current methods work while providing the possibility of further application of the PCA related methods to structural dynamic problems.