Non-proportional damage identification in steel frames

A non-proportional damage detection method capable of identifying the location and determining the severity of cross-section damage in plane steel frames is presented. The proposed method consists of two components: a damage identification component and a damage severity component. Both components make use of the change in dynamic properties of the structure as a result of damage to determine the location and severity of the damage. One significant feature of the damage identification component of the proposed method is its ability to accurately isolate the different damage regions from the structure before the damage severity component of the method is applied. Since these damage regions are usually small in comparison with the overall size of the structure, the amount of computations needed in determining the severity of the damage is drastically reduced. Another feature of the method is its relative insensitivity to noise often present in some of the measured eigenvectors or mode shapes, thus allowing reasonably good results to be obtained even from slightly contaminated data. The proposed approach is applied to several frame examples to show that it can successfully detect and quantify cross-section damage in these structures.