The purpose of this book is to compare and evaluate global methods proposed for structural damage identification that use changes in the modal properties of the structure and to provide an assessment of the effectiveness of the methodologies analyzed. A literature review on the subject of structural damage identification is presented. Methods based on changes in displacement mode shapes, the flexibility matrix, the modal curvature and methods based on the FRF-curvature, are discussed. Another purpose is to formulate new structural damage identification methodologies based on the methods examined that can be used for damage assessment of existing structures. This book should be useful to graduate students of structural engineering and professional engineers working in structural health monitoring and damage detection of structures.