The volume collects papers illustrating the work done within a research project on structural identification and diagnostics. The papers deal with problems taken from civil engineering applications and cover various topics or aspects in this field. The focus is mainly addressed to dynamic identification techniques. In a field like that of inverse problems, where the lack of a satisfactory framework of general properties may obstruct applications to practical problems, the book offers a collection of simple case studies where numerical simulation and experimental measurements are combined to get diagnostic information. It’s worth mentioning a paper that specifically confines to crack detection in beams and rods and establishes a series of rigorously proved results that may turn useful in damage detection. In particular, the paper provides the answer to a recently raised question as to the minimal number of frequency measurements needed in order to localise the crack.