SUMMARYThe use of changes in dynamically measured flexibility matrices to detect structural damage has received considerable attention during the last years. A new flexibility-based method is proposed in this study to provide an insight to the characterizations of structural damage. The presented method makes use of the eigenparameter decomposition of structural flexibility change and approaches the damage identification problem in a decoupled manner. First, a theory is developed to determine the number of damaged elements according to the number of non-zero eigenvalues of structural flexibility change. With the number of damaged elements determined, the localization and quantification algorithms are then developed. The proposed method is applied to three numerical examples and its efficiency is demonstrated through damage simulations.