Diagnosis of damage in a steel frame

In order to investigate on the state of the art of the techniques which make use of Vibration Based Inspection (VBI) to detect structural damage, recently a blind test exercise involving a steel frame has been proposed. The aim of this paper is to compare results obtained applying optimisation-based methods, which make use of genetic algorithm and simulated annealing to solve the inverse problem, and eigen-sensitivity techniques in the detection and quantification of the extent of the damage in the steel frame under test. Because of some problems in developing a mathematical model with natural frequencies in agreement with those proposed by the blind test, it has been decided to evaluate dynamic characteristics of a damaged structure by introducing damage in the FE model, while the shear-type model has been used in order to detect and assess the structural modification.