A comparison of modal flexibility method and modal curvature method in structural damage detection

Abstract

Vibration based damage detection techniques examines the changes in dynamic properties of a structure such as frequency, mode shape and damping to indicate the presence of damage. This method is preferred for its ease of implementation, non-destructive nature and its ability to identify damage that is invisible to the surface. Two vibration based damage detection methods are used in this study, namely Modal Flexibility Method and Modal Curvature Method. Although there have been numerous publications on these two methods, there is lack of study on the direct comparison of the methods. Finite element modal analysis of a reinforced concrete slab and steel frame was carried out to obtain the dynamic responses that were used to calculate the Modal Flexibility and Modal Curvature. The structural models were simulated using four damage cases: damage at single location, damage at multiple locations, damage at support location and damage at different damage severities. The comparison of the sensitivity and reliability of Modal Flexibility and Modal Curvature were evaluated using the results of these four damage cases. The results show that the sensitivity and reliability of both methods are affected by the size of the damaged area, its location relative to the support location and the number of damaged segments.